Comparing androgens and androgen receptor expression in Cobitis taenia Linnaeus, 1958 males and females

Abstract

Summary It is assumed that males and females of spined loach, Cobitis taenia are characterized by different androgen receptor patterns of expression in some of the target tissues and by different concentrations of androgens during their reproductive season. Moreover, still little is examined as to whether tissue sensitivity to androgens follows the changes in androgen concentrations across the fish reproductive cycle. This was verified by determining androgen (testosterone and 11‐ketotestosterone) concentrations in whole fish bodies using ELISA and analyzing AR gene expression in androgen target tissues (gonads, muscles and liver) using RT‐PCR. The partial sequence of the AR gene in C. taenia was also identified. The study was conducted on the spined loach, Cobitis taenia – a multiple spawning species in decline, having hybridized with closely‐related taxa to form allopolyploids. Males (18 individuals) and females (18) were collected from an exclusively diploid population (Legińskie Lake, Baltic Sea basin) in 2013 during pre‐spawning (May), spawning (June) and post‐spawning (August) seasons (six fish per sampling period per sex) using a fry trawl (with a 0.2 cm mesh). The reproductive status of the fish was verified by GSI and gonad histology. The results revealed seasonal variations in the concentration of androgens in C. taenia males and females as well as the dynamic, seasonal nature of AR gene expression in a tissue‐ and sex‐dependent manner. Furthermore, a different seasonal profile of both androgens accompanied by a different pattern of AR expression in various tissues indicated complex physiological mechanisms engaged in AR regulation. These findings appear to be a good physiological basis for further studies using more advanced molecular techniques.