Agonistic behaviour and reproductive biology of squat lobsters

Abstract

Squat lobsters are ubiquituous in many benthic habitats yet very little is known about theirbehavioural ecology. In this contribution we synthesise reports of agonistic and reproductiveinteractions of squat lobsters in order to understand the evolution of behavioural and reproductivetraits. Squat lobsters often occur in dense aggregations where individuals frequently interact but theseinteractions rarely escalate to higher levels of aggression. Ritualised behaviours may reduce thepossibility of agonistic interactions and, if escalation occurs, autotomy can help to lower the risk ofcannibalism. Reproduction in most studied species is highly seasonal, and larvae are usually releasedduring periods of high primary production. Depending on environmental conditions, females mayproduce more than one brood during a reproductive season. Female squat lobsters mate during theintermoult phase and can incubate several consecutive broods without moulting in-between. The mainmoulting period is usually after the reproductive season and starts slightly earlier in males than infemales. Sexual dimorphism in body size and chela strength is suggestive of strong sexual selection:in shallow-water species males are usually larger and stronger than females indicating that theycompete for access to reproductive females. Present knowledge suggests the existence of twoprincipal mating strategies: (i) ‘pure search’ where males roam in search for receptive females, matinginteractions are brief and the couple separates quickly after sperm transfer; (ii) ‘search and defend’where males guard reproductive females for extended periods before, and occasionally also after,copulation. Each species usually adopts just one mating strategy but initial observations suggestontogenetic changes in male mating strategies for some species. A solid understanding of matingsystem evolution in squat lobsters requires better knowledge of the mating behaviours in differentspecies and under different environmental scenarios (e.g., population densities). This information isconsidered particularly essential to achieve sustainable management of the populations of exploited species.