Effects of Hyperoxia on Thermal Tolerance and Indicators of Hypoxic Stress in Antarctic Fishes That Differ in Expression of Oxygen-Binding Proteins

Antarctic icefishes (Family Channichthyidae) are unique in lacking the oxygen carrier hemoglobin (Hb) in their blood, leaving them with only 10% of the oxygen-carrying capacity observed in closely related red-blooded fishes. Previous studies have shown that icefishes have lower critical thermal maxima (CT_MAX) than red-blooded notothenioids and that there is a positive correlation between CT_MAX and hematocrit, indicating that oxygen-carrying capacity may contribute to thermal tolerance. I tested the hypothesis that the lower CT_MAX of icefishes is associated with their reduced oxygen-carrying capacity. I also hypothesized that, as temperature rises, correlates of oxygen limitation (hypoxia inducible factor-1α and lactate) would increase to a greater extent in icefishes compared to red-blooded fishes and that this increase would be minimized under hyperoxic conditions. I sampled <i>Chaenocephalus aceratus</i> (Hb-) and <i>Notothenia coriiceps</i> (Hb+) at three temperatures (ambient, 8°C, and CT_MAX) during an experimental heat ramp (4°C * hr^-1) under normoxia and environmental hyperoxia. I have determined that a 3- to 4-fold elevation in environmental oxygen does not extend CT_MAX in either species despite a 1.7-fold reduction in plasma lactate accumulation and a 2- to 3-fold increase in oxygen utilization as indicated by the differences in arterial and venous oxygen (PaO₂-PvO₂). The absence of an effect of hyperoxia on thermal tolerance may be explained by the lack of increased cardiac (venous) oxygen supply. I have determined that cardiac lactate increases with temperature in the icefish, <i>C. aceratus</i> but not in <i>N. coriiceps</i> and that HIF-1α mRNA levels in the heart are insensitive to increases in both temperature and oxygen. My results indicate that the hearts of icefishes may be especially hypoxia-sensitive and that the inability to maintain cardiac metabolism may contribute to the relatively low thermal tolerances of channichthyid fishes.

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Biological Sciences (Arts and Sciences)

Grantor dc:publisher

Ohio University

Year dc:date

2013

Author dc:creator

• Devor, Devin Patrick

Contributors dc:contributor

• Crockett, Elizabeth

• Animal Sciences
• Biology
• Zoology
• Molecular Biology
• Experiments
• Animals
• Antarctic fish
• thermal stress
• hyperoxic treatment
• icefish
• Notothenioidei

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1362666619

OAI identifier oai:identifier

oai:etd.ohiolink.edu:ohiou1362666619