"Whale Lice" Genes Offer Clues to Whale Evolution

Nicholas Bakalar
for National Geographic News
September 28, 2005

Right whales always swim with passengers aboard: small benign parasites called cyamids. The creatures, which 19th-century whalers nicknamed "whale lice," have coexisted with the whales for millennia.

Now scientists at the University of Utah say they can use data about the evolution of these tiny crustaceans to reveal useful facts about the history of right whales.

For example, the differences between certain genes in whale lice groups suggest that the right whale separated into three distinct species five to six million years ago.

"Cyamid populations on opposite sides of the Equator appear to have been fully (or almost fully) isolated for several million years," the study authors write.

"This finding strongly supports the view that the North Atlantic, North Pacific, and southern right whales also have been isolated for several million years and therefore should be considered distinct species."

The researchers report their findings in the October issue of the journal Molecular Ecology.

Finding a Niche

Whale lice don't live freely in the water—they spend their entire lives on whales. The lice move from mother to calf and among whales in close contact with each other.

The three types of right whale each carry three distinct species of cyamid that live in separate ecological niches on the whale's body.

Cyamus ovalis occupies the whale's callosities, the distinctive patches of raised and roughened skin on the whale's head.

Another louse species, C. gracilis, lives in the pits and grooves between the callosities, while C. erraticus takes refuge in the smooth skin of the genital and mammary openings.

The animals are small, measuring roughly one-fifth to three-fifths of an inch (one to two centimeters) long. About 7,500 of these hitchhikers live on a single whale, making their colonies large enough to be visible as white patches on a whale's head and body.

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