Evolution of compound eye morphology underlies differences in vision between closely related Drosophila species

Background: Insects have evolved complex visual systems and display an astonishing range of adaptations for diverse ecological niches. Species of Drosophila melanogaster subgroup exhibit extensive intra- and interspecific differences in compound eye size. These differences provide an excellent opportunity to better understand variation in insect eye structure and the impact on vision. Here we further explored the difference in eye size between D. mauritiana and its sibling species D. simulans. Results: We confirmed that D. mauritiana have rapidly evolved larger eyes as a result of more and wider ommatidia than D. simulans since they recently diverged approximately 240,000 years ago. The functional impact of eye size, and specifically ommatidia size, is often only estimated based on the rigid surface morphology of the compound eye. Therefore, we used 3D synchrotron radiation tomography to measure optical parameters in 3D, predict optical capacity, and compare the modelled vision to in vivo optomotor responses. Our optical models predicted higher contrast sensitivity for D. mauritiana, which we verified by presenting sinusoidal gratings to tethered flies in a flight arena. Similarly, we confirmed the higher spatial acuity predicted for Drosophila simulans with smaller ommatidia and found evidence for higher temporal resolution. Conclusions: Our study demonstrates that even subtle differences in ommatidia size between closely related Drosophila species can impact the vision of these insects. Therefore, further comparative studies of intra- and interspecific variation in eye morphology and the consequences for vision among other Drosophila species, other dipterans and other insects are needed to better understand compound eye structure–function and how the diversification of eye size, shape, and function has helped insects to adapt to the vast range of ecological niches

Evolution of compound eye morphology underlies differences in vision between closely related Drosophila species

Background. Insects have evolved complex visual systems and display an astonishing range of adaptations for diverse ecological niches. Species of Drosophila melanogaster subgroup exhibit extensive intra- and interspecific differences in compound eye size. These differences provide an excellent opportunity to better understand variation in insect eye structure and the impact on vision. Here we further explored the difference in eye size between D. mauritiana and its sibling species D. simulans. Results. We confirmed that D. mauritiana have rapidly evolved larger eyes as a result of more and wider ommatidia than D. simulans since they recently diverged approximately 240,000 years ago. The functional impact of eye size, and specifically ommatidia size, is often only estimated based on the rigid surface morphology of the compound eye. Therefore, we used 3D synchrotron radiation tomography to measure optical parameters in 3D, predict optical capacity, and compare the modelled vision to in vivo optomotor responses. Our optical models predicted higher contrast sensitivity for D. mauritiana, which we verified by presenting sinusoidal gratings to tethered flies in a flight arena. Similarly, we confirmed the higher spatial acuity predicted for Drosophila simulans with smaller ommatidia and found evidence for higher temporal resolution. Conclusions. Our study demonstrates that even subtle differences in ommatidia size between closely related Drosophila species can impact the vision of these insects. Therefore, further comparative studies of intra- and interspecific variation in eye morphology and the consequences for vision among other Drosophila species, other dipterans and other insects are needed to better understand compound eye structure–function and how the diversification of eye size, shape, and function has helped insects to adapt to the vast range of ecological niches

Implications of miniaturisation in ants on their vision and visual navigation

Empirical thesis.Bibliography: pages 211-225.General introduction -- Chapter 1. Implications of miniaturisation in insects on visual navigation, vision,and brain neuropils : a systematic review -- Chapter 2. Miniaturisation affects spatial vision in ants -- Chapter 3. Miniaturisation decreases visual navigation competence in ants -- Chapter 4. Does reduction in size affect the ability to learn and use nest associated visual cues in ants? -- Chapter 5. Does size affect orientation using celestial cues? -- General conclusions -- Appendices.Miniaturisation is the evolution of extremely small body size compared to their ancestors, reduction beyond which is constrained due to design limitations. Miniaturisation is commonly observed in many animals, including arthropods. It affects morphological features, nervous system, physiology and ecology of the animal. Typically, miniaturisation leads to simplification, modification or loss of organs. As a consequence of their smaller sensory organs and absolute brain size, miniaturisation is hypothesised to result in inferior behavioural capabilities. However, unifying behavioural measures testing the hypothesis are lacking. Ants present an ideal study system to test this, since irrespective of their size, individuals face similar challenges, especially during visual navigation. In this thesis, I aim to empirically test whether miniaturisation in ants affects their vision and visual navigation behaviours. I begin with a systematic review and a meta-analysis to identify the implications of miniaturisation on vision, brain neuropils and visual navigation in insects (Chapter 1). Using a comparative approach, I studied ants of different sizes to determine how a reduction in the number of ommatidia and the size of the lens affects spatial resolution and contrast sensitivity. I show that miniaturisation decreases contrast sensitivity and spatial resolution in ants (Chapter 2). Spatial resolution is important in detecting obstacles/landmarks during navigation. I demonstrate that the reduced spatial resolution affects obstacle detection behaviour in homing ants (Chapter3). Once ants are close to their home, they pinpoint its entrance using landmarks. In an Australian bull ant Myrmecia pyriformis, I tested whether reduced body/eye size affects this behaviour. I show that a reduced size within-colony does not affect their ability to learn and use a nest-associated landmark (Chapter 4). A fundamental form of navigation involves following a compass. Using a behavioural experiment, I illustrate that this ability is not affected by a reduced number of ommatidia, suggesting that high spatial resolution may not be necessary for this behaviour (Chapter 5). Thus both physiological and behavioural studies show that there is a clear effect of miniaturisation on the animal's spatial vision and obstacle avoidance behaviour. However, miniaturisation did not affect the ability to pinpoint landmarks or to use a compass. These findings add to our understanding of the evolution of miniature ants which may be capable of various visual navigation behaviours in spite of limited sensory abilities.Mode of access: World wide web1 online resource (iv, 146 pages) illustrations (some colour

How to work with children and animals: A guide for school-based citizen science in wildlife research

Engaging school students in wildlife research through citizen science projects can be a win–win for scientists and educators. Not only does it provide a way for scientists to gather new data, but it can also con-tribute to science education and help younger generations become more environmentally aware. However, wild-life research can be challenging in the best of circumstances, and there are few guidelines available to help scientists create successful citizen science projects for school students. This paper explores the opportunities and challenges faced when developing school-based citizen science projects in wildlife research by synthesising two sources of information. First, we conducted a small, school-based citizen science project that investigated the effects of supplementary feeding on urban birds as a case study. Second, we reviewed the literature to develop a database of school-based citizen science projects that address questions in wildlife ecology and conservation. Based on these activities, we present five lessons for scientists considering a school-based citizen science project. Overall, we found that school-based citizen science projects must be carefully designed to ensure reliable data are collected, students remain engaged, and the project is achievable under the logistical constraints presented by conducting wildlife research in a school environment. Ultimately, we conclude that school-based citizen science projects can be a powerful way of collecting wildlife data while also contributing to the education and development of environmentally aware students