Chemically Mediated Mate Location and Evaluation in the Lobster, Homarus americanus

Abstract

Many aspects of lobster (Homarus americanus) social behavior have been shown to be regulated by chemical signals. Female lobsters can determine the sex of sheltered conspecifics from a distance, and will approach and attempt to enter male-occupied shelters. We investigated (1) if female attraction to male-occupied shelters and entering decisions are based upon chemical signals, particularly male urine signals, and (2) if male dominance status and female molt stage influence these female behaviors. Sheltered dominant males were fitted with urine catheters, which collect urine and prevent its release into the environment. We found that males increased urine output in response to female entering attempts. Blocking male urine release significantly reduced the incidence of female shelter approach and the time spent attempting to enter. Artificial release of male urine in the presence of a catheterized male restored female approach but not time spent attempting to enter, while artificial urine release alone did not induce either behavior. Females approached any single male, but seemed to prefer to enter shelters occupied by more dominant males. Premolt and intermolt females differed in their behaviors: premolts showed more interest in approaching dominant male shelters without much effort to enter, while intermolts appeared less likely to approach but more motivated to attempt to enter shelters. This study suggests that both intermolt and premolt female lobsters use one or more chemical signals from sheltered males for location and evaluation of potential mates. Male urine appears to carry compound(s) important for both location and entering decisions, although nonurine chemical or other sensory signals are also implicated during close-up mate evaluation.