Several months ago I had arranged for a loan from the TePapa Museum in New Zealand to examine a specimen of a rare species of deep-sea starfish that had been discovered from the SubAntarctic. (Thanks to my colleagues at the USARP for arranging to bring the specimen back to the US!)
The specimen is a member of the MYXASTERIDAE, a group of truly deep-sea (1000-3000 m) starfishes, which is one of, if not, the rarest group of starfishes in the world. Nine species in three genera are found in the Atlantic, Indian and the Pacific Oceans.
What makes any animal rare?? A combination of abundance as well as frequency of occurrence.
When most people think of the rarest deep sea echinoderm/star shaped thing, many automatically think of the so-called "sea daisy" Xyloplax which I have covered here and here.
What makes myxasterid starfish MORE rare then Xyloplax? While its true that Xyloplax has only been encountered once or twice every 15 years..there are actually about 100 specimens of each species known.
How many myxasterids are known?
Here is a shot of approximately HALF of the total number of SPECIMENS in the world. About ONE or TWO specimens of each species is known. That means you can count the TOTAL number of actual individual specimens on your hands and toes. You can count the number of specimens of each species in each genus on ONE HAND. (and just to brag-I have seen almost all of them)
But of course, there is ALWAYS more to the mystique of rare animals then their rarity.
What evolutionary novelty makes myxasterids so interesting??
Morphologically, they have an "intermediate" body form between two very evolutionary successful (and familiar) groups of starfishes:
the SOLASTERIDAE or sun stars:
and the PTERASTERIDAE or the Slime or Cushion Stars.
So, you have a starfish with multiple long-arms IN ADDITION to structures that ostensibly enable it to project the huge amounts of mucus that pterasterid starfish produce?
In fact, the type name "Myxaster" comes from the Greek Myxa for slime and of course, "aster" for star. (note that this name is similar to the hagfish name Myxine...)
Plus, you have a really SOFT slimy body, covered by fine hyaline spines on a creature that is seldom if ever encountered and you have yourself ....a mystery....
What do they eat?
Are they related to the starfish species everyone thinks?
Are they ACTUALLY really rare??
A great way to kick off the New Year! Happy 2009!!