The ontogeny of navigation in Cataglyphis ants

• Applicant: Professor Dr. Wolfgang Rössler
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 405620408

Spatial orientation is essential for almost all animal species. Cataglyphis ants are fascinating long-distance navigators. The ants return to their inconspicuous nest entrance after finding food on long foraging trips. The remarkable navigational skills largely rely on path integration, a process based on an internal skylight compass and a calibrated step counter for integrating travelled directions and distance. Whenever available, the ants also use visual landmark guidance. The neuronal mechanisms underlying the functional ontogeny of visually based navigation are still puzzling. The individual life history of Cataglyphis ants offers unique experimental access to investigate the transition from interior tasks in the dark nest to outdoor solitary foraging in bright sunlight. The proposed project focuses on two central questions using a neuroethological approach: (i) What controls the behavioural transitions from interior tasks in the dark nest to outdoor foraging in bright sunlight? (ii) How does the visual system adjust at the transition, and how do the ants learn essential navigational information at the beginning of their foraging career?(i) To understand how the ants transition from the dark nest to foraging in bright sunlight, we investigate the role of neuropetides in controlling underlying changes in behaviour. We address this by performing age- and stage-related quantitative analyses of changes in identified neuropeptides in the ants’ brains. Manipulations of selected neuropeptides by brain injection of synthetic peptides combined with behaviour tests for positive phototaxis, locomotor activity, and spatial orientation aim to unravel their function. (ii) To understand the role of neuronal plasticity in visual circuits to the central complex and the mushroom bodies during the transition, we combine behavioural manipulations (field and laboratory) with structural and functional analyses of neuroplasticity in visual circuits. Naïve ants perform stereotyped learning walks close to the nest entrance for 2-3 days prior to first foraging. Video analyses demonstrate the importance of learning walks in acquiring essential navigational information. We aim to identify the function of specific learning-walk elements by manipulations of celestial and terrestrial cues during learning walks and subsequent analyses of plasticity in the two visual pathways. We hypothesize that homeostatic plasticity adjusts both visual pathways to drastically changing light conditions at the transition, whereas learning walks lead to learning-related (Hebbian) plasticity preferentially in the mushroom bodies. We expect significant advances in understanding the neuronal mechanisms underlying the behavioural ontogeny of a powerful, visually based long-distance navigational system housed in a small insect brain.

• DFG Programme: Research Grants