Temperature dependence of electrocommunication signals and their underlying neural rhythms in the weakly electric fish, Apteronotus leptorhynchus

Weakly electric fish emit an electric communication signal that is controll ed by a highly specialized neural circuit. In Apteronotus, the continuous e lectric organ discharge (EOD) is generated by electrotonically coupled neur ons in the hindbrain pacemaker nucleus, and transient EOD modulations invol ve chemical synapses from descending midbrain and thalamic prepacemaker nuc lei. We characterized the effects of temperature change (18-32 degrees C) o n both the continuous EOD and EOD modulations, chirps, in A. leptorhynchus. EOD frequency was linearly related to temperature (Q(10) = 1.62). By contr ast, the temperature dependence of EOD amplitude changed with temperature. Amplitude increased steeply with temperature below 25 degrees C (Q(10) = 2. 0), but increased only gradually above 25 degrees C (Q(10) = 1.15). EOD wav eform, and consequently harmonic content, was also affected by temperature. The amplitude of the second harmonic was relatively high at both low and h igh temperature and relatively low at intermediate temperatures. The amplit ude of the third harmonic increased monotonically with temperature. Thus, t emperature has qualitative as well as quantitative effects on the productio n of the EOD. Chirp rate (Q(10) = 3.2) had a higher temperature dependence than that of the continuous EOD, which likely reflects its reliance on chem ical rather than electrotonic synapses. In vitro pacemaker firing frequency had a similar, but slightly higher Q(10) (1.82) than that of the EOD frequ ency. Copyright (C) 2000 S. Karger AG, Basel.