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Effects of egfra deficiency on folliculogenesis in juvenile fish ovary. At 25 dpf, the presumptive perinucleolar oocytes at PG stage could be seen in both control (egfra+/−) and mutant fish (egfra−/−). These oocytes continued to grow in size in both genotypes at 35 dpf. At 45 dpf when puberty onset occurs in female zebrafish females, PV follicles with small cortical alveoli started to appear in the oocytes of both control (egfra+/−) and mutant fish (egfra−/−). However, the PV follicles in the control continued to grow with increasing number and size of the cortical alveoli as seen at 55 dpf, whereas the growth ceased completely in the mutant with some follicles containing rudimental cortical alveoli only. Six fish were sampled at each time point for each genotype. PG, primary growth; PV, previtellogenic; black arrow, cortical alveoli; white arrow, nucleoli at the periphery of the germinal vesicle; C, chromatin threads in the germinal vesicle; GC, granulosa cells; TC, theca cells.
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