Histological, histochemical and morphometric properties of oocyte development in zebrafish (Danio rerio)

In this study, histogical, histochemical and morphometric features of ovaries from adult zebrafish (D. rerio) were invastigated by light microscopy. In zebrafish which has asynchronous ovary, oocyte development was observed in four main stages as primary growth stage (PGS), cortical alveolar stage (CAS), vitellogenic stage (VS) and mature oocyte stage (MOS). We analyzed presence and distribution of glycoconjugates in the different structures of the developing oocytes (cortical alveoli, yolk granules, ooplasm and zona radiata) by staining the cross sections with periodic acid Schiff’s (PAS), KOH-PAS, toluidin blue (TB), alcian blue (AB) and aldehyde fuchsin (AF). Cortical alveoli, yolk granules, ooplasm and zona radiata showed glycoconjugates with glycogen and/or oxidable dioles and sialic acid residues (PAS+ and KOH/PAS +). Only zona radiata stained weakly with AF and it showed low acid sulphate glycoprotein content. AB staining was negative to all parts. Measurements showed that oocytes in PGS ranged from 26-143 µm, in CAS 145-400 µm, in VS 326-617 µm and in MOS 341-764 µm in size.