Palaemonetes

The grass shrimp, Palaemonetes paludosus, was studied during a two year period from a population in southern Florida. The shrimp exhibited significant deviations from an expected sex ratio of 1:1 in certain size classes. Males were found more frequently in small to intermediate size classes while females dominated the largest size classes. Recruitment was continuous and ovigerous females were found year-round. Clutch size increased with increasing carapace length of the shrimp. A differential growth rate may account for the variations in sex ratio among different size classes found in this shrimp.

The toxicity of endosulfan, a restricted use pesticida, and copper sulfate, an anti-algal agent, ranks among the highest in all insecticidas. Both chemicals, used in agricultura fields of southern Florida, are known to be highly toxic to aquatic invertebrates. Since Palaemonetes pugio, an extensively studied brackish water shrimp species, has proven to be excellent for toxicological analysis, a closely related freshwater shrimp species, Palaemonetes paludosus, was used as the test species in this study to determine the toxicity of endosulfan and copper sulfate in freshwater. A series of static renewal 96 h bioassays (renewed every 24 h) performed on juvenile P. paludosus resulted in the 96 h lethal concentration (LC50) estimates of 0.24 mug/L (0.24 ppb) for endosulfan and 0.79 mg/L (0.79 ppm) for copper sulfate. The results of this study, when compared to other studies, indicate that P. paludosus is more sensitive to endosulfan and copper sulfate than other similar aquatic invertebrate species and is therefore an excellent toxicological indicator.