Inhibition of ovarian growth by cadmium in the fiddler crab, Uca pugilator(Decapoda, Ocypodidae)

The effect of cadmium chloride (1 mg/L) on oocyte growth of the fiddler cra b, Uca pugilator, was studied during the slow vitellogenesis phase of ovari an maturation of this carb, In. vivo experiments were done with both intact and eyestalkless crabs, The intact cadmium-exposed crabs Exhibited a signi ficantly lower oocyte diameter than the controls at the end of the 2-week e xposure period, but no significant differences were detected among the eyes talkless crabs, suggesting that the effect of cadmium could be on the sinus gland in the eyestalks, increasing secretion of the gonad-inhibiting hormo ne (GIH), To test this hypothesis, in vitro experiments were done, incubati ng pieces of ovary with and without ea eyestalk tissue, in the presence of thoracic ganglion, needed for oocyte growing due to the secretion of the go nad-stimulating hormone (GSH). only when eyestalk tissue was present in the incubation media was oocyte growth inhibited by cadmium compared to the co ntrols, These results strongly suggest that cadmium acts at least in part t o increase the secretion of GIH from the sinus gland. GIH could then in tur n act by (a) inhibiting secretion of GSH by the thoracic ganglion, (b) dire ctly inhibit the oocytes, or (c) both (a) and (b), (C) 2000 Academic Press.