Kreiter Nancy A, Wise David H
Department of Biological Sciences, University of Maryland, Baltimore County Campus, 21228, Baltimore, MD, USA.
Department of Biology, College of Notre Dame of Maryland, 21210, Baltimore, MD, USA.
Oecologia. 2001 May;127(3):417-424. doi: 10.1007/s004420000607. Epub 2001 May 1.
We conducted a food supplementation field experiment to test two hypotheses: (1) fecundity of the fishing spider Dolomedes triton is limited by a shortage of prey, and (2) the increased movement of adult female D. triton exhibited upon maturation is a foraging adaptation to lessen the impact of food limitation on egg production. Free ranging, uniquely marked adult female fishing spiders were assigned either to a food-supplemented group that received crickets in addition to their natural diet, or to a control group. Juvenile female spiders were also marked and their movement patterns were recorded, but juveniles were not offered supplemental food. Food-supplemented adult females gained weight at a faster rate and hatched more than twice as many offspring as control females. Adult females in the control group moved greater distances per day than did juvenile females. Supplemented adult females moved shorter distances per day than control females, and the movement pattern of fed adults did not differ from that of juveniles. These results support the hypotheses that adult female D. triton are food limited, and that the increased movement of adult females is a switch in foraging behavior that occurs during the reproductive period. Our finding that natural prey shortages limit egg production contrasts with laboratory-based studies of food limitation in the genus Dolomedes, and contradicts a basic assumption of a recent hypothesis that sexual cannibalism in Dolomedes is non-adaptive. These discrepancies highlight the importance of insights gained from field experiments with natural populations.
我们进行了一项食物补充野外实验，以检验两个假设：（1）捕鱼蛛（Dolomedes triton）的繁殖力受猎物短缺限制；（2）成年雌性捕鱼蛛成熟后活动增加是一种觅食适应性行为，以减轻食物限制对产卵的影响。将自由放养、带有独特标记的成年雌性捕鱼蛛分为两组，一组为食物补充组，除自然饮食外还喂食蟋蟀，另一组为对照组。幼年雌性蜘蛛也做了标记并记录其活动模式，但未给幼年蜘蛛提供补充食物。食物补充组的成年雌性蜘蛛体重增加更快，孵化的后代数量是对照组雌性蜘蛛的两倍多。对照组的成年雌性蜘蛛每天移动的距离比幼年雌性蜘蛛更远。食物补充组的成年雌性蜘蛛每天移动的距离比对照组雌性蜘蛛短，且进食后的成年雌性蜘蛛的活动模式与幼年蜘蛛没有差异。这些结果支持了以下假设：成年雌性捕鱼蛛受食物限制，且成年雌性蜘蛛活动增加是繁殖期发生的觅食行为转变。我们发现自然猎物短缺限制产卵，这与基于实验室的捕鱼蛛属食物限制研究形成对比，也与最近一个假设的基本假设相矛盾，该假设认为捕鱼蛛的性食同类行为是非适应性的。这些差异凸显了从自然种群野外实验中获得见解的重要性。
