Nest-founding in Acromyrmex octospinosus (Hymenoptera, Formicidae, Attini): demography and putative prophylactic behaviors

Abstract

Summary.Foundresses of the leaf-cutting ant Acromyrmex octospinosus in central Panamá forage for leaves as garden substrate (semi-claustral foundation). The fungal pellet and substrate usually are attached to rootlets, which are used as a platform for the garden. This arrangement keeps the garden suspended away from the earthen chamber of the underground nest during early colony growth, and we hypothesize that it serves to minimize contact between the garden and contaminants. A. octospinosus foundresses produce from 3 to 7 workers in 2.7 months after founding the nest, but workers do not forage for substrate at this time. Incipient nests died or were abandoned at a monthly rate of ca. 50 %. We show that ants routinely clean their legs before manipulating the garden substrate. We also describe how foundresses use their forelegs to rub the surface of the metapleural gland (MPG), and they then use typical grooming behaviors to pass the forelegs through the mouthparts, after which the ant then licks the garden substrate. Similarly, ants apparently use their mouths to transfer fecal droplets to their legs. We briefly discuss the functional significance of these grooming behaviors, and hypothesize that they are prophylactic behaviors that may help the foundress maintain a hygienic garden.

Genetic Diversity and Disease Resistance in Leaf-Cutting Ant Societies

“…The resistance to disease of social insects, including leaf-cutting ants, can be improved by the presence of nestmates as a result of allogrooming (Rosengaus et al 1998;Hughes et al 2002) and the enhancement of immunocompetence (Traniello et al 2002). Acromyrmex ants can actively apply the antibiotic secretions from their metapleural glands to their fungus garden (Fernández-Marin et al 2003), and it seems likely that these secretions are also transferred between nestmates by contact and grooming, as occurs with cuticular hydrocarbons (Soroker et al 1995;Lenoir et al 2001). The occurrence of a resistant genotype may therefore also benefit susceptible genotypes in the group, which could result in the greater survival of individuals in high diversity groups that was seen.…”

Differential resistance and the importance of antibiotic production in Acromyrmex echinatior leaf-cutting ant castes towards the entomopathogenic fungus Aspergillus nomius

“…These glands produce a secretion containing more than 20 different compounds in Acromyrmex octospinosus (do Nascimento et al, 1996;Ortius-Lechner et al, 2000), and these are known to have bactericidal and fungicidal properties (Maschwitz, 1974, Beattie et al, 1985Ortius-Lechner et al, 2000;Bot et al, 2002;Poulsen et al, 2002a). The spread of gland secretion over the ant cuticle has previously been thought to be passive, but recent findings suggest that ants actively groom and apply the antibiotic secretion, especially in events of fungal infection (Bot et al, 2001b;Fernández-Marín et al, 2003, making it of hygienic importance for both the individual and the colony (Beattie et al, 1985(Beattie et al, , 1986Koob, 1970, 1971;Maschwitz et al, 1970;do Nascimento et al, 1996;Bot et al, 2002;Poulsen et al, 2002b). Angus et al (1993) examined the relationship between metapleural gland cell number and ant size and found a strong positive association between the two.…”

A behavioral repertoire of Atta sexdens (Hymenoptera, Formicidae) queens during the claustral founding and ergonomic stages

“…Because the symbiotic fungus is their main food source (Quinlan and Cherrett, 1979) and not free from invading microbes Pagnocca et al, 2008;Taerum et al, 2010) they have developed a series of selfgrooming and waste disposal behaviors that protect the colony from parasites (Wilson, 1980;Currie and Stuart, 2001;Bot et al, 2001;Fernández-Marín et al, 2003). The decrease in frequency of selfgrooming behaviors observed for A. sexdens in the ergonomic stage coincides with an increase of allogrooming behaviors in which workers groom the queen (Augustin, pers.…”

“…Meanwhile, studies of claustral and semi-claustral fungus-cultivating ants have shown a similar pattern of greater investment in care of the fungus garden at the founding stage than the ergonomic (Autuori, 1942;Mariconi, 1970;Fernández-Marín et al, 2003;Seal and Tschinkel, 2007). Despite this, there is a lack of detailed information on the behavioral acts performed by claustral Attini queens.…”