EFFECT OF CADMIUM CHLORIDE ON PHYSIOLOGICAL COLOR CHANGES OF THE FIDDLER-CRAB, UCA PUGILATOR

The effects of cadmium exposure on the color change system of the fidd ler crab, Uca pugilator, were determined. Crabs were either immersed i n 10 ppm cadmium chloride solutions or injected with 8.5 mu g cadmium/ g body weight. The crabs exposed to cadmium,, either by injection or i mmersion, were less able to bring about dispersion of the pigment in t heir integumentary melanophores than were the unexposed crabs. Cadmium did not affect the;melanophores directly. This decreased black pigmen t dispersion was apparently due to effects of cadmium on the neuroendo crine processes that control the melanophores. The neuroendocrine comp lex in the eyestalk is the source of a black pigment-dispersing hormon e (BPDH). Eyestalks of crabs kept in clean water contained 3.27 times more BPDH than did the eyestalks of the cadmium-exposed crabs. Histolo gical studies revealed that cadmium exposure results in depletion of t he neurosecretory material in the eyestalks and brain. It is hypothesi zed that cadmium inhibits BPDH synthesis in neurosecretory (neuroendoc rine) cells, resulting in decreased ability of exposed crabs to disper se their black pigment. (C) 1995 Academic Press, Inc.