What is Going on with cidaroid sea urchins and their WEIRD spines??

Following the last Okeanos Explorer cruise to Puerto Rico, a got a bunch of questions from folks about what the heck was going on with the very odd looking spines of this cidaroid urchin: Cidaris blakei?

Some Etymology: "Cidaris" the genus name for this species (and the other urchins in the group)? is Latin for a headdress or tiara for ancient Persian kings The species name "blakei" is named in honor of the USS Blake, which was the vessel on which the species was collected.

Now, "normally" (which is to say in the majority of other ciadaroid urchins) the spines are pointy or blunt. Surfaces might be more smooth (as in Cidaris cidaris)

or kind of textured like so...

Cidaroid urchins are unusual in that their spines LACK skin on the surface. Remember that ALL echinoderms display their ENDOSKELETONS. What you are seeing (spines, armor, etc.) are NOT a shell or exoskeleton. All the surfaces are covered by skin (an epithelium)

Because of this, cidaroid urchin spines are affected by the environment. So, epizoics and fouling faunas grow on them. Worm tubes, barnacles, etc. 

                           

From one of my prior posts, these Antarctic urchins, called Austrocidaris, which actually can "seed" new areas with the animals that live on its spines.

So, what is Cidaris blakei doing with those wide, fan-like spines? Their unusual shape doesn't necessarily seem to display any obvious function. Defense? Some bizarre hydrodynamic function? perhaps to more effectively encourage growth of epizoics on the spines??

I also came upon this pic of C. blakei, which seems to grow a lot of critters on its spines...

from this echinoderm Scratchpad

MANY other cidaroid urchin species are known for having very unusual spine morphologies which I've shared with folks over the years. Here's a bunch for comparison

Broadly speaking, cidaroids are the only urchins that have these pretty weird spine morphologies. For what reason? Are they related to the growth on the spines?? (increase in surface area?) Defense? Reproduction? 

A curious bunch of animals. "About which, very little is known.."

Another one from the recent Okeanos 2015 Puerto Rico dive, this one was home to two serpent stars (I think.. Asteroporpa annulata)..

This one is called Chondrocidaris gigantea, a species from the Indo-Pacific, which was in the Paris collections...

Another curious species with very heavily serrated spines...

The above species seems to have a fairly heavy growth on their spines..

Another species of Chondrocidaris, C. brevispina, pic by Arthur Anker

Here's the mysterious Tylocidaris (formerly Psychocidaris) with these thickened "cortex" covering the spines... (see more here)

Some Haeckelian art showing odd cidaroid spines..

More strange treasures from the Paris Museum I've shown before.. BOTH of these urchins are different species in the genus Goniocidaris

But again, its unclear what they use the spines for..

Here's a second species with VERY different spine morphology

and there's a bunch of Paleozoic urchins that are worth checking out...

Starting next week: THREE WEEKS OF BLOGGING FROM CAPETOWN, SOUTH AFRICA!!

Strange Urchin Spines! Past and Present!

Tylocidaris clavigera from the Cretaceous of England Stunning image from the BMNH Echinoid Page. here

SEA URCHINS! Everyone kinda knows the basic idea: round spiny ball that lives in the ocean but most folks aren't as familiar with how CRAZY the spines can get. ESPECIALLY in the fossil record!

Most of these taxa are either cidaroid sea urchins or closely related to them. Cidaroids are considered a "stem group" among sea urchins. That is to say, they arise early in the evolutionary history of the group. They have a different jaw apparatus and vary in several other respects. Including the unusual absence of an epidermis from the spines, which permits growth of various other organisms on the surface. I've written about this here.  

Cidaroids may also be very important in understanding deep-sea dynamics and the historical ecology of other echinoderms, such as crinoids (feather stars). See that article here.  They have been around for quite awhile.. and have been known since the Paleozoic..

But some of the CRAZIEST urchins occur from the Mesozoic, that is during the time best known for the dinosaurs. Oceans were widespread during this time

One of these neat urchins is the Mesozoic (Jurassic to the Cretaceous) to recent cidaroid urchin, Tylocidaris.

Tylocidaris appears to have MASSIVE, club-shaped spines which were presumably used for defense..

Image of a cast by Ryan Somma

Here is some bewildering diversity of Tylocidaris spines, which all look like maces or big notched watermelons!  Presumably these were used as defense against predators.

MUCH thanks for the images from this Danish gentleman's excellent page about fossil sea urchins! 

These spines are from a Cretaceous Tylocidaris  sp.

Image by Søren Bo Andersen fr. his website

More Tylocidaris spines!

Image by Søren Bo Andersen fr. his website

 ..and still more!

Image by Søren Bo Andersen fr. his website

Interestingly, the British Museum's sea urchin website also indicates that a LIVING member of this family is still kicking around.. the unusual Psychocidaris!
Psychocidaris oshimai..

Curiously, the spines seem to be made up primarily of this weird cortex like covering...

Here's a video from a mineral/fossil show showing a bunch of fossil Tylocidaris-like urchins to a jazzy tune!

SIMILAR URCHINS...
the Jurassic Pseudocidaris mamossa Big CLUB like spines!

Image by Fernando Bravo

Asterocidaris  spp. 

And just in case you thought only fossil urchins could have all the fun! here' an assortment of neat urchins that are alive TODAY which bear bizarrely shaped spines...

But note that the spines aren't just huge and club-like.. they have all of this weird ornamentaton. What could their function be? defense? assist in reproduction somehow?

Goniocidaris sp. from the South Pacific. (MNHN Paris collection)

A second Goniocidaris species.. with very different spine patterns..

Morphology-seemingly simple and straightforward... and yet, what do the animals use them for?

Sea Star/Starfish Close Ups!

Image by Alexander Semenov

Bonjour to everyone! At the moment I am continuing my research in Paris at the Museum national d'Historie naturelle! Here are a bunch of my prior posts about studying at this incredible place!

I'll be blogging more on this shortly but in the meantime, here are some neat close ups of various starfish species!

Solaster endeca (Pacific Northwest/N. Atlantic) click here to see what the animal looks like

Image by Alexander Semenov

Crossaster papposus (Pacific Northwest/N. Atlantic) click here to see what the animal looks like

Image by Alexander Semenov

Plectaster decanus (Australia) Click here to see what the animal looks like

Image by Weedy Seadragon

Gomophia gomophia (Okinawa, Japan) click here to see what this animal looks like

Image by Okinawa Nature Photography

Nardoa sp. from the Indo-Pacific

Image by sbailliez

Echinaster callosus from the Indo-Pacific 

Images by Optical Allusion

The sand star Astropecten aranaciacus (temperate Europe, Mediterranean) click here to see it!
Note the star-shaped pillars are called paxillae. In theory they protect the papulae (aka the gills) from burial)

Image by fabbricmare

From Mediaster aequalis (west coast of N. America) a similar bunch of structures called tabula or tabular plates.. Click here to see it!

From an Australian relative of Mediaster called Nectria ocellata with some enlarged tabulae. It looks like this.

Image by ~aquaplane

 Close up surface texture of the Indo-Pacific Archaster typicus. Learn more about it here!