| 1. |
- Jezeera, M. Asmi, et al.
(författare)
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Spatial resolution and sensitivity of the eyes of the stingless bee, Tetragonula iridipennis
- 2022
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Ingår i: Journal of Comparative Physiology A. Sensory, neural, and behavioral physiology. - : Springer Science and Business Media LLC. - 0340-7594 .- 1432-1351. ; 208:2, s. 225-238
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Tidskriftsartikel (refereegranskat)abstract
- Stingless bees are important pollinators in the tropics. The tremendous variation in body size makes them an excellent group to study how miniaturization affects vision and visual behaviours. Using direct measurements and micro-CT, we reconstructed the eye structure, estimated anatomical spatial resolution and optical sensitivity of the stingless bee Tetragonula iridipennis. T. iridipennis is similar in size to the Australian stingless bee Tetragonula carbonaria and is smaller than honeybees. It has correspondingly small eyes (area = 0.56 mm2), few ommatidia (2451 ± 127), large inter-facet (3.0 ± 0.6°) and acceptance angles (2.8°). Theoretical estimates suggest that T. iridipennis has poorer spatial resolution (0.17 cycles degree−1) than honeybees, bumblebees, and T. carbonaria. Its optical sensitivity (0.08 µm2 sr), though higher than expected, is within the range of diurnal bees. This may provide them with greater contrast sensitivity, which is likely more relevant than the absolute sensitivity in this diurnal bee. Behaviourally determined detection thresholds for single targets using y-maze experiments were 11.5° for targets that provide chromatic contrast alone and 9.1° for targets providing chromatic and achromatic contrast. Further studies into microhabitat preferences and behaviour are required to understand how miniaturization influences its visual ecology.
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| 2. |
- Johansson, Christoffer, et al.
(författare)
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Multiple leading edge vortices of unexpected strength in freely flying hawkmoth.
- 2013
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- The Leading Edge Vortex (LEV) is a universal mechanism enhancing lift in flying organisms. LEVs, generally illustrated as a single vortex attached to the wing throughout the downstroke, have not been studied quantitatively in freely flying insects. Previous findings are either qualitative or from flappers and tethered insects. We measure the flow above the wing of freely flying hawkmoths and find multiple simultaneous LEVs of varying strength and structure along the wingspan. At the inner wing there is a single, attached LEV, while at mid wing there are multiple LEVs, and towards the wingtip flow separates. At mid wing the LEV circulation is ~40% higher than in the wake, implying that the circulation unrelated to the LEV may reduce lift. The strong and complex LEV suggests relatively high flight power in hawmoths. The variable LEV structure may result in variable force production, influencing flight control in the animals.
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| 3. |
- Chakravarthi, Aravin, et al.
(författare)
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High contrast sensitivity for visually guided flight control in bumblebees
- 2017
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Ingår i: Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology. - : Springer Science and Business Media LLC. - 1432-1351. ; 203:12, s. 999-1006
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Tidskriftsartikel (refereegranskat)abstract
- Many insects rely on vision to find food, to return to their nest and to carefully control their flight between these two locations. The amount of information available to support these tasks is, in part, dictated by the spatial resolution and contrast sensitivity of their visual systems. Here, we investigate the absolute limits of these visual properties for visually guided position and speed control in Bombus terrestris. Our results indicate that the limit of spatial vision in the translational motion detection system of B. terrestris lies at 0.21 cycles deg−1 with a peak contrast sensitivity of at least 33. In the perspective of earlier findings, these results indicate that bumblebees have higher contrast sensitivity in the motion detection system underlying position control than in their object discrimination system. This suggests that bumblebees, and most likely also other insects, have different visual thresholds depending on the behavioral context.
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| 4. |
- Murugavel, Baheerathan, et al.
(författare)
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Effect of artificial light on activity in frugivorous bats (Pteropodidae)
- 2023
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Ingår i: Journal of Ethology. - : Springer Science and Business Media LLC. - 0289-0771 .- 1439-5444. ; 41:1, s. 91-101
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Tidskriftsartikel (refereegranskat)abstract
- Artificial lighting at nights (ALAN) affects behaviour in many animals, especially nocturnal species. However, its effect on frugivorous bats remains less explored, especially in the family Pteropodidae. Since they rely predominantly on vision and light-based cues, ALAN at roost sites could have consequences on their behaviour, activity, and the ecosystem services they provide. In a semi-urban site in southern India, we compared the emergence-return activity of the cave-roosting Rousettus leschenaultii, between a roost in an undisturbed, naturally-lit agricultural well and an artificially-lit roost in a temple. We also compared emergence times between five colonies of the tree-roosting Pteropus giganteus (currently P. medius) that were exposed to different intensities of artificial light. Emergence-return flights at the naturally-lit R. leschenaultii roost occurred significantly earlier than at the artificially-lit roost. Peak flight activity across nights varied more in the naturally-lit than at the artificially-lit roost. Nightly flight durations (interval between peak emergence and peak return times) varied more in the naturally-lit roost, while mean flight durations were similar between these roosts. In P. giganteus, emergence was significantly earlier in the highly light-polluted roost than in the other roosts. These modified flight activities could have potential consequences on the physiology and ecology of fruit bats and requires further study. Moreover, the effect of ALAN on seed dispersal and pollination services provided by fruit bats in tropical landscapes remains to be understood.
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| 5. |
- Potier, Simon, et al.
(författare)
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Binocular field configuration in owls : The role of foraging ecology
- 2023
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Ingår i: Proceedings of the Royal Society B: Biological Sciences. - 0962-8452. ; 290:2009
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Tidskriftsartikel (refereegranskat)abstract
- The binocular field of vision differs widely in birds depending on ecological traits such as foraging. Owls (Strigiformes) have been considered to have a unique binocular field, but whether it is related to foraging has remained unknown. While taking into account allometry and phylogeny, we hypothesized that both daily activity cycle and diet determine the size and shape of the binocular field in owls. Here, we compared the binocular field configuration of 23 species of owls. While we found no effect of allometry and phylogeny, ecological traits strongly influence the binocular field shape and size. Binocular field shape of owls significantly differed from that of diurnal raptors. Among owls, binocular field shape was relatively conserved, but binocular field size differed among species depending on ecological traits, with larger binocular fields in species living in dense habitat and foraging on invertebrates. Our results suggest that (i) binocular field shape is associated with the time of foraging in the daily cycle (owls versus diurnal raptors) and (ii) that binocular field size differs between closely related owl species even though the general shape is conserved, possibly because the field of view is partially restricted by feathers, in a trade-off with auditory localization.
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| 6. |
- Kelber, Almut
(författare)
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Bird colour vision – from cones to perception
- 2019
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Ingår i: Current Opinion in Behavioral Sciences. - : Elsevier BV. - 2352-1554 .- 2352-1546. ; 30, s. 34-40
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Forskningsöversikt (refereegranskat)abstract
- Birds use spectral information for circadian control, magnetic orientation and phototaxis but most importantly for discriminating the colours of important objects such as food items or mates. Their tetrachromatic colour vision is based on four types of single cones expressing four opsin-based visual pigments and fine-tuned by the carotenoid composition in cone oil droplets. Bird colour vision is not as uniform as previously thought, and single visual pigments have been lost in several bird lineages. Diurnal birds have fine colour discrimination and good colour constancy but can generalize over similar though discriminable colours. Bird colour discrimination is ultimately limited by receptor noise but can be impaired in natural conditions, depending on light intensity and background coloration.
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| 7. |
- Kelber, Almut, et al.
(författare)
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Evolution of color vision
- 2016
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Ingår i: Human Colour Vision. - Cham : Springer International Publishing. - 9783319449760 - 9783319449784 ; 5, s. 317-354
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Bokkapitel (refereegranskat)abstract
- Research conducted in recent years has documented the widespread presence of various forms of color vision in species from across the animal kingdom, helped to develop an understanding of the basic biological mechanisms that underlie this sensory capacity, and provided some insights into the utility of color vision in the natural world. This chapter draws information from all these various sources to reveal what has been learned about the evolution of color vision. In doing so, we examine the extent and nature of animal color vision, describe various structural features of eyes and photoreceptors that condition color vision, look at photopigment opsin genes and their color vision concomitants, and comment on specific cases where progress has been made toward understanding the functional utility of color vision. Although results from a wide range of different species are considered, we focus particular attention on issues relevant to the evolution of vertebrate color vision.
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| 8. |
- Kelber, Almut, et al.
(författare)
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Spatial vision and visually guided behavior in apidae
- 2019
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Ingår i: Insects. - : MDPI AG. - 2075-4450. ; 10:12
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Forskningsöversikt (refereegranskat)abstract
- The family Apidae, which is amongst the largest bee families, are important pollinators globally and have been well studied for their visual adaptations and visually guided behaviors. This review is a synthesis of what is known about their eyes and visual capabilities. There are many species-specific differences, however, the relationship between body size, eye size, resolution, and sensitivity shows common patterns. Salient differences between castes and sexes are evident in important visually guided behaviors such as nest defense and mate search. We highlight that Apis mellifera and Bombus terrestris are popular bee models employed in the majority of studies that have contributed immensely to our understanding vision in bees. However, other species, specifically the tropical and many non-social Apidae, merit further investigation for a better understanding of the influence of ecological conditions on the evolution of bee vision.
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| 9. |
- Kelber, Almut
(författare)
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Vision : Rods See in Bright Light
- 2018
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 28:8, s. 364-366
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Tidskriftsartikel (refereegranskat)abstract
- Rods, usually associated with highly sensitive dim-light vision, contribute to vision even in bright photopic intensities. New results in mice have important implications for vision of animals with rod-dominated or pure rod retinae. Rods, usually associated with highly sensitive dim-light vision, contribute to vision even in bright photopic intensities. New results in mice have important implications for vision of animals with rod-dominated or pure rod retinae.
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| 10. |
- Mitkus, Mindaugas, et al.
(författare)
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Vision on the high seas : Spatial resolution and optical sensitivity in two procellariiform seabirds with different foraging strategies
- 2016
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 219:21, s. 3329-3338
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Tidskriftsartikel (refereegranskat)abstract
- Procellariiform or 'tubenosed' seabirds are challenged to find prey and orient over seemingly featureless oceans. Previous studies have found that life-history strategy (burrow versus surface nesting) was correlated to foraging strategy. Burrow nesters tended to track prey using dimethyl sulphide (DMS), a compound associated with phytoplankton, whereas surface-nesting species did not. Burrow nesters also tended to be smaller and more cryptic, whereas surface nesters were larger with contrasting plumage coloration. Together these results suggested that differences in life-history strategy might also be linked to differences in visual adaptations. Here, we used Leach's storm petrel, a DMSresponder, and northern fulmar, a non-responder, as model species to test this hypothesis on their sensory ecology. From the retinal ganglion cell density and photoreceptor dimensions,we determined that Leach's storm petrels have six times lower spatial resolution than the northern fulmars. However, the optical sensitivity of rod photoreceptors is similar between species. These results suggest that under similar atmospheric conditions, northern fulmars have six times the detection range for similarly sized objects. Both species have extended visual streaks with a central area of highest spatial resolution, but only the northern fulmar has a central fovea. The prediction that burrow-nesting DMSresponding procellariiforms should differ from non-responding species nesting in the open holds true for spatial resolution, but not for optical sensitivity. This result may reflect the fact that both species rely on olfaction for their nocturnal foraging activity, but northern fulmars might use vision more during daytime.
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