The undifferentiated gonad in most teleosts differentiates into one ovary or one testicle during ontogenesis, and is composed of PCGs and somatic cells, as in other vertebrates Hoar ; Parker et al. In the zebrafish, the maternal components that specify PGCs are segregated into four groups during segmentation Raz Fig 1 illustrates a statement in an Alexandrian manuscript from the first century AD.
Anim Genet 38 1 — In tilapia and medaka, Foxl2 expression is initially detected in the somatic cells surrounding germ cells in gonads that have started ovarian differentiation. Mol Interv — Mol Endocrinol 21 3 —
This supports the hypothesis that, as in other vertebrate groups, Foxl2 plays an important role in the ovarian differentiation of teleosts Liu et al. In this species, Dax1 is thought to be involved in the regulation of sexual gonadal differentiation, inhibiting transcriptional activation of genes that code for steroidogenic enzymes, similarly as in mammals Wang et al.
Sexual determination and differentiation in teleost fish. However, the triggering factor by which temperature acts has not been determined yet Miller et al. The patterns of gonadal sexual differentiation are diverse, and species may be hermaphroditic or gonochoristic, some of the latter displaying juvenile hermaphroditism.
According to Bull , genetic systems in vertebrates may operate by polygenic control mechanisms, by dominant genes simultaneous with autosomic controls and by sex chromosomes. In terms of the actual biological sculpturing involved, I haven't really been able to find much.