C. Elise Hopkins

Honors in Marine Biology

Major: Marine Biology Minor: Oceanography

Supervisor: Christopher Finelli, Biology and Marine Biology

Odor Mediated Climbing Behavior of Littoraria irrorata When Exposed to Blue Crabs

The salt marsh periwinkle, Littoraria irrorata, migrates vertically on the stems of Spartina alterniflora to escape tidal inundation and benthic predators, especially blue crabs (Callinectes sapidus), that invade the marsh at high tide. These snails also possess chemoreceptive abilities which enable them to detect predator presence and other environmental signals. We hypothesized that the presence of crabs or crab odor would cause snails to move higher on Spartina stems. To test this hypothesis, we conducted two field caging experiments in the tidal marsh adjacent to Masonboro Sound, near Wilmington NC. In spring 2008, we tested the response of snails in the field to seawater conditioned by blue crabs against an untreated seawater control. Contrary to our expectation, snails exposed to crab-conditioned water tended to be lower on Spartina stems at low tide. In fall 2009, we tested the response of snails to intact, non-feeding blue crabs. The results of this experiment suggested that snails exposed to crabs tended to be higher on Spartina stems during high tide. We also developed a lab assay to examine the snail-crab interaction in a more controlled manner. The assay shows that crabs and crab water but not ammonium, stimulates snails to climb higher on stems.