In this study, a homologous gene named plzfa was identified and characterized in medaka Oryzias latipes. Oryzias latipes plzfa was detected in all the tissues including brain, gill, muscle, liver, intestine, kidney, spleen, testis and ovary using reverse transcriptase (RT)-PCR. plzfa was detected in the oocytes of the ovary and in the spermatogonia and somitic cells of the testis by in situ hybridization. plzfa had a maternal origin with continuous and dynamic expression during embryonic development. plzfa was observed in the brain, neural rod and sensor organs including the eyes, ears and nose during embryogenesis. plzfa was also detected in the neural crest, somite, pectoral fin, intestine and skin. These results indicate that plzfa is a pleiotropic gene that may play major roles in various tissues.

One of the handicaps to successful large-scale controlled reproduction of cultured Chinese sturgeon Acipenser sinensis is that broodstocks are generally not well developed due to the lack of certain stimulating factors in the captive environment to trigger the hypothalamus-pituitary-gonad axis. Hormone treatment is one possible means to promote gonad maturation. The study goal was to ascertain the physiological response of the Chinese sturgeon to the exogenous 17b-estradiol (one of the primary female sex hormones), and estimate its possible effects on gonad development. Serum hormone testosterone (T) and 17b-estradiol (E2), biochemical and haematological parameters, were tested for 10 weeks (injected with E2 for the first 42 days then cultured for a further 28 days) with 4-year-old captive Chinese sturgeon treated in three groups: high dose (HDG, 0.5 mg kg À1 , n = 3), low dose (LDG, 0.1 mg kg À1 , n = 3), and a control group (injected with 5 ml saline/time/sturgeon, n = 2). Results show that serum E2 concentrations increased during the injection stage of E2 in both HDG and LDG groups, and decreased after injections were terminated; serum testosterone showed the opposite trend, which was mirrored in the serum triglyceride concentrations. The five other serum biochemical parameters (total protein, albumin, globulin, total cholesterol, serum magnesium) ascended during the 70-day test period, whereas the blood glucose gradually decreased, with the albumin-to-globulin ratio falling rapidly after an initial increase soon after injection. The predominant hematological finding was a severe anaemia. Blood parameter changes in the HDG were more significant than in the LDG. Depending on the serum hormone and the increase in the biochemical parameters, a potential estrogenic effect of exogenous E2 on Chinese sturgeon might be produced. However, the decrease in values for the hematological parameters indicated that the health status was somewhat impaired after the injection of E2. From the present findings it is concluded that the physiological responses of Chinese sturgeon to E2 supplementation is predominant, in a dose-dependent relationship. The results also show that a lower E2 concentration of 0.1 mg kg À1 may be sufficient to constitute the baseline dosage in any further induced maturation studies.