You are here:
PROLIFERATIVE LESIONS IN SWIMBLADDER OF JAPANESE MEDAKA ORYZIAS LATIPES AND GUPPY POECILIA RETICULATA
Citation:
Fournie, J W., W. E. Hawkins, AND W W. Walker. PROLIFERATIVE LESIONS IN SWIMBLADDER OF JAPANESE MEDAKA ORYZIAS LATIPES AND GUPPY POECILIA RETICULATA. DISEASES OF AQUATIC ORGANISMS 38:135-142, (1999).
Description:
Thirteen cases of proliferative lesions of the swimbladder were encountered in Japanese medaka Oryzias latipes and guppy Poecilia reticulata from about 10,000 medaka and 5,000 guppies used in carcinogenicity tests and histologically examined. Two of the four cases from medaka and eight of the nine from guppies occurred in untreated control specimens. The lesions affected the gas gland epithelium and included hyperplasia, adenoma, and adenocarcinoma. One medaka had hyperplasia of the gas gland epithelium and in one guppy the gland was enlarged with an increase in the number of epithelial layers. Gas gland adenomas, three cases in medaka and one in the guppy, were typically larger than the hyperplastic lesions formed expansive masses up to 1 mm in greatest dimension, and exhibited a solid or glandular growth pattern and mild cellular pleomorphism. Adenocarcinoma was the most advanced lesion and all seven cases occurred in guppies. Adenocarcinomas sometimes filled the entire swimbladder and measured up to 2.5 mm in diameter. Cells of adenocarcinomas were highly pleomorphic, with atypical nuclei, and an elevated mitotic activity. Because most of these tumors occurred in fish from control groups or in tests with noncarcinogenic compounds, the lesions observed here are probably spontaneous rather than chemically-induced. Their rare occurrence, however, makes swimbladder proliferative lesions in small fish carcinogenesis models sensitive indicators of compounds that might target cells of the gas gland.