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High levels of 11-ketotestosterone (11KT) were found (49 to 160 ng ml(-1)) in plasma of Siberian sturgeon females during the end of their reproductive cycle. These levels were measured either by specific radioimmunoassay, or both by specific radioimmunoassay and by UV absorption after HPLC (isocratic conditions, 33% methanol, 26% acetonitrile, 41% water). In order to find the origin of 11KT synthesis, ovaries were incubated (30 min and 2h at 20°C) with tritiated 17-hydroxyprogesterone (17OHP) or with tritiated androstenedione (A4). Testosterone (conversion rate from tritiated 17OHP: 4%) and 11-ketotestosterone (conversion rate from tritiated A4: 1.6%) were identified as metabolites of respectively 17OHP and A4 (TLC, HPLC and crystallization). 11β-hydroxyandrostenedione (11βOHA4) and 11β-hydroxytestosterone (11βOHT) were suggested to be intermediate metabolites. Besides interrenal and blood cells were incubated respectively with tritiated cortisol and tritiated A4. 11βOHA4 was identified in interrenal incubation (yield from tritiated cortisol: 1.2%). 11KT in interrenal (yield from tritiated cortisol: 0.14%), and 11βOHA4 and 11KT in blood cells (yield from tritiated A4: 1.6%), were suspected to be synthesized (TLC, HPLC, acetylation). No significant metabolization of tritiated cortisol could be found in liver. The possible contribution of each of these tissues to high 11KT levels found in plasma is discussed.

Sex steroid levels were dctermined in various commercial fish meals and complcte dicts. The results obtained demonstrate that estrone (E,), 17P-estradiol (El) and androgens (A) (testosterone and 11ketotestosterone), are present in diets in high quantities (up to 935f 350ng/100g for E,, 615f 190ng/100g for El and 1 100&120ng/100g for A) and with considerable variation both between diffcrent dicts, and between differcnt batches of the same diet. These high levels of sex steroids are thought to influence the sex steroid plasmatic Icvels and plasma vitellogenin content in fish.Plasma sex steroid assays in the Siberian sturgeon Acipenser barri show that plasmatic 17 0-estradiol lcvels are ncvcr significantly different betwccn males and femalcs at various stages of oogenesis and spermatogencsis, exccpt in 6 year old fcmalcs in stage IV, which corresponds to the maximum incorporation of vitellogenin. In males the plasma 17P-cstradiol levels are exceptionally high and induce vitellogenin synthesis, as dcmonstrated by various chemical and immunological techniques.

Triploidy as a result of thermal shock exposure of fertilized eggs decreases the growth rate ofOreochromis aureus as compared to their diploid controls, but this is due to the higher female ratio present in triploids (86%) and the lower growth rate of females. When females and males are considered separately, the growth rate is not significantly different in diploids and triploids. Since triploidy results in a malfunctioning steroidogenesis in females (mainly testosterone (T) and 17β-estradiol (E2)), but does not affect the growth rate, it is concluded that female gonadal steroids do not influence growth unless in pharmacological concentrations. These low levels of gonadal steroids are generally accompanied by higher levels of gonadotropin (GtH), but the difference is not always significant.Despite their lower growth rate diploid females have higher plasma concentrations of growth hormone (GH) during several months compared to the triploid females and diploid males. 3,5,3'-triiodo-L-thyronine (T3) levels, however, are comparable between diploid and triploid females (except for 1 month), but higher in diploid males in 4 of the 5 months studied. 11-ketotestosterone (11kT) is always higher in males. These results indicate that the higher growth rate of males may be related to the high circulating levels of T3 and 11kT.