Tuesday, May 29, 2012

ANAL CONES! Diadematid sea urchin mysteries!

Lembeh Strait April 2012-0026.jpg

Echinothrix from Lembeh Strait Photo (above) by Efdixon

Another day when pictures say more than words!  What is an anal cone???

The anal cone is the weird, prominent bulb-shaped bit (its white in the species below) that is sitting on the top of the test (i.e., the body) in sea urchins of the family Diadematidae, which are well-known for their big long sharp spines....

But what function does it serve?? 
The Anal cone seemingly falls into the "poorly understood" category but I did find some explanations..

Ailsa Clark from Echinoderms of the Seychelles (pg. 84)  
Another peculiarity of this family is that there is an elongated anal cone or sac which is commonly inflated like a small balloon in the centre of the upper side. This may gently roll around its attachment and is believed to have a respiratory function".

Hendler et al. (1995) in the book Sea Stars, Sea Urchins, and Allies, Echinoderms of Florida and the Caribbean note in the tropical Atlantic Astropyga magnifica
As in Diadema antillarum, the anal cone enables the animal to eject feces away from the body.
So here's a diversity of anal cones from various diadematid urchins! If they are for ejecting feces then these are some of the most aesthetically pleasing feces ejecting structures that I've seen among animals!

I believe this is Echinothrix from Hawaii
Photo above by JLambus

Astropyga from Sulawasi (photo below by pauldub)

Fire urchin

Astropyga from Indonesia
Fire Urchin Close Up

Photo above by PacificKlaus

Another by PacificKlaus. Looks to be Echinothrix? from Okinawa, Japan

Astropyga from Lembeh, Indonesia
Sea Urchin - Lensbaby macro - Lembeh

Photo above by Christian Loader

Another by Christian Loader. Maybe Echinothrix from Lembeh,
Double-spined Sea Urchin - Lensbaby macro - Lembeh

Sea Urchin Closeup
From Echinotrhix calamaris from Papua New Guinea. Photo below by jabaezam

Diadema? from tropical Atlantic
close up of spiny urchin
Photo above by marcsdad50

Echinothrix from Sulawasi (photo below by fisheyedave aka David Cropp)

Echinothrix? from Lembeh Strait (Photo by Ruary James Allan)

Here's one from Diadema (the Philippines). Photo below by maxette
sea urchin


Anna DeLoach said...

Thanks for this gem. Maybe it’s the company I keep, but this question about the bulb-like protuberance on the urchin has come up more than once - now I have the answer: Anal cones! For ejecting feces!

ChrisM said...

ha! happy to help Anna! I only wish there was more available on why diadematids have those things in the first place!

octopod said...

It's also been suggested that the Paleozoic crinoids that had anal cones (ridiculous ones!) did it to avoid parasites...and check out this paper: Physical modeling of the batocrinid anal tube: functional analysis and multiple hypothesis testing

ChrisM said...

cool thanks! here's a link to the paper. the one above is behind the U. Michigan firewall. http://bit.ly/KRsfJ0

Anonymous said...

Dear Blogger:

You have posted my Radiating Hat Pin Sea Urchin which is great.

However, you misidentify the source of this vid. This is a video I shot at Banderas Bay, Puerto Valarta, MX, in January 2011I did borrow language, which I attributed to Lembah Strait.

So Dude, please correct the text. I sincerely hope that you are going to keep this wonderful animal on your site without the erroneous text. Thanks

ChrisM said...

thank you! I've added some text to amend the locality.

Anonymous said...

The photo is still attributed to "Efdixon" Please fix. Thanks

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