Marvin Glenn A, Davis Kayla, Dawson Jacob
Department of Biology, University of North Alabama, Box 5048, 1 Harrison Plaza, Florence, AL 35632-0002, USA.
Department of Biology, University of North Alabama, Box 5048, 1 Harrison Plaza, Florence, AL 35632-0002, USA.
Physiol Behav. 2016 May 1;158:121-7. doi: 10.1016/j.physbeh.2016.02.038. Epub 2016 Mar 3.
The low-temperature limit for feeding in some salamander species (Desmognathus, Plethodontidae) has been inferred from field studies of seasonal variation in salamander activity and gut contents, which could not determine whether feeding is more dependent on environmental conditions influencing salamander foraging behavior or prey availability and movement. We performed two controlled laboratory experiments to examine the effect of short-term (acute) low body temperature on predatory behavior and prey-capture efficiency in a semiaquatic plethodontid salamander (Desmognathus conanti). In the first experiment, we quantified variation in the feeding responses of cold salamanders (at 1, 3, 5 and 7°C) to a video recording of a walking, warm (15°C) cricket to determine the lower thermal limit for predatory behavior, independent of any temperature effect on movement of prey. Experimental-group salamanders exhibited vigorous feeding responses at 5 and 7°C, large variation in feeding responses both among and within individuals (over time) at 3°C, and little to no feeding response at 1°C. Feeding responses at both 1 and 3°C were significantly less than at each higher temperature, whereas responses of control-group individuals at 15°C did not vary over time. In the second experiment, we quantified feeding by cold salamanders (at 3, 5, 7 and 11°C) on live, warm crickets to examine thermal effects on prey-capture ability. The mean feeding response to live crickets was significantly less at 3°C than at higher temperatures; however, 50% of salamanders captured and ingested prey with high efficiency at this temperature. We conclude that many individuals stalk and capture prey at very low temperatures (down to 3°C). Our results support a growing body of data that indicate many plethodontid salamanders feed at temperatures only a few degrees above freezing.
一些蝾螈物种（无肺螈科的半蹼螈属）进食的低温极限是通过对蝾螈活动和肠道内容物季节性变化的野外研究推断出来的，这些研究无法确定进食更多地是依赖于影响蝾螈觅食行为的环境条件，还是猎物的可获得性和活动情况。我们进行了两项对照实验室实验，以研究短期（急性）低温对一种半水生无肺螈蝾螈（康氏半蹼螈）捕食行为和猎物捕获效率的影响。在第一个实验中，我们对处于低温状态（1、3、5和7°C）的蝾螈对一只行走的、温暖（15°C）的蟋蟀的视频记录的进食反应进行了量化，以确定捕食行为的较低热极限，而不考虑温度对猎物活动的任何影响。实验组的蝾螈在5和7°C时表现出强烈的进食反应，在3°C时个体之间以及个体内部（随时间）的进食反应有很大差异，而在1°C时几乎没有进食反应。1和3°C时的进食反应明显低于每个更高温度时的反应，而对照组个体在15°C时的反应随时间没有变化。在第二个实验中，我们对处于低温状态（3、5、7和11°C）的蝾螈捕食活的、温暖的蟋蟀的情况进行了量化，以研究温度对猎物捕获能力的影响。对活蟋蟀的平均进食反应在3°C时明显低于更高温度时；然而，50%的蝾螈在这个温度下高效地捕获并摄取了猎物。我们得出结论，许多个体在非常低的温度（低至3°C）下跟踪并捕获猎物。我们的结果支持了越来越多的数据，这些数据表明许多无肺螈蝾螈在仅比冰点高几度的温度下进食。
