Furthermore, according to their cellular characteristics, 11 oocytes substages were distinguished: 1) oogonia
(Og), 2) chromatin nucleolus (Cn), 3) early perinucleolus (Pn1), 4) late perinucleolus (Pn2), 5) oil globule (Li), 6) yolk globule (yg), 7) early vitellin globule (Ev1), 8) late vitellin globule (Vo2), 9) postvitelogenic (Pvo), 10) germinal vesicle migration (Gvm), and 11) germinal vesicle breakdown (Gvb) (Fig.
Biometry of oospores and oogonia
of Pythium (Oomycetes): the independent taxonomic value of calculated ratios.
In recent years, dogmatic view that oogonia
and oocytes cannot be renewed in mammals after birth was challenged when Tilly and her colleagues (Tilly et al., 2009) and others (Woods et al., 2012; Pan et al., 2016) reported that the rate of oocyte loss through follicular atresia and ovulation was much higher than the net rate of oocyte decline.
The reserve fund of sex cells was represented by oogonia
, primary growth oocytes, and cortical alveoli oocytes in all examined ovaries.
Based on the microscopic diagnosis of the germ lineage, cysts with a batch of oogonia
surrounded by prefollicle cells, pachytene oocytes, primary growth oocytes, early and late secondary growth oocytes, a full-grown oocyte (Figure 2 and Table 1) and oocyte maturation (Figure 3J) were recognized in S.
The ovaries of the analyzed fish were covered by the tunica albuginea, which emits septa towards the lumen forming the ovigerous lamellae, where there were nests of oogonia
and oocytes at different stages of development.
Histological investigations have suggested that the remarkable size of these hyperplasic ovaries versus normal ovaries is due to a greater proliferation of neoblasts transforming into oogonia
(Gremigni and Banchetti, 1972; Benazzi, 1974).
Nine weeks postfertilisation, the PGCs begin to differentiate into the oogonia
; by 12 weeks, they begin expansion through mitotic divisions; and by 16 weeks, meiosis commences .
Primordial germ cells (PGCs) undergo mitotic proliferation to form a finite number of oogonia
during prenatal life.
Unsuccessful completion of this process can lead to upregulation of apoptosis which is required to eliminate malfunctioned oogonia
and to protect cell survival; this can further promote activation of primordial follicles to primary follicles.
In fish having a reproductively inactive gonad in which no mature germ cells were present, only oogonia
and early stage (pre-vitellogenic) oocytes were present and TG tissue occupied approximately 50% of the gonad complex (Figure 3c).
A new species of Pythium with ornamented oogonia
fromAlgeria, Mycologia, JSTOR.