Hepatic transcriptomic and metabolic responses of hybrid striped bass (Morone saxatilis × Morone chrysops) to acute and chronic hypoxic insult

Authors: Beck, Benjamin; Fuller, Adam; LI, CHAO - Auburn University; Green, Bartholomew - Bart; Rawles, Steven - Steve; Webster, Carl; PEATMAN, ERIC - Auburn University

Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2016
Publication Date: 1/21/2016
Citation: Beck, B.H., Fuller, S.A., Li, C., Green, B.W., Rawles, S.D., Webster, C.D., Peatman, E. 2016. Hepatic transcriptomic and metabolic responses of hybrid striped bass (Morone saxatilis × Morone chrysops) to acute and chronic hypoxic insult. Comparative Biochemistry and Physiology. 18(Part D):1-9.

Interpretive Summary: One of the most important factors in the management of aquaculture ponds is the level of oxygen in the water. Periods of low oxygen levels (termed hypoxia) can cause fish to become stressed, lose their appetite, or even result in death. In a previous experiment with hybrid striped bass, we found that hypoxia led to lower food intake, which resulted in the reduced ability to retain the nutrients from food and caused slower growth. In this study we wanted to understand how hybrid striped bass responded to short-term and long-term hypoxia at the molecular level. We found that the levels of over 1,400 genes were changed under conditions of short-term and long-term hypoxia. The genes that changed under hypoxia were primarily related to fat metabolism, cell death, and cell growth. This study offers a detailed view of what happens in the tissues of hybrid striped bass over time during low oxygen conditions, and provides researchers with new information on what biological processes are affected. These findings will enhance future efforts to identify molecular markers in fish that are better suited to tolerate hypoxia in ponds.

Technical Abstract: Hypoxia is a state of oxygen deficiency that can lead to impairment of organismal function or in extreme cases, death. Irrespective of their environment, at some point in their life cycle farmed fish will likely experience varying degrees of hypoxia, particularly during summer months. The temperate basses of the genus Morone are an economically valuable and ecologically important group of fishes, particularly in the United States, where they are popular as both recreational sportfish and farmed foodfish. Previously, we characterized the effects of hypoxia on performance metrics of hybrid striped bass and found that hypoxia led to reduced feed intake, which resulted in lower nutrient retention and growth. However, the precise molecular mechanisms contributing to these disparate phenotypes were unknown. Given the importance of hypoxia on the management and captive rearing of Morone, we examine here the transcriptional responses of hybrid striped bass to acute and chronic hypoxia. We highlight unique and shared signatures between hypoxic treatments and the bioenergetic consequences of chronic oxygen deprivation on hepatocellular function. We found that over 1,400 genes were differentially expressed under conditions of chronic or acute hypoxia. The genes perturbed by hypoxic insult were primarily related to lipid metabolism, cellular death, and cellular proliferation. This study offers a more comprehensive view of the tissue-specific and temporal changes in gene expression during hypoxia, and reveal new mechanisms of hypoxia tolerance in teleosts.