Fig. 3

Histological analysis of wild-type and germ line deficient gonads during sex-differentiation. Hematoxylin and Eosin stained sections of gonads from 25 dpf to 50 dpf. The gonad is outlined by a hashed line in some panels. (A-D) Gonads from wild-type and germ line deficient fish at 25 and 30 dpf. Wild-type gonads have stage 1b perinuclear oocytes with associated somatic pre-follicle cells (white arrowheads) whereas dnd-MO treated siblings have only somatic gonadal tissue. (E-G) Wild-type gonads at 35 dpf. Three developmental phases are found: (E) juvenile ovary, where healthy stage 1b oocytes are present; (F) “transition”, where the oocytes are degenerating (*) and the gonad is in the process of transitioning to a testis; and (G) testis, where oocytes are no longer present, but spermatogonial cells are present in cyst-like structures (black arrowheads denote one spermatogonial cyst). (H) Gonads from 35 dpf dnd-MO injected fish have no germ cells and no apparent organization of testes structures. (I-K) Wild-type gonads at 50 dpf, individuals are at various developmental stages: (I) oogenesis progresses in some animals; (J) gonads in transition are still found, where oocytes are intermixed with testis tissue; and (K) progression of spermatogenesis and clear organization of testis tubules is also apparent. (L) At 50 dpf, morphogenesis of testes tubules becomes apparent in germ line deficient testes. Scale bars are 10 μm.