Pinheiro M S, Andreotti E Silva R A, Santos S A
CPACT, Embrapa, Pelotas, RS, Brazil.
Braz J Biol. 2001 May;61(2):323-7. doi: 10.1590/s0034-71082001000200016.
Three options of water temperatures in a thermal gradient that changed from 22 to 35 degrees C were offered to Pantanal caiman (Caiman croocodilus yacare) hatchlings. Animals from two nests were submitted to temperatures during 19 days (Nest 1 -- 20 caimans caught in the nature hours after hatching), corresponding to 1 to 7 observations periods, and 13 days (Nest 2 -- 20 animals obtained by artificial incubation) relative to observation period 8. Caimans remain fasting during experimental period. Hatchlings were allocated in a enclosure containing three styrofoam boxes (120 L) disposed side by side enclosed by wire netting and filled with water to the top. Thus, the animals were free to access the boxes, which temperatures were changed at the end of each observation period to avoid position effects. Air temperature was keep close to 22 degrees C by air conditioning and water temperature was controlled by thermostats. The trial was divided in three phases determined by elimination of the less frequented temperature and its substitution by another temperature. In a first phase of the experiment that contained 1, 2 and 3 observation periods, the thermostats were regulated to 22 degrees C (BoxD), 26 degrees C (BxC) and 32 degrees C (BxA). In phase 2 to 26 degrees C, 29.5 degrees C (BxB) and 32 degrees C, including 4, 5 and 6 periods. In the third phase that included 7 and 8 periods, the thermostats were adjusted to 29.5 degrees C, 32 degrees C and 35 degrees C (BxE). The number of caimans in each box was recorded two to three times a day (8:00, 14:00 and 17:00h) before pointed water temperature. Mean water temperatures (+ standard deviation) and respective caiman frequency means by box/temperature were: Phase 1 (BxD/22.3 +/- 1.2 degrees C - 10.3%; BxC/27.0 +/- 2.4 degrees C - 32.0% and BxA/31.2 +/- 1.1 degrees C - 57.6%); Phase 2 (BxC/26.6 +/- 2.8 degrees C - 13.3%; BxB/29.3 +/- 2.2 degrees C - 27.7% and BxA/31.3 +/- 1.2 degrees C - 59.0%) and Phase 3 (BxB/29.5 +/- 3.6 degrees C - 23.7%; BxA/31.0 +/- 2.2 degrees C - 31.9 and BxE/34.0 +/- 2.2 degrees C - 44.4%). Observing that in the phases 1 and 2 the box with hottest water (CxA) was more frequented. In the phase 3, the difference between higher and smaller frequency straiten to 20.7%, in relation to almost 46.5% in phases 1 and 2, indicating that water temperatures between 29.5 and 35 degrees C resulted in body temperatures more next to the comfort zone, in the experimental conditions.
研究人员为潘塔纳尔凯门鳄（Caiman croocodilus yacare）幼鳄提供了水温在22至35摄氏度之间呈热梯度变化的三种选择。来自两个巢穴的幼鳄分别接受了19天（巢穴1——20只在自然环境中孵化数小时后捕获的凯门鳄）和13天（巢穴2——20只通过人工孵化获得的幼鳄）的水温处理，分别对应1至7个观察期，以及相对于观察期8的13天。在实验期间，凯门鳄一直处于禁食状态。幼鳄被放置在一个围栏中，围栏内并排设置了三个聚苯乙烯泡沫箱（120升），并用铁丝网围起来，箱内注满水至顶部。这样，幼鳄可以自由进入这些箱子，每个观察期结束时会改变箱子的水温，以避免位置效应。通过空调使空气温度保持在接近22摄氏度，水温由恒温器控制。试验分为三个阶段，通过剔除较少被选择的水温并替换为另一种水温来确定。在实验的第一阶段，包括1、2和3个观察期，恒温器被调节至22摄氏度（箱D）、26摄氏度（箱C）和32摄氏度（箱A）。在第二阶段为26摄氏度、29.5摄氏度（箱B）和32摄氏度，包括4、5和6个观察期。在包括7和8个观察期的第三阶段，恒温器被调整至29.5摄氏度、32摄氏度和35摄氏度（箱E）。在记录指向的水温之前，每天两到三次（8:00、14:00和17:00）记录每个箱子中的凯门鳄数量。各箱/水温的平均水温（±标准差）和相应的凯门鳄频率平均值为：第一阶段（箱D/22.3±1.2摄氏度——10.3%；箱C/27.0±2.4摄氏度——32.0%；箱A/31.2±1.1摄氏度——57.6%）；第二阶段（箱C/26.6±2.8摄氏度——13.3%；箱B/29.3±2.2摄氏度——27.7%；箱A/31.3±1.2摄氏度——59.0%）；第三阶段（箱B/29.5±3.6摄氏度——23.7%；箱A/31.0±2.2摄氏度——31.9%；箱E/34.0±2.2摄氏度——44.4%）。可以观察到，在第一阶段和第二阶段，水温最高的箱子（箱A）被选择的频率更高。在第三阶段，最高频率和最低频率之间的差异缩小到20.7%，而在第一阶段和第二阶段这一差异接近46.5%，这表明在实验条件下，29.5至35摄氏度的水温使体温更接近舒适区。
