EFFECTS OF TEMPERATURE ON MITOCHONDRIAL-FUNCTION IN THE ANTARCTIC FISH TREMATOMUS-BERNACCHII

Effects of temperature on O-2 consumption by mitochondria of the Antar ctic fish Trematomus bernacchii were compared with effects obtained wi th mitochondria from tropical (Sarotheridon mossambica) and temperate zone fishes (Sebastes carnatus and Sebastes mystinus). Arrhenius plots of O-2 consumption versus temperature exhibited slope discontinuities (''breaks'') at temperatures (Arrhenius break temperatures: ABTs) ref lective of the species' adaptation temperatures. The ABT for mitochond ria of T. bernacchii is the lowest reported for any animal and is simi lar to 12 degrees C below the value predicted by a regression equation based on ABT data for several invertebrates and fishes. The temperatu re at which the acceptor control ratio (ACR), an index of efficiency o f coupling of electron transport to synthesis of ATP, began to decreas e with rising temperature also reflected adaptation temperature. The d ecrease in ACR with rising temperature began at similar to 18 degrees C for mitochondria of T. bernacchii, in contrast to similar to 35 degr ees C for mitochondria of Sarotheridon mossambica. Maintaining T. bern acchii at 4 degrees C for 2 weeks led to no changes in ABT or in the r esponse of ACR to temperature. The thermal sensitivities of mitochondr ia of T. bernacchii reflect the high level of cold adaptation and sten othermy that is characteristic of Antarctic Notothenioid fishes.