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Notothenioids in Warming Waters: Can the Biophysical and Biochemical Properties of Ventricular Membranes Explain Cardiac Performance in Antarctic Fishes?

Evans, Elizabeth R
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1565963976395966

Abstract Details

2019, Master of Science (MS), Ohio University, Biological Sciences (Arts and Sciences).
Unprecedented increases in sea surface temperatures may pose a significant threat to the finfish fauna associated with the continental shelf of the Southern Ocean, which is dominated, in terms of biomass, by fishes of the suborder Notothenioidei. These animals are noted for their extreme stenothermy, and the absence of circulating hemoglobin (Hb) in one notothenioid family, the Channichthyidae or icefishes. Previous studies have shown that icefishes have a reduced thermal tolerance compared to red-blooded notothenioids from the area surrounding the Western Antarctic Peninsula. Though the mechanism(s) underlying upper thermal limits in notothenioids (or in ectothermic animals more generally) is (are) not fully understood, several studies indicate that inability to maintain cardiac performance at elevated temperatures may play an important role. I hypothesized that biophysical and biochemical properties in the ventricular membranes of notothenioids could help to explain interspecific differences in heart rate variability and cardiac collapse. In this study, I determined membrane integrity (quantified as membrane leakage) and membrane fluidity (quantified as fluorescence depolarization) over a range of temperatures from ambient (0°C) to 20°C in membranes prepared from heart ventricles of six species of notothenioids including representatives from the white blooded family Channichthyidae (Hb-), which also differentially express cardiac myoglobin (Mb), and the red-blooded family Nototheniidae (Hb+). The species investigated included Chaenocephalus aceratus and Champsocephalus gunnari (Hb-/Mb-), Chionodraco rastrospinosus and Pseudochaenichthys georgianus (Hb-/Mb+), and Gobionotothen gibberifrons and Notothenia coriiceps (Hb+/Mb+). In addition, I measured membrane phospholipid composition and cholesterol contents in order to determine the lipids underlying the biophysical properties. I found that membranes from the icefishes exhibit the greatest fluidity, yet membranes of the red-blooded fishes are 1.2-times more thermally sensitive to changes in fluidity. Membranes from the group including C. aceratus and C. gunnari (Hb-/Mb-) display a leakage that is nearly 1.5-fold greater than the leakage of membranes from the group including G. gibberifrons and N. coriiceps(Hb+/Mb+), and membranes from the group of Hb-/Mb- icefishes exhibit the greatest degree of thermal sensitivity to leakage, particularly between 0-5°C. Lipid analysis shows that cholesterol content in membranes from the icefishes (both Mb- and Mb+) is nearly half that of the red-blooded (Hb+/Mb+) fishes, and phosphatidylethanolamine (PE content is approximately 1.5-fold greater in both groups of icefishes. Membrane phospholipids have a higher degree of unsaturation and longer acyl chain length in icefishes than in membranes of red-blooded fishes. Membrane lipid composition can at least partly account for variation in membrane biophysical properties, and when considered together, the biophysical and biochemical data indicate that membrane integrity in the icefishes is more thermally sensitive than in membranes of the red blooded notothenioids. The data are consistent with the hypothesis that limits to cardiac performance are associated with breach of membrane integrity and/or membrane hyperfluidization among notothenioids.
Elizabeth Crockett, Dr. (Advisor)
79 p.
Biochemistry; Biology; Physiology
membrane; cardiac; phospholipid; cholesterol; fluidity; integrity; Antarctic fishes; temperature

Recommended Citations

Citations

  • Evans, E. R. (2019). Notothenioids in Warming Waters: Can the Biophysical and Biochemical Properties of Ventricular Membranes Explain Cardiac Performance in Antarctic Fishes? [Master's thesis, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1565963976395966

    APA Style (7th edition)

  • Evans, Elizabeth. Notothenioids in Warming Waters: Can the Biophysical and Biochemical Properties of Ventricular Membranes Explain Cardiac Performance in Antarctic Fishes? . 2019. Ohio University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1565963976395966.

    MLA Style (8th edition)

  • Evans, Elizabeth. "Notothenioids in Warming Waters: Can the Biophysical and Biochemical Properties of Ventricular Membranes Explain Cardiac Performance in Antarctic Fishes? ." Master's thesis, Ohio University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1565963976395966

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Ohio University and OhioLINK.