Histopathological health of cultured Pacific oyster, Crassostrea gigas

Abstract

Histopathological health of Pacific Oyster (Crassostrea gigas) was evaluated between different sizes based on the body length and body weight. The samples were collected in an oyster production facility located in Tongyeong City of the southern coastal area of South Korea. For the histological examination, six (big sized) and six (small sized) one-year old oysters and six (big sized) and six (small sized) two-year old oysters were collected for sampling I. For sampling II oysters were divided into three groups, six (big sized) and six (small sized) oysters for each group for sampling II. For sampling III, oysters were collected from two different farms and nine (big sized) and nine (small sized) from each farm were sacrificed in each group. The total length and body weight were11.36 ±1.29 cm and 21.92 ± 5.31 g for big sized oysters and 7.98± 0.82 cm and 9.97 ± 3.24 g for small sized oysters .In the case of sampling II, 12.4± 1.47 cm and 17.51 ± 4.22 g for big sized and 8.18 ± 0.71 cm and 10 .23 ± 2.68 g for small sized . In the sampling III, 12.07± 1.16 cm and 22.10± 5.03 g for big sized and 9.10 ±0.84 cm and 13.24 ± 3.8 g for small sized oysters respectively. Significantly, the hemocytic infiltration in Leydig’s tissue, atrophic changes of digestive gland and parasitic infestation were recognized in the sampled animals. The hemocytic infiltration were detected in the Leydig’s tissue in body, mantle and beneath gastrointestinal tracts with the various intensiveness. The absorptive epithelium of digestive glands showed various degrees of atrophic changes The 3rd sample had protozoan parasitic infestation. The morphological characteristic of parasites revealed the parasites had several points of similarity to Bonamia, causative agent of oyster mass mortality. Although hemocytic infiltration were detected and observed with various degree of severity by using histopathological routine analysis method, there were no significant differences in severity of the lesions between small sized and big sized oyster groups during this examining periodoftheyear(JanuarytoMarch,12).