Meeting Abstract
23.2 Tuesday, Jan. 4 Monogamy in the sea: social monogamy in two mantis shrimp species inhabiting coral backreefs WRIGHT, ML*; CALDWELL, RL; Univeristy of California Berkeley; University of California Berkeley wrightml@berkeley.edu
Conditions that may lead to the evolution of social monogamy (when males and females form social pairs) include an even sex ratio, even resource distribution, mate guarding, and the need for biparental care. These conditions have been well studied in vertebrates, but little is known about their applicability in non-vertebrates. The socially monogamous mantis shrimps Pullosquilla litoralis and Pullosquilla thomassini provide an opportunity for studying the causes of monogamy in crustaceans. They inhabit coral backreef ecosystems that are characterized by high biodiversity coral heads distributed over sand flats. Both species live in heterosexual pairs in U-shaped burrows in sandflats and exhibit biparental care. To examine how demography and spatial heterogeneity affect pairing behaviors in these mantis shrimps, we recorded the distribution of mantis shrimp burrows along 11 transects in a 625 m^2 quadrant in a coral back reef in Moorea, French Polynesia. Burrows were collected along each transect. The percentage of burrows with eggs, the sex ratio, and percentage of burrows with pairs were determined from the collections. A significantly larger percentage of burrows with pairs had eggs than burrows with single individuals, suggesting that pairs are more reproductively successful than single individuals. Mantis shrimp density increased with increasing distance from coral heads. P. litoralis females were significantly larger than males, while P. thomassini females showed the same trend. There was no effect of either density or distance from coral heads on size, sex ratio, or pairing behavior in either species. This research suggests that the heterogeneity of the coral backreef affects the distributions of P. litoralis and P. thomassini, but further study is needed to determine if this affects the mating behaviors of these species.
