Meeting Abstract
Stenothermic teleosts C. aceratus (lack hemoglobin, Hb-) and N. coriiceps (possess hemoglobin, Hb+) live on the Antarctic shelf at ~0°C. Hb- fishes are less tolerant to rise in temperature (T) than Hb+ animals. As part of a larger effort to investigate underpinnings of this difference (see Biederman, Crockett, this meeting), our study examines the neural component of thermal tolerance of these fishes. Freely swimming fishes responded to ambient warming in a biphasic manner, with an increase in motoric behaviors (MB) followed by a decline until loss of equilibrium (LE) occurred (onset temperature (OT) ~14°C in Hb- and ~16°C in Hb+). Both fishes increased locomotion (OT ~6°C in both species, peak at ~9.5°C in Hb- and ~11°C in Hb+) and displayed bilateral pectoral fin movement without motion (OT ~6degC in Hb- and ~10°C in Hb+, diminishing before LE). Maladaptive MB of N. coriiceps included fin and body jerks (OT ~6.5°C) and were all biphasic. C. aceratus displayed no maladaptive MB until seconds before LE. Local warming of the cerebellum in anesthetized fishes resulted in biphasic (an increase followed by a decline) changes in Purkinje cell (PC) action potential firing rate and pattern, with no differences between Hb+ and Hb- species. Irrigation of anesthetized fishes with warmed water (with the cerebellum chilled) led to a decline in PC firing rate in both species (OT lower in Hb+ than in Hb-), followed by cessation of spiking (OT not different between the species). We conclude that a central neural component is involved in responses of both Hb- and Hb+ fishes to warming, and is more susceptible to T elevations in Hb+ species. The relationships between constituents of this component are yet to be determined. Supported by NSF ANT-1341602.
