Chemosensory Orientation of the Rock Crab Cancer irroratus

Abstract

The importance of chemical cues in the foraging behavior of the rock crab, Cancer irroratus, was investigated. Crabs were presented with mussel prey located upstream, downstream, or cross-stream. Trials were conducted under both light and dark conditions. With the prey upstream, the crabs exhibited the shortest search time and 100% searching success. There was a significant difference between flow direction treatments, but there were no significant differences between light and dark treatments. When presented with mussel extract and a seawater control, crabs approached the source of the current. Analysis of search patterns revealed differences in search time, path length and straightness, and total number of turns. Chemoreception was the predominant mode of prey detection and was used in guiding crabs to their prey. Large variabilities in the search path and search path parameters were exhibited, and there was no fixed search pattern for orientation toward food while foraging. It is suggested that rock crabs employed both chemotaxis and rheotaxis for locating odor sources.