Effect of elevated temperature on membrane lipid saturation in Antarctic notothenioid fish

Vanita C Malekar; James D Morton; Richard N Hider; Robert H Cruickshank; Simon Hodge; Victoria J Metcalf

doi:10.7717/peerj.4765

Effect of elevated temperature on membrane lipid saturation in Antarctic notothenioid fish

PeerJ. 2018 May 18:6:e4765. doi: 10.7717/peerj.4765. eCollection 2018.

Authors

Vanita C Malekar¹, James D Morton¹, Richard N Hider¹, Robert H Cruickshank², Simon Hodge³, Victoria J Metcalf⁴

Affiliations

¹ Department of Wine, Food and Molecular Biosciences, Faculty of Agriculture and Life Sciences, Lincoln University, Christchurch, New Zealand.
² Department of Ecology, Faculty of Agriculture and Life Sciences, Lincoln University, Christchurch, New Zealand.
³ Department of Agricultural Sciences, Faculty of Agriculture and Life Sciences, Lincoln University, Christchurch, New Zealand.
⁴ Office of the Prime Minister's Chief Science Advisor, University of Auckland, Auckland, New Zealand.

Abstract

Homeoviscous adaptation (HVA) is a key cellular response by which fish protect their membranes against thermal stress. We investigated evolutionary HVA (long time scale) in Antarctic and non-Antarctic fish. Membrane lipid composition was determined for four Perciformes fish: two closely related Antarctic notothenioid species (Trematomus bernacchii and Pagothenia borchgrevinki); a diversified related notothenioid Antarctic icefish (Chionodraco hamatus); and a New Zealand species (Notolabrus celidotus). The membrane lipid compositions were consistent across the three Antarctic species and these were significantly different from that of the New Zealand species. Furthermore, acclimatory HVA (short time periods with seasonal changes) was investigated to determine whether stenothermal Antarctic fish, which evolved in the cold, stable environment of the Southern Ocean, have lost the acclimatory capacity to modulate their membrane saturation states, making them vulnerable to anthropogenic global warming. We compared liver membrane lipid composition in two closely related Antarctic fish species acclimated at 0 °C (control temperature), 4 °C for a period of 14 days in T. bernacchii and 28 days for P. borchgrevinki, and 6 °C for 7 days in both species. Thermal acclimation at 4 °C did not result in changed membrane saturation states in either Antarctic species. Despite this, membrane functions were not compromised, as indicated by declining serum osmolality, implying positive compensation by enhanced hypo-osmoregulation. Increasing the temperature to 6 °C did not change the membrane lipids of P. borchgrevinki. However, in T. bernacchii, thermal acclimation at 6 °C resulted in an increase of membrane saturated fatty acids and a decline in unsaturated fatty acids. This is the first study to show a homeoviscous response to higher temperatures in an Antarctic fish, although for only one of the two species examined.

Keywords: Antarctic fish; Climate change; Homeoviscous adaptation; Lipid saturation; Membrane fluidity; Membrane remodelling; Notothenioids; Phospholipids; Temperature acclimation; Thermal adaptation.

Grants and funding

The field study for this experiment was supported by Antarctica New Zealand. Funding for biochemical analysis and paper writing was supported by Lincoln University New Zealand. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.