Temperature modulates testis steroidogenesis in European eel

[EN] This study evaluates the effects of temperature on hCG-induced spermatogenesis in European eel (Anguilla anguilla), subjected to three thermal regimes: T10: 10 degrees C (first 4 weeks), 15 degrees C (next 3 weeks) and 20 degrees C (last 6 weeks); T15: 15 degrees C (first 4 weeks) and 20 degrees C (last 9 weeks); and T20: constant 20 degrees C for the duration of the experiment. At 10 degrees C, maturation stopped in the A spermatogonial stage (SPG1), and no further maturation was observed until the temperature was >= 15 degrees C. With the aim of explaining these results, the influence of temperature on steroidogenic enzyme gene expression and steroid synthesis was tested. The initial synthesis of androgens (T and 11-KT) increased at SPG1, and was not influenced by temperature. Likewise, the gene expression of the steroidogenic enzymes linked to androgen synthesis (aacyp11a1, aacyp17-I and aa11 beta HSD) also increased at SPG1. In contrast, no correlation was seen between the increase in E2 and the aacyp19a1 gene expression peak in the testes, with E2 increasing as a consequence of the seawater acclimation carried out before hormonal treatment, and peaking the aacyp19a1 gene expression at B spermatogonial stage (SPG2).Aacyp21 gene expression was also higher at SPG2, and this stage was only reached when the rearing temperature was >= 15 degrees C. In conclusion, androgen synthesis is not dependent on temperature, but further maturation requires higher temperatures in order to induce a change in the steroidogenic pathway towards estrogen and progestin synthesis. This study demonstrates that temperature plays a crucial role in European eel maturation, even perhaps controlling gonad development during the reproductive migration. (C) 2016 Elsevier Inc. All rights reserved.This study was funded by the European Community's 7th Framework Programme under the Theme 2 "Food, Agriculture and Fisheries, and Biotechnology", grant agreement no245257 (PRO-EEL), VLC/CAMPUS Program (SP.20140630) and by the MINECO (REPRO-TEMP; AGL2013-41646-R). V.G. and I.M. had predoctoral grants from MINECO (BES-2009-020310) and Generalitat Valenciana, respectively. M.C.V. and M.M. have predoctoral grants from UPV (2011-S2-02-6521) and Generalitat Valenciana (Programa Grisolia), respectively. D.S.P. was supported by MICINN and UPV (PTA2011-4948-I) and was granted with a Short-Term Scientific Mission to make the steroids analyses in Tromso by COST Office (COST Action FA1205: Assessing and improving the quality of aquatic animal gametes to enhance aquatic resources. The need to harmonize and standardize evolving methodologies, and improve transfer from academia to industry; AQUAGAMETE).Peñaranda, D.; Morini, M.; Tveiten, H.; Vilchez Olivencia, MC.; Gallego Albiach, V.; Dirks, R.; Van Den Thillart, GE.... (2016). Temperature modulates testis steroidogenesis in European eel. Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology. 197:58-67. https://doi.org/10.1016/j.cbpa.2016.03.012S586719