Histological observations on the oocyte development in the Picnic seabream, Acanthopagrus berda (Forsskål 1775).

Histological analysis was carried out on ovarian development in the picnic seabream, Acanthopagrus berda (Forsskål 1775) caught in the estuarine waters of Calicut, Kerala, India from January to December 2016. Four developmental phases of oocyte development were identified viz., oogonia proliferation and transformation into the primary oocyte, primary growth phase, secondary growth phase and maturation phase and these are similar to those described for other species. The reproductive development process begins in a very young ovary with the formation of oogonia, the cells originally derived from special primordial germ cells formed early in the embryonic development; their multiplication and differentiation are followed by the release of mature oocytes. Oocyte development stages observed in A. berda were chromatin nucleolus, early perinucleolar, late perinucleolar, lipid vesicle stage I oocyte, lipid vesicle stage II oocyte, primary yolk granule stage, secondary yolk granule stage, tertiary yolk granule stage, hydrated oocyte and atretic oocyte. The oocytes entered the maturation phase when they attained the maximum size of 459.6±71.83 µm. Histological examination of the mature ovaries showed the presence of all the different oocyte stages in the ovary of A. berda with an asynchronous mode of ovarian development shortly before spawning, indicating that the species is a multiple spawner. [ABSTRACT FROM AUTHOR]