Friday, November 4, 2011

Yet another coelacanth?

I have a fondness for coelacanths, and I'm not sure why. Maybe it was my adolescent fascination for all things cryptozoological. Maybe it's that mysterious creationist obsession with living fossils. I don't know, but I do like hearing about coelacanths.

Coelacanths (pronounced seal-a-canths) are weird fish that were thought to be extinct until a recently-living specimen was discovered off the coast of South Africa in 1938. Coelacanths are weird because they are lobe-finned fish. Instead of having fins typical of modern fish, the lobe-finned fish have bony structures that support their fins. Lobe-finned fish (not the coelacanth) are believed to represent the type of fish that land animals might have evolved from. Modern coelacanths are deep-sea fish, with a well-known population living off the coast of the Comoros Islands in the Indian Ocean (the one caught off South Africa was evidently a stray). In the late 1990s, a second species was discovered off the coast of Indonesia. Since about 2004, there have been many coelacanths caught off the coast of Tanzania. Those Tanzanian specimens are the subject of a new study by Nikaido et al. in this week's PNAS.

Looking at the mitochondrial genomes of 21 Tanzanian coelacanths, they found evidence that the specimens caught off the north coast of Tanzania are genetically distinct from those caught off the south coast and from the Comoran coelacanths. The north Tanzanian population is nowhere near as distinct as the Comoran and Indonesian species, but the DNA still suggests that the north Tanzanian coast has its own breeding population. So it's not as cool as finding a new species, but still neat to learn that the Comoran coelacanths are more widespread than we previously suspected.

Nikaido et al. 2011. Genetically distinct coelacanth population off the northern Tanzanian coast. PNAS 108:18009-18013.

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