Assessment of spermatogenesis and plasma sex steroids in a seasonal breeding teleost: a comparative study in an area of influence of a tributary, downstream from a hydroelectric power dam, Brazil
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River damming and building of hydroelectric power plants interrupt the reproductive migration routes and change the major physicochemical parameters of water quality, with drastic consequences for populations of migratory fishes. The goal of this study was to evaluate proliferation and cell death during spermatogenesis and serum profiles of sex steroids in Prochilodusargenteus, from the São Francisco River, downstream from the Três Marias Dam. A total of 257 adult males were caught quarterly during a reproductive cycle in two sites: the first 34 km of the river after the dam (site 1) and the second 34–54 km after the dam (site 2), after the confluence with a tributary, the Abaeté River. Seasonal changes in the testicular activity associated with morphometric analyses of germ cells as well as proliferation and testicular apoptosis support a more active spermatogenesis in fish from site 2, where higher levels of sex steroids and gonadosomatic index (GSI) were also found. In site 1, fish presented low serum levels of testosterone, 17β-estradiol and 17α-hydroxyprogesterone and a low GSI during gonadal maturation. Spermatogonial proliferation (PCNA) and apoptosis (TUNEL) were more elevated in fish from site 1, but spermatocytes were mainly labelled in fish from site 2. Overall, these data demonstrate changes in testicular activity and plasma sex steroids in a neotropical teleost fish living downstream from a hydroelectric dam, supplying new data on fish reproduction in regulated rivers. Moreover, morphometric analyses associated with sex steroids profiles provide reliable tools to assess fish spermatogenesis under environmental stress conditions.
KeywordsProchilodusargenteus Proliferation Apoptosis Sex steroids São Francisco River
The work was supported by grants from Brazilian Research Foundations: FAPEMIG, CNPq and CAPES. We are thankful to the Hydrobiology and Hatchery Station of Três Marias—CODEVASF for furnishing the fish and allowing the execution of this study. We would like to thank Stephen Latham for reviewing the English version of the manuscript and also Dr. Luiz Renato de França and his collaborators for valuable contribution to improve the study.
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