Restriction of pedicel-flagellum joint in the antennae negatively impacts recruitment but not exploration in ants.

Abstract

Background: The antennal flagellum movement relative to the pedicel, helps insects detect different cues and interpret their surroundings. Antennae play a crucial role in the tandem run recruitment process, where one ant follows another ant to reach the destination by maintaining a continuous physical contact, mostly using antennae, throughout their journey. In this study, we investigate how the restriction in movement of the pedicel-flagellum joint impacts the exploratory walk and recruitment during relocation in Diacamma indicum, a tandem running tropical ponerine ant.

Methods: We studied the exploratory walk of ants by examining a total number of 72 individuals from four categories, i.e. no antennae restriction (NR), both antennae restriction (BR), right (RR) or left (LR) antennae restriction. The relocation process was studied by comparing 10 unrestricted and 8 antennae restricted colonies contrasting the dynamics. The movement dynamics of both the individual ants and tandem pairs were examined by analysing their heading direction, speed, sinuosity, straightness, and step lengths.

Result: Restricted ants showed no significant change in speed, path shape and step length in their exploratory walk compared to the unrestricted ants. Restricted colonies performed the relocation at the cost of higher latency and transportation time due to the involvement of comparatively lower numbers of tandem leaders as compared to unrestricted colonies. Irrespective of restriction status, all the tandem pairs were significantly oriented toward the new nest. From the leader's point of view, BR leaders showed lower speed, more winding paths and higher proportion of small steps in comparison to unrestricted tandem pairs, while RR leaders hardly became tandem leaders. From the follower's point of view, RR and BR followers showed significantly lower speed.

Conclusion: This study showed that the restriction in the pedicel-flagellum joint has no impact on the exploration walk in ants but negatively impacts the relocation process by affecting the tandem run recruitment. In the next step, it is essential to understand the functionality of the pedicel-flagellum joint and how ants compensate for loss of information from a sensory modality.