Control of nest water losses through building behavior in leaf-cutting ants (Acromyrmex heyeri)

Abstract

Like many ants inhabiting temperate regions, leaf-cutting ant colonies of a number of Acromyrmex species build thatched nests that achieve more stable temperatures than those of the environment. Workers are expected to counteract short-term variations in nest microclimate by modifying the thatch structure, for instance by reducing thatch thickness or by permeating the thatch with openings so as to favor heat exchanges with the outside. Such thermoregulatory responses may compromise the control of nest humidity because of the concomitant water losses resulting from the escape of humid air to the environment. We asked whether water losses through the thatch trigger deposition of nest material as a regulatory response for humidity control. In a laboratory colony of A. heyeri, we defined four equidistant spots on the nest thatch through which losses of air with different humidities were experimentally simulated. The deposition of building material on the spot was recorded as indicative building response. Results showed that material deposition occurred significantly more frequently with higher humidity content of the air leaving the spot. Dry air leaving the nest hardly triggered material deposition. The observation of a continuous turnover of thatch material indicates that the building of a nest thatch is a permanent process, and that short-term responses for the control of nest climate, as the deposition of building material to suppress an outflow of humid air, are guided by specific cues such as the humidity content of the air stream.

Managing leaf-cutting ants: peculiarities, trends and challenges

“…69 Pathogens are not the only threat to the fungus garden, and a suitable microclimate is also necessary for the desired cultivation and yield; leaf-cutting ants are able to relocate their gardens to suitable nest chambers and to heavily invest in building, repairing and maintaining nest structure. 74,75 In addition, fungus-cultivation generates large amounts of degraded plant material, which are frequently contaminated with fungal competitors and other microorganisms that are potentially detrimental to the garden wileyonlinelibrary.com/journal/ps and the colony. 22,75 -77 The containment of these waste products in isolated internal nest chambers or external piles, away from the fungus garden, aided by hygienic behaviors (e.g.…”

The effect of increase in the temperature on the foraging of Acromyrmex lobicornis (Hymenoptera: Formicidae)

“…This group is defined on the basis of its feeding habits and consists of Atta and Acromyrmex genera, the dominant herbivores of the Neotropics that can harvest up to 17% of the primary productivity (Hölldobler and Wilson 1990). They have harvesting patterns associated with ranges of the following: specific temperatures for each species and their activity ceases outside those ranges (Hölldobler and Wilson 1990;Pilati and Quirán 1996;Bollazzi 2008;Bollazzi and Roces 2011); temperatures for the close regulation of cultivating symbiotic fungi -the protein source of the colony (Bollazzi and Roces 2010;Mueller et al 2011); and territorial behavior (Hölldobler and Lumsden 1980) and aggressive behavior between colonies, associated with the dear enemy phenomenon (Fisher 1954;Dimarco et al 2010). In the Attini tribe, Acromyrmex lobicornis Emery has the widest geographical distribution in Argentina, being found from the north down to the 44°S parallel in the province of Chubut (Kusnezov 1978;Farji-Brener and Ruggiero 1994).…”

Spatially Heterogeneous Nest-Clearing Behavior Coincides with Rain Event in the Leaf-Cutting Ant Atta cephalotes (L.) (Hymenoptera: Formicidae)

“…Wind and temperature on the other hand are drivers for nest ventilation, and responding to and circumventing unfavorable climatic conditions within the nest by modifying/adjusting nest architectural features are a well-known adaptive behavior in many ant species (Jonkman 1980, Horstmann & Schmid 1986. Fast a dj u s t m e n t s a b ov e g r o u n d l i k e co n s t r uc t io n / deconstruction of thatches are also known for some LCA species (Bollazzi & Roces 2010). Wind-induced nest ventilation is more important for open habitat species, like Atta vollenweideri (Forel) that live in clayish soil that limits gas and water movements (Cosarinsky & Roces 2011) or Atta capiguara (Gonçalves) and Atta laevigata (Smith) where nest shape acts on CO 2 /O 2 sink-source dynamics (Bollazzi et al 2012).…”