Novel Insights into the Ontogeny of Nestmate Recognition in Polistes Social Wasps

Abstract

The importance of early experience in animals’ life is unquestionable, and imprinting-like phenomena may shape important aspects of behaviour. Early learning typically occurs during a sensitive period, which restricts crucial processes of information storage to a specific developmental phase. The characteristics of the sensitive period have been largely investigated in vertebrates, because of their complexity and plasticity, both in behaviour and neurophysiology, but early learning occurs also in invertebrates. In social insects, early learning appears to influence important social behaviours such as nestmate recognition. Yet, the mechanisms underlying recognition systems are not fully understood. It is currently believed that Polistes social wasps are able to discriminate nestmates from non-nestmates following the perception of olfactory cues present on the paper of their nest, which are learned during a strict sensitive period, immediately after emergence. Here, through differential odour experience experiments, we show that workers of Polistes dominula develop correct nestmate recognition abilities soon after emergence even in absence of what have been so far considered the necessary cues (the chemicals spread on nest paper). P. dominula workers were exposed for the first four days of adult life to paper fragments from their nest, or from a foreign conspecific nest or to a neutral condition. Wasps were then transferred to their original nests where recognition abilities were tested. Our results show that wasps do not alter their recognition ability if exposed only to nest material, or in absence of nest material, during the early phase of adult life. It thus appears that the nest paper is not used as a source of recognition cues to be learned in a specific time window, although we discuss possible alternative explanations. Our study provides a novel perspective for the study of the ontogeny of nestmate recognition in Polistes wasps and in other social insects.

Ontogeny of Nestmate Recognition in Social Hymenoptera

“…Moreover, worker discrimination abilities were lowest in colonies where the odour changes due to usurpation were largest, indicating a possible process of comparison between the previously learned odour and the new one, i.e., the odour of the parasite (Costanzi et al 2013). The occurrence of preimaginal learning for template formation in P. dominula wasps has been recently proposed also by us (Signorotti et al 2014a). We showed that workers, taken from their natal comb when the natural emergence occurs, displayed correct discrimination abilities at the age of five days, regardless of their olfactory experience during the first four days of adult life.…”

“…This suggests that the recognition cues were present on the young gynes' body but were not used by them to form the referent template (Gamboa et al 1986b). However, P. dominula workers reared in isolation (without nestmates or nest material) for four days from birth are able to perform correct discrimination between nestmates and non-nestmates (Signorotti et al 2014a), suggesting the possible occurrence of self-referencing for template formation during the first days of life, at least in this species.…”

“…Similarly, young Polistes metricus workers fail to recognize nestmates if they have spent the first four days of their adult life on a comb washed with solvent to remove nest surface compounds . However, in Polistes dominula workers, template formation appears to happen in a different way since the absence of nest material (or the presence of alien nest material) during the first four days of adult life does not affect nestmate recognition ability (Signorotti et al 2014a).…”

“…metricus, Singer and Espelie 1992). Indeed, a recent study conducted on P. dominula, an Old World species, suggested the possible implication of other life stages, such as pre-imaginal ones, in which the learning process for the template formation could occur (Signorotti et al 2014a). …”

“…We showed that workers, taken from their natal comb when the natural emergence occurs, displayed correct discrimination abilities at the age of five days, regardless of their olfactory experience during the first four days of adult life. Ecological pressures might have led to the evolution of an advantageous precocious cues learning in P. dominula wasps (Signorotti et al 2014a), a species characterized by high rate of inter-and intraspecific social parasitism (Cervo 2006). …”