Histological observation of gonads during breeding and non-breeding season of Neolissochilus hexagonolepis from Tamor River, Nepal

Abstract

The present investigation was carried out to analyze the histomorphological features of gonads of Neolissochilus hexagonolepis. The study revealed that the gonads of N. hexagonolepis pass through six stages of maturation within a year viz. immature, maturing virgin and recovering spent, ripening, mature, spawning and spent. The testes were found to be of lobular type and the ovaries of the fish were observed to be of cyst ovarian type. The histological study revealed that the testes of N. hexagonolepis undergo considerable changes in shape, size, colour, volume, length and occurrence of various types of spermatogenic cells within their lobules during different phases of reproductive cycle of the fish. Similarly, the histological sections of the ovaries revealed several stages of developing oocytes in the ovigerous lamellae and the developing oocytes were found to be passing through chromatin nucleolus stage, early and late peri-nucleolus stage, yolk vesicle stage, yolk stage and migratory nucleus stage. Several pre-vitellogenic follicles as well as vitellogenic and mature yolky eggs were observed to show atresia in the ovaries of the fish.