Larval regulation of worker reproduction in the polydomous ant Novomessor cockerelli

Abstract

Although workers in many ant species are capable of producing their own offspring, they generally rear the queen's offspring instead. There are various mechanisms that regulate worker reproduction including inhibitory effects of ant brood. Colonies of the ant Novomessor cockerelli are monogynous and polydomous resulting in a large portion of nest workers being physically isolated from the queen for extended periods of time. Some workers experimentally isolated from the queen in laboratory nests lay viable eggs, which develop into males. We investigate the mechanism that regulates worker fertility in subnests separated from the queen by giving queenless worker groups queen-produced larvae, queen-produced eggs, or no brood. Our findings show that larvae delay the time to worker egg-laying, but eggs have no effect. Larval inhibition is a likely mechanism that contributes to the regulation of worker reproduction in N. cockerellli because larvae are easily transported to subnests that do not contain a queen.

Ant workers produce males in queenless parts of multi-nest colonies

“…We did not find any evidence for queen-produced brood inhibiting worker reproduction, in contrast to what has been reported previously for honeybees 35,36 and ants [37][38][39] . Instead, queenless subcolonies that contained larvae from the original colony, produced larger numbers of eggs than queenright subcolonies or queenless subcolonies without brood.…”

“…All 30 queenright subcolonies and 10 of the queenless subcolonies received 25 workers and 25 larvae of all developmental stages from the initial colony. The remaining 20 queenless subcolonies consisted of 25 workers without larvae to investigate a possible influence of brood from the original colony on reproduction as reported, e.g., for Novomessor ants 37 . To be later capable of distinguishing between workers from queenright and queenless subcolonies, workers in queenright colonies were marked by clipping the right tarsae of the middle leg, workers of queenless colonies by clipping the left tarsae.…”

Brood recognition and discrimination in ants

“…Indeed, interspecific brood adoption by worker ants has been widely reported (Table 3), lending support to the notion that ant brood pheromones-by definition, substances that elicit reactions from conspecifics-do not exist. Careful work on brood odors in the fire ant S. invicta (reviewed in Tschinkel 2006), as well as recent studies on a number of different species spanning the ant phylogeny have demonstrated that the presence of brood influences adult behavior and reproductive physiology (Heinze et al 1996;Endler et al 2004;Teseo et al 2013;Ebie et al 2015;Ulrich et al 2016;Chandra et al 2018), and that this inhibition can be caused by larval contact odors alone (Villalta et al 2015). While these results seemingly provide support for the idea that ant brood pheromones exist, studies testing whether such brood odors act in a species-specific manner are still lacking.…”

A small family business: synergistic and additive effects of the queen and the brood on worker reproduction in a primitively eusocial bee

“…Queen pheromones have been identified in a small number of species (Hefetz, 2019;Le Conte and Hefetz, 2008) and possible mechanisms of their action are still debated (Keller and Nonacs, 1993;Smith and Liebig, 2017;Villalta et al, 2018), but queens and workers are not the only parties to the conflict over reproduction in social societies. Juveniles also have a stake in the matter and are involved in reproductive conflict with other juveniles and adults (Ebie et al, 2015;Schultner et al, 2017;Starkey et al, 2019a,b;Ulrich et al, 2016).…”

“…One exception is the honey bee Apis mellifera, where the role of the brood has been extensively examined, showing that pheromones produced by the brood regulate worker reproduction and maturation (Maisonnasse et al, 2010(Maisonnasse et al, , 2009Mohammedi et al, 1998). Several recent studies further highlight the role of the brood in regulating worker reproduction and behavior in ants (Ebie et al, 2015;Ulrich et al, 2016) and bumble bees (Starkey et al, 2019a). However, even in these species, the interplay between the roles of juveniles and adults remains understudied, partly because in eusocial insect societies, queen and brood exert their influence on workers simultaneously, and the effects of the queen and the juveniles are difficult to disentangle.…”