Influence of the polychlorinated biphenyl preparation Aroclor 1242® on color changes of the fiddler crab Uca pugilator

The melanin in the melanophores of specimens of the fiddler crab, Uca pugilator, exposed to 2, 4, and 8 ppm solutions of the polychlorinated biphenyl (PCB) preparation, Aroclor 1242^®, became less dispersed than in untreated specimens. This effect was dose-dependent. It was probably due to the PCB itself and not to polychlorinated dibenzofurans which are contaminants of commercial PCBs. The decreased melanin dispersion appeared to be related to a decrease in the rate of release of melanin-dispersing hormone from eyestalk neuroendocrine cells into the hemolymph. Eyestalks of crabs kept for 4 days in Aroclor 1242 contained 4 times as much melanin-dispersing hormone as did control crabs. When injected into isolated legs, did hemolymph from control crabs. Aroclor 1242 did not appear to have a direct effect on the pigment-dispersing mechanism of the melanophores.