These desert fish flub social cues after eons of isolation

These desert fish flub social cues after eons of isolation ...

After a long isolation, getting out into the community becomes difficult. Ask the Pahrump poolfish, loners in a desert for some 10,000 years.

The Empetrichthys latos fish has a chubby, torpedo-shaped tail and a smiling mouth. The last one, however, has been found in a spring-fed oasis in the Mojave Desert's Pahrump Valley, about an hour's drive west of Las Vegas. Various stranded species over time evolved to adapt to the peculiarities of their private microlakes.

“We like to think that Darwin, if he had a different travel agent, might have come to the same conclusions just from the desert,” says evolutionary biologist Craig Stockwell of North Dakota State University in Fargo. From afar, the spring looked “just like a little clump of trees,” according to ecologist Shawn Goodchild, who is now based in Lake Park, Minn. The pahrump poolfish's entire native range is about the length of an Olympic swimming pool.

Biologists feared the fish would be doomed in the 1960s. The spring's flow rate had dropped by about 70 percent as irrigation for agricultural farms in the desert sucked out water. And predators arrived: a kid's discarded goldfish. Conservation managers fought back, but neither poison nor dynamite wiped out the newcomers. And then, in August of 1975, the Manse Spring dried up.

Some poolfish have been moved to other springs by conservation managers, but the long-isolated species seemed to ignore the hazards of living with other kinds of fishes in their new environment.

Researchers mixed in nonscary dechlorinated tap water with pureed fish bits as an experiment. Fathead minnows (Pimephales promelas) spooked out of the water and huddled low in the tank, while Pahrump poolfish spooked out of the upper water as if the corpse taint was no danger, according to Stockwell and colleagues in the Aug. 31 Proceedings of the Royal Society B.

Stockwell and a colleague were pondering about some rescued poolfish in cattle tanks when nearby dragonflies caught the researchers' attention.

The young prowl underwater as dangerous predators before dragonflies mature into sparkling aerial marvels. In stunts similar to those seen in a sci-fi film, many dragonfly nymphs can shoot their jaws out from their heads to grab prey, including fish eggs and larvae, according to Stockwell. That approach may be utilized in the future.

Fish that people thought were nave may be wiser in a different way. Especially after isolation in a desert with dragons.

You may also like: