Scientists discover a ‘sister’ in the flea’s family tree
ERIK Tihelka wants you to consider the flea. Or rather, the student at the University of Bristol in Britain wants you to reconsider this tiny insect.
If you’ve thought about fleas, it’s perhaps when you’ve seen a pet dog scratching as the parasites bite him to feed on his blood. Tihelka is a paleoentomologist. He studies insects preserved as fossils. When he and his colleagues thought of fleas, it was in terms of a centuries-long mystery. Where did fleas fit in the ‘tree of life?’ Figuring out how living things are related to one another is called taxonomy.
“For 200 years people have been studying insects, and we understood their evolutionary groups,” says Tihelka. Except fleas. “People suggested they were close to beetles, or close to flies, or actually a type of fly that adapted to feeding on blood. But they evaded our understanding.”
Tihelka says that’s because fleas are strange. “They don’t have wings, and their anatomy is modified to (make them) specialised parasites of birds and mammals. It’s hard to find similarities with other insect groups.”
Tihelka and his colleagues were determined to figure out the mystery. They looked at information from about 1,400 genes of fleas and their possible relatives. They discovered that a family of seven rare species of scorpionfly, called nannochoristidae, turned out to be fleas’ closest living relative. Tihelka calls them the ‘sisters to all the fleas’.
Nannochoristidae are found in New Zealand, southeastern Australia, Tasmania and Chile. But their origins go back to the Permian Period. Sometime between 290 and 165 million years ago, members of nannochoristidae may have started to change. They evolved from insects that fed on nectar into insects that fed on blood. These ancient flea relatives, some of which were about threequarters-of-an-inch-long (huge for fleas), may even have fed on the blood of dinosaurs.
Reclassifying the tree of life is something that happens often as scientists gain knowledge. Tihelka says it happens with insects, too. Scientists once thought termites were their own group of insects. Then they figured out that they’re actually “a group of cockroaches with a social lifestyle,” Tihelka says. His research on fleas suggests they should be reclassified as scorpionflies.
Tihelka and his research group plan to continue studying fleas and scorpionflies to see whether they can find more links between the two. After that, he says, insects will keep him busy for a long time.
“Insects are present in all ecosystems and make up twothirds of all described animals,” he points out.
In addition, there are 400 million years’ worth of extinct insects in the fossil record. Some people refer to the Age of Dinosaurs or the Age of Birds. “But we (knew all along) it’s been the Age of Insects,” says Tihelka.
Still, that age is threatened. Some scientists are fearing an “insect apocalypse” or the elimination of insects. Many species of insects around the world are declining in numbers.
“The only time there was a slump was at the PermianTriassic boundary,” 250 million years ago, says Tihelka. Ninety per cent of all species went extinct. “That was as close as we got to wiping all insects out. But other than that, they’ve been successful.”
Only time will tell if that success will continue. —The Washington Post