Behavioual Adaptations to Light Deprivation

Fast and Furious - Tōhoku Drift

by Kristina Corthals
Doctoral thesis
Date of Examination:2018-12-18
Date of issue:2019-03-20
Advisor:Dr. Bart RH Geurten
Referee:Prof. Dr. Martin Göpfert
Referee:Prof. Dr. André Fiala
Referee:Prof. Dr. Gregor Bucher
Referee:Prof. Dr. Ralf Heinrich
Referee:Dr. Jan Clemens
Referee:PD Dr. Roland Dosch
Persistent Address: http://dx.doi.org/10.53846/goediss-7355

 

 

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Abstract

English

Similar to most non-sedentary animals, Drosophila shows a wide range of visually guided behaviours and their functionality is crucial for survival. Previous studies showed that visual impairment significantly reduced the courtship success of male Drosophila. However, the dark-fly strain which was raised under constant dark condition since 1957 survived in a vision-less environment for over 1500 generations. I analysed the behavioural adaptations of the dark-fly strain in both courtship and locomotion strategy to the decades of sensory depression. In dark-fly males several behavioural adaptations can be observed: they replace the typically competitive courtship strategy with a cooperative approach. Without visual information about the location of the female, male dark-flies produce a significantly increased courtship song volume. Additionally, the dark-fly strain shows evidence for a sex-specific co-evolution: compared to wildtype Drosophila, the dark-fly strain shows an increased hearing ability. However, dark-fly females show a reduced sensitivity of the auditory system in relation to dark-fly males. During locomotion, insects use optic flow, the retinal image shift induced by self-motion, to gain 3D-information. Translational movements result in faster movement of close objects across the retina than distant ones, whereas all objects move with the same speed during rotational movements. Therefore, only translational movements provide distance information. Insects overcome this problem by utilizing a saccadic movement strategy, consisting of very short and fast rotations separated from translational movements. Congruously, Drosophilae display a saccadic strategy during walking and flying. During walking, dark-raised flies abandon the separation of translation and rotation in favor of a newly emerged strategy: the Tōhoku Drift. This new strategy optimises the tactile field, rather then the visual input and allows dark-fly to cover more area when moving in a vision-less environment.
Keywords: Drosophila; Courtship; Vision; Locomotion; Saccadic Strategy; Behaviour; Behavioural Adaptations; dark-fly; dark-adapted Drosophila; Exploration
 
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