Latitudinal variation in the reproductive biology of the burrowing ghost shrimp Callianassa filholi (Decapoda : Thalassinidea)

Population structure and reproductive ecology of the burrowing ghost shrimp Callianassa filholi Milne-Edwards, 1878 were studied in populations along a latitudinal gradient throughout New Zealand during the breeding season. S ize-frequency distributions revealed unimodal populations, with predominant ly sexually mature shrimp. All populations showed an unbiased sex-ratio, an d there appeared to be no significant difference in size (carapace length, CL) between sexes. At the same time, CL and size at maturity differed signi ficantly between populations; however, a general increase in sizes from nor th to south was not consistent throughout the latitudinal range studied. Th e timing of the breeding cycle differed significantly between populations, and breeding started earlier in southern populations. Number of embryos (fe cundity) increased linearly with female CL at each location, but rates diff ered significantly between populations. Embryo size was not related to numb er of embryos, and the former increased significantly with latitude. With t he exception of embryo size, observed differences in body size/size at matu rity and reproductive timing between C. filholi populations are thought to be determined by food availability rather than temperature. Thus, further s tudy is suggested on these aspects of thalassinid reproductive biology.