Going out into society after a long isolation becomes uncomfortable. Just ask the fish in Pahrump’s pool, lonely in a desert for some 10,000 years.
This hand-sized fish (Empetrichthys latos) is shaped like a chubby torpedo and has a mouth that appears almost to smile. Until the 1950s, this species had three forms, each evolving in its own spring. Now only one survives, which developed in a spring-fed oasis in the Mojave Desert’s Pahrump Valley, about an hour’s drive west of Las Vegas.
Fish in a desert are not that rare when you look at the long term (Serial number: 01/26/16). In a previous life, some desert valleys were ancient lakes. When the region’s lakes dried up, the fish became trapped in the remaining pools. Over time, several stranded species adapted to the peculiarities of their private microlakes, and a desert fish version of the various Galapagos finches emerged.
“We like to say that Darwin, had he had a different travel agent, could have come to the same conclusions from the desert alone,” says evolutionary biologist Craig Stockwell of North Dakota State University in Fargo.
The deserted “island” where e. latos evolved was Manse Spring on a private ranch. From a distance, the spring looked “like a little clump of trees,” recalls ecologist Shawn Goodchild, who now lives in Lake Park, Minnesota. Olympic pool.
In the 1960s, biologists feared that the fish were doomed. The flow of the spring had been reduced by 70 percent because the irrigation of farms in the desert absorbed the water. And disastrous predators arrived: the goldfish discarded by a child. Conservation managers fought back, but neither poison nor dynamite killed the newcomers. And then, in August 1975, Manse Spring dried up.
Conservationists had moved some pool fish to other springs, but the long-isolated species just didn’t seem to have the dangers of living with other types of fish. Predators easily caught the fish from the pool in their new home.
Laboratory evidence from faked fish murder scenes may help explain why. For example, the researchers contaminated the aquarium water with pieces of mashed fish. In an expected reaction, fathead minnows (Pimephales minnows) was startled by traces of dead minnows floating in the water and huddled in the tank. Pahrump’s pool fish in blender-skin polluted waters of his kind kept swimming in the upper waters as if the corruption of corpses was no more terrifying than tap water. Literally. Stockwell and his colleagues can tell that because they did a scary test with non-chlorinated tap water that isn’t scary. Poolfish didn’t curl up then eitherreports the team on August 31 Proceedings of the Royal Society B.
Later, however, Stockwell and a colleague were mulling over some rescued pool fish in livestock tanks when nearby dragonflies caught the researchers’ attention.
Before dragonflies mature into resplendent aerial wonders, the young prowl underwater like vicious predators. In moves worthy of terrifying aliens in a sci-fi movie, many dragonfly nymphs can shoot their jaws from their heads to scoop up prey, including fish eggs and fish larvae. With young dragonflies hanging around the bottom of a pool and plants, pool fish moving up in the water column “would be a good way to reduce their risk,” says Stockwell. Testing of that idea has begun.
Fish that people thought were foolishly naive may be smart in a different way. Especially after isolation in a desert with dragons.