Female Size as a Determinant of Larval Size, Weight, and Survival Period in the Coconut Crab, Birgus latro

Abstract

Larger females generally produce larger offspring with superior qualities because larger body size can reduce susceptibility to predation and starvation. The removal of larger and older individuals from populations can decrease the survival qualities of offspring through maternal influences, and affect subsequent recruitment. Although negative impacts of larger individual-selective fishing need to be taken into consideration in resource management, there have been very few studies on maternal influences in decapod crustaceans despite the fact that this group includes large numbers of important biological resources. Thus, this study examined the effects of female body size on larval body size, weight, and survival period in the coconut crab, Birgus latro, in laboratory experiments. Ovigerous crabs having well-developed eggs were collected in filed and then first stage zoeae were collected from each female in laboratory. Both larval size and dry larval weight increased significantly with increasing female size. Larvae hatched from larger females showed significantly longer survival periods under non-fed conditions. These results suggest larger coconut crab females produce larvae with superior survival qualities. Present harvesting for coconut crab resources selectively removes larger males despite the fact that coconut crab females only mate with males larger than, or approximately equal to, themselves. Therefore, large females have fewer opportunities to mate under the present harvesting system. Larger male-selective harvesting could have greater negative impacts on the reproductive rate of coconut crabs than expected because larval quality is reduced.