Tuesday, September 13, 2011

The Smithsonian-California Deep-Sea Starfish Connection! The Sunflower Star's Deep-sea cousin-Rathbunaster californicus!

Historical trivia is always kind of weird and interesting. If you know a place or an animal's scientific history well enough, its amazing the funny little coincidences and convergences that play out.

Here's a great example, inspired by a recent set of articles on one of the Smithsonian's most prominent scientist/administrators Richard Rathbun!! Part 1 and Part 2.
So, there's this deep-sea starfish that lives off the coast of California, Oregon and Washington (and by deep I mean about 130-700 meters deep, the continental shelf).

Its called Rathbunaster californicus!
Its got 12-20 arms. Gets pretty big (about a foot across) and occurs abundantly on soft bottoms, among other places. Here's some video..

Biology of this animal is pretty neat! There's a full paper by Lynn M. Lauerman (formerly of MBARI and Scripps) from 1998 in the Bulletin of Marine Science 63(3): 523-530 which outlines diet and feeding behavior of this species in Monterey.

Basically-in addition to other feeding scavenging/predatory modes, such as feeding on heart urchins (see this older post from 2009), they can also use their arms to capture SWIMMING prey!

Such as this krill
and these myctophid fish!
among other things-Rathbunaster eats?

MANY moving crustaceans (including shrimps and amphipods), swimming worms (tomopterids), and even some jellies (siphonophores)!!

SO, if there's ONE thing that I hope all of you get from reading the Echinoblog? Its that at least some STARFISH catch things that MOVE faster than them! Another example is the large, Antarctic bottom predator Labidiaster (click here and on the pic to see other examples of starfish that catch moving prey items!)
So, Rathbunaster is pretty cool, eh?? Well, guess what? THERE's MORE!!

You may have already picked up on this-

the genus name RATHBUNASTER is an honorific of Doctor Richard Rathbun of the Smithsonian!

A combination of the surname "Rathbun" and "-aster" which means "star" in Latin. The "californicus" species name refers to the place where the animal was collected.

The name literally translates to "Rathbun's California Star".
Here's a scan of the original description....

and who to name this new species (back in 1906) other than Walter K. Fisher-the famous starfish biologist and Director of Stanford University's Hopkins Marine Station-himself??
Fisher was likely grateful to Rathbun, as Fisher was actually given the "OK" by Richard Rathbun to study this species and MANY other species of the North Pacific.

Bear in mind that at the time, the marine fauna of this region was only JUST becoming known, even to scientists. And so, being THE authority on any particular fauna or group was what you did back then and the big guns got access to the best material!

Here is a quote from Fisher in the preface to his major 3 part treatise on the starfish of the North Pacific..
I had completed special reports on collections Nos. 2 and 3 when the collection from the U.S. National Museum, sent by Dr. Richard Rathbun, Assistant Secretary of the Smithsonian Institutution, was received. This is probably the largest and most complete single collection ever assembled from a restricted region (the west coast of North America). Doctor Rathbun at one time contemplated working up this material, and to that end made a preliminary sorting of specimens in several groups. He was however, prevented by routine work from carrying out his plans.
As if this wasn't enough... the study of this starfish even takes you to an intersection with the famous intertidal biologist Ed "Doc" Ricketts, the biologist made famous by John Steinbeck's novel Cannery Row!

This quote from the Fisher (1928) monograph of forcipulate starfish:
Several live specimens captured in about 300 fathoms off Santa Cruz and presented to the Hopkins Marine Station by Mr. E.F. Ricketts were kept in an aquarium for a week in water about 12 degrees higher than the 42 or 43 degrees F to which they were accustomed at their normal depth. These specimens were kept in subdued light and were fairly active. Small crabs and shrimps allowed to fall on the abactinal surface were instantly seized and held by the numerous batteries of crossed pedicellariae of the spine sheaths. In some cases,the prey was then seized by the tube-feet and carried rapidly to the mouth. In others, the victims succeeded in escaping. Doubtless in normal circumstances this species reacts as quickly and vigorously as Pycnopodia.
Well, now, that's interesting. He mentions the nearly world-famous Sunflower star Pycnopodia helianthoides!!
But sadly, only a select few know about the very similar but taxonomically distinct Rathbunaster. (sort of like Pycnopodia's lesser known sister)

Hmmmmm... They DO sort of look alike dont' they??

Fisher outlined the definition of Rathbunaster pretty thoroughly in his papers and maintained that they were unrelated and very distinct from each other. Going so far as to place them in separate families.

I've literally taken apart the skeleton of Rathbunaster and Pycnopodia and compared them. They were similar (as many multi-rayed specis are) but in many ways VERY different.

Morphology can be frustratingly vague. How were they related? How distantly? How closely? A mystery.

Flash forward to my recent DNA paper with Dave Foltz in the Zoological Journal of the Linnaean Society!

Our molecular tree shows the two, Pycnopodia and Rathbunaster as VERY closely related sister-taxa!
Shown here in the context of the immediate clade
When two taxa occur as "sister taxa" like this on a DNA tree (at this level) a number of interpretations are possible
  • They are the same. And one should be taxonomically subsumed into the other.(i.e., one name is redundant and by convention can be made obsolete by international regulation)
  • They are legitimately two separate distinct groups that might simply be very closely related.
  • We haven't sampled enough taxa and this doesn't show the full picture... yet.

Much remains to be discovered about the evolution/separation/ecology of Pycnopodia and Rathbunaster..

And so, in many ways the pendulum has swung from coast to coast.

From Richard Rathbun to Walter K. Fisher (who described) and then to me, travelling from California to Washington DC.
Any of you California/West coast DNA types ready to take on the challenge of Rathbunaster/Pycnopodia and return the pendulum to the west coast??

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