Many types of fish live in variable environments, meaning they must constantly adapt to changes in water salinity, temperature, and chemical content (i.e., pollutants). Therefore, exactly how a fish responds – in order to keep surviving, growing, and reproducing – is a subject of deep interest for scientists and commercial aquaculture producers who rely on controlled environments.
Ongoing work in the Laboratory of Fish Endocrinology and Environmental Physiology, part of the Dept. of Human Nutrition, Food and Animal Sciences, may provide some clues. In three lines of work, the HNFAS investigators are helping to better understand 1) how fish hormones mediate the impact of a rise in temperature, 2) how the actions of these hormones are affected by age, and 3) how chemicals and pollutants released in the environment can interfere with fish growth and reproduction.
“Our NSF-, NIH-, and NOAA-funded projects are targeted to better understand how specialized cells can sense the environment, respond to environmental change, and regulate functions essential for survival, such as salt-and-water balance, as well as functions essential for animal production, such as growth and reproduction,” says Andre Seale, principal investigator who is overseeing the research groups.
The mechanisms responsible for how fish detect changes in salt concentration may be also at play when fish respond to a rise in temperature, notes HNFAS grad student Daniel Woo. He recently presented the evidence at the 45th annual Albert L. Tester Memorial Symposium and the 6th Biennial Conference of the North American Society of Comparative Endocrinology.
“This is because the cells that play an important role in detecting changes in salinity, through changes in volume and release of the hormone prolactin, also increase in volume and prolactin release when the temperature rises,” explains Andre.
Are cells that make those adjustments, in response to environmental changes, affected by age? In a new study, “Age-Dependent Decline in Salinity Tolerance in a Euryhaline Fish,” Andre and collaborators make the case that age does affect those cells, at least in regard to changes in salinity. Their study appears in a recent Frontiers in Aging.
“Older fish have a lower capacity to survive a transfer from fresh water to seawater,” he says. “The ability to acclimate between widely changing salinities is a key characteristic of the Mozambique tilapia, a fish commonly used in aquaculture due to its environmental resilience. At least partly underlying this decline in salinity tolerance is a reduction in the responsiveness of older fish to the hormone, prolactin.”
In a review of ‘endocrine-disrupting chemicals’ – chemicals and pollutants that cause adverse effects in organisms by disrupting the actions of hormones – Fritzie Celino-Brady presents a comprehensive analysis of the experimental approaches used for investigating their effects on fish growth and reproduction. Her article, “Experimental Approaches for Characterizing the Endocrine-Disrupting effects of Environmental Chemicals in Fish,” appears in Frontiers in Endocrinology.