Climate change alters fish spermatogenesis through different mechanisms

Desde hace siete años, jóvenes investigadores de la Universidad de León y de la portuguesa Tras os Montes e Alto Douro (UTAD) se unen para compartir su pasión por la ciencia en las Jornadas ibéricas de Genética y Biotecnología/Jornadas de Genetica e Biotecnología, un congreso que nació en la ciudad Portuguesa de Vila Real y que, desde hace siete ediciones, organiza también la Facultad de Ciencias Biológicas y Ambientales convirtiéndolo así en un evento internacional para los estudiantes de grado, master, doctorado u otros de ambas universidades.

Celebradas del 13 al 15 de marzo de 2024 en Vila Real (Portugal).

Climate change poses serious short and medium-term threats to aquatic environments [1]. In fish, as ectotherm organisms, many biological processes can be affected by temperature. Among them, gametogenesis is a highly temperature-sensitive process, critical for offspring recruitment success [2]. However, the consequences of climate change during gametogenesis are diverse and depend on the different phenomena considered (including an increased average temperature due to global warming, drought, heatwaves, etc.). In fact, our group has previously reported a decrease of sperm quality in rainbow trout (Oncorhynchus mykiss) after a heatwave phenomenon [3]. The aim of this study was to elucidate the underlying mechanisms triggering a decrease in sperm quality after a heatwave. For this purpose, samples from rainbow trout male breeders not exposed (CTRL) and exposed to a thermal stress (TS) mimicking a naturally occurring heatwave event were taken at two sampling points: sampling 1 (S1), climax of the heatwave; and sampling 2 (S2), when normal temperature was restored. Blood plasma samples were taken at S1 and S2 to analyse cortisol and sex hormone testosterone levels through ELISA, and redox balance markers (Total antioxidant status (TAS), and Glutathione peroxidase (GPX) and Superoxide dismutase (SOD) activities) through enzymatic reactions. At S2, gonad samples were also collected to assess the expression of redox response genes (serpinh1, sod1, cat and gpx1b2) by qPCR. In S1, results showed a significant decrease in testosterone concentration and TAS activity in the TS group compared to CTRL individuals (T-test; p<0.05, n=8). In contrast, blood cortisol levels were significantly higher in TS males in respect to the CTRL group (T-test; p<0.05, n=8). In S2, significantly higher activities of GPX and SOD were observed comparing TS with CTRL males (T-test; p<0.05, n=6), while the cortisol values were maintained. However, at the sampling 2 no significant differences were observed in testosterone concentration and TAS activity. At molecular level, the gene expression of serpinh1, sod1, cat and gpx1b2 was also upregulated in the gonads when compared TS and CTRL groups. Present results explain why sperm quality in rainbow trout decreased after a heatwave. Furthermore, we provide new insights on how climate change affects farmed fish and their economic consequences, and allow to design data-driven strategies to mitigate and/or adapt aquaculture to contemporaneous climate change effects.

Work funded by REPHEAT (PID2021-127782OA-100) and BIONATUR (TED2021-131893B-100) projects.

Peer reviewed