EFFECTS OF TEMPERATURE ON MITOCHONDRIA FROM ABALONE (GENUS HALIOTIS): ADAPTIVE PLASTICITY AND ITS LIMITS

Abstract

The effects of temperature on mitochondrial oxygen consumption, membrane fluidity and cytochrome c oxidase activity were measured for five species of eastern Pacific abalone (genus Haliotis) found at different latitudes and tidal heights. Mitochondria were isolated from freshly collected individuals and from specimens that had been acclimated in the laboratory to temperatures spanning the extremes of each species' known habitat temperature range. The temperatures at which Arrhenius plots of respiration rate of mitochondria from freshly collected abalone exhibited sharp breaks in slope were found to correlate with the habitat temperature at the time of capture of each species. Membranes isolated from freshly collected abalone living at warm temperatures (Haliotis cracherodii and H. corregata) were significantly less fluid (as determined by the fluorescence polarization of the probe 1,6-diphenyl 1,3,5-hexatriene) than were membranes from species captured at cooler temperatures (H. rufesens and H. kamtschatkana kamtschatkana). Laboratory acclimation significantly shifted the temperature of mitochondrial thermal inactivation in an adaptive manner in the eurythermal species, H. fulgens, H. corregata and H. rufesens, but did not alter this property significantly for mitochondria from the stenothermal species, H. k. kamtschatkana. Laboratory acclimation resulted in temperature-compensatory changes in membrane fluidity in all species except H. rufesens. The temperatures at which cytochrome c oxidase activity was inactivated also shifted in an adaptive manner in some species. Acclimation of mitochondrial respiration, membrane fluidity and cytochrome c oxidase activity occurred only over the ranges of temperature at which each species is common, suggesting that there is a relationship between acclimatory ability and the biogeographical distribution of congeneric species.