In the seagrass meadows of the Gulf of Mexico, Chicoreus and Phyllonotus marine snails feed on Chione clams by slowly drilling a hole through the shell wall. That process can take a week, while the snails risk losing their prey to another snail or being attacked themselves by fish, crabs or other predators.
High levels of competition should favor faster feeding, said Geerat Vermeij, professor of geology at UC Davis and an author on the paper. The snails can get a quicker meal by drilling through the thinnest part at the shell's edge -- but risk getting their feeding proboscis nipped off by the closing shell.
The pattern of drill holes in fossil shells can give insight into what life in the ocean was like millions of years ago and how it compares to today.
In the laboratory, Gregory Dietl, a postdoctoral researcher at the University of North Carolina who is now at Yale University, UC Davis graduate student Gregory Herbert (now at the University of South Florida) and Vermeij found that when modern-day snails had to compete for food with other snails, they began edge-drilling their prey. When they were separated, they went back to slow wall drilling.
"They have the same gene pool, but you can elicit different behaviors depending on the competitive environment," Vermeij said.
A severe but regional extinction event at the end of the Pliocene
Epoch 1.7 million years ago seems to have tilted the balance from
high competition to low competition, according to
Contact: Andy Fell
University of California - Davis