CONSPECIFIC RECOGNITION AND HOST CHOICE IN A PEA CRAB, PINNIXA-CHAETOPTERANA (BRACHYURA, PINNOTHERIDAE)

The pea crab Pinnixa chaetopterana (Brachyura: Pinnotheridae) lives in the tubes of the host polychaetes Chaetopterus variopedatus and Amphi trite ornata. While attraction to host odor cues is common in symbiote s, P. chaetopterana resident in Chaetopterus tubes apparently show no attraction to water-borne cues from either host. Because crabs residen t in Amphitrite tubes are significantly reduced in their maximum body size and thus clutch size, switching between hosts should occur. We th erefore tested the hypothesis that the crabs use odor cues from conspe cifics or from the competing crab Polyonyx gibbesi (Anomura: Porcellan idae) when locating a new host. Crabs collected from Amphitrite are si gnificantly attracted to Chaetopterus hosts which contain a mixed sex pair of conspecifics. Females show a strong tendency to avoid hosts co ntaining Polyonyx, but males do not. Neither sex is attracted to unocc upied Chaetopterus or Amphitrite hosts, but both are significantly att racted to isolated conspecifics. This attraction could serve as a reli able means of locating suitable new hosts when switching hosts in the field. Attraction to conspecific odors would also increase the chances of finding a suitable mate already present in a new host.