Eyeless Australian Cave Fish Found to Have Closest Relatives in Madagascar
Posted on August 29, 2012
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. DNA analysis 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.
The cave fishes, of the genus Typhleotris in Madagascar and Milyeringa in Australia, are less than 100 millimeters long. They 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 total darkness.
Prosanta Chakrabarty, an assistant professor and curator of fishes at Louisiana State University's Museum of Natural Science, says, "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. 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."
One of the new species discovered by the researchers, which will be named in a future publication, is a novelty among cave fishes because it is fully and darkly pigmented. The analysis the researchers conducted for this fish's tree of life shows that it evolved from a pigment-free ancestor, indicating that some subterranean forms can "reverse" themselves for this character.
The research paper was published here in PLoS ONE.