Histological analysis revealed significant differences (p<0.001) among treatments in oocyte size and the proportion of previtellogenic and vitellogenic
oocytes (See Table 2).
During the secondary vitellogenesis stage, the histological sections showed a prominence (80%) of secondary vitellogenic
stage oocytes (late vitellin globule oocytes), which occupied a considerable portion of the ovary; a few previtellogenic oocytes (chromatin nucleolus, early chromatin perinucleolus and late chromatin perinucleolus) were found (20%) interspersed among the vitellogenic
Cumaranatunga (1985) and Tyler and Sumpter (1996), observed increased number of atresia in group-synchronous Rainbow trout ovaries at vitellogenic
In this regard, recent reports indicate that apple snails and probably other gastropods have evolved an alternative vitellogenic
mechanism whereby perivitellins, unlike vitelline of other invertebrates, are synthesized as already functional in the albumen gland (Cadierno et al., 2017).
In the ovaries of these females, vitellogenic
oocytes (diameter varied from 525 to 960 [micro]m) had developed simultaneously (Fig.
Frequency of the vitellogenic
oocyte diameter ([micro]m) of the ovaries of the piranha Serrasalmus marginatus sampled on the upper Parana River floodplain.
Histologically, mature ovaries of the analyzed fishes were filled with vitellogenic
oocytes with diameters varying between 586.7 [+ or -] 26.5 and 616.6 [+ or -] 59.4 [micro]m (Fig.
The first one was composed of not vitellogenic
oocytes (2B stage = 70.0%; 2C stage = 54.9%).
oocytes (STAGE IV) showed average diameter ([+ or -] SD) of 797.65 [+ or -] 136.10 [micro]m (Figure 5).
Estradiol alongwith other ovarian steroids, is an important regulator of vitellogenic
growth of the devleoping oocytes .
The oviduct extends posteriorly to unite with the uterus and the main vitellogenic
For means of measurement, only oocytes from mature (MA) females (i.e., females with pre-vitellogenic follicles which are selected for maturation), oocytes from ripening (MR) females (i.e., those with vitellogenic
follicles), and oocytes and eggs from ripe (RE) females (i.e., those undergoing oviposition) were used.