Monday, December 8, 2008

pt. 1-Cookie Starfish vs. Starfish Cookies!

Happy Holidays! I thought I would take a holiday theme to this week's blogs!

What is more full of holiday cheer then...Christmas Cookies! And what do I think of when I see Christmas Cookies?

Goniasterids!! Specifically the Goniasteridae, a huge family of largely cold-water starfish. Probably one of the most diverse of ALL the starfish. They typically have heavily calcified bodies and have sharp-well defined bodies.

Some of these taxa which have a perfectly pentagonal shape...i.e...The "cookies"!!!
Almost all "cookie" goniasterids have some morphological similarities, plus some interesting (if similar) etymologies!

The marginal plate series, those big plates that form the exterior outline of each one?? Usually pretty thickened and well-defined. Bodies are pretty stocky and heavily calcified....

Let's look at a few!

1. Tosia. As we've previously discussed, the name is latin for "inestimable". I recently reviewed this group and they are a really neato group of animals. "True" Tosia lives only in Australia, mostly in shallow-water.
(Tosia australis)
2. Glyphodiscus. Another group, I worked on...The name means "glyph" (=carved or engraved) and "discus", an allusion to the shape resembling dinner plates (i.e., discoid) carved out of limestone!

Glyphodiscus lives in the central & south Pacific in deep-water (continental shelf). Sadly, not much is known about them alive. But they are approximately coin-shaped (about 2-3 cm diamter) and are perfectly smooth.

3.Sphaeriodiscus. One of the the most taxonomically perplexing group of "cookie" goniasterid starfish.

Helen Clark (formerly of the New Zealand Institute of Water & Atmosphere) described one South Pacific species...Sphaeriodiscus irritatus.

Sphaeriodiscus refers to the "spherical" shape and "discus" to the discoid shape...And the species epithet "irritatus" is a direct reference to the irritating path of taxonomic determination!4. Eknomiaster. A weird, new goniasterid (Eknomiaster beccae figured here) from the South Pacific (New Zealand & New Caledonia). The name is derived from the Greek Eknomios which means marvellous or unusal..and it certainly is!

On the surface...a starfish that almost looks like it was assembled out of a model kit from tiles.... But!! You turn it upside down and look at the "oral" side..and voila!! A surprise!! Wheee!!
One big pedicellariae ( jaw-like structure) in each section!
And others have even MORE!
5. Peltaster! Peltaster is a widely distributed goniasterid. Its not entirely clear why Peltaster is all that much different from Sphaeriodiscus (above)...
Found in the Atlantic, Indian and Pacific oceans, usually in subtidal (in the Mediterranean) to deep (Indo-Pacific).

The name "pelta" actually means "small-shield" coupled with "aster" for star...The "small-shield" part alludes to the plates on the surface

We often forget that there's a BIG difference between living animals and dead specimens.

Its shallow enough that you can photograph it with SCUBA and observe it doing stuff like this....
Is there significance to the "cookie" shape? Defense? Functional constraint?

What's going on with the big puffiness???

One thing we do know? The "cookie" shape has been around for awhile!

PART 2!! On Thursday....."Cookie" starfish in the PAST!!!!


Miriam Goldstein said...

Agh! Eknomiaster's giant pedicellariae are scary! How big ARE they???

ChrisM said...

About 4-5 cm in, the peds are essentially flush. Still not clear on what they do...

Cephalopodcast said...

Happy Holothuridays to you and yours! May all your growth rings be bright.

Snail said...

Those seastars look even tastier than the real cookies.