Navigation in the context of relocation in a tandem-running ant Diacamma indicum

Mukhopadhyay, Snigdha (2021) Navigation in the context of relocation in a tandem-running ant Diacamma indicum. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Snigdha Mukhopadhyay (14RS002)) 14RS002_DBS.pdf - Submitted Version Restricted to Repository staff only Download (11MB)

Abstract

Navigation is important for animals to move from one place to another efficiently and animals need to move from one place to another in many aspects of their lives such as foraging, migration, finding breeding ground and mates or relocating to a new shelter. Thus, navigation would influence both survival and fitness of organisms. Navigation mechanisms have been well studied in social insects like honeybees, wasps and ants, mostly in the context of foraging. Colony relocation in social insects is a goal-oriented task that involves the movement of the whole colony, including the reproductive individual(s), brood and stored resources from one location to another, and thus, efficient navigation during relocation would be particularly important. In this thesis, we report the navigation mechanism and use of sensory inputs during colony relocation in a ponerine ant species Diacamma indicum that uses tandem running to recruit all its nestmates during relocation. The process of tandem running involves some members of the colony (leaders) who are informed about the new nest leading other members (followers) to the goal, a new nest in this case, one at a time. In the course of this thesis, we investigated the importance of different sensory information used by tandem leaders during relocation and whether it impacts their capacity to find the shortest path from the old nest to the new nest. We started by investigating the importance of visual landmarks during relocation. In chapter 2, we found that the presence of landmarks near the nest entrance reduced the transportation time, while the presence of landmarks along the relocation path did not influence the transportation of the colonies. The displacement of these landmarks from the nest entrance significantly affected the path efficiency of the individual tandem leaders while the displacement of visual landmarks along the path did not alter the path length as compared to the path-length before the displacement. In order to probe the importance of visual inputs further, we examined whether these ants are capable of relocating in the absence of any visual landmark by making them relocate in the dark and after occulting both the compound eyes of the ants in separate experiments. We found that these ants successfully transported all the colony members without losing a single member even in the absence of vision, albeit at a lower efficiency, by using thigmotactic cues. In chapter 3, we investigated whether these non-trail laying ants were capable of minimizing their path during relocation within an open arena and when they were provided with defined paths of different lengths. Tandem leaders were capable of path minimization in both contexts and they transported their nestmates by the shortest path. In chapter 4, we found that with temporarily complete impaired vision, they did not stop to relocate their colony, if the colony was under stress. Finally, in chapter 5, we investigated the importance of tactile senses during tandem running by partial restriction of the antennae. While leaders were still capable of performing tandem runs, there were frequent interruptions, thereby extending the whole relocation process. Throughout the study, we explored the dynamics at the level of the colony and at the level of individual ants by following 130 colonies and about 9000 transporters receiving different treatments and comparing them with appropriate control experiments, followed by hypothesis testing. To summarize, we found that these ants not only minimized their relocation path in the absence of trails, they successfully navigated to the new nest even when they had compromised visual and tactile sensory inputs without any compromise on colony cohesion but at the cost of additional time. This exploration of the role of different sensory inputs in an ant species which uses only tandem running to recruit nestmates provides unique insights that will expand our knowledge of how organisms navigate their environment.

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