| Summary: | [EN] Recent studies found that cold seawater stimulates the brain-pituitary-gonad axis and induces early sexual development in male European eels (Anguilla anguilla). These results suggest that cold seawater could be used as a pretreatment to the standard hormonal method applied to induce sexual maturation in order to obtain higher sperm quantity and quality. The objective of this work was to evaluate the effects of pretreatments with cold seawater (10°C) of different duration (0 or control, 1, 2 and 4 weeks) on the process of spermatogenesis and reproductive performance, in a total of 88 male eels; as well as their effect on plasma steroid levels and at the cellular level. The fish were organized in 8 aquaria with 10 fish each, which were distributed, in pairs, in a total of 4 pretreatments (2 aquaria/pretreatment). Ocular, fin, hepatosomatic and gonadosomatic indices were determined. As for steroids, blood concentrations of estradiol (E2), testosterone (T) and 11-ketotestosterone (11-KT) were analyzed. At the testicular histology level, cell percentages of undifferentiated spermatogonia (SPGund), differentiated type A spermatogonia (SPGAdiff) and early type B spermatogonia (SPGBearly) were determined. Males treated at 10 °C for 1, 2 and 4 weeks showed an increase in biometric indices and plasma androgen and E2 levels compared to the control group. In addition, males maintained at 10°C for 4 weeks showed a higher proportion of SPGAdiff compared to SPGAund. These results, therefore, suggest that a cold seawater pretreatment promotes early sexual maturation. However, low sperm quality in the pretreated groups revealed that pretreatment at 10°C followed by traditional hormonal treatment with recombinant human chorionic gonadotropin (hCGrec) at 20°C negatively affects spermatogenesis. Males that were subjected to a water temperature of 10°C for 1, 2 and 4 weeks had a rapid and time-dependent response to hCGrec treatment (compared to control group males maintained at 20°C). However, their spermiation period was ...
|
|---|