Photo Synthesis

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Crinoids, a class of marine animals in the phylum Echinodermata, are pretty creatures. The photo at right shows a crinoid perched on a Malaysian reef with its fluffy arms extended for feeding. Looking at the photo, it’s easy to see how they acquired their common name, Feather Stars.

This is how divers usually see crinoids, and this is how they are most often photographed. As pretty as crinoids are — and they come in a vast array of colors — photographs of the whole animal don’t reveal much about the animal’s structure or behavior. Whole-animal photos of creatures like this should be just a starting point. A photo study of an animal, or class of animals, should include close-up and macro photos as well.

Today I present three close-up photos of crinoids that show something of their structure. Tomorrow I will continue with some macro photos that reveal even more about crinoids.

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In the photo above, you can see the arrangement of the animal’s feathery, many-jointed arms around a central disc. The animal’s mouth is in the disc, which is covered by many cirri. Crinoids are filter feeders. They capture tiny bits of organic matter suspended in the water that passes over the pinnules on their arms. The food is then transported inward, down the length of the arms to the mouth.

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This second close-up photo is an aboral view of the same individual. (It can be difficult to photograph this view, but this very accommodating individual happened to choose a protruding strand of wire coral as its perch, so I was able to swim around behind it to take the photo!) Here we have a good view of the form and function of the cirri on the underside of this crinoid. These cirri are used for mobility: the crinoid can skitter along using the cirri like little feet. Then once the animal finds a suitable perch, it uses its cirri to hold itself in place. In this case, the cirri are wrapped around the wire coral in a tight grasp.

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As filter feeders, crinoids optimally position themselves in places where currents — tidal and otherwise — pass over them. The cirri of crinoids have tiny hooks at the ends, which help them to hold on and stay in place during feeding. While this may be functional for the crinoids, should they decide to perch on a soft surface, those hooks on the cirri can do damage. In this final photo (a different individual and probably a different species than the previous two photos), a crinoid has decided to perch on a sponge and has dug into the sponge’s flesh with its cirri. As you can see, the sponge has been damaged (although it will likely heal over in time).

About the photos: The crinoid in the image at the top of the page was photographed at Pulau Sipadan, Malaysia. The three close-up images were taken at Manado Tua, off the northeastern tip of Sulawesi Island, Indonesia.

Comments

  1. #1 Martin
    August 12, 2009

    Here we have a good view of the form and function of the cirri on the underside of this crinoid. These cirri are used for mobility: the crinoid can skitter along using the cirri like little feet. Then once the animal finds a suitable perch, it uses its cirri to hold itself in place.

    I didn’t know crinoids could move once they’d settled someplace. I’d like to see this – can someone direct me to a video? Thanks.

  2. #2 B. N. Sullivan
    August 12, 2009

    Hello Martin – There are some crinoids that are sessile; you may be thinking of those. They have a stem that is attached to the substrate, and they don’t move about. The crinoids in these photos do move about, using their cirri for mobility. There are still other kinds of crinoids that move about not on cirri, but by using some of their arms to ‘swim’ (short distances, of course) and to push themselves/crawl along surfaces.

    I don’t know of a video showing crinoids moving about, but perhaps someone else does?

  3. #3 Sojournposse
    August 12, 2009

    Pulau (with a u; it means island) Sipadan. But never mind – your photos are awesome.

  4. #4 B. N. Sullivan
    August 12, 2009

    Hello Sojournposse – Thanks for the kind words, and also for catching that typo. I just fixed it. I hate it when proper names are misspelled and I’m mortified that I didn’t catch that myself!

  5. #5 Kevin Z
    August 12, 2009

    These are absolutely fantastic! Way to pay attention to morphological detail. It makes a taxonomist like me squeal with delight!

    For Martin, we’ve posted a brief video of a deep sea crinoid moving along the seafloor at Deep Sea News. It is very eerie. And yes it is absolutely real!
    http://deepseanews.com/2008/10/the-27-best-deep-sea-species-25-stalked-crinoids/

  6. #6 B. N. Sullivan
    August 12, 2009

    Hi Kevin – Glad you like the photos, but no squealing please. :-D

    Thanks very much for posting the link, which I encourage readers to click on. Not only is there a brief video clip of a stalked crinoid crawling (!), but some good still photos of stalked crinoids, too.

    For Martin –
    Earlier today I searched on YouTube to see if I could find any videos showing motile crinoids. I was amazed at how many crinoid videos there were. Here’s a link to the YouTube search result: http://tinyurl.com/crinoid You can see videos of swimming, crawling, and ‘flying’ crinoids.

  7. #7 Martin
    August 13, 2009

    B.N. and Kevin Z., thanks very much for those links. That’s quite possibly the coolest thing I’ve seen in a long while. Reminds me why I hang out here.

  8. #8 hiphop
    August 15, 2009

    It’s interesting that those tattoos do a better job of realistically representing the cephalopod eye (the one that’s visible in each, anyway!) than most cartoons do. There are probably cartoony versions of cephalopods on tattoos too though.

  9. #9 sikiƟ
    March 26, 2010

    clear clean water! A day in rice and that phone is as good as new.(Now if that’s a solution of NaOH or HCL, well then, that’s a different story.

    You want bad, have that cell phone drop into a privvy on the Appalachian Trail

  10. #10 oyun hileleri
    May 9, 2010

    It’s interesting that those tattoos do a better job of realistically representing the cephalopod eye (the one that’s visible in each, anyway!) than most cartoons do. There are probably cartoony versions of cephalopods on tattoos too though.

    thanks…nice good post..

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