Dietary supplementation with nerolidol improves the antioxidant capacity and muscle fatty acid profile of Brycon amazonicus exposed to acute heat stress.

An increase in water temperature in the Amazon River has elicited concerns about commercially important fish species associated with food security, such as matrinxã (Brycon amazonicus). Studies have demonstrated the positive effects of diets supplemented with plant-based products that combat heat stress-induced oxidative damage. The aim of this study was to determine whether dietary supplementation with nerolidol prevents or reduces muscle oxidative damage and impairment of the fillet fatty acid profile of matrinxã exposed to heat stress. Plasma and muscle reactive oxygen species (ROS) and lipid peroxidation (LPO) levels were significantly higher in fish exposed to heat stress compared to fish not exposed to heat stress, while plasma superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity was significantly lower. The total content of saturated fatty acids (SFA) in fillets was significantly higher in fish exposed to heat stress compared to fish not exposed to heat stress, while he total content of polyunsaturated fatty acids (PUFA) was significantly lower. Nerolidol prevented the increase of muscle LPO and plasma ROS and LPO levels in fish exposed to heat stress, and partially prevented the increase in muscle ROS levels. Diets containing nerolidol prevented the inhibition of muscle GPx activity in fish exposed to heat stress, and partially prevented the decrease of plasma GPx activity. The nerolidol-supplemented diet prevented the increase of fillet SFA in fish exposed to heat stress, while partially preventing the decrease of PUFA. We conclude that acute heat stress at 34 °C for 72 h causes plasma and muscular oxidative damage, and that homeoviscous adaptation to maintain membrane fluidity can represent a negative impact for fish consumers. A nerolidol diet can be considered a strategy to prevent heat stress-induced oxidative damage and impairment of muscle fatty acid profiles.

Molecular characterization of different preproGnRHs in Astyanax altiparanae (Characiformes): Effects of GnRH on female reproduction.

Gonadotropin-releasing hormone (GnRH) is a key molecule in the initiation of the hypothalamic-pituitary-gonadal axis. Thus, knowledge about GnRH may contribute to the effectiveness of species reproduction. Using a Neotropical tetra Astyanax altiparanae as a fish model species, the GnRH forms were characterized at the molecular level and the role of injected GnRHs in vivo was evaluated. The full-length complementary DNA (cDNA) sequences of preproGnRH2 (612 bp) and preproGnRH3 (407 bp) of A. altiparanae were obtained, and the GnRH1 form was not detected. The cDNA sequences of preproGnRH2 and preproGnRH3 were found to be conserved, but a change in the amino acid at position 8 of the GnRH3 decapeptide of A. altiparanae was observed. All the injected GnRHs stimulated lhß messenger RNA (mRNA) expression but not fshß mRNA expression, and only GnRH2 was able to increase maturation-inducing steroid (MIS) levels and possibly stimulate oocyte release. Furthermore, only GnRH2 was able to start the entire reproductive hormonal cascade and induce spawning.