As expected, any endocrine pathways pertaining to sex-change involves the major sex hormones.
Cardwell and Liley (1991) assayed the different hormones present at the different stages of the sex-change process in the protogynous stoplight parrotfish (Sparisoma viride). Pre-change females are characterzed by 11-ketotesoosterone, testosterone, and highlevels of 17b-estradiol. Mid-change fish had hgher levels of 11-ketotestosterone nand decreased levels of 17b-estradiol . Males had high levels of 11-ketotestosterone and testosterone. Interestingly, sneaker males had low levels of 11-ketotestosterone, high levels of testosterone, and high levels of 17b-estradiol. Indicative of their respective sex, the fish of different sexes will have different coloration schemes. In this study, Cardwell and Liley suggest that 11-ketotestosterone is one of the key components for color change.
Shapiro (1988) has outlined the hormonal pathway in which the female gonads change to male in the disinhibition model:
In protogynous fish, the ovary secretes prostaglandin as part of normal hormonal cycling Due to a certain response, the prostaglandin stiumulates the hypothalamus, which in turn, stimulates the pituitary to release prolactin and leuteinizing hormone (Ojeda et al., 1977; McMahon et al., 1979). It is this combination of prolactin and leuteinizing hormone which cause the ovary to convert into a functioning testis (Chan et al., 1975). The importance of hormones in this process cannot be understated. It is these messengers which are responsible for stimulating the internal physiology of the fish to undergo sex-change.
