Giant ants of the South American genus Dinoponera are unusual in lacking a separate queen caste. Instead, colonies comprise outwardly identical workers, a subset of which mate and lay eggs. Are the ants inwardly identical as well? Not at all, according to a new study by Chris R. Smith et al in PLoS ONE. Foraging ants are lean, with low fat reserves, while workers and reproductives deep in the nest have ample body fat:
Eusocial species exhibit pronounced division of labor, most notably between reproductive and non-reproductive castes, but also within non-reproductive castes via morphological specialization and temporal polyethism. For species with distinct worker and queen castes, age-related differences in behavior among workers (e.g. within-nest tasks versus foraging) appear to result from physiological changes such as decreased lipid content. However, we know little about how labor is divided among individuals in species that lack a distinct queen caste. In this study, we investigated how fat storage varied among individuals in a species of ant (Dinoponera australis) that lacks a distinct queen caste and in which all individuals are morphologically similar and capable of reproduction (totipotent at birth). We distinguish between two hypotheses, 1) all individuals are physiologically similar, consistent with the possibility that any non-reproductive may eventually become reproductive, and 2) non-reproductive individuals vary in stored fat, similar to highly eusocial species, where depletion is associated with foraging and non-reproductives have lower lipid stores than reproducing individuals. Our data support the latter hypothesis. Location in the nest, the probability of foraging, and foraging effort, were all associated with decreased fat storage.
source: Smith CR, Suarez AV, Tsutsui ND, Wittman SE, Edmonds B, et al. (2011) Nutritional Asymmetries Are Related to Division of Labor in a Queenless Ant. PLoS ONE 6(8): e24011. doi:10.1371/journal.pone.0024011