实验围栏内越冬眼镜蛇体温调节和低温耐受性的无线电遥测

RADIOTELEMETRY OF THERMOREGULATION AND THERMALTOLERANCE ON CHINESE COBRAS (NAJA ATRA) OVERWINTERING IN A LABORATORY ENCLOSURE~*

用SB 2T内置热敏无线电发射器、HOBO和TINYTALK数据记录块等电子设备研究实验室围栏内越冬眼镜蛇 (Najaatra)的体温调节和低温耐受性。围栏内总平均气温 (10 6℃ )与总平均巢温 (10 9℃ )无显著差异 ,但气温变化幅度 (- 2 0～ 37 4℃ )大于巢温变化幅度 (6 5～ 14 5℃ )。眼镜蛇体温变化幅度 (3 4～34 1℃ )介于气温和巢温的变化幅度之间 ,平均体温的个体间差异显著 ,总平均体温 (15 0℃ )大于平均气温和平均巢温。最低体温的平均值为 8 9℃ ,与经验估测的眼镜蛇低温耐受极限 (9 0℃ )相近。白天气温高于15℃时能见到巢外调温个体 ,其体温记录次数约占处于此条件下的个体总体温记录次数的 2 9%。巢外调温个体的体温高于处于晚间和白天 15℃以下气温个体的体温 ,亦高于处于白天 15℃以上气温但不进行巢外调温个体的体温。处于白天 15℃以下气温个体的体温低于晚间个体的体温。处于白天 15℃以上气温但不进行巢外调温个体的体温与处于晚间和白天 15℃以下气温个体的体温无显著差异。处于晚间和白天 15℃以下气温个体的体温与气温呈显著的正相关 ,表明眼镜蛇在低温和缺乏热斑块的环境中是体温调节的顺应者。气温高于 15℃时 ,进行巢外调温和不进行巢外调温个体的体温均与气温无关 ,表明眼镜蛇在气温?

We used commercially available electronic temperature recording devices, temperature sensitive radiotransmitters (Holohil, SB 2T) and HOBO and TINYTALK dataloggers with an internal temperature sensor, to study thermoregulation and thermal tolerance in adult Chinese cobras ( Naja atra) overwintering in an enclosure built in our laboratory. After being implanted with radiotransmitters according to procedures outlined by Reinert (1992), cobras were released into the enclosure. We received signals (pulses) from each radiotransmitter at 3 hour intervals from 06:00 to 24:00 h, and visually checked the number of individuals thermoregulating outside the nest during the day. Air and nest temperatures were automatically recorded at 1 2 hour intervals over a 24 hour period, using HOBO and TINYTALK dataloggers, respectively. The overall mean air temperature in the enclosure did not differ from the overall mean nest temperature, but air temperatures varied over a much wider range (-2 0 to 37 4 ℃) than nest temperatures (6 5 to 14 5 ℃). Body temperatures varied from 3 4 to 34 1 ℃, a wider range than that of nest temperatures but narrower than that of air temperatures. The mean body temperature differed among individuals, with the overall mean body temperature (15 0 ℃) being higher than the overall mean air and nest temperatures. The mean lowest body temperature was 8 9 ℃, which was similar to the empirically estimated lower limit (9 ℃) of thermal tolerance for the species. Cobras could thermoregulate outside the nest using available warm spots in the enclosure during daytime when air temperatures were higher than 15 ℃. Recordings of body temperature for these individuals accounted for approximately 29% of the total recordings for all individuals under the same conditions. Cobras thermoregulating outside the nest maintained higher body temperatures than did individuals inside the nest both at night and during the day when air temperatures were either lower or higher than 15 ℃. During the day when air temperatures were lower than 15 ℃ cobras maintained lower body temperatures than at night. Cobras that did not thermoregulate outside the nest when daytime air temperatures were higher than 15 ℃ maintained almost the same body temperatures as at night and during the day when air temperatures were lower than 15 ℃. Body temperature was positively correlated with air temperature when temperatures were lower than 15 ℃, but varied independently with air temperature during the day when air temperatures were higher than 15 ℃. The results imply that this species can be a thermo conformer at low temperatures without warm spots for thermoregulation but a thermo regulator at relatively high temperatures with warm spots. A prolonged exposure of cobras to temperatures lower than 9 ℃ was lethal, but a brief exposure of cobras to the temperatures lower than their lower limits of thermal tolerance does not necessarily increase the mortality of animals.