NiCE: The intersection of pollutants and temperature on the neurobiology of reproduction

University Of Oregon Eugene, Eugene OR

Investigators

Abstract

A species will not survive if it does not reproduce. Successful reproduction in fish combines the quality of eggs and sperm with behaviors that result in mixing of these two types of reproductive cells. Observations suggest that changes in temperature and environmental toxins may critically impact reproduction of many fish species by shifting the ratios of males to females in the population, by affecting sperm and egg quality, and by changing reproductive behavior. Understanding how environmental variables affect these aspects of reproduction has broad impact because a decrease in reproductive efficiency of pivotal fish species would imperil important human food sources and damage the ecology of many aquatic environments. This project examines the effects of elevated temperatures and the pollutant dioxin on reproductive success of zebrafish as a stand-in for many fish species. These studies have scientific importance and are novel because the interactions of temperature and pollutants on fish reproduction have not previously been investigated. Results will inform on the mechanisms of reproductive resilience in fish and help predict how resilient fish species will be to future changes in the environment. The project also includes public outreach in the form of a museum exhibit and engaging educational material for children. Acute temperature changes of ~10°C can alter fish sex ratios and reduce gamete quality. Similar temperature changes can also alter neuronal function and synaptic transmission in most vertebrates. How ‘subtle,’ yet persistent, average temperature changes (2-6°C) might affect these properties to modulate reproduction remain unknown. Pollutants such as 2,3,7,8 –tetrachlorodibenzo-p-dioxin (TCDD, dioxin) affect signaling of estrogen, an important hormone for gonad development and for establishing sex-appropriate reproductive behaviors. The researchers hypothesize that temperature rise and low-level pollutants impact the same or interacting neural and/or gonadal pathways to affect fish sexual reproduction. As a consequence, subthreshold perturbations, meaning modest temperature rise and low-level dioxin exposure, combine to produce significant effects on reproductive success. Leveraging the genetic and experimental tractability of the zebrafish, proposed studies examine changes in behavior, neuronal development and function, and sex phenotypes caused by a 2-6°C average increase in temperature over an individual’s lifetime. They also examine the effect of environmentally relevant levels of dioxin on these same variables, and whether temperature rise and dioxin exposure synergize to detrimentally affect zebrafish reproductive efficiency at the neuronal, behavioral, and gonad development levels. This research will provide critical information on the potential of a critical decrease in reproductive efficiency of pivotal fish species, which could reduce an important human food source and damage the ecology of many aquatic environments. This project is supported jointly by Division of Integrative Organismal Systems in the Directorate for Biological Science of NSF and the Kavli Foundation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.