For organisms relying on an aerobic metabolism, a constant oxygen (O₂) supply must be available to energy demanding tissues. In this thesis. the effects of hypoxia exposure and altered ionoregulatory demands on O₂ uptake of the larval zebrafish (Danio rerio) were evaluated. In Chapter 2, it was hypothesized that a pre-exposure to hypoxia would alter the O₂ uptake capacity of 4- and 7-days post-fertilisation (dpf) larvae through a modified vasculature system. Additionally, using a genetic knockout line, the role of Hif-1α in regulating cutaneous O₂ flux (JO₂) was tested. It was predicted that hypoxia-exposed larvae would display a higher JO₂ across the body due to a hypoxic, acclimatory response, explained by an increased vascularity and supported by an increased whole-body O₂ consumption (ṀO₂) and decreased critical O₂ tension (Pcrit). Consequently, this response was expected to be negated in the Hif1aa⁻/⁻ab⁻/⁻ larvae. Ultimately, JO₂ measured using the scanning micro-optrode technique (SMOT) remained unchanged between WT and Hif1aa⁻/⁻ab⁻/⁻ and normoxia- and hypoxia-exposed larvae, a finding which was supported by an unchanged vascularity across all treatments. The results from this chapter suggest that changes in hypoxia performance mediated by Hif-1α are unrelated to cutaneous JO₂ and vascularity. In Chapter 3, the aerobic costs of ion transport in 4 dpf larval zebrafish was assessed. We hypothesized that changes in rates of Na⁺ uptake evoked by acidic or low Na⁺ rearing would result in changes in ṀO₂ and/or JO₂, measured at the ionocyte-expressing yolk sac epithelium using SMOT. Ultimately, it was found that the measured JO₂ and ṀO₂ did not correlate with the corresponding Na⁺ uptake rate triggered by the acidic and low Na⁺ rearing environment. Thus, we conclude that the aerobic costs of ion uptake by ionocytes in larval zebrafish, at least in the case of Na⁺, are below detection using whole-body respirometry or cutaneous SMOT scans, providing evidence for a low aerobic cost for ion regulation in zebrafish larvae.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/41258 |
| Date | 30 October 2020 |
| Creators | Parker, Julian |
| Contributors | Perry, Steve |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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