Resource allocation among worker castes of the leaf-cutting ants Acromyrmex subterraneus subterraneus through trophallaxis

Abstract

The division of labor between the different worker castes of leaf-cutting ants may reflect in their capacity to exchange liquids by trophallaxis. The crop capacity of and trophallactic exchanges between different size classes of worker leaf-cutting ants of the sub-species Acromyrmex subterraneus subterraneus were investigated. Size classes were defined from head capsule widths and crop capacity of each class was determined following ad libitum feeding on dye solution. Experiments were carried out to investigate trophallactic exchanges between donor ants and recipient ants of each class size combination on a one to one basis. An experiment was also performed to investigate dye distribution within mini-colonies following introduction of three classes of donor ants. Worker ants were categorized into four size classes from their head capsule widths (C1=0.8-1.0 mm; C2=1.2-1.5 mm; C3=1.6-2.0 mm; C4=2.1-2.4 mm). C1 ants crop capacity was 0.13 microL; C2: 0.21 microL; C3: 0.52 microL; C4: 1.03 microL. Ants of each class previously fed on the dye solution (donors) were placed individually with an unfed ant of each class (recipients) and the presence of dye solution, passed from the donor to the recipient by oral trophallaxis was observed after 1h. Results showed that all classes of donor ants performed trophallactic exchanges with all recipient classes. However, statistically fewer exchanges were seen for C2 donor ants when placed with C3 recipient ants. Ten donor ants of each of three classes (C2, C3 and C4) were introduced into mini-colonies without queen ants. It was observed that C1 and C2 ants were poor recipients, whilst C3 and C4 received the highest percentages of dye. Within 10h of introducing the donor ants, 14 to 20% of their nest-mates had received dye solution, with 58 to 77% of dye passed to recipients. These studies show the altruistic nature of "food-laden" leaf-cutters and indicate that ants involved in garden maintenance activity are less likely to receive liquids from foraging workers.

Diet type modifies ingestion rates and trophallactic exchanges in leaf‐cutting ants

“…The maximum crop volumes of A. subterraneus workers observed were lower than those recorded by Moreira et al. (, ), with mean values of ca. 0.66 μl following feeding on liquid diets.…”

“…The results confirm the occurrence of oral trophallaxis in A. sexdens workers, which was first described for this species by Da Silva et al (2009). The maximum crop volumes of A. subterraneus workers observed were lower than those recorded by Moreira et al (2006Moreira et al ( , 2010, with mean values of ca. 0.66 ll following feeding on liquid diets.…”

“…Previous experiments by our group showed that the dye had no adverse effects on ant survival and no behavioral modifications were observed following feeding on this dye (Moreira et al., ). The dye is not absorbed during passage through the digestive tract (Erthal et al., ).…”

“…Although it is believed that many ant species exchange food by trophallaxis (Wilson, 1971), only four studies to date have described and quantified this behavior in leafcutting ants (Moreira et al, 2006(Moreira et al, , 2010Da Silva et al, 2009;Richard & Errard, 2009). In previous studies by our group (Moreira et al, 2006(Moreira et al, , 2010, trophallaxis performed by Acromyrmex subterraneus subterraneus (Forel) (henceforth: A. subterraneus) workers was quantified following ingestion of liquid nutrient sources.…”

Symbiotic bacteria on the cuticle of the leaf-cutting ant Acromyrmex subterraneus subterraneus protect workers from attack by entomopathogenic fungi

“…(a) Insects Acromyrmex subterraneus subterraneus worker ants were obtained from a single colony recently collected in the field (Bom Jardim: 22809 0 07 00 S and 42825 0 10 00 W) and maintained in the laboratory as previously described [16]. Only worker ants with a head capsules of greater than 2 mm and supporting an extensive growth of bacterial bio-film on the cuticle (score 12 using the bacterial bio-film scale created by Poulsen et al [17]) were used.…”