RT: Analysis of embryo production in a caridean shrimp guild from a tropical seagrass meadow

Embryo production was compared among nine caridean shrimp species inhabiting seagrass meadows in a tropical location, the north coast of Puerto Rico. Reproduction occurred through-out the year in all species. During a short life span (less than one year), females reproduced continuously after reaching maturity, producing successive broods of embryos at short inter-vals. Analysis of allometry in brood size (number of embryos/brood) as a function of female size (carapace length) was done by calculating slopes of brood size/female size regressions with log transformed variables. Increase in brood size with female size was isometric in seven species and showed positi veallometry in two others. However, the relationship of species mean log brood size on species mean log female size was negatively allometric, indicating that females of smaller species produced relatively larger broods for their size than did females of larger species. Analysis of covariance corroborated this conclusion. Log brood size means adjusted for differences in female size were significantly different among species, and adjusted species brood means were negatively correlated with species female size. The mechanism for enhanced reproductive output (in terms of brood size) in smaller species is unclear. In some crustacean groups, reduced embryo size has been selected for as a means of increasing brood size. Additionally, since embryo size and incubation period (duration of embryonic develop-ment) showed a significant positive correlation in this group of caridean species, smaller embryo size would also result in shorter incubation periods and thus larger numbers of broods per reproductive period. However, there was no relationship between species embryo size and species female size in this group, indicating that d inferential selection among species on embryo size as a means of increasing reproductive output has not occurred.