Activity of warm receptors in Boa constrictor raised at various temperatures

Nine young specimens of Boa constrictor were raised for 4 years in a climatic chamber at an ambient temperature of 30 degrees C under artificial illumination. Seven boas were raised at 23 degrees C under the same conditions. At the end of the adaptation period, mean body weight of the warm adapted boas was 9.6 +/- 0.8 kg and that of the cold adapted ones 5.9 +/- 0.3 kg. Static and dynamic activities of single specific trigeminal warm fibers were recorded when applying static temperatures of 20, 23, 26, 29, 32, 35 and 38 degrees C and dynamic warming steps of 3 degrees C, the initial temperatures being 20, 23, 26, 29, 32 and 35 degrees C. Eighty-nine warm fibers were examined in the warm adapted and 62 fibers in the cold adapted group. The average static frequencies between 29 and 35 degrees C were higher in the warm adapted animals, the respective values for both groups at 32 degrees C being 16.5 and 12 s-1. The average peak frequencies for dynamic warming were 80 s-1 for both groups, but the temperature of the dynamic maximum was shifted from 32 degrees C in the warm adapted to 26 degrees C in the cold adapted boas. At 32 and 35 degrees C the average peak frequencies were higher in the warm adapted animals. The whole fiber population contained various groups with static maxima between 23 and 35 degrees C. Long-term adaptation modified mainly the static and dynamic discharge of the low-temperature fibers. The fiber group with a static maximum at 29 degrees C showed a crossing of the static and dynamic frequency-temperature curves. In the higher temperature range the warm adapted animals had a higher and in the lower temperature range a lower static and dynamic frequency.