A study has found the enigmatic Chiapas catfish, Lacantunia enigmatica, to be most closely related to the African claroteid catfishes.
Publishing their results in the latest issue of the journal Proceedings of the Academy of Natural Sciences of Philadelphia, John Lundberg, John Sullivan, Roco Rodiles-Hernndez and Dean Hendrickson studied the molecular phylogeny of the Chiapas catfish using fragments of the nuclear genes rag1 and rag2 and found it to be most closely related to the African catfish family Claroteidae.
The Chiapas catfish was described as belonging to a new family of catfishes (Lacantuniidae) last year, and is restricted to southern Mexico. (See Chiapas catfish, Lacantunia enigmatica, placed in new family).
The time at which the claroteids and lacantuniids diverged is estimated to be around 75 to 94 million years ago, long after Africa and South America were thought to have separated (the traditional explanation for freshwater fish distribution across the Atlantic is via drift vicariance of Africa and South America).
The authors discuss two alternative hypotheses to explain the observed pattern of distribution, i.e. from Africa to Mexico via eastern Asia, the Beringian land bridge and western North America, and from Africa to Mexico via Europe.
In the latter hypothesis, it is postulated that freshening of warm surface waters the Arctic and north Atlantic may have created corridors of warmer freshwater through which freshwater fishes might have dispersed.
For more information, see the paper: Lundberg, JG, JP Sullivan, R Rodiles-Hernndez and DA Hendrickson (2007) Discovery of African roots for the Mesoamerican Chiapas catfish, Lacantunia enigmatica, requires an ancient intercontinental passage. Proceedings of the Academy of Natural Sciences of Philadelphia 156, 39"53.