The stage of ovarian development affects organ expression of vitellogenin as well as the morphometry and ultrastructure of germ cells in the freshwater prawn Macrobrachium amazonicum (Heller, 1862).

The objective was to characterize vitellogenin expression in the ovary and hepatopancreas, and to describe the morphometry and ultrastructure of oocytes, in the freshwater prawn Macrobrachium amazonicum at various stages of ovarian development. Five ovarian stages were defined: (I) immature, (II) maturing, (III) mature, (IV) spawned, and (V) reorganized. Ovaries and hepatopancreas were analyzed by immunohistochemistry for vitellogenin expression. Vitellogenin expression in both ovary and hepatopancreas was predominantly widespread, beginning at Stage I, peaking at Stage III, and decreasing in Stages IV and V. Characterization of the ovary included measurement of the following germ cell types: oogonia (OG), and previtellogenic (PV), early vitellogenesis (EV), advanced vitellogenesis (AV), and mature (M) oocytes. Mean ± SD diameter of OG and EV oocytes in Stages I (14.2 ± 5.5 and 119.8 ± 15.7 µm) and II (17.9 ± 4.8 and 114.3 ± 34.6 µm), respectively, were significantly different from that in Stages IV (16.6 ± 4.7 and 107.0 ± 24.6 µm) and V (14.4 ± 4.1 and 101.0 ± 25.2 µm). Both scanning and transmission electron microscopy enabled identification of EV, AV and M oocytes based on the presence of a nucleus, and the organization and distribution of yolk in the cytoplasm. In summary, vitellogenesis occurred both in the hepatopancreas and ovary, with the ovary expressing vitellogenin starting as early as Stage I. This process promoted accumulation of yolk and growth of oocytes, thus favoring sexual maturation of females. This knowledge may be applied to improve production of farmed M. amazonicum.

Quantification, morphology and ultrastructure of preantral follicles of buffalo (Bubalus bubalis) foetuses.

The objective of this study was to determine the number, morphology and ultrastructure of preantral ovarian follicles of buffalo (Bubalus bubalis) foetuses at different ages. Quantification revealed number of primordial, primary and secondary follicles of 48,857 ± 17,506, 26,000 ± 20,452, 18,428 ± 10,875 and 18,375 ± 19,690, 225 ± 349, 326 ± 288 at 12-34 cm and 35-60 cm crown rump length (CRL), respectively. Follicular diameter values were 28.9 (± 3.4), 34.7 (± 5.9) and 59.4 (± 12.6) µm; oocyte diameters were 21.7 (± 2.8), 24.3 (± 3.4) and 33.0 (± 7.7) µm, and the numbers of follicular cells in the follicle equatorial section were 7.1 (± 1.4), 12.0 (± 2.4) and 13.8 (± 2.4) for primordial, primary and secondary follicles, respectively. The primordial follicle consisted of an oocyte surrounded by a layer of flattened follicular cells with a normally eccentric oocyte nucleus. Dispersed Golgi complex, smooth endoplasmic reticulum, rounded mitochondria and several lipid vesicles were observed in the cytoplasm and cell junctions between the follicle cell membranes and the oocyte. This work describes the number, morphometry and ultrastructure of preantral follicles of buffalo foetuses, concluding that folliculogenesis is established between 8 and 34 cm CRL and that follicle number varies individually and according to age and that further studies are needed in this species.