Frontiers in Marine Science (Nov 2015)
Androgens and androgen receptor in different ploidy Cobitis loaches
Abstract
The diploid-polyploid Cobitis populations in Poland are dominated by gynogenetic allotriploid females coexisting with the low number of individuals of parental species, spined loach C. taenia and danubian loach C. elongatoides, and allotetraploids of both sexes. The low number of diploid Cobitis males in mixed diploid-polyploid populations and the data of sterility of tetraploid Cobitis males raise the question about their reproduction ability. The reproductive potential of male fish is strongly subjected to androgenic control. Androgens, testosterone (T) and 11-ketotestosterone (11-KT), delivers a broad range of physiological effects in male fish by binding to androgen receptor (AR). The androgens-AR crosstalk is the key factor sustaining male fish reproductive processes. The aim of the study was to investigate the testicular concentration of androgens (T and 11-KT) and the expression of AR gene and protein in different ploidy Cobitis males: C. taenia, C. elongatoides and tetraploids Cobitis during the reproductive season. All the loaches under study have been karyologically verified. The analysis of androgens concentration was based on ELISA test, whereas the AR gene and protein expression was evaluated by real-time PCR and Western blot, respectively. The study revealed the ploidy-dependent testicular concentration of androgens in Cobitis males. Furthermore, the effect of ploidy level on AR gene and protein expression in the testes of Cobitis males has been demonstrated. In general, tetraploid Cobitis males appered to exhibit lower levels of both AR gene and protein expression when compared to diploid Cobitis males. The results may indicate that disturbances in testicular steroidogenesis together with the disorders in androgenic respone may contribute to sterility of tetraploid Cobitis males. However, further studies have to be undertaken to better explore the reproductive physiology of polyploid Cobitis males in order to explain the functioning of diploid-polyploid populations.
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