DIVE DRY WITH DR. BILL #881: SO WHICH SPECIES IS IT!
I wrote recently about the species definition that many biologists use in determining what a critter is. The only "new" species I've ever discovered was in a drawer of fossils in the paleontology lab at Harvard's Museum of Comparative Zoology. I recognized it as a unique species of helicoplacoid, an extinct group of echinoderms related to present day starfish and sea urchins. When I showed it to Prof. Stephen Jay Gould (yep, later the author of The Panda's Thumb and many other popular books on evolution), he was thrilled. Later Dr. J. Wyatt Durham at UC Berkeley wrote up the scientific description of the new species.
A decade or so ago, I "discovered" another “new” echinoderm species out on Farnsworth Bank. Well, actually others had seen it before me, but no one knew what it was. I'm referring to what we then called the red spotted starfish (or sea star if you are PC). Farnsworth was the only place I ever saw this species (at least that's what I thought).
Later, I learned of a similar sea star collected by Jeff Bozanic on seamounts down off Baja. I contacted Dr. Gordon Hendler, curator at the LA County Museum, to learn more. Dr. Hendler had named it Hacelia bozanici after Jeff. I was relieved to finally have an answer to one of the many questions I had about marine life. After all, it is the questions and discoveries I make while diving that have kept me going all these years.
BUT... the answer turned out not to be an answer after all. Other scientists decided that the red spotted starfish was actually Pharia pyramidata. I was shocked at this re-assignment since I was familiar with that species from my days of diving in the Sea of Cortez as a marine biologist on board Lindblad Expeditions eco-cruise ships. The Pharia I knew from those waters was commonly called the YELLOW spotted starfish. Why? Duh, because it had yellow to greenish spots. Certainly not red!
Although I am by no means an expert taxonomist, I still question this re-assignment. Although they are definitely similar in appearance, why have I never seen a red spotted sea star in Mexican waters, or a yellow spotted sea star in our waters? Also the pattern of spots on the Mexican individuals is much denser than that on our local ones.
The magnificent new field guide, Beneath Pacific Tides by Jensen et al. states that this species feeds on corals. I wonder if it is chowing down on our beautiful purple hydrocoral, Stylaster californicus, which is one of the attractions on Farnsworth Bank. If so, perhaps dietary differences could explain the red spots on our local variant.
I may be in the minority (of one?) on this issue, but I remain skeptical! Or is it stubborn? I think the question needs to be looked at more closely than the superficial resemblance. Hopefully some molecular biologist will compare the DNA of our red spotted starfish with that of its presumed relatives in Mexico, and species of Hacelia as well. That should yield a definitive answer.
© 2020 Dr. Bill Bushing. For the entire archived set of nearly 900 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Pharia pyramidata from Farnworth Bank and from the Sea of Cortez.
I wrote recently about the species definition that many biologists use in determining what a critter is. The only "new" species I've ever discovered was in a drawer of fossils in the paleontology lab at Harvard's Museum of Comparative Zoology. I recognized it as a unique species of helicoplacoid, an extinct group of echinoderms related to present day starfish and sea urchins. When I showed it to Prof. Stephen Jay Gould (yep, later the author of The Panda's Thumb and many other popular books on evolution), he was thrilled. Later Dr. J. Wyatt Durham at UC Berkeley wrote up the scientific description of the new species.
A decade or so ago, I "discovered" another “new” echinoderm species out on Farnsworth Bank. Well, actually others had seen it before me, but no one knew what it was. I'm referring to what we then called the red spotted starfish (or sea star if you are PC). Farnsworth was the only place I ever saw this species (at least that's what I thought).
Later, I learned of a similar sea star collected by Jeff Bozanic on seamounts down off Baja. I contacted Dr. Gordon Hendler, curator at the LA County Museum, to learn more. Dr. Hendler had named it Hacelia bozanici after Jeff. I was relieved to finally have an answer to one of the many questions I had about marine life. After all, it is the questions and discoveries I make while diving that have kept me going all these years.
BUT... the answer turned out not to be an answer after all. Other scientists decided that the red spotted starfish was actually Pharia pyramidata. I was shocked at this re-assignment since I was familiar with that species from my days of diving in the Sea of Cortez as a marine biologist on board Lindblad Expeditions eco-cruise ships. The Pharia I knew from those waters was commonly called the YELLOW spotted starfish. Why? Duh, because it had yellow to greenish spots. Certainly not red!
Although I am by no means an expert taxonomist, I still question this re-assignment. Although they are definitely similar in appearance, why have I never seen a red spotted sea star in Mexican waters, or a yellow spotted sea star in our waters? Also the pattern of spots on the Mexican individuals is much denser than that on our local ones.
The magnificent new field guide, Beneath Pacific Tides by Jensen et al. states that this species feeds on corals. I wonder if it is chowing down on our beautiful purple hydrocoral, Stylaster californicus, which is one of the attractions on Farnsworth Bank. If so, perhaps dietary differences could explain the red spots on our local variant.
I may be in the minority (of one?) on this issue, but I remain skeptical! Or is it stubborn? I think the question needs to be looked at more closely than the superficial resemblance. Hopefully some molecular biologist will compare the DNA of our red spotted starfish with that of its presumed relatives in Mexico, and species of Hacelia as well. That should yield a definitive answer.
© 2020 Dr. Bill Bushing. For the entire archived set of nearly 900 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Pharia pyramidata from Farnworth Bank and from the Sea of Cortez.
