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Echinodermata! Starfish! Sea Urchins! Sea Cucumbers! Stone Lillies! Feather Stars! Blastozoans! Sea Daisies!Marine invertebrates found throughout the world's oceans with a rich and ancient fossil legacy. Their biology and evolution includes a wide range of crazy and wonderful things. Let me share those things with YOU!

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    Working late alone in the lab, going through a dish of marine inverts collected from a random sample in the Pacific Ocean and you find...something.

    Sometimes someone is around to share it with, sometimes not. What does THAT feel like? This video isn't mine but it gives me the same feeling of discovery.

    I just found this and I don't know what it is.  THAT's saying something..


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    The Beast
    Image by Ken-Ichi
    This year it will be FIVE years since I began the Echinoblog in 2008. I always used to worry about having new topics to write about-but I'm quite happy to say that I've yet to run out of fantastic images or new discoveries to be shared.

    Today is a good case in point.A GREAT new story from the journal Invertebrate Biology (go here)by two of my favorite colleagues,Will Jaeckle at the Illinois Wesleyan Universityand Richard Strathmann at Friday Harbor Laboratoriesin Washington.. a NEW paper that MUST be shared!
    This week, Echinoblog brings you: 
    A sea cucumber that feeds not just using its mouth but ALSO via its butt!!

    First, Let's look at some basics...
    Jaeckle and Strathmann were studying the Pacific Northwest species Parastichopus californicus-the handsome fellow pictured above (and below)!  These occur along the west coast of North America in relatively shallow water...
    Cucumber1_6377 copy1a
    Image by Bill Pennell
    Here is the primary way that sea cucumbers feed-by using the feeding tentacles surrounding their mouth to ingest tiny food particles or sediment.. as such..

    As it turns out, sea cucumbers (and many other invertebrates) use their anus as an opening for pumping water in and out of their bodies!
    Image by bswift
    This whole water pumping into and out of the mouth/anus thing is actually pretty common- a bunch of worms, crustaceans and other echinoderms perform this same thing.

    As a generaltiy-sea cucumbers can pump quite a bit of water in and out through their anus-with tropical species measured between 40 to 860 milliliters/hour..that translates to about 3.6 to 4 cups of water per hour! 

    Sea cucumbers are essentially a big fleshy tube with a mouth and a butt that pumps water through itself!  Here's the basic anatomy below...
    Note those two bluish/white, feathery branches that come off the cloaca and the anus... those are called the respiratory trees.  That is where water enters via the anus and is used to respire or "breathe". The cloaca has muscles that PUMP the water in! 

    So, shocking sea cucumber secret # 1!!Sea cucumbers "breathe" through their anus! 

    Here's an actual pictures of these below from Jaeckle and Strathmann's paper (Fig. 1)
    Note that one branch of these structures
    Water enters through the anus and is pumped via the cloaca (and the cloacal muscles) into the respiratory trees (=long tubes with lots of branches), where there is gas exchange or "breathing". 

    Note the structure labelled rete mirabile, which is a network of blood vessels which interaces with the gut. That will be important later on!

    There's a LOT of water that flows through these areas, so conceivably, could these be used for ANOTHER purpose?  Such as.... feeding?

    Jaeckle and Strathmann set to find out! They used biological tracers such as the isotope Carbon-14 which they applied to various algae cells and other nutrients that were added to seawater.

    Evidence for the Anus as a Second Mouth!
    Folllowing the trail of traced algae through the sea cucumber, Jaeckle and Strathmann tracked the isotopes throughout the body and found out where they were most abundant.

    Enter The Rete Mirabile! (this sounds like a great episode of Star Trek doesn't it?) Basically after exposing the sea cucumber to tagged algae they found the tags taken in and were present in highest abundance in the Rete Mirabile which connects the respiratory trees with the gut..

    This supports the notion that organic food is drawn in from the respiratory trees and eventually transferred to the gut..
    Fig. 3 from Jaeckle & Strathmann
    They looked at specific tissue cross-section of the inside of the respiratory trees. Lo and behold the blue bits in the picture reveal that they are inside and being absorbed!
    On top of everything else, histology of the INSIDE of the respiratory trees shows internal tissues that you might expect to find in a gut: such as microvilli (tiny finger like doodahs that serve to absorb or secrete. We have these in our intestine) as well as certain kinds of cells in the stomach lining that are recognized in other animals for digesting food.

    Note above that they also found tiny ciliates (protozoans) swimming around inside living commensally. ANOTHER feature common to spaces where food is digested.
    Image by bswift
    It had been suggested before that the respiratory trees were used only for respiration/breathing. 

    But the evidence above suggests but rather something more akin to digestion or UPTAKE of nutrient-like material 

    In other words: They use their anus as a SECOND MOUTH!

    This phenomena is what the authors term "Bipolar Feeding"

    To be sure, its not likely that this means of feeding is as substantial as its primary feeding mode (taking organic materials from sediment or from the bottoms via the mouth) but it does appear to be significant. Also, obtaining food in this way may be an important way to supplement its main feeding mode.

    Perhaps the sea cucumber version of an  apéritif with dinner?

    How does this fit into the "Big Picture"??
    At first glance, all of this sounds more like just weird butt stuff..
    But let's remember that this mode of feeding is probably present in a LOT of sea cucumbers, which are ecologically important. Such as this post about tropical sea cucumbers being important to sea grass ecology.   And bear in mind thatnutrient cycling is an important considerationthese days. A LOT more nutrients go INTO sea cucumbers than perhaps was realized. 

    Another indicator of how echinoderms might be the ecological "canaries in the coal mine" perhaps?

    Information like this may seem like an unusual natural history factoid but conceivably things like this can ultimately be VERY important to the big picture... 

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    A cool find that a student (Eric T.) fr. American U. found while working on a project.. Solaster endeca with the arm from what looks like Asterias rubens
     Here is the predator alive...
    Solaster endeca
    and the prey (where the arm comes from)
    Asterias forbesi, dorsal

    Solaster is one of the few starfish which is known to feed primarily (at least in some species) on OTHER starfish!  Here was something I wroteawhile back on the Pacific Solaster dawsoni...

    morning sun star- solaster dawsoni
    and here is a nice pic of the North Pacific S. dawsoni feeding on Hippasteria
    It is so fearsome that EVEN the sunflower star Pycnopodia RUNS from it!

    andhere's a nice bit about when starfish are eating and uh... overreach...

    NOM! NOM! NOM!

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    This looks like it might be Ophiopsila. A brittle star with long arms that lives in a burrow... but maybe a brittle star person can tell me otherwise??

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    Isocrinid stalked crinoids from the Mariana Arc in the tropical Pacific.via NOAA

    So, the other day someone complained to me that the Echinoblog didn't do enough with fossils. So, this week FOSSIL CRINOIDS to the MAX! 

    The fossils below look like the ones above..kinda. Isocrinids? from the Jurassic. Image by Kevin Zim.
    Jurassic crinoids

    Some nice crinoids from the Houston Museum of Natural Science. Not sure which species. Images by malts8
    (HMNS) Crinoid Plate at the Houston Museum of Natural Science
    (HMNS) Houston Museum of Natural Science -- Crinoid Pair
    These are the crinoid Jimbacrinus bostocki from the Permian of Australia. More info at the Museum Victoria page here. Images by malts8
    (Australia) Jimbacrinus bostocki from the Houston Museum of Natural Science
    (Australia) Jimbacrinus bostocki  Crinoid
    An awesome rhombiferan (Caryocrinities ornatus)-not quite a crinoid-but something closely related. Another image by malts8
    (New York) Caryocrinites ornatus
    Pentacrinus (Mesozoic to Cenozoic) Image by fa11ing_away
    A nice Seirocrinus subangilaris from the Jurassic Poseidonia slate of Germany. Image by Zoltan.sylvester

    Phanocrinus formosas and Tholocrinus spinosus from the Mississippian-Glen Dean Formation in Grayson Co. KY. Image by malts8
    (Kentucky) Phanocrinus formosas and Tholocrinus spinosus Crinoids
    Cool looking Zeacrinites magnoliaeformis fr. the Mississippian-glen Dean Formation in Grayson Co., YI. Image by malts8
    (Kentucky) Zeacrinites magnoliaeformis Crinoid
    Onychocrinus exsculptus. Mississippian? (Paleozoic) Image From the Houston Museum of Natural Science
    Onychocrinus exsculptus
    More from the Mississippian! Talarocrinus planus. Image by G.S. Springer
    Talarocrinus planus (crinoid)
    Ampelocrinus mundus?
    Ampelocrinus mundus? (crinoids)
    From the Mississippian of Iowa. Dichocrinus inornatus, and Rhodocrinites kirbyi. These fossil pics from Piedmont Fossil- The Iowa Historical Museum
    some nice fossiliferous limestone
    A veritable FOREST of crinoids! Rhodocrinites kirbyi, Dichocrinus inornatus, Pachylocrinus globosus, and Rhodocrinus nanus along with unidentified brachiopod and bryozoan.
    Multiple Crinoids
    Agaricocrinus splendens from the Mississippian
    Agaricocrinus splendens
    Onychocrinus exculptus from the Mississippian of Crawfordsville Indiana
    Onychocrinus exculptus

    So, remember awhile back when I wrote this controversial post about swimming/floating crinoids?? There was this diagram that had been presented about how this one crinoid, Scyphocrinites enjoyed a pelagic type lifestyle with a positively buoyant "float"
    Here are some neat photos of what these floats look like in similar crinoid species.

    In this case, from Camarocrinus ulrichi. Images by malts8
    (Oklahoma) Crinoid  --  Camarocrinus ulrichi  Schubert
    (Oklahoma) Crinoid  --  Camarocrinus ulrichi  Schubert
    They are sometimes abundant in the field!
    (Oklahoma) Camarocrinus Crinoid Flotation Bulbs

    And down in the Cambrian we have...Gogia, an Eocrinid blastozoan (a different but closely related group of echinoderms similar to proper crinoids) Cambrian, from the Langston Formation, Spence ShaleImage by malts8

    (Utah) Gogia sp. Langston Formation - Spence Shale

    Are there echinoderms I'm not giving enough time to? Let me know!

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    Today, a little diversion from echinoderm as we feature, once again, the stunning invertebrate zoology photography of Arthur Anker featuring some of his favorite animals!

    A "strawberry crab" (Pelia mutica) from the Honduras
    Strawberry crab (Pelia mutica), Honduras

    wow! A festive decorator spider crab called Cyclax suborbicularis (Majidae) from Moorea, French Polynesia
    Carnival time !

    A "christmas lights crab (Paractaea rufopunctata)
    Christmas lights crab (Paractaea rufopunctata)

    The spectacular deep-water crab Rochinia crassa
    The spectacular deep-water crab Rochinia crassa

    An awesome looking leucosiid crab, Heteronucia venusta from Guam
    Heteronucia venusta (Leucosiidae), Guam

    A stunning Chilean hermit crab (Pagurus edwardsi) infested by a parasitic barnacle (=a rhizocephalan called Peltogasterella gracilis)
    A Chilean hermit crab (Pagurus edwardsi) infested by a rhizocephalan (Peltogasterella gracilis)

    A striking striped crab, Liopetrolisthes mitra
    Liopetrolisthes mitra, striped colour morph

    An interesting grapsid crab, from French Polynesia
    Metopograpsus thukuhar (Grapsidae), French Polynesia

    A gorgeous polka dot xanthid crab, Cycloxanthops vittatus from Panama
    Cycloxanthops vittatus, Panama

    Stunning red xanthid crab, Liomera rubra from Guam
    Liomera rubra (Xanthidae), Guam

    Fire crab! (Hirsutodynomene sp.)
    Fire crab (Hirsutodynomene sp)

    More polka dots! (Trapezia tigrina)
    Coral crab (Trapezia tigrina), Guam

    A flat-rock elbow crab, Cryptopodia fornicata
    Flat-rock elbow crab (Cryptopodia fornicata)

    and wow..there's more which I will add in another post some day!

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    Things got a bit busy this week  and I've been discovering the wonders of the natural history side of DeviantArt!

    MANY creative and wonderful artists out there and I thought it would be cool to showcase some of the notable ones, especially the ones that can be compared against the "originals"

    Frankly, I'm pretty impressed. At one time, a LOT of these animals were known only to a handful of specialists in the world. And NOW?People make them into art!! That's amazing!

    Here's a few...
    Enypniastes! The deep-sea Swimming Sea cucumber! I blogged about these HERE.

    Enypniastes eximia by *NocturnalSea on deviantART

    Swimming Sea Cucumber Enypniastes eximia by ~JadaFitch on deviantART

    Swimming Sea Cucumber by ~veeohlay on deviantART
    Here are some video of the original inspiration!

    SEA PIGS! The sea cucumber called Scotoplanes! I wrote a bit on this HERE.

    Sea Pig by ~YavKementari on deviantART
    and holiday classics!

    Yeti Crab Santa by *NocturnalSea on href="">deviantART
    An interesting one with a Chinese art theme

    Sea Pigs by ~HangingLeaf on deviantART

    Sea Pig by ~ToonSkribblez on deviantART
    A digital sea pig

    cute as a sea pig by ~apostlebird on deviantART
    Here's a link to a neat one called "Sea Pig Nouveau" that sadly, was not embeddable..but click here.

    and of course, here's the original..

    What follows here are some PALEOZOIC fossils, with added colors and "reconstructed" onto a Paleozoic sea bottom as if they were alive...
    I try to compare some of these with actual fossils...

    Ophiocistioids!Strange Paleozoic forms! I wrote about these only awhile ago HERE.

    Volchovia species by =avancna on deviantART

    Sollasina and Eucladia by =avancna on deviantART
    Here is an actual fossil of the ophiocistioid Eucladia from Yale's collection

    Cystoid echinodermsfrom the Paleozoic!  I'll blog more about the various Paleozoic echinoderms some day, but there's easily as many extinct echinoderm fossil groups (most of them with stems) as living groups.   This image has a nice assortment of them from the Ordovician of New York..

    Glyptocystites multiporus by =avancna on deviantART
    Here are the three primary critters for comparison! The light olive one in the upper right corner, wrapped around the bryozoans is called Cupulocrinus jewetti
    Image by Paleoportal. Photo by Joe Koniecki
    The artist indicates the blue individual as the cystoid Pleurocystites squamosus 
    Image from Paleoportal. Photo by Joe Koniecki
    Here's another.. the brown one with all the unusual spines? tentacles along the sides? Is identified as Glyptocystites multiporus. Here's a fossil from the Ordovician in Ontario for comparison
    Image from Paleoportal. Photo by Joe Koniecki
    NEXT WEEK! Antarctica!

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    This week a 2011 vol. 119(5): 457-466 paper  from the Journal of Geology by Antarctic biologist James McClintock, my colleagues at the University of Alabama (M. Amsler, R. Angus, R.C. Challener, J.B. Schram, C.D. Amsler), myself and colleagues at the University of South Florida (J. Cuce and B. Baker).

    Our paper addresses how Antarctic echinoderms but specifically sea stars (=starfish) and brittle stars are likely to be vulnerable as the climate changes, creating a more acidic ocean environment.

    Here is a quick video that nicely summarizes the broader phenomena of Ocean Acidification (abbreviated OA)

    But here is where we add further details-the acidification? affects different kinds of calcium carbonate (the material which composes shells, coral skeletons, etc.) differently...

    Most of the shells and skeletons that you read about in the news are usually made either out of different forms of calcium carbonate-either aragonite (wikipedia has a nice summary here) or calcite. Aragonite is usually what's seen as associated with shells, skeletons, etc.. 

    But, of course, echinoderms being echinoderms have something a little different going on... Echinoderms have skeletons with a high concentration of magnesium (Mg). 

    Their skeletons are composed of Mg-calcite (magnesium calcite)

    One can see many recent stories about how aragonite in shells is easily dissolved by ocean acidification.

    Mg-calcite is even MORE soluble (and more vulnerable) than aragonite! 

    Looking at Mg-calcite in Antarctic Echinoderms
    McClintock and his team sampled some 26 species of echinoderms, representing all 5 living classes (sea stars, brittle stars, crinoids, sea urchins, sea cucumbers) and analyzed them for % composition of Mg calcite. 

    The sampled specimens showed that skeletal components in Anatarctic echinoderms met the defined standards for "high-Mg-calcite species"(MORE than 4% Mg-calcite by mol%)
    Sea stars

    Of all the echinoderms? Which had the HIGHEST amount of Mg-calcite by % weight??
    Several species of Starfish! 

    I would note that ophiuroids were not heavily sampled-below but in all liklihood they are just as if not more important here..

    Specfically, this very widespread species, Porania antarctica  dsplayed among the HIGHEST % weight of Mg-Calcite
    Photo by Dirk Shories at this site.
    In the above image-the animal looks quite fleshy but in a dried one can see there's actually quite a bit going on...
    And here are some rather large Macroptychaster in a pic seen around the world..but you can see how big they get. The % of Mg-calcite is quite high in this and many other Antarctic asteroid species...
    One major conclusion: Antarctic echinoderms-especially sea stars (starfish) have high amounts (in terms of % of total weight) of Mg-calcite in their skeletons.  

    Mg-calcite is more inclined to dissolve as a result from OA and therefore makes them highly vulnerable to dissolution!
    This total amount of Mg-calcite was compared relative to OTHER %of Wt. values across different latitudes (0=equator, higher = closer to Antarctica)

    Note the datapoints indicated by the RED ARROW. Those are the data from Antarctic taxa.

    There's a global pattern that shows that those echinoderms close to the tropics have, by weight, the greatest % of Mg-calcite.  This makes sense when you think about how heavily calcified tropical starfish are (such as this Protoreaster nodosus)
    Protoreaster nodosus

    So, if tropical echinoderms have the greatest % of Mg-calcite by weight, why are we worried the MOST about POLAR species???

    An excellent question.  Here are some answers.

    1.  Temperature is an important part of the "calcium carbonate in sea water" ocean chemistry dynamic. Cold water settings, such as the Arctic and the Antarctic have shown the most dramatic decreases in the amount of calcium carbonate available for shell/skeleton building as ocean acidification increases.  Thishas been shown most recently in pteropod mollusks (click here for ref)

    2. Mg-calcite is most vulnerable to dissolution.A study on coralline algae (that's algae which builds a skeleton for itself using the mineral Mg-calcite) showed that when 8-12% by wt. of a calcite skeleton is composed of Mg-calcite it becomes HIGHLY soluble.. Look above at the Table 2 from the paper most sea stars have 9 to 10% by wt. Mg-calcite skeletons!

    3. Echinoderms are a dominant force in the Antarctic. They have HUGE biomass. In other words there's a LOT of them and they're important to the global carbon cycle.  Notice the large numbers of sea stars in the video below...That is a lot of Mg-calcite...
    Thus, Antarctic species may not have the highest % of Mg-calcite across the full "band" of possibilities but they are among the MOST vulnerable.

    So-all this leads to an important realization:  

    Echinoderms, probably sea stars, will probably be an important, I daresay, critical indicator of  which faunas will be affected as climate change continues and  ocean acidification creates a more acidic ocean environment.  

    This could affect the larval development, the physiology or the ecology of these species. Its also important to realize that echinoderms have an endoskeleton as opposed to a shell which is what you see in other studied taxa...  MUCH more remains to be studied. 

    Its also interesting to note the prior extinctions of echinoderms and other echinoderms from Antarctica as I've mentioned here , possibly during the Eocene glaciation event.

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    Chloeia flava
    Image by Ben Naden
    Chloeia is a fairly conspicuous polychaete worm in the family Amphinomidae which apparently occurs widely throughout the Indo-Pacific. About 27 species..and honestly I'm not sure if everything that is labelled C. flava in the videos and pics IS correctly identified but here's a round up of videos and pics while I am distracted by a job interview!

    This one shows some burrowing action at the end...


    Here's one eating...

    This one is a stunning iridescent green! Image by friscodive
    Chloeia sp.

    Chloeia fusca.  Image by Ben Naden
    Chloeia fusca

    Another similar one. Image by divemecressi
    Peacock bristle worm - Chloeia flava

    And yet another by friscodive
    Chloeia flava 01 - Nudi Pixel

    An awesome one from the Panama Canal. Image by Arthur Anker
    Fireworm (Chloeia sp) from Panama Canal

    Back atcha next week with more echinoderm blog love!

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    Tentacles of the warty pink sea cucumber (Colochirus quadrangularis)
    Fantastic image by Arthur Anker-Colochirus quadrangularis 
    Today, we welcome spring with these awesome brightly colored sea cucumbers from the tropical Indo-Pacific!

    My thanks again to Arthur Anker, WildSingapore and other photographers who have put their images up to enjoy!

    Warty pink sea cucumber (Colochirus quadrangularis)
    Fantastic image by Arthur Anker-Colochirus quadrangularis

    Pink-orange sea cucumber (Cercodemas anceps)
    Cercodemas anceps by Arthur Anker
    Another Cercodemas from Wildsingapore!
    Pink warty sea cucumber (Cercodemas anceps)
    Pink warty sea cucumber (Cercodemas anceps)
    A nice one of Cercodemas with the feeding arms extended
    Pink warty sea cucumber (Cercodemas anceps)
    And here's BOTH Cercodemaas AND Colochirus! 
    20061108 d6668

    Pseudocolochirus olivaceus. Images below by Arthur Anker, Singapore Marine Biodiversity Survey. Sea apple - the most colourful sea cucumber in the worldSea apple - the most colourful sea cucumber in the world

    Another nice Pseudocolochirus shot by Jeff Mullins (underwater komodo)
    Sea Apple - Cannibal Rock - Komodo
    The feeding end of Pseudocolochirus. Image by Arne Kuilman
    Power feeder (Pseudocolochirus violaceus)
    A nice close up of the tentacles in a sea apple. Image by Pat M. Williams
    Sea Apple

    and finally, here's  a video of one in its habitat (this one from Hong Kong)

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    thanks to Paul G. for the photo!
    Greetings! Today for the FIFTH ANNIVERSARY (began April 9th, 2008) of the Echinoblog a special topic!  One so controversial and so earth shattering that it will pit Friend vs. friend! Sibling vs. sibling! Spouse vs. spouse! Mentor vs. student! 

    A topic that has found bitter and vicious debate at museums, aquariums, marine biology and even paleontology programs around the world!

    Undoubtedly upon this post reaching public circulation, many of my colleagues will probably stop returning my email and spit upon me as I walk by them (although some of them do that anyway!)

    I speak of course, of the dreaded "Starfish or Sea star (seastar)??" controversy!

    Which common name should we use for these frequently encountered and familiar marine animals??? 

    But where to start?  Let's define some terms, so this discussion doesn't get completely out of hand.

    Let us make no mistake-when we talk of this debate that we speak of members of the ASTEROIDEA. 

    1. Starfish/Sea Star is a term that VERY SPECIFICALLY refers to the ASTEROIDEA-one of five living classes within the phylum Echinodermata (the others include sea urchins, sea cucumbers, crinoids, and ophiuroids). 
    2. It is incorrect to refer to OPHIUROIDS as "sea stars" or "starfish", per se.  Ophiuroids are an altogether DIFFERENT class of animals from asteroids. Go HERE to see some characters that tell them apart.  Common names of ophiuroids include: brittle stars, serpent stars, basket stars. I find it acceptable that certain echinoderms are referred to as "XXXX  stars" under certain circumstances. A separate class of echinoderm-the Crinoidea (lacking a stalk), for example are often called "Feather stars." I'm cool with that. The specific terms "sea stars" and "starfish" should only be applied to ASTEROIDS.
    3. Note that this is one of the few groups in which the common name DOES correspond to a 'real' classification. Terms such as "crab", "coral", or "jellyfish" actually do NOT refer to a single natural classification of animal-but rather several similar looking kinds of often distantly related animals. This video about "jellyfish" explains the issue nicely:
    There is also one more caveat-that we restrict this discussion treats only MODERN animals. In the Paleozoic there are fossil animals that blur the line between asteroids and ophiuroids. This gets trickier and is a discussion left for another day... 

    Here we go.. Asteroid vs. Starfish vs. Sea Star!!!
    There are THREE, Latin-based, English terms- as outlined below: "asteroid" (from the scientific name Asteroidea), "starfish", and "sea star." This discussion comes up over and over..and seldom seems to find resolution...  Here then are a list and discussion of these terms and the back-and-forth over the terms..

    Note that the terms "starfish" and "sea star" do not reflect different morphologies within the Asteroidea the way that say, common names for ophiuroids do (e.g., Basket stars and the Gorgonocephalidae). So there really has been quite a commotion over these two terms as they find standardized use...

    These reflect various arguments I have heard/collected over the years. While I have my conclusions at the bottom...please feel free to take these different perspectives to your classrooms, aquarium education courses, and grad school discussion groups to discuss at your pleasure!  Yell at me in the comments if you wish! 

    1. The term "asteroid" (from class Asteroidea)
    We Should Use the Term Asteroid Because:
    The latin name from the group, ASTEROIDEA was officially put to paper by the notedFrench zoologist Henri Marie Ducrotay de Blainvillein 1830 from the Greek aster and eidos referring to "star (as in the sky)" and "form or likeness."

    Nouns are derived from the scientific name.. so "asteroids" is technically the proper term for animals that we would refer to as "sea stars" or "starfish".

    We Should NOT Use: No, we can't use the term "asteroid" because it might be confused with a giant space rock hurtling through space! OH NOES!
    From Nat Geo article about asteroid collision
    2. The term "Starfyshe"(starfish)?
      DO use the term Starfish!
      1. The word starfish is widely used and "I" like it.So why change what ain't broke?
                Google recovers 13, 200,000 hits relating to "starfish"including use in religion, politics, obscene rock lyrics, hitting the bed and splaying out on the surface, charity organizations, nuclear bombs, and yes, sometimes it even refers to animals!

      2. So what if the word is a misnomer? 
      Plenty of words in the English language are inaccurate. Greenland is icy and Iceland is green! Sea horses aren't horses! Why can't we just put up with one more? That's life! C'est la vie! 

      3. Starfish is the oldest known western term. (thanksto John Lawrence, at USF for the info)  According to the Oxford English Dictionary (OED) this dates back to 1538 referring to "Stella, a   sterre, also a sterrefyshe."(from Elvot, dic.) This usage corresponds to the first definitiion given for "fish" in the OED: "In popular language, any animal living exclusively in the water"

      These days of course, our terminology has been much revised based on tons of evidence showing classifications among animals and we acknowledge that "fishe" had a much different meaning 475 years ago, but the term has stuck with us and its not likely to be going away anytime soon. 

      I'll bet that scientists and students are probably not as big a majority user of the term "starfish" as they believe themselves to be. The term is widely used throughout the many aforementioned outside disciplines and probably won't find much change even if scientists begin to radically suppress the term...

      Don't use the Term Starfish!
      Starfish are NOT fish!  The term is inaccurate since any MODERN definition of "fish" refers to proper vertebrates and NOT invertebrates! Inaccurate terms are SO confusing! People and students who have not had basic biology will not know that asteroids are NOT fish! Oh Noes!

      3. The term "Sea Star (or Seastar)"? (yes there's even a controversy over whether "sea star" is one or two words!)

      USE the term Sea Star!
      1. The term is more accurate. Asteroids aren't true fish so why call them that ?? (other than historical tradition, which is dumb!).

      2. ALL the other western countries use "sea star" why don't we? We should do that too! Its consistent!  Get with the program! Don't you want to be doing what all the cool countries are doing?  (e.g., German=seesterne, Spanish=estrella de mar, French=étoile de mer and I believe even the Chinese word means "ocean star")

      Don't Use the term Sea Star
      1.  The term Sea Star gets less use than Starfish. "Seastar" (one word gets 2,660,000 hits) but note that "sea star" (two words gets 475,000,000 hits-but many of these may be random combinations of "sea" and "star"). Its dumb that we use such a wishy washy word that other countries use!

      2.  Sea Stars are not stars.  Asteroids may not be "fish" but nor are they big burning balls of space gas! I once used the "sea stars are not stars" thing jokingly-but it turns out, the reference to stellar bodies has a real basis!

      The FIRST definition for "sea star" in the OE dictionary (and indeed Websters as well) (date uncertain) is of a "star which guides mariners at sea", the Star of the Sea, with only the SECOND definition referring to proper asteroids.
      Blue Star.
      Blue Star. by negombo83 on Flickr
      Earliest usage in reference to the animal I have record of:
      1569... A kind of fishe called Stella or Sea starre, bycause it hath the figure of a painted starre (fr. Fenton-Secret Wond. Nature)
      Curiously a subsequent definition reads
      1594..The fishes called Sea-starres, that burne one another by excessive heat. (fr.Nashe, Unfort. Trav.) 
      3.  Asteroids are not always star-shaped! Sometimes they are pentagonal...almost to the point of being round..
       Other times flat and almost paper-like..
      And still others can be almost ball-shaped

      Dispelling a Myth about "sea star" as political correctness
      In the 90s (or thereabouts) there was a huge revolution in educational programs across museums and aquariums throughout the US, and inevitably beyond. Many of the various common names ended up getting names that people felt were more accurate. So jellyfish were called sea jellies. Hagfish were called sea hags and so on.

      At about the same time was the big "political correctness" revolution from the late 80s, early 90s which was intended at diffusing offense and infusing more respectful terminology among public and political dialog-with extensive changes to almost all terminology.
      Here is a full workup of that scene at Wikipedia.

      Naturally, it was widely assumed that common names in science had befallen the same fate. But as indicated above.. the term "sea star" has been around since the 1700s.  And across different languages. And since, ultimately, asteroids DON'T really care WHAT you call them, it does seem unecessary to apply political correctness to echinoderms.

      Are European terms the only one we should consider?

      At a certain point in this discussion it becomes readily apparent that the "common name" argument for asteroids emphasizes the western/English terms. Do terms for starfish in other languages offer more attractive options?  Let's look at a few!

      *hitode (ヒトデ). This word means "palm" in Japanese.Here is a post I wrote about Japanese starfish names!  Records of the term hitode date back to 1712!
      *tapak sulaiman.In Malay, this word literally translates to "Solomon's Footprint"! Snazzy, eh?
      *불가사리  In Korean, the word for starfish refers to "Immortality"!!!

      (my thanks to Yoichi Kogure, Marcus, Tai-Lin and Taekjun for their helpful insights!)
      These are all awesome. and hmm.. Solomon's Footprint is a pretty cool name for an asteroid!

      Ultimately, though these terms seem to work out best in their homelands where the cultural context makes the terms more useful (and perhaps less confusing in English). Although I dunno... I'm still kinda  fond of Solomon's footprint..

      What was the oldest name again? 
      1538: sterrefyshe
      1569: sea starre
      1712: hitode
      Yup. Its "starfish" and not technically "sea star" if you're a big taxonomic synonymy fan but not a big fan of "starfish"..uh.. sorry... 
      Within the international rules that dictate proper scientific names for animal species, it is generally accepted that the OLDEST term has seniority over the others. 

      But does that change anything for people who prefer "sea star"?  Probably not. These rules generally only apply to the proper Latin species names and not the "common" or popular names. But as far as established 'legal' criteria goes this is one of the few which seems to apply.  And it does seem to be the "senior" name...

      Finish it up! I ain't got all day!
      These are things that are not negotiable

      1. Asteroids are starfish/sea stars. NOT ophiuroids (aka brittle stars). I often see a wide variety of individuals in the popular arena apply the terms mistakenly. That is improper use and thus, is disapproved of. Hrrumph!! Double Hrrmumph! PLEASE STOP IT! 

      2.  The term "asteroid" is technically correct. As indicated above, this is a NOUN based on the actual scientific name of the animal?  HERE YOU GO. But of course, we could still confuse a big space rock with a giant interstellar starfish. 

      I prefer to use "asteroid" as a scientist of course, but barring that?  

      Many languages have different words for the same thing. I accept that there are different words with the same meaning.  I trust context to decide usage. I tend to use "sea star" around students and/or an audience that might not be familiar with asteroids. I use "starfish" around people who know better.. and I use "asteroid" among my colleagues..but obviously there is interchange.

      But yes, please know that a "starfish" is NOT a fish before you begin using it. :-)

      Over the years, the whole argument has started to sound kind of silly...

      1. We can't use "asteroid" because we could confuse it with a space rock! Oh NOES!
      2.  Okay. Let's use starfish or sea star instead.
      3. We CAN'T use starfish because people would confuse it with a FISH! But I HATE the term "sea star!" Not always star-shaped! Blah! blah!
      5. Asteroid?
      6. Oh NOES! Space Rock!
      HAPPY 5th ANNIVERSARY from the Echinoblog! 

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      porania pulvillus-01
      Image by Geir Friestad via Flickr. Norway I think.
      I've always been a big fan of how the vast body of available images and crowd-sourced information can be beneficial to scientists but also interesting and engaging to the citizen scientist!  From tracking down videos and images of rarely seen benthic ctenophores (here) to helping to locate invasive brittle stars! (here)

      As I've said in the past-images and videos collected by everyone..from amateur divers on Flickr to pics aggregated on websites such as the Encyclopedia of Life contain MASSIVE amounts of potential observations (and thus data)!! 

      But of course, the images have to be recognized first.  How often do discoveries like this happen?  Sometimes new species are found on Flickr (such as this new lacewing species)

      I've blogged about how crowd sourcing and citizen science has discovered new and unpublished (or at least very poorly known) commensal behavior in sea stars, fishes and their commensals (here!) and today another discovery!  

      But not in the exotic Indo-Pacific but in the cold to temperate water familiar North Atlantic!! 

      Our subject is a starfish called Porania pulvillus (aka the "red cushion star"-one of many), one of many summary accounts of this species can be found here. It is an uncommon but recognized species in the North Atlantic from both the North American and European sides...  Porania is a member of the Poraniidae which is an unusual group occuring mostly in deep-sea and cold-water habitats, occurring from roughly 10 to 300 (often deeper in some places) meter depths . Surprisingly little is known about them...

      The story starts with a picture...
      Yesterday, I received an inquiry from my colleague at EOL- Dr. Jen Hammock who forwarded me a link to the picture below from the SERPENT Media Archive!  SERPENT is a coalition of industry and academic organizations that work to share images of the deep-sea with the public..(here) to see more.

       She asked me "What's going on here?" "Is this feeding on sea pens a thing?"
      from this EOL page via SERPENT Media Archive
      Indeed it was a "thing!"

      But let's take a quick step back and get started with all the players! 

      What we know...
      First: the species..... Porania pulvillus! A nicer pic is here: 

      Note that the white "dots" above and the finger-like yellow bits below are the papulae- aka the gills! This is how the animal "breathes".. Image by Mark Craig
      Close-up of a Cushion Starfish
      In 1915, zoologist James F. Gemmill described what he observed to be filter feeding using the numerous tiny cillia covering the body of this species.

      Dr. Gemmill was quite an authority..being an  M.A., M.D. D.Sc, F. Z.S."!!! And is pretty well known historically for a number of significant contributions.  He dropped little red carmine particles (basically a  red dye made up of a fine powder) on P. pulvillus and watched them move over the surface..

      A quick reminder about basic biology of this (and all starfish). The epidermis COVERS the body! The epidermis is in turn covered by tiny hair-like structures called cilia, which are usually in constant motion.

      These little particles were moved over the body and apparently headed towards the mouth. Here's his diagram showing the little arrows apparently indicating how water was flowing to the mouth.
      Fig. 2 from Gemmill 1915
      And this description as a "filter feeder" has stuck. Even a relatively recent paper (here) from 2005 describes them as "suspension feeders." But are they truly???  Is that all there is to the story?  Could they be predators? Opportunists? 

      A paper in 1973 (here), one of the first SCUBA accounts documented that they fed on "soft corals" such as this Alcyonium digitatum-the so-called "Dead Man's Fingers"
      Porania on Alcyonium digitatum
      Image by Christine Howson via Flickr
      The paper reports that this species feeds on brachiopods and even tunicates! Perhaps P. pulvillus is sort of an opportunistic predator in addition to the "suspension feeding" with mucous threads?

      Is this Porania pulvillus getting ready for a big banquet? Or is this the echinoderm version of those "1 dog, 1 pig, and a cat" pet adventure stories?
      Image by
      But getting back to the picture...
      It turns out that what we are seeing here is probably something unreported! NEW!!  A previously undocumented feeding interaction!!
      From this EOL page via SERPENT
      So, that Porania pulvillus was FEEDING (that's what it appears to be doing) on this sea pen (called Pennatula phosphorea). Image was from 124 meter depth in the North Sea, west of Shetland.

      Here's a nicer pic of the sea pen...
      pennatula phosphorea
      Image by Jarle Strømodden via Flickr

      Again-this was a NEW discovery! What does it mean for this animal's ecology? Does it mainly feed on yummy cnidarians?  Is the species more opportunistic than thought?  More predatory than previously thought??

      And of course.. there's the impact on the bottom fauna.... I've written about goniasterids that feed on deep-sea coral (here) and here's a video about them from MBARI a few years back...

      These types of interactions are important owing to our interest in deep-sea corals and their role in biodiversity and conservation of deep-sea ecosystems..

      But after looking at the pic above from the SERPENT pool on EOL, I discovered several more...

      Some further interesting feeding observations of Porania pulvillus, such as this one of it hunched over this rock and possibly feeding on the polychaete worm Pomatocerus sp. (which makes up the tubes). And of course, there could be hydroids or other encrusting goodies on there as well...
      EOL page link here SERPENT Media
      Here were a couple that showed P. pulvillus CLEARLY hunched on and probably feeding on something-but it was unclear exactly what it was.  Dead sea pen maybe??
      From this EOL page working w/ SERPENT Media
      From the EOL page here SERPENT Media
      And here we have P. pulvillus feeding on another mysterious gooey blob...
      From EOL page by SERPENT media
      The one below was labelled as "Porania pulvillus" but at least most of these look like the goniasterid Ceramaster granularis, another species with a large disk and triangular arms...These look like they're hunched over the sponges.  Looks very much like feeding...

      But either way with whichever species, here's ANOTHER great example of a behavior that hasn't been published on as yet.. 
      From the EOL page SERPENT Media archive

      Bear in mind-if these things had been thought of as primarily suspension feeders for years and years-and it turns out they're big time predators???  That would represent a big shift in understanding the ecosystem/food web in this area. Sometimes it can all be in the details..

      So.. really ALL kinds of neat legitimately important observations from this pretty vast pool of data fr. SERPENT/EOL!

      And there's MORE??

      With my appetite teased I spread out a little more and went looking on Flickr!

      Feeding on some green stuff! Algae? Hydroids? Image by Gordon.Milligan
      Red cushion star
      Or maybe gettin' ready to go after those tunicates in the upper right hand corner?
      Red cushion star

      Feeding?  Or getting ready to spawn? 
      Red cushion starfish and shrimp
      Image by Mark Craig via Flickr
      So, I've spoken about how poorly known the "spawning on tippy toes" posture is...Here was the link to that post

      What does this say? 
      What I see when I look at these pictures is inspiration.  ANY of these observations- the feeding or the spawning posture might be the beginning of someone's research project...or be relevant to one. 

      It seems strange to think -but this blog has more on the "natural history" of this species than has been published since that last account in 1973!  Many of these pictures have been floating around the internet for YEARS. Funny to think of "natural history" and "data mining" as terms that go together here, but here they are indeed a strange marriage....

      Thanks to Jen Hammock, EOL, the SERPENT Media Project and all the photographers cited!

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      Thanks to this weeks' blog, a new mystery photograph from Diver/photographer George B, who sent me an image of this strange swelling on Porania pulvillus. Image was taken from the west coast of Scotland at 20 m depth.

      Is it feeding and have a distended disk (as other starfish do here)? Does it have a parasite? Some kind of tumor?  Not sure it has ever been reported before!!!

      This is a neat highlight, that even though you have a species which has been recognized since 1776 and lives in the North Atlantic where many divers and scientists are active, many of these species remain poorly known.

      It also highlights the value of crowd sourcing. Images on Flickr and YouTube add so many more eyes and observations...

      Thanks again!

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      Images here from the Encyclopedia of Life
      This week, something about the many different KINDS of asteroids (aka sea star or starfish!) that are found throughout the world. Data for this, is from a paper I wrote with Dan Blake last year for PLOS One. You can download it for free here based on info at the World Asteroidea Database.

      I can't tell you how many times I've read something about starfish in pop culture or even in pop sci-and the writer assumes that starfish are the SAME all over the world! As if there was only one type.

      This gets to be let me just make sure everyone knows: There's a LOT OF DIFFERENT KINDS OF STARFISH. And they live in different places all around the world.

      Similarly, I've talked about my field work in Antarctica and in the middle of my story, someone stops me to ask "Wait, there are starfish IN ANTARCTICA??"

      So here are five things about the diversity of sea stars that will razzle your dazzle and make you a favorite at echinoderm-themed invertebrate zoology parties (esp. those where people are ignorant of starfish)!

      1. How Many Starfish Species Are there?
      At the moment? There's about 1900 species of accepted (living) starfish in the database. That runs a bit lower than the larger numbers quoted elsewhere (such as here),  but I assure you, that I am doing everything I can to kick that 1900 up a notch every chance I get!

      Here's a post where I keep track of many of my new species!

      More importantly, that's 1900 species in 36 FAMILIES. That means there's 36 different distinct groupings found all throughout the world in different habitats at different depths in different settings. So, its not just 1900 different kinds spread out all over the place- its 1900 species divided up into 36 distinct body types adapted to living in many different ecological niches!! (note that 1900 is a rounded figure due to questionable status for some names)

      For those who need to know: the full list is in the PLOS paper listed above. So feel free to click and go!

      Of the many weird kinds, there's Tremaster, as I discussed here awhile back.. 
      There's the deep-sea brisingids! Crazy lookin' things that live in the deeps! Here

      This Antarctic monster! Labidiaster annulatus!            The Slime Stars! Yay Mucus!

      Predatory Sun Stars!     And just for good measure- here's a neat assortment from Hawaii! 

      2. Where Do Starfish Live? 
      All echinoderms, including sea stars, live in the ocean-on the sea bottoms (although their larvae swim in the water column). They are among the few groups of animals which live exclusively in marine habitats.

      Starfish live in all the oceans! Atlantic! Pacific! Indian! Arctic! Southern!

      And in answer to the question "Do starfish live in Antarctica?" and "Under the Ice?"  Yes!

      The video below is from the famous "brinicle" video released awhile back showing starfish (Odontaster validus, probably) getting around some hardcore Antarctic ice! (narrated by 30 Rock celebrity Alex Baldwin!)

      And many starfish also live in the deep-sea (below 200m).

      Of the 36 living families of sea stars, nineteen of them occur exclusively in the deep-sea (436 species)! Four families are mostly deep sea but with some shallow-water members (1191 species) and several families include large numbers of deep-sea members. Only 8 families live ONLY in tropical habitats (218 species).
       It turns out that MOST starfish live in cold-water (or temperate) settings, such as the deep-sea or in the polar or near polar regions!

      So among those deep-sea starfish species, which ones live most deeply?  As it turns out several starfish groups occur in the deep abyss below 5000 meters!

      One of the most commonly encountered deep-sea asteroid groups at that depth is the Porcellanasteridae.
      Image from the EOL page
      They usually live buried in mud, devouring massive amounts of sediment, presumably absorbing digesting various goodies present in it.  This feeding mode is similar to the more shallow-water mud stars, which I profiled here.

      Another group known to occur down to 6000 meters? Brisingids (go here to learn more) in the family Freyellidae...

      Easily half a dozen families of asteroids are represented at the 5000+ meter depth range!Its unclear how many go deeper than 6000 however...

      3. Which Group of Sea Stars is Most Diverse? (i.e., Which one has the most species?)
      What's weird about this question is that the group with the MOST number of species is probably the group you are least familiar with...  Enter:  The Goniasteridae! 

      Ding!Ding! This group rings in at a whopping 256 species in 65 genera! Deep sea! Tropical! Antarctic! Shallow! Goniasterids are everywhere (but mostly in cold-water places, in the deep sea)! 

      But usually, in out of the way places, so they don't really turn up in places where people encounter them. So not many folks think of them you ask  "what does a starfish look like?"

      Goniasterids vary in size and shape as you can see.. but some get REALLY large! Such as this monstrous Mariaster giganteus from Japan !!   (held by my colleague Yoichi Kogure!)

      Goniasterids are diverse-and there remain MANY different species yet to be discovered....They are ecologically important in deep-sea AND shallow waters.

      I'll probably do a full post on this group at some point-but in the mean time here's a bunch so far!
      Tosia-the biscuit star: hidden species and brooding behavior! here!

      New genera and species of deep-sea corallivores! here!  and some video!

      4. How Many Undescribed Starfish Remain to be found? 
      Image by Island_girl
      Its hard to make estimates about stuff that doesn't exist yet!  How many more species are out there to be discovered?  What is my best estimate???

      Sea stars/starfish are big, obvious creatures. One would think that we have found most of them...but you'd be wrong!

      One subject group: The Goniasteride has 256 species in 65 genera. Out of the total # of genera and species:  14% (approx n=9) of genera  and 12% (approx n=31) of species were discovered ONLY recently (since 2001).

      I have further unpublished data on many MORE new goniasterids! Which suggests that the total number of newly discovered genera could go up to 37% and the number of new species could go up to 32%!!

      These are rough estimates from one group. Most people might expect that new species would be found in inaccessible and poorly studied places such as the deep-sea or perhaps in distant tropical lands such as New Caledonia.  But another possible source may already be right in front of us....

      Cryptic species are those which are distinguished by genetics or reproductive differences, some other source of evidence OTHER than external morphological characteristics to demonstrate they are separate species. Molecular genetics shows great potential as a tool to discover diversity where cryptic species are concerned...

      Again, the case of Tosia-the biscuit star: hidden species and brooding behavior! here! is a great example.

      5.  How Long Have We Observed Starfish in the Fossil Record? 
      Hudsonaster USNM 40882, early asteroid from the Ordovician.  Copyright Dan Blake. Image via
      Starfish are old. And their history will doubtlessly fill another post on the Echinoblog some day. A general account of the fossil history of the Asteroidea can be found here.  But the short version is this..

      Some very early ancient forms (i.e., predecessors to modern day "proper" asteroids) are observed in the Paleozoic (540 to 250 million years ago!).

      But we really don't start to see modern asteroids until the Mesozoic, that is early Triassic....where the record is poorly preserved...
      Left to right: Trichasteropsis weissmanni (specs. MHI 843/1, SMNS 3173/5 and Noriaster barberoi (MPUM 8420) on far right. Images copyright Dan Blake, Images via
      But basically, from then on, ALL modern asteroids continue on to the Recent. In other words, starfish which are alive today are part of the same lineage which has been around since the Triassic (250 to 200 million years ago). A distinct, separate lineage from those in the very, much older Paleozoic. 

      But just to give everyone a "landmark" to gauge what I'm talking about:  YES. Starfish are OLDER than dinosaurs. 

      Some starfish deposits from the Cretaceous are very well preserved and so, when T. rex was running around, starfish were there, doing their thing.  Thanks to some excellent fossil preservation, we know that some of them looked like this...

      Metopaster parkinsoni
      Fr. Discovering Fossils UK
      Also M. parkinsoni, I believe...
      Calliderma schulzei
      Calliderma Schulzei
      Image by Claire H
      But, fossil goniasterids were highly diverse and the number of fossil species is very high. The actual number of fossil "species" is difficult to compare with living species owing to differences in what geologists called "species" versus what biologists observed in living animals. Uh.. trust me, its complex and I'll get into it another day.

      But yes. Starfish have been around for quite a long time. Longer than humans (and primates). Longer than dinosaurs. 

      To sum up this week?
      1. There are about 1900 species of starfish and that number is climbing.
      2. They live everywhere in the ocean! Especially in cold-water habitats like the deep-sea!
      3. The family Goniasteridae is the MOST diverse (i.e. most number of species)
      4. MANY more species of asteroids remain to be discovered!
      5. The fossil record shows that starfish have been around for a LONG time, since before big reptiles roamed the Earth!

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      Fantastic image by Chelsea L. Wood
      Today we look at some neat examples of flatworms that live in echinoderms!

      And to the flatworm and parasitic worm people reading this? YES, I know flukes aren't free-living flatworms. It rhymed! So go with it for now. thanks for your patience!

      Flatworms aka the Platyhelminths (in Greek-literally the "flat worms") look like living carpets. They are mostly predatory, but may also feed on small organic particles and live all over the place. They can be parasites, such as tapeworms or free-living beasts such as the one featured in the collage below.

      These include the familiar Dugesia-that you find in high school biology (brown with arrow shaped head and two weird eyes) to these big, colorful species that live throughout the tropical Atlantic and Pacific. There are some 4500 recognized species of free-living flatworms..
      Polyclad flatworm collage
      An awesome collage by Arthur Anker!
      Papers that were used today:  this paper by George Shinn (1981)-Hydrobiologia 84: 155-162
      another in Biological Bulletin 169: 182-198 (also by Shinn) and this one, from Canadian J. of Zoology 61(4): 750-760 which describes the species living in the sea cucumber

      What's interesting about the ones that I'll be talking about is that none of these is exclusively parasitic (such as a tapeworm or a trematode). These are free-living species..but they live INSIDE the body cavities of echinoderms!  

      Think of it as if you ended up living in the intestine or the body cavity of a whale. Lots of space there and potentially...a  lot of food. Plus protection from predators, the elements and a safe place to reproduce!

      So, technically they aren't really parasites (where the host 'loses') they are commensals that are considered just kind of benign.
      Image from WallaWalla University Inverts site! 
      It makes sense. Sometimes, an animal with a huge internal body cavity can be a home. We've seen the classic pearlfish and even when clams that live inside the throats of sea cucumbers.

      It turns out that there's something in the neighborhood of SEVENTY species of different free-living flatworms that live in echinoderms as hosts! A nice list of these can be found in this paper here.

      Most of these hosts appear to be sea cucumbers with sea urchins and sea stars. Some in cold water but also in the tropics!  Crinoids and brittle stars seem to be among the minority as hosts for flatworms..probably because there's not much "living space" inside their body cavity. Or maybe they're just not as well studied?

      Here are two well-documented worms from the North Pacific coast.. one that lives in several Pacific urchins and one in a North Pacific sea cucumber...

      The Urchin as a "House" for flatworms! 
      Urchins on the west coast of North America (in the Pacific Northwest) include the well-known purple sea urchin (Strongylocentrotus purpuratus)
      Purple Sea Urchin - Strongylocentrotus pupuratus
      Image by Joe McKenna
      And the giant red urchin (Strongylocentrotus franciscanus)
      Red Sea Urchin
      Image by Dan Hershman
      and the deep-sea Allocentrotus fragilis
      Image by NOAA Photo Library

      ALL of these are often inhabited by this beast! Syndisyrinx franciscanus
      Image by Chelsea L. Wood
      Syndisyrinx franciscanus lives in the digestive tract of its host and apparently, infested urchins have been found with up to 186 worms!!! (an average of about 29/individual)
      Image by Chelsea L. Wood
      This one is called Syndesmis dendrastrorum 
      From the EOL page for S. dendrastrorum
      and it lives in the common Pacific Northwest sand dollar Dendraster excentricus!! (seen below alive with spines)
      Sand Dollar (Dendraster excentricus)
      Image by Patrick Warren
      or perhaps more familiar if seen like this? Spines removed...
      Eccentric Sand Dollar (Dead) - Dendraster excentricus
      Image by Cheryl Moorehead
      Even the familiar Pacific Sand Dollars can HAVE WORMS!!!  Ya' learn something new every day!

      What do they do in there?Mostly, these live in the intestine feeding on the host's intestinal lining (the tissue) AND apparently also like to eat on the symbiotic protists (the ciliates) that ALSO live in the intestine of the host.  But this apparently doesn't create any detrimental effects on the host. So-commensal rather than parasitic.

      Apparently, the worms produce egg capsules are released into the intestine of the host and released outside with the feces.  When the capsules are eaten by a new host, they become active.... probably a reaction to the intestinal fluid and proceed to live out their new life in the new host's intestine.

      Flukes in Cukes! 
      A free-living worm lives in the Pacific NW sea cucumber Parastichopus californicus.
      California Sea Cucumber (Parastichopus californicus)
      Image by T. Van Nunnery
      This beast is called Anoplodium hymanae, a worm that is named for the famous Invertebrate Zoologist Libbie Hyman
      Image by Chelsea L. Wood
      These are a little more aggressive than the ones that live in sea urchins.

      This species reaches the body cavity by penetrating the wall of the intestine..usually through the respiratory trees (feathery structures colored in blue in the pic).  I've briefly mentioned this area as where some sea cucumbers can feed via their butt!

      The eggs are spread out via the anus with the feces until they are devoured by a host.

      Similar to the ones in urchins, the larvae hatch in response to digestive fluids in the intestine of the host. Get into the intestine, move to the respiratory trees and then further move out into the body cavity of their new host!
      Image by Chelsea L. Wood
      Starfish got worms too!
      So, there aren't a lot of records of flatworms that live in/among sea stars. Six were recorded in asteroids..and oddly enough, the one below was not included. So maybe its something new?

      Description of this pic indicated the cold-temperate North Atlantic asteriid species Leptasterias littoralis. Is this a commensal flatworm moving within the tube foot groove? Moving around on the surface?  Something new? A convergence of two species by chance?
      Starfish & Flat Worm
      Image by Nick Sleptov
      For more worm-starfish relations?

      Go to this pic of Echinaster callosus and look closely at the short, striped things crawling on the swellings!    this one has a tighter shot that shows them a little more easily..note the brown squares with the white stripes.. (and includes a shrimp to boot!) WOO!  Acoel flatworms? 

      How many remain to be discovered?? 

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      Today, here in Washington DC, we have an overcast day with a rather dreary storm raining down on us..and a quick skim through the news is filled with all kinds of blah and bad news, Sequester is the buzz of the town.. so..meh.  What to do??

      A striking yellow/greenish Pseudoceros dimidiatus from Osprey Reef,Coral Sea.

      Pseudoceros dimidiatus
      Photo by Richard Ling
      A brief zoology lesson: Flatworms are members of the phylum Platyhelminthes. This is the group of worms which includes many parasitic forms, such as the tape worms and trematodes as well as several free-living species that live on land, in freshwater and in the ocean.

      If you remember those funny arrow-headed ones that you could cut and via regeneration give it two or more heads? That was a flatworm!  Many, many species are found throughout the world.

      Free living flatworms are mostly predatory-feeding on immovable animals, such as tunicates to other smaller animals and worms. There's a LOT of different species with many interesting biological stories! Some (go here) are mimics with nudibranchs! 

      But most folks don't realize just how colorful and gorgeous they are in the tropics!  Here is a bunch....

      Pseudoceros bifurcus from Kenya.
      Pseudoceros bifurcus 02
      Photo by Jim Anderson
      Another of the same species (P. bifurucs) from Singapore apparently feeding on some tunicates.
      Red-tipped flatworm (Pseudoceros bifurcus), eating Pink ascidian?
      Photo by Wild Singapore
      Pseudoceros laingensis from Straits of Johore
      Purple-spotted flatworm (Pseudoceros laingensis)
      Photo by Arthur Anker
      Sorry, this one didn't have a name.. Amazing to look at though... From French Polynesia.
      flatworm 2-2
      Photo by Pauline Bosserelle
      Another flatworm I don't have a name for.. but apparently from the Philippines
      Flatworm 5608-2
      Photo by "Jason" aka Jasdivr
      Another one without a name.. This one from Oahu, Hawaii!
      Divided Flatworm
      Photo by Bill Stohler
      Possibly Cycloporus sp. on its tunicate host/food (Didemnum molle) fr. Wori Bay, Sulawasi
      unidentified Flatworm on the surface of a Tunicate (Didemnum molle) - Wori Bay
      Photo by Christian Loader
      Pseudoceros susanae?  A beauty from the Maldives!
      Susan's Flatworm
      Photo by Chris Dow
      Another stunning Pseudoceros susanae? from the Maldives
      Photo by Philippe Guillaume
      Purple flatworm! From Bali.
      Photo by Ben Naden
      Pseudobiceros bedfordi, the so-called "Persian carpet flatworm." This one from Dayang, Malaysia
      Persian Carpet Flatworm, Dayang
      Photo by Dyana Wu

      A neat one with a different texture! A "papillose flatworm"  Thysanozoon/Acanthozoon? From Madang, Papua New Guinea.

      Cute papillose flatworm (Thyzanozoon sp / Acanthozoon sp ?)
      Photo by Arthur Anker
      Thysanozoon sp. from Panama.
      Thysanozoon sp, Panama
      Another gorgeous pic by Arthur Anker
      Acanthozoon sp. from the Philippines
      Photo by Eunice Khoo
      and that's just the marine ones!  the land ones get even better! but I'll save those for another day....

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      Ochre Seastar (Pisaster ochraceus) Feb 19, 2012. Patrick's Point SP., Humboldt Co., CA (1 (1)
      Image by RJadams55
      One of the things I love about biology is when you have an animal which has been studied down to the wire and become so familiar that people take it for granted, and then you discover something completely new about it!!!

      And that in turn gives you insight into past events and other things around you. Cryptic? Yes..but I will explain.

      This week's post is from Kurtis Hayne and A. Richard Palmer, University of Alberta in Edmonton
      who have written a swell, new paper in the Journal of Experimental Biology 216: 1717-1725 (here)
      (my thanks to Kurtis for an offprint of the paper).

      It studies the reaction of the classic workhorse starfish Pisaster ochraceus as it reacts to one of the harshest of environmental stresses:  the ocean itself! WAVES!!      SPLOOSH!
      Hang On!
      Image by Lance and Erin Willett
      Hayne and Palmer collected numerous individuals in and around Barkley Sound near the Bamfield Marine Sciences Center on Vancouver Island.  Individuals were collected and measured to assess values for drag and lift. Some were tagged and returned to the field for various field transplant experiments (look below).

      Specimens were also surveyed in the field and correlated with the power of various wave forces.

      Their findings!
      1.  Sea stars in wave-exposed sites had narrower arms and were lighter per unit arm length than those from sheltered sites. On average, animals from the most exposed sites were 12% narrower at the base compared to the most sheltered!

      2. Body form was tightly correlated with the maximum velocity of breaking waves across four different localities and over time.

      3. Sea stars were transplanted between sheltered sites to more wave-exposed sites revealing that they became LIGHTER per unit arm length, developing narrower arms after 3 months! There was a tight correlation between water flow and the body shape which strongly supported the idea that wave force was affecting the body shape.

      This figure 7 very nicely summarizes their findings. The animal on your left ("A") is an example of an animal from "most sheltered" going right to the one on the lower right from "most wave exposed".

       and the small box "D" even shows the extent that the abactinal spine/granules show density and a heavier degree of calcification between a sheltered (orange on the left) vs. an exposed (purple on the right) individual.  

      The exposed form below is overall smaller in size, weigh less, and with a higher aspect ratio (arms narrower, etc.) and with a more dense skeleton.   
      1. This is thought to aid the individuals in a wave-exposed environment from being washed away. Not as much lift and not as much drag.
      2. The heavier granules offer more protection against the crashing forces of the waves.
      3. BUT, having a higher aspect ratio comes with some costs:
                a. such as being more prone to overheating. Sheltered are much more effective at resisting
                    overheating and water loss. Although heating may be offset by cooling temperatures from
                     waves and such..
                b. having smaller areas available for gonads. This results in lower overall production of
                     reproductive material and so on..

      Image by jkenning
      we saw more starfish on the second day

      Image by Shannon Robalino
      Pisaster ochraceus

      The protected body form
      These make more sense in protected areas away from the harsh, crashing wave-swept regions:
      Some dynamics...

      1. Larger animals are more likely to be caught and washed out to shore. (greater drag and lift at play)
      2. BUT the larger, thicker size involves more water retention and thus better thermoregulation and better cooling.
      3. Greater volume for gonads! More potential offspring!

      from Scenic Beach State Park in Washington
      Ochre Sea Star
      From Samantha Russell
      Pisaster ochraceus

      Bear in mind-that in order to test these interpretations, animals were actually transplanted between protected vs. wave-swept areas. Transplanted animals (from protected to the exposed wave-swept areas) decreased in mass and increased in aspect ratio over time. 

      Environemntal factors directly affected the body shape of ochre stars!

      Biophysics Meets old fashioned Taxonomy!
      Probably the neatest footnote to all of this was that these differences in different forms of Pisaster was observed by several naturalists in California, early in the 20th Century.

      The great Stanford starfish biologist and Director of the Hopkins Marine lab, Walter K. Fisher identified several "forma" or distinct morphological variants of Pisaster ochraceus in his giant 3 volume monograph documenting and describing the asteroids of the Pacific Northwest from 1930.(sadly the Asteriidae is not in the volume linked).
      Fisher even observed that the differences in three of these forma seemed to be based on the degree of calcified skeleton, i.e., how built up the spines were...
      It is difficult to escape the inference that the characteristic small spinelets of the abactinal area are correlated with queit water, but that this is ot the only factor is evidenced by the presence, along with confertus, of forma ochraceus and nodiferus, the latter found on open coasts and also in deep water (Monterey Bay).
      The variant nodiferus is Hayne and Palmer's "exposed coast" morphological form. Fisher's comments about the inconsistency of abactinal spinelet shape/size suggest there remains even more variation and other factors to consider in future studies..

      Sometimes, these "forma" turn out to be distinct taxa-perhaps subspecies or species. But sometimes its just some variation in body form in reaction to the environment.

      Just as if we took a flabby, couch potato from his comfy TV room with silk bedsheets and put that person into an underground mine to dig minerals for a living. We would perhaps see changes in musculature, bone structure, and maybe even hair/eye color.

      So there you have it! A cool convergence between a modern biophysics story with a fun footnote from classical taxonomy/natural history!
      Are these considerations we might apply to other intertidal asteroids in similar settings? (Stichaster australis from New Zealand). Image by Jon Mollivan

      Want to know more about the Ochre Star: Pisaster ochraceus?
       Here's my post about Pisaster ochraceus ecology and role in climate change. 

      and what explains all the color variation in Ochre Stars?? (here)

      Want to see a sea urchin that lives in a high-energy wave swept environment? See Colobocentrotus! The Shingle Urchin.

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      Sea Star -  Bunaken - North Sulawesi - Indonesia 06-01-2008 4-22-03 PM 4000x3000
      This fantastic image by Tyson Jerry from North Sulawesi
      By now, a bunch of people have seen the incredible collection of close-up asteroid photos by Alexander Semenov and I reviewed them for the Smithsonian here.

      Those pictures were close ups of asteroids from cold-water settings in the North Pacific & North Atlantic. There's a very different fauna of asteroids in those parts of the world compared to the tropics.

      Most of the starfish in the tropical Indian and Pacific Oceans show a lot of granules, spination and armor and of course are composed of very different families of asteroids compared to those which live in the far North.

      If you'd like to see some pics of the mouth armor in these types of starfish go here!

      I start with the above : a STUNNING shot of Protoreaster nodosus, a commonly encountered sea star found throughout the Pacific.  Shots below are macro shots showing skeletal features and colors of different tropical, Indo-Pacific starfish species.

      More close up on Protoreaster with more pointed spines. Image by Nick Robertson Brown (Frogfish Photos)

      What are these weird threads? Feeding tentacles from a benthic ctenophore? Gametes?  Weird. Photo by MerMate (Eunice Khoo)
      Fuming star

      The strange soft-warty structures are a distinguishing feature on the surface of Echinaster callosus! Function unknown. Images by Optical Allusion
      Warty seastar (Echinaster callosus)

      Warty seastar (Echinaster callosus)

      Warty seastar (Echinaster callosus)

      Some fantastic detail on the ophidiasterid Nardoa. Image by Stephane Bailliez
      Warty sea star

      Here's a close up on Gomophia gomophia. Image by Okinawa Nature Photography (Shawn Miller)
      Starfish, Gomophia gomophia

      An awesome close up of the disk on Fromia nodosa from the Maldives. Image by Philippe Guillaume.

      Close up of Fromia indica. Image by Jesse Claggett

      The papulae (aka the gills) and spines of Acanthaster planci-the Crown of Thorns starfish. Image by Barry Fackler.
      macro echinodermata

      This one shows a close up of the gills of Acanthaster planci. Image by David Garcia Fonseca.
      Estrella de Mar Corona de Espinas // Crown of Thorns Starfishh...MACRO!

      Wow! First record of the brittle star Ophiactis? living on the spines of Pentaceraster. Image by Maractwin
      Starfish detail

      another tight shot of a brittle star (Ophiothela?) living on the asteroid Nardoa. Image by deco4macro
      The same kind of star sans ophiuroid. Image by samui13coconut13

      Surface spines on Pentaceraster. The tiny white circles on the brown spaces are papulae aka the gills. Image by Friscodive.
      Sea star abstract 13]
      Surface close up on the cushion star Culcita novaeguineae from the Maldives. Image by Frédérique Jaffeux. All the white pores are papulae aka the gills.
      Cushion Sea Star
      From the Sand star Luidia maculata Image by Kok Sheng
      Eight-armed sea star (Luidia maculata)
      And another L. maculata by [WJ]

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      Araesoma thetidis
      In February of this year, my friends at the New Zealand Institute of Water and Atmosphere (namely Owen Anderson) published a new paper describing not one but SEVEN new species of deep-sea sea urchins! Here in the journal Zootaxa.

      The original NIWA press release is here.  These urchins have been getting all sorts of keen press, includinghere in the N.Z. Herald and here in The Sun.  And of here on New Zealand's Maori news..

      and I thought.. EVERYONE needs to know more about these exciting urchins! and so today is a bit of a "refresher" on echinothurioid sea urchins!

      I wrote a short summary about these for Deep Sea News several years ago...(here)  and wrote a short bit about the commensal relationships between these urchins and fish here.

      The quick summary version is:
      1. Mostly deep-sea urchins found all over the world (many in greater than 1500 m depths-in NZ they range from 100 to 5000 m!), but with some shallow water relatives (aka the Fire urchins, I'll save these for another day)
      2. They often have very sharp and poisonous spines. And yes, the deep-sea ones too...
      3. They "walk" around on the sea bottom with special spines that have hoof like tips
      4. They were described FIRST as fossils and the living animals were found AFTER...
      When the animals are alive they look kind of like this:
      Deep Sea Urchin - Submarine Ride 2540 Feet
      An Atlantic species by Hankplank
      On this purple species from the Pacific (Tromikosoma maybe? this isn't one of the new ones described by Anderson), you can see the white hoof-like spine tips that the urchins use to "walk" along the bottom..
      Spiny sea urchin
      Image by Neptune Canada
      Here is a pic showing the oral surface (ie the bottom). The mouth is at center and as you can see it is surrounded by spines with those white "hoof" like tips. These are what the animals use to "walk" along the bottom of the sea floor.
      Sea Urchin underbelly
      Also by Neptune Canada

      Here's the spine close up showing the "walking tip"
      Image from the NIWA Benthic Inverts Facebook page
      Or sometimes like this Atlantic Phormosoma placenta which has the mysterious floating "bags" (containing spines).
      Image from SERPENT project here

      But sadly, when they are brought up on the deck of the ship, the water rapidly drains from their very soft body and they are often left as a shadow of their former self....
      From the NIWA page on this story
      As a result of this "deflated" appearance, they are often called a variety of names: "pancake urchin", "leather urchin", "bag urchin", or "beret urchin." However in Anderson's new paper he feels a new common sobriquet would be most accurate-the Tam O Shanter urchin!!!

      For those who are not as keen on Scottish headwear, a "Tam o Shanter" is a cap, sort of like a beret (wikipedia here)  and you can sort of see the resemblance.
      Tam O' Shanter
      Image by DrHaggis
      dsc_0055 (2)
      Image by H2omom.2006
      Even alive, looking down on one, you can sort of see the resemblance..(note however this is not one of Anderson's new species)
      Sea Urchin and Brittle Stars
      Image by Neptune Canada!
      Owen's paper (here) describes a whopping SEVEN species in two genera. That's pretty significant given that MOST of these urchins were described in the early part of the 20th Century/late 19th.

      These were all discovered and described by looking at a variety of different characteristics. Some as straightforward as body color as well as spine shape and location. But some characteristics are more subtle. These are the individual pieces of pedicellariae-little claw like structures that are present on all sea urchins..which were studied using a Scanning Electron Microscope to yield distinct shapes...
      Fig. 28 from Anderson 2013
      He also reviewed the many echinothurioid urchins in the New Zealand waters, in addition to the seven known species, Anderson described/reviewed a further nine species (7 were new) culminating in a count of some 16 species of these urchins in the region!, including this beauty... Araeosoma thetidis!! (described by Hubert Lyman Clark in 1909)
      Figure 28 from Anderson 2013
      What other species will be found?  Here's a brand new report about two new sea pens! 

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      Fire Urchin
      Image by Aboireoujtulchien
      Last week I reviewed deep-sea echinothurioid urchins aka the "tam o shanter urchin" aka the "pancake" urchin, etc., etc.  I spoke of these more generally in an earlier post. But for some reason I've not had a chance to really showcase their shallow water relatives!
      From SERPENT
      Shallow water echinothurioid urchins are "proper" fire urchins. As opposed to these other "fire colored" spiny urchins, such as Astropyga which are diadematoid urchins. A completely different group!!

      "Spiny" urchins are distinguished by the presence of an Anal Cone. See that white bulb on top? THAT is where the poop comes out!  You don't see that in "proper" fire urchins as we'll be seeing.. Note also that the spines are much longer.
      Astropyga radiata
      (image by Ben Naden)
      I've discussed Astropyga on the blog before (here)...

      These urchins all belong to the genus Asthenosoma which includes six species spread throughout the Indo-Pacific region.  Here's a neat video that gives you an idea of what they look like..

      Yes, the colors are a huge shift in appearance, but similar to their deep-sea cousins, Asthenosoma also has the distinctive "walking" spines...

      On this image of Asthenosoma varium the walking spines form a fringe around the lower oral side composed of distinctly yellow spines. My understanding is that most of these prefer soft, muddy bottoms.
      Asthenosoma varium
      Image by Ben Naden
      Compare to the walking spines on this deep-sea echinothurioid.
      Spiny sea urchin
      Image by NEPTUNE Canada
      From there we start to see more differences as the spines seem to be bunched up in bundles...
      But they remain venomous...
      fire sea urchin
      Image by JianXu
      Some workers have hypothesized that the poisonous spines in deep-water echinothuroids function as hypodermic needles (here by Roland Emson & Craig Young)

      And if its not clear by now, YES. They're pretty damn venomous. My understanding is that its very painful.. but typically not lethal.

      and they certainly do seem like they do, don't they??
      fire urchin IMG_6889
      Image by Bruce Magun
      Fire urchin's spines
      Image by Daniel Stassen

      Close ups! showing some of the brillaint colors, spine patterns and etc.. I suspect most of these are Asthenosoma varium
      Fire urchin!
      Image by MerMate
      Image by Daphna130
      Fire urchin
      Image by lupopeye
      Magnificant Fire Urchin
      Image by maractwin
      fire urchin
      Image by Nick Hobgood
      fire urchin
      Image by B. Maither
      Fire Urchin Close-Up
      Image by Russell Taylor
      Here's some differing species from around the Indo-Pacific

      From the Red Sea, Asthenosoma marisrubi with a more mellow look...
      Foto-2008-05-08 21.31.25
      Image by Key of Life
      Here are the spines..still basically the same but different color and slightly different shape..
      Asthenosoma marisrubri
      Image by Le Congre
      Asthenosoma spp. showing many different colors...
      Coleman Shrimp and fire urchin
      Image by S1mon Mar5h
      Image by Clark Chang
      IBAb-292 Fire urchin, Asthenosoma varium
      Image by Jesse Claggett
      Fire urchin
      Image by Richard Barnett
      What's even MORE interesting? These urchins have tiny critters which live as commensals(?) among the highly poisonous spines! (this neat vid also shows a LOT of close up details)
      Urchin Riders from liquidguru on Vimeo.
      Some of the little buggers actually "hollow" out a space, clearing out spines where they can live! You can see the bare patch on this one...
      Coleman shrimp
      Tiny Shrimp
      Image by Klaus Stiefel
      In addition to all the various crustaceans, Amazingly. Here is a benthic ctenophore (which I've written about here) ON A FIRE URCHIN!! (the white blobby bits are the feeding tentacles)  Mind. blown!!  and incidentally.. a likely first occurrence recorded....
      Ctenophore on a Fire Urchin
      Image by Mark Atwell

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