Editing Sexual differentiation (section)

==Other animals==
The first genes involved in the cascade of differentiation can differ between taxa and even between closely related species. For example: in [[zebrafish]], the first known gene to induce male differentiation is the ''amh'' gene. In tilapia, it is ''tDmrt1'', and in southern catfish, it is ''foxl2''.<ref name=":72">{{Cite book|last=Pandian|first=T. J.|title=Genetic Sex Differentiation in Fish|date=2012-06-05|publisher=CRC Press|doi=10.1201/b12296|isbn=978-0-429-08641-0}}</ref>

In fish, because modes of reproduction range from [[gonochorism]] (distinct sexes) to self-fertilizing [[Hermaphrodite|hermaphroditism]] (where one organism has functioning gonadal features of multiple sexes), sexual differentiation is complex. Two major pathways in gonochores exist: one with a nonfunctional, undifferentiated phase leading to delayed differentiation (secondary), and one without (primary), where differences between the sexes can be noted before hatching.<ref name=":62"/> Secondary gonochorists remain in the [[bipotential]] phase until a biotic or abiotic cue directs development down one pathway. Primary gonochorism, without an intersex phase, follows classical pathways of genetic sex determination but can still be later influenced by the environment.<ref name=":62"/> Differentiation pathways progress, and secondary sex characteristics such as anal fin bifurcation and ornamentation typically arise at [[puberty]].<ref name=":72" />

In birds, research on ''[[Gallus gallus domesticus]]'' has shown that determination of sex is likely cell-autonomous, i.e., that sex is determined in each [[somatic cell]] independently of, or in conjunction with, the [[Cell signaling|hormone signaling]] that occurs in other species.<ref name=":2">{{Cite journal|title=Sex Determination and Sexual Differentiation in the Avian Model|last1=Chue|first1=J|last2=Smith|first2=C|journal=The FEBS Journal|date=2011-01-31|volume=278|issue=7|pages=1027–34|doi=10.1111/j.1742-4658.2011.08032.x|language=en|pmid=21281451|s2cid=24751510}}</ref> Studies on [[Gynandromorphism|gynandromorph]] chickens showed that [[mosaicism]] could not be explained by hormones alone, pointing to direct genetic factors, possibly one or a few Z-specific genes such as [[Doublesex|double-sex]] or [[DMRT1]].<ref name=":2" />