Cone snails wander in circles, lose focus with boosted CO₂

Cone snails are normally stealthy hunters, but they become clumsy and unfocused in water with increased levels of carbon dioxide.

Oceans absorb CO₂ from the atmosphere. As atmospheric CO₂ levels rise, those in the oceans do too, changing the chemistry of the seawater.

Cone snails (Conus marmoreus) that spent several weeks in water dosed to simulate CO₂ levels expected at the turn of the century had trouble catching their favorite snack, jumping snails. Only 10 percent caught and ate their prey, compared with 60 percent of snails living in water with current CO₂ levels, researchers report February 1 in Biology Letters.

While the higher-CO₂ snails were more active in general, they moved in “wiggly lines, and some even went in a circle,” says study coauthor and marine biologist Sue-Ann Watson of James Cook University in Townsville, Australia.

In a previous study, Watson showed that jumping snails were less able to escape attacking cone snails when exposed to higher levels of CO₂. Together, the studies are the first to show the effects of ocean acidification on the behavior of both invertebrate predators and their prey, Watson says.