Saturday, 27 August 2011

Milly: Ugly Fish pt 9

Milly: Ugly Fish pt 8

"Here you are" said Alan, all blasé, as he passed me something he had picked out of the trawl net. It looked like a dead hand on the end of a stick and smelt like one too; I didn't have a clue what I was looking at. The more learned scientists told me it was a stalked crinoid, a sea lilly, part of the Phylum Echinodermata, so related to starfish, sea cucumbers and sea urchins. As I looked closer I realised that it was much more attractive than a decomposing fist, with many intricate feathery arms that I imagined would actually look quite nice when underwater.

Having a gander at the feeding arms of the crinoid, note the long
stalk in the background, these can be 1 metre long! Image: Zan
Close up of the main body of the crinoid
showing the stem leading to the calyx
and then the feeding arms at the end.
Image: Zan

Another species of deep-sea stalked crinoid called Moulin Rouge
(Proisocrinus ruberrimus) photographed on the sea floor. Pretty sexy, for a crinoid.
Image: National History Museum

These fascinating creatures look like plants (hence the name 'sea lily') but have the features of animals such as a basic gut, a simple nervous system and a fully functional circulatory system that transports nutrients, gases and waste products around the body. The many feathery arms found near the mouth (and also unfortunately the anus) are used to filter out small particles in the water where it is trapped in sticky secreted mucus and pushed into the mouth.

They are sometimes referred to as 'living fossils' as they seem to remain relatively unchanged morphologically since their radiation during the Paleozoic Era (about 550-250 million years ago).

A fossil stalked crinoid,
looks a lot like the modern version.
Image: web
Shallow water crinoids are often free-swimming, and crinoids with long stalks, such as the one from our trawl, are usually found at depth, anchored to the ocean floor (ours was found at about 4500m). I say anchored...but scientists recently observed sea lilies up-rooting and crawling along the sediment, seems there is yet more to be discovered about these strange animals....


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Michael Bok said...

"A fossil stalked crinoid, looks a lot like the modern version."

Don't tell the creationists...

scuba gear package said...

Thanks a lot for sharing this amazing article with us.
Nature is so wonderful.