Alarm response of the marine mud snail,Nassarius obsoletus: Specificity and behavioral priority

Although the alarm response is likely an antipredator device, conclusive evidence for its effectiveness in reducing predation is lacking, and the apparent balance between feeding attraction to less related species and alarm response to more related species was further examined by manipulating the snails' diet.

Abstract

Nassarius obsoletus, N. vibex, andN. trivittatus were exposed to juices of conspecifics and taxonomically and ecologically related gastropod species. Conspecific juices caused the strongest alarm responses, while those from taxonomically related species (congeners) induced less pronounced responses. Juices from nonrelated species induced no alarm response with one notable exception, the strong alarm response ofN. trivittatus toUrosalpinx cinerea juices. Nonrelated gastropod species induced stronger feeding responses than more closely related species. The strongest feeding responses, however, were induced by juices from nongastropod mollusks. The apparent balance between feeding attraction to less related species and alarm response to more related species was further examined by manipulating the snails' diet. Starvation resulted in a great reduction of conspecific alarm responsiveness. Following the resumption of feeding, the original responsiveness was again observed. Although the alarm response is likely an antipredator device, conclusive evidence for its effectiveness in reducing predation is lacking. One of the predators ofNassarius obsoletus which may be responsible for maintenance of an alarm response is the green crab,Carcinus maenas.