January 27, 2016 by Bob
Yirka report
(Phys.org)—A team of researchers from several
institutions in the U.S. has found evidence that suggests that pupfish living
in Devils Hole are not nearly as ancient as has been previously assumed. In
their paper published in the journal Proceedings of the Royal Society
B, the team describes a genetic study they conducted on the fish and
others that are related to them, and what they found as a result.
The existence of small,
goldfish sized, dark blue fish living in a water filled fissure in the Mojave
Desert has led to many theories regarding how they got there and how they have survived.
For many years, the consensus has been that they got there due to flooding
during the Pleistocene epoch, approximately 10 to 20,000 years ago. How they
managed to survive for so long in such a remote, small and hot environment has
been a mystery. But now, new evidence suggests that the pupfish may not have
been living in the Hole for nearly that long.
Prior research has shown
that the pupfish are a unique species—with features that are unique to them
alone among pupfish, such as the lack of a dorsal fin, bigger eyes and darker
scales. To learn more about the origins of the species, which scientists have
described as having the smallest range of any vertebrate on Earth, the group
conducted a genetic analysis of 56 pupfish from around the Death Valley area
(including one of the pupfish from Devils Hole which was found dead) and other
parts of the world, sequencing over 13,000 different stretches of DNA—a process
that allowed them to create a family tree. To gauge the historical age of the
pupfish from Devils Hole, the team averaged the rate of gene mutations in its
cousins. Doing so showed that the fish likely first inhabited their isolated
environment approximately 105 to 830 years ago and then evolved very quickly to
allow them to survive.
The researchers did not
find any evidence that might explain how the fish got there during that time
frame, but suggest it is possible that people living in the area put them there
as a means of maintaining a food source in the desert, or perhaps birds carriedfish eggs
from other, less remote water sources.
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