Similar-looking blind fish couldn’t have swum across the world, so did they evolve separately?

Where would a fish want to go be?  A goby fish wants to go be in dark caves.  The BBC News announced that “Goby fish 6,000km apart share eyeless common ancestor.”  Herein lies a puzzle: blind gobies in Madagascar and Australia are very similar.  How will evolutionary theory explain this?  Reporter Jonathan Ball said, “A study in PLoS One showed Madagascan and Australian cave fish inherited their blindness from a common ancestor”  (Source: Chakrabarty P, Davis MP, Sparks JS (2012) The First Record of a Trans-Oceanic Sister-Group Relationship between Obligate Vertebrate Troglobites. PLoS ONE 7(8): e44083. doi:10.1371/journal.pone.0044083).

Though living in different parts of the world the cave fish shared important features: they were small — under 10cm in length — eyeless, colourless and lived in freshwater, limestone caves.  How such similar fishes came to be living on different sides of the world was the question the researchers wanted to answer.

They considered convergent evolution: “When separate species are exposed to the same selective pressures they often come up with the same solutions — a process known as convergent evolution.”   An alternate possibility is that these species inherited their particular characteristics from a common ancestor: “In the case of the cave fish, an alternative possibility was that their odd features — or traits — were adaptations inherited from an ancestor common to both.”

A genetic comparison suggested the latter:

Though separated by thousands of kilometres of ocean, the cave-dwelling fish of Madagascar and north-western Australia were genetically more similar to each other than to any other goby: they inherited their unusual suite of characteristics from a common ancestor.

“That they’re 6,000 km apart in Madagascar and Australia is pretty remarkable,” observed Dr Chakrabarty….

Continue Reading on crev.info