EFFECT OF CADMIUM ACCUMULATION ON SERUM VITELLOGENIN LEVELS AND HEPATOSOMATIC AND GONADOSOMATIC INDEXES OF WINTER FLOUNDER (PLEURONECTES-AMERICANUS)

Vitellogenin (Vg) is an egg yolk precursor protein that is produced in the liver and transported to developing oocytes in the gonad by the blood. Contaminants in the environment may affect its production by the liver as well as its uptake by the gonad, threatening the development and survival of winter flounder embryos or larvae. In order to study the effects of cadmium contamination on serum Vg levels (measured as alkali-labile phosphate or ALP), female winter flounder were exposed to 25 or 50 mug/L cadmium in seawater for 71 days. The exposure began in early November when Vg production begins, and ended in mid-January, when Vg levels peak. At the end of the exposure period, blood samples were taken from each fish, refrigerated, and allowed to clot overnight. The sera were collected by centrifugation the following day and frozen. Weights of the liver, both gonads, and the entire fish were recorded for later calculation of hepatosomatic (HSI) and gonadosomatic indices (GSI), respectively. Liver samples were also taken for measurement of cadmium levels. Serum ALP levels rose with increasing HSI. Both HSI and ALP decreased with increasing cadmium concentration in the liver. Lower serum Vg may result in lower fecundities for the adults and smaller yolk sacs for the larvae reducing the overall reproductive success of the winter flounder population.