New News for Old Fish

The coelacanth (pronounced 'see-la-canth') holds an interesting place in both ichthyology and the history of ichthyology.  Many of us are familiar with the image of this large, speckled fish, easily identified by the thick lobes that characterize its fins.  Surely it commanded a few moments of simultaneous intrigue and eyebrow-raising in Ichthyology or Evolution 101. 

Coelacanth (Source: smithsonian.edu)

In fact, until 75 years ago this fish was thought to have been extinct.  As the story goes, Marjorie Courtenay–Latimer stumbled upon the fish in 1938 during a routine investigation for her South African museum collection of Indian Ocean fish landings.  Latimer suspected this was a novel specimen, and quickly made some sketches that were dispatched to a more authoritative ichthyologist (and chemistry professor) named Smith.  Of course, the importance of her coelacanth find was immediately confirmed, and thus began the 14-year search for a second specimen.





For years, the coelacanth and its lobed fins was held up as a link between those water-dwelling organisms and the tetrapods.  Both the coelacanth, the lungfish, and primitive tetrapods share the class Sarcopterygii.  Furthermore, the coelacanth is routinely referred to as a 'living fossil', owing to it's apparent consistent morphology over hundreds of millions of years.

Despite the coelacanth's unique history, this past week researchers published an article in the journal Nature suggesting now that the coelacanth genome has been reported, the lungfish should be considered the closest living relative to early tetrapods.  Of course, the lungfish and coelacanth are already closely related, but owing to the glacially-slow rate of changes in coelacanth genes (for example, the coelacanth today looks like it did 300 million years ago!), the researchers propose that the lungfish and its faster changing genome is, more appropriately, the link to tetrapods.

Lungfish (Source: zoochat.com)

So what does this mean for the coelacanth?  Will we no longer look at the coelacanth in awe and mentally animate this fish extending its lobes and crawling up on land?  Of course we will.  Although the genomes has been described, the coelacanth will continue to fascinate fish biologists, and the story of the coelacanth will continue to be told and inspire new fish biologists.

Perhaps the greatest value of the coelacanth is the lesson of how limitless the ocean and its inhabitats are, and how much more we have to learn. That, for example, we can assume something has been extinct for 70 million years, until it casually appears in a fishing net.  Decoding a genome and linking fish to tetrapods is incredibly important, but let's not forget the exciting moments of scientific discovery that remind us how everything we think we know about fish can change in a moment!

And as for the future of the coelacanth itself, I have to assume it's not too worried.  What's another couple million years to a coelacanth? 

Steve Midway


Check out the full paper (open access) here!

And if you really want to burn some time, put on a pot of coffee and watch this: