Genetic and morphometric comparisons of squat lobster, Munidopsis scobina (Decapoda: Anomura: Galatheidae) populations, with notes on the phylogeny of the genus Munidopsis

Specimens of the galatheid Munidopsis scobina were collected from two stations on the continental slope off Oman, at depths of 900 and 1000 m, using an Agassiz trawl. Starch gel electrophoresis, across 10 enzyme loci, was carried out on 427 specimens. Genetic variability was calculated for both populations using a number of parameters. F-statistics were used to estimate genetic variance within (FIS) and between (FST) populations. Significant deviations from Hardy-Weinberg expectations were detected at one locus (Gotb). Analyses of FIS revealed significant differences from zero at Gotb and Pgm, as a result of heterozygote deficiency. No relationship was observed between size of individuals and genotype. The number of genetically effective migrants per deme per generation (Nem) was calculated using both FST and private alleles methods. Nem values were theoretically sufficient to offset the effects of genetic drift. Additional morphometric analyses were carried out on Munidopsis scobina from the two populations. Individuals were sexed (n=2476 individuals) and ten parameters measured (n=1238). All specimens were examined for parasites (either bopyrid isopod or rhizocephalan). Significant male-biased sex ratios were observed in both populations (p<0.01). In addition, significant differences in size-frequency distributions (p<0.01) were recorded both within sites between sexes, and within sexes between sites; possibly related to a size-dependent response to hypoxia. Significant differences also were observed in mean cheliped length between sexes (p<0.01), potentially indicating that male M. scobina exhibit agonistic behaviour. The genetic relationships of Munidopsis scobina to four other species of Munidopsis (M. crassa, M. parfaiti, M. spinihirsuta and M. subsquamosa) and the confamilial Galathea squamifera were also examined using allozyme loci. Within the genus Munidopsis, pairwise comparisons of genetic identity were within the normal range expected for congeneric species. Comparisons between G. squamifera and Munidopsis spp. were within the range expected for confamilial genera.