MATING BEHAVIOR OF SQUAT LOBSTERS – FIRST INSIGHTS

THIEL, MARTIN; LOVRICH, GUSTAVO A.

Congreso; 7th International Crustacean Congress; 2010

Solid knowledge of reproductive parameters is key to sustainable management of exploited crustaceans. The past decade has seen important advances in our knowledge in the reproductive biology of commercially important decapods, but the mating behavior of squat lobsters has evaded description. Recent studies are offering first insights about the mating behavior of squat lobsters. Females of all three studied species (Munida gregaria, Cervimunida johni, Pleuroncodes monodon) mate during the intermolt phase. Females can produce consecutive broods (2+) during a given reproductive season. Ovaries matured while females incubated a brood and thus latency between consecutive broods is relatively short, i.e. females release larvae and mate again within 1-7 days. Some females of C. johni and P. monodon produced 4 broods without molting in between.   During non-competitive mating interactions (1 male + 1 female), males first hold the females by their chelipeds. In C. johni, precopulatory mate guarding may last for days or weeks, in M. gregaria for hours, while in P. monodon it is extremely brief to absent. The copula begins by the male guiding (C. johni) or pulling (P. monodon) the female into a sternum-to-sternum position. Copula is short (often < 60 s) culminating in spermatophore transfer. After the copula male C. johni immediately engage in postcopulatory mate-guarding, which may last for several hours and usually ends after the female has completed spawning. Postcopulatory mate-guarding is very brief (minutes) or absent in P. monodon. During mating interactions males exhibit only minor agonistic behaviors towards other males as shown by competitive experiments (2 males + 1 female) with M. gregaria.   The species-specific differences in the duration of mate-guarding are also reflected in the degree of sexual dimorphism. The species with the strongest sexual dimorphism (C. johni) exhibits extensive mate-guarding, while the species with minor sexual dimorphism (P. monodon) shows almost no mate-guarding. Since the large, mate-guarding, males are most susceptible to fishing (especially in C. johni), and females of all studied species have to remate for every consecutive brood, it appears recommendable to avoid fishing during the reproductive period, or at least delay it until all males and females have produced one successful brood. Future studies should examine male and female reproductive potential at different densities of competitors, and furthermore whether female brood size decreases during the reproductive season (due to declining fecundity, degenerating pleopods or to male exhaustion of sperm reserves). This information, in combination with sound data on population density and demography in the field, will allow defining practical measures for sustainable management.