Thursday, January 14, 2010

More Exotic Hawaiian Starfish! Valvaster and Astropecten!

Today, MORE Exotic Hawaiian starfishes sent to me to ID!! Thanks to Gordon Hendler (Los Angeles County Museum) who found the specimens and Cory Pittman, who photographed the specimens!

Let me caveat that Astropecten (family Astropectinidae) is VERY hard to identify from pictures! In a professional sense, having vouchers is the best way to ID them..

First, Astropecten polyacanthus Like all Astropecten (there are 2 in shallow-water Hawaii), this species burrows into the sea bed and live under a fine veneer of unconsolidated sediment, where they feed on various small, molluscan fare..snails, clams, etc.

This beast is about 2 inches in diameter and was collected in Maui from about 9.0 m. It is distinguished from the 2nd species by having spines in each interradius and adults should only have one spine per superomarginal plate (but this is difficult from pictures)A second specimen (also discovered by Hendler/ photographed by Pittman) from Maui at about 10 m is possibly a Astropecten triseriatus myobrachius. This specimen was only about an inch in diameter.
This species differs slightly, in having 2-3 spines per plate and is missing the spines pointing aborally (i.e., upward) in each interradius..

Although, this seems like A. t. myobrachius to me, its entirely possible that this is some kind of juvenile of the species above with smaller features.

THESE are the kinds of FACTORS that make taxonomic identification difficult (and challenging)!

Valvaster striatus
(family Ganeriidae), has been known for awhile (described by Lamarck in 1816) but we know NOTHING about it except for the name. Its definitely a RARELY encountered, but thankfully, easy to identify, species in Hawaii (known from Oahu and Maui), but is known widely throughout the Indo-Pacific including Guam, the Philippines, Australia, and the Indian Ocean. in less than 20 m depth. Found and photographed by Cory Pittman.We DO know something about the etymology of its name, of course. Notice that on the side of the animal, are large bivalved pedicellariae, which are sort of like big clamps that sit on the lateral side of the animal (see white circles below). Hence Valv for the valves on each pedicellariae and -aster for star.. And the adjective striatus refers to the striated patterns on the body surface
Color in this species varies....This one is darker with green where others are more red...
This animal was from Guam and is a borrowed image from Gustav Paulay's excellent FMNH site on Indo Pacific animals.

Note that this one in Wikipedia? NOT Valvaster (looks like an oreasterid or a goniasterid). Pls. make a note of it!

Have a great weekend everyone!

1 comment:

Predomalpha said...

Quite interesting, are you good at identifying South Australian species?

FYI I didnt find this, someone else it. It looks like a Astropecten vappa, but A.triseriatus isnt out of the question.