Ectosymbionts and immunity in the leaf-cutting ant Acromyrmex subterraneus subterraneus

Abstract

Associations with symbiotic organisms can serve as a strategy for social insects to resist pathogens. Antibiotics produced by attine ectosymbionts (Actinobacteria) suppress the growth of Escovopsis spp., the specialized parasite of attine fungus gardens. Our objective was to evaluate whether the presence or absence of symbiotic actinobacteria covering the whole ant cuticle is related to differential immunocompetence, respiratory rate and cuticular hydrocarbons (CHs). We evaluated these parameters in three worker groups of Acromyrmex subterraneus subterraneus: External workers (EXT), internal workers with actinobacteria covering the whole body (INB) and internal workers without actinobacteria covering the whole body (INØ). We also eliminated the actinobacteria by antibiotic treatment and examined worker encapsulation response. INB ants showed lower rates of encapsulation and respiration than did the EXT and INØ ants. The lower encapsulation rate did not seem to be a cost imposed by actinomycetes because the elimination of the actinomycetes did not increase the encapsulation rate. Instead, we propose that actinobacteria confer protection to young workers until the maturation of their immune system. Actinobacteria do not seem to change nestmate recognition in these colonies. Although it is known that actinobacteria have a specific action against Escovopsis spp., our studies, along with other independent studies, indicate that actinomycetes may also be important for the individual health of the workers.

Communication and Social Regulation in Termites

“…In their comparison of the social biology of basal ants and termites, Thorne and Traniello (2002) explain that disease resistance and management, which influence the reproductive organization of colonies and their division of labor (which are also strongly influenced by nesting and feeding ecology), may have been significant factors in the evolution of sociality since social insects are particularly vulnerable to infections (Wilson-Rich et al 2009). Self-medication is widespread in animals (de Roode et al 2013), but social insects develop a plethora of other strategies to resist pathogens, including associations with symbiotic organisms (Chouvenc et al 2013;de Souza et al 2013). Corpse management is another essential adaptation to social life (Sun and Zhou 2013).…”

Leaf-Cutter Ant Parasitoids: Current Knowledge

“…De Souza et al [53] evaluated encapsulation rates and cuticular hydrocarbon profiles in Acromyrmex subterraneus but did not relate one to the other because they were interested in answering another type of question.…”

Molecules to Ecosystems: Actinomycete Natural Products In situ

“…Interestingly, recent evidence suggests that the direct interaction of actinomycetes with their leaf-cutter ant hosts is beneficial for worker ant protection from pathogenic fungi and bacteria (Schoenian et al, 2011; Mattoso et al, 2012; de Souza et al, 2013). With high resolution mass spectrometry (LC-ESI-HR-MS), and matrix-assisted laser desorption ionization (MALDI) imaging on the bodies of the ants, Schoenian et al (2011) identified valinomycins, actinomycins, and antimycins from Streptomyces isolates associated with the integument of Acromyrmex echinatior workers.…”

“…Furthermore, the immunity of Acromyrmex subterraneus ants with and without their symbiotic actinomycetes was evaluated. In their study, de Souza et al (2013) observed that young worker ants lose their bacterial coating and mature into older, external worker ants. Furthermore, they found that in the absence of their associated bacteria, the young ants had an altered innate immune response, indicating that the actinomycetes confer protection to young internal workers until their immune systems have matured (de Souza et al, 2013).…”