Researchers make a giant Oregon find -- a water flea -
The discovery of a species, part of an unknown family of animals, illustrates the limits of knowledge about threatened ecosystems
The strange creatures were lurking in seasonal ponds just north of Medford and baffled the veteran biologist who shelved them in his lab for nearly five years. He was puzzled for good reason. The animals -- small as a grain of sand but with hairy, shrimplike appendages -- had never been discovered before.
Then, the scientist's graduate assistant joined in for a close look, only to show astonishment at finding a new species of water flea that represents an entirely unknown family of water fleas.
The researchers named the critter "hairy water flea," with the Oregon-based official name Dumontia oregonensis, after prominent Belgian ecologist Henri Dumont and the state of discovery.
The find is striking evidence that entirely "new" creatures remain to be discovered on Earth, despite rampant species decline and especially in unusual, but increasingly vanishing, ecosystems.
Stanley Dodson, a professor and freshwater ecologist at the University of Wisconsin at Madison, confesses that he misidentified the mysterious organisms when they arrived at his lab in 1998. But the riddle of their identity kept his curiosity alive enough to engage graduate student Carlos Santos-Flores.
"Carlos came back very worried, saying, 'This is something very different,' " recalls Dodson, who has studied water fleas for nearly 40 years. "We soon realized we had a surprising, once-in-a-century discovery."
Dodson and Santos-Flores, now at the University of Puerto Rico at Mayaguez, describe their findings in the current issue of the journal Hydrobiologia.
Six-hundredths of an inch long, the hairy water flea came from the Nature Conservancy's Agate Desert Preserve, a 53-acre site once slated for industrial development. It was found in three of the preserve's vernal pools, shallow depressions that fill with water from December to April before drying out in the spring and summer.
Although barely visible without magnification and hardly charismatic, water fleas have important jobs. They help maintain water quality by curbing the growth of algae that is a large part of their diet, and they are a key source of food for fish. In shallow waters, such as the Medford pools, they are a popular menu item for birds and amphibians.
Water fleas are not fleas, however. They are shelled crustaceans more closely related to shrimp.
"I tell my classes that when they eat a lobster to examine its parts closely, because water fleas have those same parts, except they're miniaturized," Dodson said.
What sets the hairy water flea apart from the other 450 species of water fleas is that it combines the two food-gathering filters that had, until now, split water fleas into two broad groups.
One group is made up those with comblike scrapers on their feet and crawl along the bottoms of lakes and ponds scouring algae and bacteria off rocks. The other group -- including the common Daphnia used as aquarium food -- filter algae from the water with long, feathery filters on their legs.
Dodson erred in his early observations.
"I initially identified it by looking on the outside, and it looked like it had some of these spines, or scrapers," Dodson said. "But when Carlos looked inside, it had feathery filters. So it combines the characteristics of the two major groups."
The hairy water flea is thus an unusually fit specimen, with six pairs of feathery legs and a claw on its abdomen to clean debris from its legs. Little is known about the animal's behavior, however, including its reproductive habits, with no males having been found.
"Some water fleas reproduce asexually, and there are no males; and some water flea species produce males and have normal sex," Dodson said. "But we don't know whether this new animal is reproducing asexually or sexually."
Oregon's hairy water flea may be a missing link, it turns out -- an animal with anatomical features shared by all the different branches of the water flea family.
"This animal resembles the predicted ancestral animal" that may give clues as to how water fleas may have evolved, Dodson said. The oldest fossils of water fleas date back to more than 100 million years.
Female water fleas lay what are known as "resting" eggs, which can survive in the harshest of conditions. Dodson said the eggs are "very resistant to death -- they go right through ducks and fish that have eaten them." Being a tough egg is required in the hot Agate Desert Preserve, where the pools are dry until the return of cool water, when the eggs hatch and grow.
The mystery critters arrived on Dodson's desk in 1998 after the Nature Conservancy began a survey to determine what invertebrates lived in the vernal pools.
Darren Borgias, southwest Oregon stewardship ecologist for the Nature Conservancy, said the goal was to compare the inhabitants of the vernal pools near Medford to a wider array of such pools that can be found throughout Northern and Central California.
Borgias said samples were first taken by students from Southern Oregon University, then later by Ed Hoover, a field ecologist with the conservation organization. Unidentified water fleas were packed up and sent to Dodson for examination.
"These vernal pools are temporary bodies of water, and only animals and plants that are adapted to the changeable environment occur there," Borgias said.
The Nature Conservancy set up the Agate Desert Preserve in 1987 on donated land to help protect the unusual ecosystem. The site had been slated to become an industrial park.
It's not the first surprise to emerge from the Agate Desert's vernal pools. In 1998, researchers discovered an imperiled species of freshwater shrimp called the vernal pool fairy shrimp. Previously, the shrimp, listed as threatened under federal law, was thought to exist only in California -- particularly in the well-known Mono Lake, on the eastern flanks of the Sierra Nevada range.
"You can pretty well be guaranteed that you're going to discover new things because there hasn't been that much exploratory biological work here," Borgias said. "And the smaller the organism gets, the less likely there's been an opportunity for a person to investigate them."
"These ponds are really a rare habitat that could have easily been lost. This is the only place where people have found this water flea, and I strongly encourage Oregon scientists to look around and see if they can find some more.
"As we all found out, you never know what's waiting out there to be discovered."
Richard L. Hill: 503-221-8238; firstname.lastname@example.org
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