No abstract

No abstract

No abstract

Antarctic notothenioid fishes are highly stenothermal as a result of living under relatively stable conditions for millions of years. In a warming climate, preservation of membrane structure and function at elevated body temperatures will be critical to the survival of these species. Many ectothermic organisms can respond to thermal variation by altering membrane compositions to preserve membrane structure (i.e., homeoviscous adaptation). It is largely unknown to what extent Antarctic notothenioids possess the capacity to remodel their biological membranes in response to thermal change. We studied effects of thermal acclimation on physical (fluidity, permeability, oxygen solubility) and biochemical (lipid composition) properties of plasma membranes from the gills of an Antarctic notothenioid, Notothenia coriiceps. Animals were acclimated to 0 and 5°C for a minimum of 6 weeks. Plasma membranes were prepared from the gill, and membrane fluidity was measured from 0 to 30°C. Cholesterol contents and phospholipid compositions were analyzed in membranes, and permeability to water was measured in gills at both 0 and 4°C. Oxygen partition coefficients were determined in membrane samples to assess oxygen solubility. Membrane fluidity was reduced in the 5°C‐acclimated group, compared with animals held at 0°C (P<0.0001) and exhibited perfect (100%) homeoviscous efficacy. Membranes from 5°C‐acclimated fish also contained 1.2‐fold greater cholesterol (P<0.01) and 1.1‐fold greater long‐chain fatty acids (i.e., fatty acids with at least 20 carbon molecules per chain) (P<0.05). Water permeability was reduced 1.5‐fold with 5°C acclimation (P<0.05), exhibiting near‐perfect (96%) homeostatic efficacy. In contrast, oxygen solubility of membrane lipids was unchanged. The biochemical alterations with acclimation are in accord with changes in both fluidity and permeability, suggesting lipid restructuring occurred to conserve membrane structure at elevated temperature. Taken together, these results provide evidence of homeoviscous adaptation, and conservation of permeability, with temperature acclimation in gill plasma membranes from an Antarctic notothenioid.Support or Funding InformationSupported by NSF ANT 1341602 and the Ohio University Student Enhancement Award fund.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

It is documented that after temperature acclimation, the killifish Fundulus heteroclitus shows differences in the activities of a number of enzymes including lactate dehydrogenase (LDH), an important catalyst in anaerobic respiration. Less well understood is the temporal pattern of change in activity from one temperature to another. We acclimated fish to 22°C, and shifted the temperature such that an equilibrium was reached at 4°C after 9 hours. During the shift, we collected liver and white muscle samples and assayed homogenates for the specific activity of LDH. After three hours, LDH activity in liver increased from 22.2 µmol·min‐1·mg protein‐1 to 75.1 µmol·min‐1·mg protein‐1 , but then dropped by nine hours to 25.4 µmol·min‐1·mg protein‐1. Conversely, LDH activity in muscle decreased from 154 µmol·min‐1·mg protein‐1 to 61.3 µmol·min‐1·mg protein‐1 and continued to decrease at a slowed rate. These data demonstrate that F. heteroclitus adjusts LDH activity extremely rapidly in response to temperature change. We are currently determining the response to the opposite temperature shift (4 to 22°C), and we plan to assess several enzymes associated with aerobic respiration and other aspects of metabolism. Together, these analyses will help us determine which major metabolic pathways are most critical to this species during rapid temperature change. Grant Funding Source: Supported by the Guerrieri Foundation and the Salisbury University Department of Biological Sciences