Hawaiian Deep Sea-Urchins!!! Below the Surface of a Tropical Paradise!

So, following up on the Hawaiian deep-sea starfish post from a few weeks ago...I thought it would be cool to show some other echinoderm diversity...and who doesn't love sea urchins???
A brief background on where these pictures came from... These were ALL taken by the Hawai'i Undersea Research Laboratory (HURL) at the University of Hawai'i at Manoa and are all species that live in deep-water in and around the Hawaiian Islands. HURL operates two manned submersibles..the Pisces V and the Pisces VI.
I went down and deep-sea stalked my echinoderm loves in the Pisces V back in 2000. The following are not images from that expedition but a mix of pix from past voyages of HURL's Pisces V submersible... Thanks to Chris Kelley at HURL for allowing me to use them!

1. Aspidodiadema hawaiiensis. Here's a neat species that is also observed in the Bahamas. It has these long freaky spines, which they use to MOVE.

These urchins remind me of the giant black spy spider robot from Johnny Quest....


2. Phoromosoma bursarium. What survey of deep-sea echinoderms is complete without some echinothuriids?? I wrote up a blog on these for Deep-Sea News awhile back as one of the 27 BEST Deep-Sea species (it made the top 10!).

Basically, these are weird urchins that walk around on hoof-like spines. Some genera have these big puffy sacs of unknown function.
But one thing I HAVE experienced from firsthand observation-those spines on these critters? They STING. A colleague of mine at MBARI experienced this during the North Pacific Expedition last year.

3. Chaetodiadema pallidum. There's not very much known about this species, but in and around the Hawaiian region between 50 and 402 m on fine sediment.
These can be VERY abundant... and bringing up a bunch of them doesn't do them justice when they are observed on video arranged in these almost unnatural distribution patterns... spooky!
Who needs science fiction when you've got reality?

4. Chondrocidaris gigantea..Speaking of freaky... Here's one of the shallower-water urchins that you see in deeper waters.. Note that the spines are completely covered over by overgrowth..sponges or other encrusting invertebrates, perhaps?

In this species and other cidaroid urchins (you'll be seeing these below) the spines LACK epidermis and you get all kinds of weird things growing on them..

Here's a little bit I wrote up on them last year...(a bit dated by the holiday theme)
5. Prionocidaris hawaiiensis. Another urchin about which we know very little...
Except that we know where they occur in 92-214 meters? They are VERY abundant!
6. Histocidaris variabilis. What's weird with this one? It has BARNACLES that grow on the spines!! Similar in some ways to the way that Chondrocidaris has sponges and etc. on the spines...
7. Acanthocidaris hastigera. Not much known about this one..but dang, its cool-looking ain't it?
8. Caenopedina pulchella These are neat because the coloration on the spines is actually EMBEDDED in the spine calcite. So, even the preserved ones are red and green!
9. Phrissocystis multispina This is one of the weirder ones... This is a spatangoid urchin (i.e., a sea biscuit) and the group is known primarily from the fossil record.

But the living ones are VERY fragile. I've held dry specimens..and the sediment in the gut can literally cause the bottom of these to fall out from under them.
Thanks to Craig Young, Kevin Ecklebarger and J.L. Cameron we also know a little about its very strange-looking sperm and reproductive biology.

Enjoy! Seeya guys next week!