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| 2. |
- Dacke, Marie, et al.
(författare)
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How Dung Beetles Steer Straight
- 2021
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Ingår i: Annual Review of Entomology. - : Annual Reviews. - 0066-4170 .- 1545-4487. ; 66, s. 243-256
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Tidskriftsartikel (refereegranskat)abstract
- Distant and predictable features in the environment make ideal compass cues to allow movement along a straight path. Ball-rolling dung beetles use a wide range of different signals in the day or night sky to steer themselves along a fixed bearing. These include the sun, the Milky Way, and the polarization pattern generated by the moon. Almost two decades of research into these remarkable creatures have shown that the dung beetle's compass is flexible and readily adapts to the cues available in its current surroundings. In the morning and afternoon, dung beetles use the sun to orient, but at midday, they prefer to use the wind, and at night or in a forest, they rely primarily on polarized skylight to maintain straight paths. We are just starting to understand the neuronal substrate underlying the dung beetle's compass and the mystery of why these beetles start each journey with a dance.
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| 3. |
- Li, Meng, et al.
(författare)
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Potential for identification of wild night-flying moths by remote infrared microscopy
- 2022
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Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5662. ; 19:191
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Tidskriftsartikel (refereegranskat)abstract
- There are hundreds of thousands of moth species with crucial ecological roles that are often obscured by their nocturnal lifestyles. The pigmentation and appearance of moths are dominated by cryptic diffuse shades of brown. In this study, 82 specimens representing 26 moth species were analysed using infrared polarimetric hyperspectral imaging in the range of 0.95–2.5 µm. Contrary to previous studies, we demonstrate that since infrared light does not resolve the surface roughness, wings appear glossy and specular at longer wavelengths. Such properties provide unique reflectance spectra between species. The reflectance of the majority of our species could be explained by comprehensive models, and a complete parametrization of the spectral, polarimetric and angular optical properties was reduced to just 11 parameters with physical units. These parameters are complementary and, compared with the within-species variation, were significantly distinct between species. Counterintuitively to the aperture-limited resolution criterion, we could deduce microscopic features along the surface from their infrared properties. These features were confirmed by electron microscopy. Finally, we show how our findings could greatly enhance opportunities for remote identification of free-flying moth species, and we hypothesize that such flat specular wing targets could be expected to be sensed over considerable distances.
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| 4. |
- Céchetto, Clément, et al.
(författare)
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Visual detection threshold in the echolocating Daubenton’s bat (Myotis daubentonii)
- 2023
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 226:2
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Tidskriftsartikel (refereegranskat)abstract
- All bats possess eyes that are of adaptive value. Echolocating bats have retinae dominated by rod photoreceptors and use dim light vision for navigation, and in rare cases for hunting. However, the visual detection threshold of insectivorous echolocating bats remains unknown. Here, we determined this threshold for the vespertilionid bat Myotis daubentonii. We show that for a green luminous target, M. daubentonii has a visual luminance threshold of 3.2(±0.9)×10−4 cd m−2, an intensity corresponding to the luminance of an open cloudless terrestrial habitat on a starlit night. Our results show that echolocating bats have good visual sensitivity, allowing them to see during their active periods. Together with previous results showing that M. daubentonii has poor visual acuity (∼0.6 cycles deg−1), this suggests that echolocating bats do not use vision to hunt but rather to orient themselves.
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| 5. |
- de Vries, Liv, et al.
(författare)
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Comparison of Navigation-Related Brain Regions in Migratory versus Non-Migratory Noctuid Moths
- 2017
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Ingår i: Frontiers in Behavioral Neuroscience. - : Frontiers Media SA. - 1662-5153. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Brain structure and function are tightly correlated across all animals. While these relations are ultimately manifestations of differently wired neurons, many changes in neural circuit architecture lead to larger-scale alterations visible already at the level of brain regions. Locating such differences has served as a beacon for identifying brain areas that are strongly associated with the ecological needs of a species—thus guiding the way towards more detailed investigations of how brains underlie species-specific behaviors. Particularly in relation to sensory requirements, volume-differences in neural tissue between closely related species reflect evolutionary investments that correspond to sensory abilities. Likewise, memory-demands imposed by lifestyle have revealed similar adaptations in regions associated with learning. Whether this is also the case for species that differ in their navigational strategy is currently unknown. While the brain regions associated with navigational control in insects have been identified (central complex (CX), lateral complex (LX) and anterior optic tubercles (AOTU)), it remains unknown in what way evolutionary investments have been made to accommodate particularly demanding navigational strategies. We have thus generated average-shape atlases of navigation-related brain regions of a migratory and a non-migratory noctuid moth and used volumetric analysis to identify differences. We further compared the results to identical data from Monarch butterflies. Whereas we found differences in the size of the nodular unit of the AOTU, the LX and the protocerebral bridge (PB) between the two moths, these did not unambiguously reflect migratory behavior across all three species. We conclude that navigational strategy, at least in the case of long-distance migration in lepidopteran insects, is not easily deductible from overall neuropil anatomy. This suggests that the adaptations needed to ensure successful migratory behavior are found in the detailed wiring characteristics of the neural circuits underlying navigation—differences that are only accessible through detailed physiological and ultrastructural investigations. The presented results aid this task in two ways. First, the identified differences in neuropil volumes serve as promising initial targets for electrophysiology. Second, the new standard atlases provide an anatomical reference frame for embedding all functional data obtained from the brains of the Bogong and the Turnip moth.
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| 6. |
- Reber, Therese, et al.
(författare)
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Bumblebees perform well-controlled landings in dim light
- 2016
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Ingår i: Frontiers in Behavioral Neuroscience. - : Frontiers Media SA. - 1662-5153. ; 10:SEP
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Tidskriftsartikel (refereegranskat)abstract
- To make a smooth touchdown when landing, an insect must be able to reliably control its approach speed as well as its body and leg position—behaviors that are thought to be regulated primarily by visual information. Bumblebees forage and land under a broad range of light intensities and while their behavior during the final moments of landing has been described in detail in bright light, little is known about how this is affected by decreasing light intensity. Here, we investigate this by characterizing the performance of bumblebees, B. terrestris, landing on a flat platform at two different orientations (horizontal and vertical) and at four different light intensities (ranging from 600 lx down to 19 lx). As light intensity decreased, the bees modified their body position and the distance at which they extended their legs, suggesting that the control of landing in these insects is visually mediated. Nevertheless, the effect of light intensity was small and the landings were still well controlled, even in the dimmest light. We suggest that the changes in landing behavior that occurred in dim light might represent adaptations that allow the bees to perform smooth landings across the broad range of light intensities at which they are active.
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| 7. |
- Stone, Thomas, et al.
(författare)
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An Anatomically Constrained Model for Path Integration in the Bee Brain
- 2017
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Ingår i: Current Biology. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 27:20, s. 11-3085
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Tidskriftsartikel (refereegranskat)abstract
- Path integration is a widespread navigational strategy in which directional changes and distance covered are continuously integrated on an outward journey, enabling a straight-line return to home. Bees use vision for this task-a celestial-cue-based visual compass and an optic-flow-based visual odometer-but the underlying neural integration mechanisms are unknown. Using intracellular electrophysiology, we show that polarized-light-based compass neurons and optic-flow-based speed-encoding neurons converge in the central complex of the bee brain, and through block-face electron microscopy, we identify potential integrator cells. Based on plausible output targets for these cells, we propose a complete circuit for path integration and steering in the central complex, with anatomically identified neurons suggested for each processing step. The resulting model circuit is thus fully constrained biologically and provides a functional interpretation for many previously unexplained architectural features of the central complex. Moreover, we show that the receptive fields of the newly discovered speed neurons can support path integration for the holonomic motion (i.e., a ground velocity that is not precisely aligned with body orientation) typical of bee flight, a feature not captured in any previously proposed model of path integration. In a broader context, the model circuit presented provides a general mechanism for producing steering signals by comparing current and desired headings-suggesting a more basic function for central complex connectivity, from which path integration may have evolved.
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| 8. |
- Chen, Hui, et al.
(författare)
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Adaptive migratory orientation of an invasive pest on a new continent
- 2023
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Ingår i: iScience. - 2589-0042. ; 26:12
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Tidskriftsartikel (refereegranskat)abstract
- Many species of insects undertake long-range, seasonally reversed migrations, displaying sophisticated orientation behaviors to optimize their migratory trajectories. However, when invasive insects arrive in new biogeographical regions, it is unclear if migrants retain (or how quickly they regain) ancestral migratory traits, such as seasonally preferred flight headings. Here we present behavioral evidence that an invasive migratory pest, the fall armyworm moth (Spodoptera frugiperda), a native of the Americas, exhibited locally adaptive migratory orientation less than three years after arriving on a new continent. Specimens collected from China showed flight orientations directed north-northwest in spring and southwest in autumn, and this would promote seasonal forward and return migrations in East Asia. We also show that the driver of the seasonal switch in orientation direction is photoperiod. Our results thus provide a clear example of an invasive insect that has rapidly exhibited adaptive migratory behaviors, either inherited or newly evolved, in a completely alien environment.
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| 9. |
- Rutowski, R. L., et al.
(författare)
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Visual acuity and sensitivity increase allometrically with body size in butterflies
- 2009
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Ingår i: Arthropod Structure & Development. - : Elsevier BV. - 1467-8039. ; 38:2, s. 91-100
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Tidskriftsartikel (refereegranskat)abstract
- In insects, the surface area of the compound eye increases with body size both within and between species with only a slight negative allometry. This increase in surface area permits changes in eye structure that affect the eye's acuity and sensitivity, two features of eye performance that cannot be simultaneously maximized. Hence, as eye size varies within a lineage, so will the compromises between features that maximize acuity and those that maximize sensitivity. We examined these compromises in four species of nymphalid butterflies that varied in body mass over almost two orders of magnitude. The largest of these species was crepuscular and so additionally may indicate the potential effect of life style on eye structure. Across these species, as body size increased, facet diameters increased while interommatidial angles decreased. Finally, the eye parameter was fairly constant across species except in the crepuscular species in which some notably large values were observed in the frontal visual field. Based on our measurements, large butterflies have more acute and more sensitive vision than smaller butterflies. However, full understanding of the behavioral implications of this relationship awaits information on the temporal resolution of their eyes because typical flight velocities also increase with body size. (c) 2008 Elsevier Ltd. All rights reserved.
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| 10. |
- Wallace, Jesse Rudolf Amenuvegbe, et al.
(författare)
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Camera-based automated monitoring of flying insects in the wild (Camfi). II. flight behaviour and long-term population monitoring of migratory Bogong moths in Alpine Australia
- 2023
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Ingår i: Frontiers in Insect Science. - 2673-8600. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The Bogong moth Agrotis infusa is well known for its remarkable annual round-trip migration from its breeding grounds across eastern and southern Australia to its aestivation sites in the Australian Alps, to which it provides an important annual influx of nutrients. Over recent years, we have benefited from a growing understanding of the navigational abilities of the Bogong moth. Meanwhile, the population of Bogong moths has been shrinking. Recently, the ecologically and culturally important Bogong moth was listed as endangered by the IUCN Red List, and the establishment of a program for long-term monitoring of its population has been identified as critical for its conservation. Methods: Here, we present the results of two years of monitoring of the Bogong moth population in the Australian Alps using recently developed methods for automated wildlife-camera monitoring of flying insects, named Camfi. While in the Alps, some moths emerge from the caves in the evening to undertake seemingly random flights, filling the air with densities in the dozens per cubic metre. The purpose of these flights is unknown, but they may serve an important role in Bogong moth navigation. Results: We found that these evening flights occur throughout summer and are modulated by daily weather factors. We present a simple heuristic model of the arrival to and departure from aestivation sites by Bogong moths, and confirm results obtained from fox-scat surveys which found that aestivating Bogong moths occupy higher elevations as the summer progresses. Moreover, by placing cameras along two elevational transects below the summit of Mt. Kosciuszko, we found that evening flights were not random, but were systematically oriented in directions relative to the azimuth of the summit of the mountain. Finally, we present the first recorded observations of the impact of bushfire smoke on aestivating Bogong moths – a dramatic reduction in the size of a cluster of aestivating Bogong moths during the fire, and evidence of a large departure from the fire-affected area the day after the fire. Discussion: Our results highlight the challenges of monitoring Bogong moths in the wild and support the continued use of automated camera-based methods for that purpose.
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