ACCUMULATION OF TESTOSTERONE-4-C¹⁴PROPIONATE IN LARVAL GONAD OF THE MEDAKA,ORYZIAS LATIPES*

Uptake and clearance of exogenous estradiol-17β and testosterone during the early development of coho salmon (Oncorhynchus kisutch), including eggs, alevins and fry

“…Selective accumulation of androgens and estrogens has been demonstrated in the undifferentiated gonad of the medaka (Hishida 1962(Hishida , 1965. After immersion treatments similar to those carried out in this study, autoradiography of whole embryos showed that, apart from the yolk, E 2 and T are selectively accumulated mainly by the gonads, skin and brain in coho salmon embryos at the eyed-egg, alevin and fry stage (Piferrer, Shah and Donaldson, unpublished observations), precisely the tissues shown to secrete and/or metabolize steroids in fish (Kime 1993;Fagerlund and McBride 1978;Callard 1983, respectively).…”

“…Furthermore, the uptake and of several natural and synthetic androgens. Investiclearance of gonadal steroids when administered at gations include those of Schreck (1973), in rainbow higher doses, as required for hormonal sex control, trout (Oncorhynchus mykiss); Fagerlund and were investigated in medaka (Oryzias latipes) McBride (1978) and Fagerlund and Dye (1979), in (Hishida 1962(Hishida , 1965, tilapia (Oreochromis mossambicus) and rainbow trout (Johnstone et al 1983), blue tilapia (Oreochromis aureus) (Goudie et al 1986a, b), Nile tilapia (Oreochromis niloticus) (Curtis et al 1988), rainbow trout (Cravedi et al 1989) and in hybrids between 0. niloticus and 0. aureus (Rothbard et al 1990). Characteristics of most of the studies cited above were the use of yearling fish and the oral route of administration.…”

Endocrine and environmental aspects of sex differentiation in fish

“…The physiological effects of steroid treatments on the differentiation of gonads has received very little attention. Selective incorporation and accumulation of radiolabelled steroids have been demonstrated in the gonads of medaka [86][87][88]. In rainbow trout, E 2 or MT treatments performed on all-male and all-female populations at the onset of the first feeding inhibited the in vitro production of steroids in both sexes, and did not induce the gonadal steroid secretion pattern of the opposite sex [48].…”

The lasting impact of Toki-o Yamamoto's pioneering chapter on fish sex determination and differentiation: A retrospective analysis of its contributions to reproductive biology and influences on aquaculture and fisheries sciences

“…In contrast, working with medaka, Yamamoto noted that androgens and estrogens were highly specific in their effects on sex differentiation (e.g., no paradoxical feminization) and, as mentioned above, they required very low doses to induce sex reversal. Based on these observations, and that of Hishida (1962) who localized labeled sex steroids in juvenile gonads, Yamamoto (1969) concluded that a sex steroid-based control of sex differentiation was likely operating in fishes, but also noted that research on the specific steroidal pathways utilized was at a very early stage of what should be "promising areas of research." As you will see in Section 3.2 below, his prediction was correct.…”