Comparative analysis of mandible morphology in four ant species with different foraging and nesting habits

Mandibles of ants can be considered as one of the most vital tools for the survival and success of their colonies since these are extensively utilised for defence, nest maintenance and foraging activities. We hypothesised that mandibular design is strongly dependent on the respective ecological niche and foraging habit of an ant species. In the present study, we compared the external morphology and zinc content in the mandibles of four species of ants by using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The ant mandible morphology varied significantly in accordance with their species-specific foraging and nesting strategies. The sickle-shaped mandibles of the strongly predaceous, Oecophylla smaragdina worker ants were characterised by a large number of pointed teeth which would be of immense utility for subduing the prey, while the shovel-shaped, highly sclerotized mandibles of Cataglyphus longipedem ants appear to be adaptations for the solitary scavenging habit and nest maintenance in arid habitats. The large-sized mandibles of Camponotus compressus ants and the stout mandibles of the predatory, Tetraponera. rufonigra forager ants, have apparently evolved for collection of sugary secretions by the former and for the solitary foraging and arboreal nesting habit of the latter. The mandibular zinc content was highest in T. rufonigra ants and the lowest in the mandibles of the sugar-loving Cm. compressus ants. The diversity in the arrangement of bristles and the type of mandibular concavities, have also evolved accordingly. Thus, this study might prove to be instrumental in evaluating the various physical mechanisms involved in the evolution of insect mandibles for their defined function.