Investigating visual and tactile associations in an ant Diacamma indicum

Chandak, Parth (2022) Investigating visual and tactile associations in an ant Diacamma indicum. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Parth Chandak (17MS188)) 17MS188_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (23MB)

Abstract

Learning is important for organisms living in environments that are complex and unpredictable. In such organisms, it is important to integrate information from various sources and associate them, through experience, with stimuli that serve as predictors of events that follow. This form of learning, known as associative learning, allows animals to maximise the probability of survival through optimisation of experience and information use. Among insects associative learning has been studied in honeybees, cockroaches, fruit flies, houseflies and ants. In ants, associative learning is of great importance as it allows them to use sensory cues for efficient navigation outside and inside the nest. Indeed, several studies have shown that ants, can associate olfactory, visual, tactile and directional cues with a reward. In the present study, we investigate visual and tactile cue learning in an ant Diacamma indicum. Our experiments present pupae as a motivation for learning paradigms. Pupae are of particular importance to colonies as they contribute to reproductive fitness without requiring much care. The presence of many species in nature that steal brood and observation of opportunistic brood theft, with preference to pupae, in D. indicum underlines their substantial ecological value. In comparison to conventional sources of motivation – food, relief from a negative stimulus, and praising or petting – pupae serve as a higher and ecologically more relevant source of motivation. We study associative learning in individual ants using a Y-maze setup with two different cues on the arms. The sample size for each experiment was 20 (N). We begin by investigating visual associative learning. We find that ants can learn to differentiate between contrasting visual cues (white dots vs black dots) and between tactile cues (rough and smooth surface) placed along the ground. We proceed to investigate preference between visual and tactile cues. Our findings indicate that ants prefer tactile cues over visual ones when placed in conflict. Interestingly, where the tactile cue used in association is rough, ants take decisions significantly in favour of the tactile than visual cue (17 out of 20 times, p < 0.01) and spend greater proportion of time on the former (p < 0.01). But in the case of smooth tactile cue, the ants show no preference during decision making towards either of the cues (9 out of 20 times in favour of tactile, p = 0.16), but overall spend greater proportion of time in contact with the tactile cue (p = 0.04). This may reflect an inherent preference for rough surfaces. Finally, we find that the tactile sense of D. indicum is specific to the roughness of the tactile cue when using 80 Grit Sandpaper and 220 Grit Sandpaper. To summarise, using pupae as motivation, we find that D. indicum can learn to associate visual cues with a reward, prefers tactile over visual cues when placed in conflict and has specificity to the roughness of the tactile cues provided. Along with previous reports on the importance of visual and tactile sensory inputs during relocation in D. indicum, our findings not only showcase the potential for using pupa as a novel reward but show that individual ants are capable of associative learning, which is a step forward in understanding the sensory capabilities of these superorganisms.

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