A team of researchers from Louisiana State University and the American Museum of Natural History has discovered that two groups of blind cave fishes on opposite sides of the Indian Ocean are each other's closest relatives. Through comprehensive DNA analysis, the researchers determined that these eyeless fishes, one group from Madagascar and the other from similar subterranean habitats in Australia, descended from a common ancestor before being separated by continental drift nearly 100 million years ago. Their study, which appears in the journal PLOS ONE this week, also identifies new species that add to existing biological evidence for the existence of Gondwana, a prehistoric supercontinent that was part of Pangaea and contained all of today's southern continents.
"This is the first time that a taxonomically robust study has shown that blind cave vertebrates on either side of an ocean are each other's closest relatives," said Prosanta Chakrabarty, an assistant professor and curator of fishes at Louisiana State University's Museum of Natural Science. "This is a great example of biology informing geology. Often, that's how things work. These animals have no eyes and live in isolated freshwater caves, so it is highly unlikely they could have crossed oceans to inhabit new environments."
The cave fishes, of the genus Typhleotris in Madagascar and Milyeringa in Australia, are smallless than 100 millimeters longand usually lack pigment, a substance that gives an organism its color and also provides protection from the sun's ultraviolet radiation. These characteristics, coupled with a lack of eyes and enhanced sensory capabilities, allow cave fishes to survive in complete darkness. For this reason, the fishes have very restricted distributions within isolated limestone caves. It's also why the newfound genetic relationship between the trans-oceanic groups is an exciting geological find.
"The sister-group relationship between
|Contact: Kendra Snyder|
American Museum of Natural History