Sucrose acceptance threshold: a way to measure sugar perception in ants

Abstract

Variation in the perception of sweet taste is a well-known phenomenon in the animal kingdom. Wellestablished protocols for measuring sucrose responsiveness in non-social insects and honeybees have made it possible to understand many aspects of their biology and behaviour. Ants are also advanced social insects that present a plethora of life histories with diverse strategies and behaviours; however, a universal paradigm possible to measure this response in different ant species has not yet been developed. Here, we present a protocol for measuring the sucrose acceptance threshold (SAT) under controlled conditions in harnessed ants with different feeding habits. By testing the response to antennal and palp sucrose stimulation and using the occurrence of licking as the response, we developed a non-ambiguous evaluation that allowed easy detection of threshold changes. The results showed that the response to both antennal and palp stimulation varied widely among species. Some species licked in response to antennal stimulation while others did so in response to palp stimulation. Using the appropriate kind of stimulation, we tested the SAT protocol in ants of different genera and ants of the same species with different levels of sugar reserve. The differences detected in both cases imply that the protocol is appropriate for measuring and detecting variations in sugar perception in ants.

Sensitivity and feeding efficiency of the black garden ant Lasius niger to sugar resources

“…Consequently, ants have evolved chemosensory and behavioural traits to detect, exploit and monopolise the most valuable sugar producers efficiently. In this respect, the feeding response of foragers to sucrose is a widelyused and reliable indicator of the motivation of ants to exploit sugary resources (Faribele and Josens, 2012;Josens and Roces, 2000).…”

“…The first experiment assessed how the energetic return drawn by the ants from a sugar solution was influenced by its concentration in carbohydrates. We chose sucrose as a reference sugar to investigate how concentration influenced food intake as previously done for other ant species (in the genus Camponotus (Faribele and Josens, 2012;Josens et al, 1998;Josens and Roces, 2000), Rhytidoponera (Dussutour and Simpson, 2008), Linepithema, Cephalotes and Acromyrmex (Faribele and Josens, 2012)). We compared the feeding response of L. niger scouts over a range of sucrose concentrations; specifically, 0.001, 0.01, 0.1, 0.5, 1 and 2.5 M. Groups of five L. niger scouts were randomly taken out of the foraging arena of one colony and allowed to explore the experimental set-up during 5 min.…”

“…Furthermore, because ant responses were usually measured for just one sugar concentration, knowledge remains limited about how glucophagy by the ant individuals that discover the food source evolves for increasing sugar concentrations. Dose-response curves are only well-established for sucrose: previous studies have quantified the propensity of foragers to recruit nestmates (Beckers et al, 1993;Detrain et al, 1999;Dussutour and Simpson, 2008;Jackson and Châline, 2007;Wilson, 1962) along with several feeding variables, such as food acceptance, crop load, feeding time and ingestion rates (Dussutour and Simpson, 2008;Faribele and Josens, 2012;Josens et al, 1998;Josens and Roces, 2000). In contrast, the feeding response curves of ants remain unknown for the other sugars that are commonly found in nectar and honeydew.…”

Sucrose responsiveness, learning success, and task specialization in ants

“…Responses to food are flexible and may change among individuals in several ant species (e.g., Josens et al 1998;Falibene et al 2009;Schilman 2011). Interindividual differences in sucrose responsiveness were found in immobilized workers of various ant species, which were stimulated with different concentrations of sucrose solution (Falibene and Josens 2012). The possible relationship between these differences, learning success, and behavioral specializations within the colony remains, however, unknown.…”

“…This high selectivity for sucrose is adaptive in a scenario in which inactive workers serve as sucrose storers for the colony. The low SRS found in these ants could relate to the fact that crop filling induces a decrease in sucrose responsiveness (Falibene and Josens 2012). Nurses, which are younger than foragers and inactive workers (Hölldobler and Wilson 1990), responded to intermediate sucrose concentrations.…”