The current study investigated the impact of methoprene during different phases of oogenesis in the freshwater crab Travancoriana schirnerae Bott, 1969 (Decapoda: Gecarcinucidae), a non-target organism abundant in the wetlands of Wayanad, Kerala, India. Sublethal doses of methoprene impaired ovarian growth as evidenced by reduction in gonadosomatic values, fall in mean oocyte diameter and histopathological changes in all the phases of oogenesis. A significant drop in the proportion of mature oocytes in the experimental crabs were noticed, i.e. methoprene treatment delayed the growth of avitellogenic oocytes to previtellogenic and previtellogenic to early, middle or late vitellogenic stages. Reduction in proliferation of oogonia in the germinal zone and ruptured oolemma in chromatin nucleolus and perinuclear stage oocytes was persistent. Histopathological changes in the primary vitellogenic oocytes include karyoplasmic clumping, perinuclear space atresia, shrinkage and vacuolation of ooplasm, reduction in size of yolk globules and vacuolated globules and degeneration of follicle epithelium. Methoprene negatively affected yolk platelet formation as evidenced by the irregularly fused and distorted yolk platelets of late vitellogenic oocytes. The observed cellular deformities possibly suggest the direct effects of methoprene on the oocytes through general metabolism and growth or through hormones controlling ovarian growth.
Effect of Methyl Farnesoate Administration on Ovarian Growth and Maturation in the Freshwater Crab Travancoriana schirnerae
