MORPHOMETRIC AND REPRODUCTIVE TRAITS OF TROPICAL CARIDEAN SHRIMPS

Life-history traits were studied in one marine and four fresh-water sh rimps from tropical regions of western South America: Palaemon northro pi, P. pandaliformis, Macrobrachium acanthurus, and M. olfersii (Palae monidae). Occasional data are given for Macrobrachium carcinus and an atyid shrimp, Potimirim potirnirim. Size was measured as total body le ngth (TBL), carapace length (CL), and telson length (TL), weight as dr y weight (W), and realized fecundity as number of eggs per female. Siz e and W of eggs were determined in an early stage of development. Rela tionships between measurements of size, weight, and fecundity are desc ribed with regression equations. Significant species- and sex-specific variation was found in the slopes of the allometric TBL-W relationshi p. In the 2 species of Palaemon, females grew to a larger size than ma les; they showed also a steeper W increase with increasing TBL. Opposi te patterns were observed in M, acanthurus and M. olfersii, suggesting different traits on the generic level. The minimum sexable size (mini mum size of males with appendix masculina) was unrelated to the specie s-specific maximum size. Size at the onset of female maturity (minimum size with eggs) was larger in M. acanthurus than in the other species (29 versus 20-22 mm); W at the onset of female maturity increased wit h the maximum size of a species. Regressions of egg number on TBL indi cated the highest overall level as well as the strongest size-dependen ce of fecundity in M. olfersii; these parameters were lowest in P. pan daliformis. The reproductive output (RO:W of egg mass in relation to f emale body W) was lowest in the only marine species studied here, P. n orthropi (14.4 versus 18.6-21.7%). With the possible exception of the RO, the life-history traits of these tropical shrimps appear unrelated to the climatic origin or habitat of a species.