It’s hard to muster sympathy for lice. Most of the parasites seem to be doing fine—living, feeding and multiplying on their hapless hosts. But lice that live on dolphins have it tough. Their hosts are slippery and fast-moving; the lice spend their lonely lives clinging tight and hoping to meet just one other louse they can mate with. And while these parasites can teach scientists about the evolution and behavior of ocean mammals, it’s not clear how the lice themselves survive at all.
Syncyamus aequus is a whale louse, but it doesn’t live on whales and it’s not really a louse. The 30 or so species called whale lice are crustaceans, like crabs—not insects, like the lice that live on humans. Each species infects certain kinds of cetaceans (the group that includes whales, dolphins and porpoises); S. aequus only lives on dolphins. Whale lice do have some similarities to human lice: They can only live on a host’s body, and they spread when two animals rub against each other. But whale lice feed on skin, not blood. And their hosts live in the ocean.
“The main problem for whale lice is how to minimize the chances of being washed off,” Natalia Fraija-Fernández and Francisco Javier Aznar, of the University of Valencia in Spain, told me over email. To dig in and hold on tight, the lice have evolved flattened bodies, sharp claws on their legs, and spiny bellies. They hunker down in skin folds and other relatively protected spots.
It’s not easy to study the lice that live on elusive underwater animals. Researchers managed some studies back in the days of commercial whaling, Fraija-Fernández and Aznar say. These days, scientists can study the parasites in countries where whaling is still legal, or try to grab them off of slow-moving whales in the wild. Or they can wait for a whale to be stranded or accidentally killed.