Effects of mirex on the larval development of blue crab

The effects of 0.01, 0.1, 1.0 and 10.0 ppb mirex on the development of blue crabs,Callinectes sapidus, from hatching to first crab stage are described. None of the concentrations of mirex showed any appreciable effect on the larvae during the first five days. Thereafter 0.01 ppb and 0.1 ppb mirex were found to be sublethal. These concentrations had no effect on the duration of development from hatching to megalopa or from hatching to first crab stage. Concentrations of 1.0 ppb and 10.0 ppb mirex proved to be acute. No one stage of development was particularly sensitive to 0.01 ppb mirex, but in the other three concentrations some stages were more sensitive (statistically) than others. The results of residue analyses are given for larvae reared in four concentrations of mirex at different periods of development. Residues of mirex in developmental stages increased with concentration, but biological magnification was greatest in larvae reared in the lowest concentration of mirex and lowest in larvae reared in the highest concentration.