Histological and morphological changes associated with ovarian development of speckeled shrimp Metapenaeus monoceros (Fabricius, 1798) conservation and management

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 on histomorphology viz., pre-vitellogenic, early vitellogenic, late vitellogenic, vitellogenic and spent. Mean values of GSI increased from 0.353 (immature ovary) to 6.98 (fully mature), thus recording a 20-fold increase. Pre-vitellogenic ovary contained primary oogonial cells, secondary oogonial cells and pre-vitellogenic oocytes. Early vitellogenic stage was characterized by the dominance of perinucleolar oocytes. Folliculogenesis commenced during this stage. Late vitellogenic and vitellogenic ovaries were characterized by rough granular cytoplasm which was fully eosinophilic due to accumulation of yolk and the mean ova diameters during these stages were 170 μm and 230 μm respectively. Cortical rods, which are characteristic features of fully mature oocytes of penaeid shrimp were not encountered during the present study in any of the oocyte development stage.