Halboth Florian, Roces Flavio
Department of Behavioral Physiology and Sociobiology, Biocenter, University of Würzburg, Würzburg, Germany.
PLoS One. 2017 Nov 16;12(11):e0188162. doi: 10.1371/journal.pone.0188162. eCollection 2017.
Nest ventilation in the leaf-cutting ant Atta vollenweideri is driven via a wind-induced mechanism. On their nests, workers construct small turrets that are expected to facilitate nest ventilation. We hypothesized that the construction and structural features of the turrets would depend on the colony's current demands for ventilation and thus might be influenced by the prevailing environmental conditions inside the nest. Therefore, we tested whether climate-related parameters, namely airflow, air humidity and CO2 levels in the outflowing nest air influenced turret construction in Atta vollenweideri. In the laboratory, we simulated a semi-natural nest arrangement with fungus chambers, a central ventilation tunnel providing outflow of air and an aboveground building arena for turret construction. In independent series, different climatic conditions inside the ventilation tunnel were experimentally generated, and after 24 hours, several features of the built turret were quantified, i.e., mass, height, number and surface area (aperture) of turret openings. Turret mass and height were similar in all experiments even when no airflow was provided in the ventilation tunnel. However, elevated CO2 levels led to the construction of a turret with several minor openings and a larger total aperture. This effect was statistically significant at higher CO2 levels of 5% and 10% but not at 1% CO2. The construction of a turret with several minor openings did not depend on the strong differences in CO2 levels between the outflowing and the outside air, since workers also built permeated turrets even when the CO2 levels inside and outside were both similarly high. We propose that the construction of turrets with several openings and larger opening surface area might facilitate the removal of CO2 from the underground nest structure and could therefore be involved in the control of nest climate in leaf-cutting ants.
切叶蚁Atta vollenweideri蚁巢的通风是通过风致机制驱动的。在它们的蚁巢上，工蚁建造了一些小塔楼，预期这些塔楼有助于蚁巢通风。我们假设塔楼的建造和结构特征将取决于蚁群当前的通风需求，因此可能会受到蚁巢内部当前环境条件的影响。因此，我们测试了与气候相关的参数，即流出蚁巢空气的气流、空气湿度和二氧化碳水平是否会影响Atta vollenweideri蚁的塔楼建造。在实验室中，我们模拟了一种半自然的蚁巢布局，包括菌室、提供空气流出的中央通风隧道以及用于塔楼建造的地上建筑区域。在独立的系列实验中，通过实验产生通风隧道内不同的气候条件，24小时后，对建造的塔楼的几个特征进行量化，即塔楼的质量、高度、开口数量和表面积（孔径）。即使通风隧道中没有气流，在所有实验中塔楼的质量和高度也相似。然而，二氧化碳水平升高导致建造出具有几个较小开口和更大总孔径的塔楼。在5%和10%的较高二氧化碳水平下，这种效果具有统计学意义，但在1%二氧化碳水平下则不显著。建造具有几个较小开口的塔楼并不取决于流出蚁巢空气与外部空气之间二氧化碳水平的强烈差异，因为即使内部和外部的二氧化碳水平同样高，工蚁也会建造有许多小孔的塔楼。我们提出，建造具有多个开口和更大开口表面积的塔楼可能有助于从地下蚁巢结构中去除二氧化碳，因此可能参与切叶蚁蚁巢气候的调节。
