Volkan Aksoy

Behavioural analysis of chromatic and achromatic vision in the ant Formica cunicularia (Hymenoptera: Formicidae).

Responses of Formica cunicularia foragers to monochromatic light stimuli of 370, 440, 540, 590 and 640 nm were evaluated in different experimental conditions using a Y-maze apparatus and a circular orientation platform. The results showed that foragers responded significantly to all test wavelengths at certain intensities but could only discriminate 370 and 540 nm from alternatives irrespective of intensity changes. Furthermore, they were also capable of discriminating two long wavelengths, 590 and 640 nm, using a photon catch mechanism by their green photoreceptors. Foragers also discriminated stimuli pairs of same wavelengths based only on intensity differences they provide. The overall results show that F. cunicularia foragers have a dichromatic colour vision system based on inputs of two possible photoreceptor types sensitive to UV and green. The results also yielded evidence showing that their visual systems provided foragers a sensitivity also for wavelengths corresponding to blue and red ranges of the spectrum.

Eye structure, activity rhythms, and visually-driven behavior are tuned to visual niche in ants

Insects have evolved physiological adaptations and behavioral strategies that allow them to cope with a broad spectrum of environmental challenges and contribute to their evolutionary success. Visual performance plays a key role in this success. Correlates between life style and eye organization have been reported in various insect species. Yet, if and how visual ecology translates effectively into different visual discrimination and learning capabilities has been less explored. Here we report results from optical and behavioral analyses performed in two sympatric ant species, Formica cunicularia and Camponotus aethiops. We show that the former are diurnal while the latter are cathemeral. Accordingly, F. cunicularia workers present compound eyes with higher resolution, while C. aethiops workers exhibit eyes with lower resolution but higher sensitivity. The discrimination and learning of visual stimuli differs significantly between these species in controlled dual-choice experiments: discrimination learning of small-field visual stimuli is achieved by F. cunicularia but not by C. aethiops, while both species master the discrimination of large-field visual stimuli. Our work thus provides a paradigmatic example about how timing of foraging activities and visual environment match the organization of compound eyes and visually-driven behavior. This correspondence underlines the relevance of an ecological/evolutionary framework for analyses in behavioral neuroscience.

Experience Based Use of Landmark and Vector Based Orientation During Homing by the Ant Formica cunicularia (Hymenoptera: Formicidae)

Homing paths of Formica cunicularia foragers from an artificial food reward were analyzed on a familiar terrain and in displacement experiments on a familiar and an unfamiliar terrain. Foragers were tested either when relatively new to a foraging route (untrained group) or after a day’s experience with it (trained group). Untrained foragers followed direct homing paths to the nest site when tested in the familiar terrain but followed tortuous paths when displaced to the unfamiliar terrain. Trained foragers behaved similarly to untrained ones when tested from the food reward to the nest site in the familiar terrain but their behavior changed in displacements. Irrespective of the familiarity of the displacement site, these foragers followed paths taking them to the expected nest sites. The results showed that foragers did not rely on chemical cues for homing and revealed that untrained foragers disregarded path integration and were directed to the nest site when it is in their visual panorama. On the contrary, trained foragers may have relied on path integration on familiar and unfamiliar terrain. The results also demonstrated that experience greatly affected the preferential use of visual and vector based cues by foragers during homing.

Spectral sensitivities of ants – a review

Ants constitute one of the most intriguing animal groups with their advanced social lifes, different life histories and sensory modalities, one of which is vision. Chemosensation dominates all other modalities in the accomplishment of different vital tasks, but vision, varying from total blindness in some species to a relatively well-developed vision providing ants the basis for visually-guided behaviors, is also of importance. Although studies on ant vision mainly focused on recognition of and guidance by landmark cues in artificial and/or natural conditions, spectral sensitivities of their compound eyes and ocelli were also disclosed, but to a lesser extent. In this review, we have tried to present current data on the spectral sensitivities of the different ant species tested so far and the different methodological approaches. The results, as well as the similarities and/or discrepancies of the methodologies applied, were compared. General tendencies in ants’ spectral sensitivities are presented in a comparative manner and the role of opsins and ant ocelli in their spectral sensitivity is discussed in addition to the sensitivity of ants to long wavelengths. Extraocular sensitivity was also shown in some ant species. The advantages and/or disadvantages of a dichromatic and trichromatic color vision system are discussed from an ecological perspective.