GONADAL STATE OF THE OYSTER CRASSOSTREA ANGULATA CULTIVATED IN TAIWAN

Reproductive health of the common cupped oyster Crassostrea angulata cultivated in Taiwan was estimated through histological examination and semiquantitative analysis of their gonads. Oysters were collected in 4 aquaculture sites along the western coast of Taiwan (Hsiangshan, Chiku, Beimen, and Putai), where the major sources of industrial pollution are located, and off Penghu Island in the southern part of the Taiwan Strait, a comparatively clean resort area. The oysters from Hsiangshan had the lowest gonad maturity index (GMI) and the highest index of pathological alterations (IPA; P < 0.001); greater numbers of oysters with undifferentiated gonads (30%) and a green mantle (66.7%) were also present here. Most prominent gonad pathologies were atresia of oocytes and hemocytic infiltration of gonadal tissue. Oysters from Penghu had the highest GMI and the lowest IPA, whereas oysters from Chiku, Beimen, and Putai had intermediate values. Soft tissues of oysters from Hsiangshan contained 3,761.0 +/- 1,201.0 mu g/g dry weight Cu, 3,761.0 +/- 1,201.0 mg/g Zn, and 1.5 +/- 0.06 mg/g Cd, which is about 17 times, 3 times, and 1.5 times greater than the corresponding metal concentrations in the tissues of oysters from Penghu. Gametogenesis impairment in oysters cultivated in Taiwan are likely caused by environmental pollution.