Universidade de São Paulo, Instituto de Biociências, Rua do Matão, 277, Cidade Universitária , São Paulo , Brasil CEP 05508-090.
Biol Open. 2012 Sep 15;1(9):827-30. doi: 10.1242/bio.2012703. Epub 2012 Jul 9.
Leafcutter ants (Atta sexdens rubropilosa) (Forel 1908) have an elaborate social organization, complete with caste divisions. Activities carried out by specialist groups contribute to the overall success and survival of the colony when it is confronted with environmental challenges such as dehydration. Ants detect variations in humidity inside the nest and react by activating several types of behavior that enhance water uptake and decrease water loss, but it is not clear whether or not a single caste collects water regardless of the cost of bringing this resource back to the colony. Accordingly, we investigated water collection activities in three colonies of Atta sexdens rubropilosa experimentally exposed to water stress. Specifically, we analyzed whether or not the same ant caste foraged for water, regardless of the absolute energetic cost (distance) of transporting this resource back to the colony. Our experimental design offered water sources at 0 m, 1 m and 10 m from the nest. We studied the body size of ants near the water sources from the initial offer of water (time = 0) to 120 min, and tested for specialization. We observed a reduction in the average size and variance of ants that corroborated the specialization hypothesis. Although the temporal course of specialization changed with distance, the final outcome was similar among distances. Thus, we conclude that, for this species, a specialist (our use of the word "specialist" does not mean exclusive) task force is responsible for collecting water, regardless of the cost of transporting water back to the colony.
叶片切叶蚁（Atta sexdens rubropilosa）（Forel 1908）具有复杂的社会结构，完全分化为不同的等级。当蚁群面临环境挑战，如脱水时，由专业群体开展的各项活动有助于确保蚁群的整体成功和生存。蚂蚁能够感知巢内湿度的变化，并通过激活多种行为来做出反应，这些行为可以增强水分吸收并减少水分流失。但是，不清楚是否有单一等级的蚂蚁无论带回资源的代价如何都会收集水分。因此，我们在三个实验性暴露于水分胁迫的 Atta sexdens rubropilosa 蚁群中调查了水分收集活动。具体来说，我们分析了无论带回这种资源的绝对能量成本（距离）如何，是否由相同的蚁群等级进行水分采集。我们的实验设计在离蚁巢 0、1 和 10 米的地方提供了水源。我们在提供水的初始时间（时间=0）到 120 分钟，研究了靠近水源的蚂蚁的体型，并对其进行了专业化测试。我们观察到蚂蚁的平均体型和方差减小，这证实了专业化假说。尽管专业化的时间进程随着距离的变化而变化，但最终结果在不同距离之间是相似的。因此，我们得出结论，对于这种物种，一个专业（我们使用“专业”一词并不意味着排他性）的特遣部队负责收集水分，而不考虑将水分带回蚁群的成本。
