Table 1. Criteria for accurate staging of early meiotic oocytes.

Characteristics are details of specific oocyte stages, including size, morphological features, molecular markers and cellular organization, defining them as criteria for correct oocyte staging. An updated nomenclature for these stages is provided. The features described are depicted schematically in Fig. 6A.

Stage	Nomenclature	Mitosis or meiotic function	Size (diameter in µm)	DNA condensation	Telomere distribution	Nucleolus	Nuclear shape	Centrosome	Cellular organization
Oogonia	Oog	mitotic	9–11	Not condensed	Random intranuclear	1–3 in the center of the nucleus	Round	Perinuclear	Cyst
Leptotene	St.IA-Leptotene	Double strand breaks formation and beginning of synapse	8–9	Does not appear condensed	Radial on nuclear envelope	1–3 in the center or periphery	Round	Perinuclear	Nest (likely a cyst)
Early Zygotene	St.IA-Early Zygotene	Synapse	10–12	Does not appear condensed	Tightly clustered in one pole of the nuclear envelope	1 in the periphery of the nucleus	Round	Perinuclear, apposing telomere cluster	Nest (likely a cyst)
Late Zygotene	St.IA-Late Zygotene	Synapse	13–16	Condensed into chromosomes	Clustered in one pole of the nuclear envelope, but more loose	1 in the periphery of the nucleus	Round	Perinuclear, apposing telomere cluster	Nest (likely a cyst)
Pachytene	St.IB-Pachytene	Double strand breaks repair and Homologous recombination	17–19	Condensed into chromosomes	Radial on nuclear envelope	1 in the periphery of the nucleus	Nuclear cleft	In the nuclear cleft cytoplasm	Individual (starting to accumulate somatic follicle cells)
Diplotene	St.IB-Diplotene	Chiasmata persist, meiosis arrested in dyctate	20+	Condensed – “lampbrush chromosomes” starting at diplotene	Random intranuclear	Multiple in the periphery of the nucleus (“perinucleolar stage” starting at diplotene)	Nuclear cleft (most prominent at 20–25µm and gradually receding, complete sphere at ~45–50µm)	In the nuclear cleft cytoplasm, dissociate at >25µm	Individual (continuing folliculogenesis)