Histological and morphological changes associated with ovariandevelopment of speckeled shrimp Metapenaeus monoceros(Fabricius, 1798)

Abstract

Histological techniques and gonadosomatic index (GSI) were applied to validate macroscopic classification of ovaries in Metapenaeus monoceros. The five ovarian maturity stages based on gross morphology were correlated with those based onhistomorphology viz., pre-vitellogenic, early vitellogenic, late vitellogenic, vitellogenic and spent. Mean values of GSIincreased from 0.353 (immature ovary) to 6.98 (fully mature), thus recording a 20-fold increase. Pre-vitellogenic ovarycontained primary oogonial cells, secondary oogonial cells and pre-vitellogenic oocytes. Early vitellogenic stage wascharacterized by the dominance of perinucleolar oocytes. Folliculogenesis commenced during this stage. Late vitellogenicand vitellogenic ovaries were characterized by rough granular cytoplasm which was fully eosinophilic due to accumulationof yolk and the mean ova diameters during these stages were 170 µm and 230 µm respectively. Cortical rods, which arecharacteristic features of fully mature oocytes of penaeid shrimp were not encountered during the present study in any of theoocyte development stage.