Differential Effects of Food Restriction and Warming in the Two-Spotted Goby: Impaired Reproductive Performance and Stressed Offspring

Abstract

Climate change is a growing threat to marine organisms and ecosystems, and it is already modifying ocean properties by, for example, increasing temperature and decreasing pH. Increasing water temperature may also lead to an impairment of primary productivity and an overall depletion of available zooplankton. Understanding how the crossover between warming and zooplankton availability impacts fish populations has paramount implications for conservation and mitigation strategies. Through a cross factorial design to test the effects of ocean temperature and food availability in a temperate marine teleost, Pomatochistus flavescens, we showed that hindered feeding impacted sheltering and avoidance behaviour. Also, low food availability impaired fish reproduction, particularly male reproduction, as the expression of cyp11b1, a gene with a pivotal role in the synthesis of the most important fish androgen, 11-ketotestosterone, was significantly reduced under a low food regime. In contrast, temperature alone did not affect reproductive success, but offspring showed increased saturated fatty acid content (embryos) and increased lipid peroxidation (larvae). Altogether, food availability had a stronger effect on fitness, showing that coping with elevated temperatures, an ability that may be expected in shallow-water fish, can be indirectly impacted, or even overwhelmed, by the effects of ocean warming on primary productivity and downstream ecological processes.

Fish reproduction in a warming world: vulnerable points in hormone regulation from sex determination to spawning

“…Elevated temperature downregulation of steroidogenesis leads to lower circulating E 2 (similar to high temperature-induced masculinization; see §2a), which diminishes vitellogenin and choriogenin synthesis by the liver [55,56], impairs secondary/vitellogenic oocyte growth and chorion formation, and, ultimately, results in fewer or smaller eggs and lower egg viability [14]. Adult male fish have also been observed in some species to exhibit changes in HPG axis function at high temperatures [14,[56][57][58], although effects for males vary more across species than for females. Reductions in brain gnrh1 mRNA levels, pituitary Fsh β-subunit (fshb) and Lh β-subunit (lhb) mRNA levels, testicular gonadotropin receptor and steroidogenic enzyme expression, and circulating T and 11-KT have been reported in males of some fishes at elevated temperature [14,16,17,56,58].…”

“…Adult male fish have also been observed in some species to exhibit changes in HPG axis function at high temperatures [14,[56][57][58], although effects for males vary more across species than for females. Reductions in brain gnrh1 mRNA levels, pituitary Fsh β-subunit (fshb) and Lh β-subunit (lhb) mRNA levels, testicular gonadotropin receptor and steroidogenic enzyme expression, and circulating T and 11-KT have been reported in males of some fishes at elevated temperature [14,16,17,56,58]. Those changes in HPG axis signalling are likely responsible, in part, for the delayed sperm maturation, lower semen volumes, or reduced sperm motility observed in some fishes subjected to elevated temperature (e.g.…”