Free and conjugated androgen and progestin levels in the serum of stellate sturgeon (Acipenser stellatus Pallas) males treated with female coelomic fluid By L. Bayunova 1,2 , T. Semenkova 1 , A. V. M. Canario 3 , A. Gerasimov 1 and I. Barannikova 4 1 Central Laboratory of Fish Reproduction, St Petersburg, Russia; 2 Sechenov Institute of Evolutional Physiology and Biochemistry of the Russian Academy of Sciences, St Petersburg, Russia; 3 CCMAR, Universidade do Algarve, Campus de Gambelas, Faro, Portugal; 4 St Petersburg State University, Universitetskaya embankment, St Petersburg, Russia Summary Based on the supposition that female coelomic fluid contents have a certain chemical influence on sturgeons, blood serum concentrations of free and conjugated testosterone (T), 11- ketotestosterone (11KT), 17,20b,21-trihydroxy-4-pregnen- 3-one (20bS), 17,20b-dihydroxy-4-pregnen-3-one (DHP), 11-desoxycortisol (S) and free progesterone (P 4 ) have been measured by radioimmunoassay (RIA) and enzyme-linked immuno-sorbent assay (ELISA) in stellate sturgeon (Acipenser stellatus Pallas) males treated with female coelomic fluid (CF); CF steroid levels have also been analyzed. After treatment a significant elevation of free 20bS and glucuronidated DHP and S levels and the decrease of free T and KT levels have been observed. The obtained data support the idea that the components of CF may play some part in pheromonal effects for sturgeon reproduction. Introduction It is well recognized that sex steroids play an important role in hormonal control of the reproduction in the animal kingdom, including fish (Kime, 1993; Barannikova et al., 2002). Fish use reproductive steroids as endogenous signals between reproduc- tive tract and brain and as exogenous signals (pheromones) for gamete maturation synchronization and for spawning interac- tions among conspecifics. Sex steroids and their metabolites, as well as prostaglandins, have been demonstrated to have pher- omonal effects at least in some Teleostei (see review by Stacey and Sorensen, 2002; Sorensen et al., 2004; Burnard et al., 2008). One of the best known pheromonal systems in teleosts is described for goldfish (Carassius auratus) which releases pre- and post-ovulatory pheromones (Kobayashi et al., 2002; Sorensen and Stacey, 2004). The main pre-ovulatory phero- mones are androstendione, maturation inducing steroid 17,20b-dihydroxy-4-pregnen-3-one (DHP) and its sulphated metabolite, the main postovulatory pheromones are prosta- glandin F2a and a metabolite 15-keto-prostaglandin F2a. Coelomic fluid (CF) has a pheromonal function including behavioral reactions in the spawning fish (Stacey and Goetz, 1982; Kasumyan, 1993; Scott and Vermeirssen, 1994). The amount of CF (or ovarian fluid or peritoneal fluid) which is released together with the eggs is about 10–30% of the total egg volume in the Salmonidae (Lahnsteiner and Weismann, 1999), and about 15–20% – in the Acipenseridae (Ginsburg and Dettlaff, 1969). As the amount of ovarian fluid is high it may surround the eggs during spawning. In brown trout (Salmo trutta f. fario), ovarian fluid in comparison to water, prolongs the duration of sperm motility for >5 min and the fertilizability of eggs for >10 min independent from the quality of the egg batch from which the ovarian fluid derived; these stabilizing effects are related to the inorganic composi- tion of ovarian fluid (Lahnsteiner, 2002). The aim of this investigation was to analyze free and conjugated (sulphated and glucuronidated) testosterone (T), 11-ketotestosterone (11KT), 17,20b,21-trihydroxy-4-pregnen- 3-one (20bS), 17,20b-dihydroxy-4-pregnen-3-one (DHP), 11-desoxycortisol (S) and free progesterone (P 4 ) levels in the CF and in the serum in stellate sturgeon (Acipenser stellatus Pallas) males treated with female CF in order to proof that the CF components may have a role in pheromonal communica- tions in sturgeons. Material and methods Animals Stellate sturgeon (Acipenser stellatus Pallas) wild breeders were captured from the Volga River delta during May–June 2005 and transported (over 18–20 h) to the Zitnenskiy Sturgeon Hatchery (Volga River delta) using a special transport loading boat. After delivery to the Sturgeon Hatchery stellate sturgeon males (n = 7, 4.8 ± 0.17 kg body weight) were placed in the indoor 12.5 m 2 -tank (1 m deep) using a flow of river water (about 0.05 m 3 min )1 ) and held 6 days. Water temperature was 21.2–22°C during holding period in the tanks and during the experiment. After delivery stellate sturgeon females were kept in the outdoor special holding pond (1000 m 2 , 1.2–1.7 m deep; usually the loading density in the pond is one female per 10 m 2 ) using a flow of river water (about 0.5 m 3 min )1 ). Water temperature was 15.5–17.2°C during the holding period in the ponds. After 10 days of the pond holding period four females (n = 4, 7.1 ± 1.16 kg body weight) were maintained in the indoor 12.5 m 2 -tank (1 m deep; flow of river water was about 0.05 m 3 min )1 ) and treated by LH-RH-A (desGly 10 -[D-Ala 6 ]- Pro 9 -NH 2 -Et-LH-RH) to induce final maturation (FM). The temperature was 20.4–21.4°C during this period. Dissolved oxygen was 8.1–8.3 mg l )1 during at experiment and the pH ranged from 7.4 to 7.6. Experimental design The water level in the tank with males was decreased from 1 to 0.14 m during experiment. CF (0.7 L) was collected from ovulated females 24 h before the experiment and stored J. Appl. Ichthyol. 27 (2011), 655–659 Ó 2011 Blackwell Verlag, Berlin ISSN 0175–8659 Received: May 27, 2010 Accepted: January 6, 2011 doi: 10.1111/j.1439-0426.2011.01686.x U.S. Copyright Clearance Centre Code Statement: 0175–8659/2011/2702–0655$15.00/0 Applied Ichthyology Journal of