| 1. |
- Smolka, Jochen, et al.
(författare)
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Night sky orientation with diurnal and nocturnal eyes: dim-light adaptations are critical when the moon is out of sight
- 2016
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Ingår i: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 111, s. 127-146
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Tidskriftsartikel (refereegranskat)abstract
- The visual systems of many animals feature energetically costly specializations to enable them to function in dim light. It is often unclear, however, how large the behavioural benefit of these specializations is, because a direct comparison in a behaviourally relevant task between closely related day- and night-active species is not usually possible. Here we compared the orientation performance of diurnal and nocturnal species of dung beetles, Scarabaeus (Kheper) lamarcki and Scarabaeus satyrus, respectively, attempting to roll dung balls along straight paths both during the day and at night. Using video tracking, we quantified the straightness of paths and the repeatability of roll bearings as beetles exited a flat arena in their natural habitat or under controlled conditions indoors. Both species oriented equally well when either the moon or an artificial point light source was available, but when the view of the moon was blocked and only wide-field cues such as the lunar polarization pattern or the stars were available for orientation, nocturnal beetles were oriented substantially better. We found no evidence that ball-rolling speed changed with light level, which suggests little or no temporal summation in the visual system. Finally, we found that both diurnal and nocturnal beetles tended to choose bearings that led them towards a bright light source, but away from a dim one. Our results show that even diurnal insects, at least those with superposition eyes, could orient by the light of the moon, but that dim-light adaptations are needed for precise orientation when the moon is not visible.
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| 2. |
- Dacke, Marie, et al.
(författare)
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A dung beetle that path integrates without the use of landmarks
- 2020
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Ingår i: Animal Cognition. - : Springer Science and Business Media LLC. - 1435-9448 .- 1435-9456. ; 23, s. 1161-1175
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Tidskriftsartikel (refereegranskat)abstract
- Unusual amongst dung beetles,Scarabaeus galenusdigs a burrow that it provisions by making repeated trips to a nearby dung pile. Even more remarkable is that these beetles return home moving backwards, with a pellet of dung between their hind legs. Here, we explore the strategy thatS. galenususes to find its way home. We find that, like many other insects, they use path integration to calculate the direction and distance to their home. If they fail to locate their burrow, the beetles initiate a distinct looping search behaviour that starts with a characteristic sharp turn, we have called a 'turning point'. When homing beetles are passively displaced or transferred to an unfamiliar environment, they initiate a search at a point very close to the location of their fictive burrow-that is, a spot at the same relative distance and direction from the pick-up point as the original burrow. Unlike other insects,S. galenusdo not appear to supplement estimates of the burrow location with landmark information. Thus,S. galenusrepresents a rare case of a consistently backward-homing animal that does not use landmarks to augment its path integration strategy.
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| 3. |
- 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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| 4. |
- El Jundi, Basil, et al.
(författare)
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The brain behind straight-line orientation in dung beetles
- 2019
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 222
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Forskningsöversikt (refereegranskat)abstract
- For many insects, celestial compass cues play an important role in keeping track of their directional headings. One well-investigated group of celestial orientating insects are the African ball-rolling dung beetles. After finding a dung pile, these insects detach a piece, form it into a ball and roll it away along a straight path while facing backwards. A brain region, termed the central complex, acts as an internal compass that constantly updates the ball-rolling dung beetle about its heading. In this review, we give insights into the compass network behind straight-line orientation in dung beetles and place it in the context of the orientation mechanisms and neural networks of other insects. We find that the neuronal network behind straight-line orientation in dung beetles has strong similarities to the ones described in path-integrating and migrating insects, with the central complex being the key control point for this behavior. We conclude that, despite substantial differences in behavior and navigational challenges, dung beetles encode compass information in a similar way to other insects.
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| 5. |
- Yilmaz, Ayse, et al.
(författare)
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Mechanisms of spectral orientation in a diurnal dung beetle
- 2022
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : Royal Society Publishing. - 0962-8436 .- 1471-2970. ; 377:1862
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Tidskriftsartikel (refereegranskat)abstract
- Ball rolling dung beetles use a wide range of cues to steer themselves along a fixed bearing, including the spectral gradient of scattered skylight that spans the sky. Here, we define the spectral sensitivity of the diurnal dung beetle Kheper lamarcki and use the information to explore the orientation performance under a range of spectral light combinations. We find that, when presented with spectrally diverse stimuli, the beetles primarily orient to the apparent brightness differences as perceived by their green photoreceptors. Under certain wavelength combinations, they also rely on spectral information to guide their movements, but the brightness and spectral directional information is never fully disentangled. Overall, our results suggest the use of a dichromatic, primitive colour vision system for the extraction of directional information from the celestial spectral gradient to support straight-line orientation.
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| 6. |
- Dreyer, David, et al.
(författare)
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Evidence for a southward autumn migration of nocturnal noctuid moths in central Europe
- 2018
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Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 221
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Tidskriftsartikel (refereegranskat)abstract
- Insect migrations are spectacular natural events and resemble a remarkable relocation of biomass between two locations in space. Unlike the well-known migrations of daytime flying butterflies, such as the painted lady (Vanessa cardui) or the monarch butterfly (Danaus plexippus), much less widely known are the migrations of nocturnal moths. These migrations - typically involving billions of moths from different taxa - have recently attracted considerable scientific attention. Nocturnal moth migrations have traditionally been investigated by light trapping and by observations in the wild, but in recent times a considerable improvement in our understanding of this phenomenon has come from studying insect orientation behaviour, using vertical-looking radar. In order to establish a new model organism to study compass mechanisms in migratory moths, we tethered each of two species of central European Noctuid moths in a flight simulator to study their flight bearings: the red underwing (Catocala nupta) and the large yellow underwing (Noctua pronuba). Both species had significantly oriented flight bearings under an unobscured view of the clear night sky and in the Earth's natural magnetic field. Red underwings oriented south-southeast, while large yellow underwings oriented southwest, both suggesting a southerly autumn migration towards the Mediterranean. Interestingly, large yellow underwings became disoriented on humid (foggy) nights while red underwings remained oriented. We found no evidence in either species for a time-independent sky compass mechanism as previously suggested for the large yellow underwing.
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| 7. |
- Franzke, Myriam, et al.
(författare)
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Spatial orientation based on multiple visual cues in non-migratory monarch butterflies
- 2020
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Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 223
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Tidskriftsartikel (refereegranskat)abstract
- Monarch butterflies (Danaus plexippus) are prominent for their annual long-distance migration from North America to their overwintering area in Central Mexico. To find their way on this long journey, they use a sun compass as their main orientation reference but will also adjust their migratory direction with respect to mountain ranges. This indicates that the migratory butterflies also attend to the panorama to guide their travels. Although the compass has been studied in detail in migrating butterflies, little is known about the orientation abilities of non-migrating butterflies. Here, we investigated whether non-migrating butterflies - which stay in a more restricted area to feed and breed - also use a similar compass system to guide their flights. Performing behavioral experiments on tethered flying butterflies in an indoor LED flight simulator, we found that the monarchs fly along straight tracks with respect to a simulated sun. When a panoramic skyline was presented as the only orientation cue, the butterflies maintained their flight direction only during short sequences, suggesting that they potentially use it for flight stabilization. We further found that when we presented the two cues together, the butterflies incorporate both cues in their compass. Taken together, we show here that non-migrating monarch butterflies can combine multiple visual cues for robust orientation, an ability that may also aid them during their migration.
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| 8. |
- Immonen, Esa Ville, et al.
(författare)
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Anatomical organization of the brain of a diurnal and a nocturnal dung beetle
- 2017
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Ingår i: Journal of Comparative Neurology. - : Wiley. - 0021-9967. ; 525:8, s. 1879-1908
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Tidskriftsartikel (refereegranskat)abstract
- To avoid the fierce competition for food, South African ball-rolling dung beetles carve a piece of dung off a dung-pile, shape it into a ball and roll it away along a straight line path. For this unidirectional exit from the busy dung pile, at night and day, the beetles use a wide repertoire of celestial compass cues. This robust and relatively easily measurable orientation behavior has made ball-rolling dung beetles an attractive model organism for the study of the neuroethology behind insect orientation and sensory ecology. Although there is already some knowledge emerging concerning how celestial cues are processed in the dung beetle brain, little is known about its general neural layout. Mapping the neuropils of the dung beetle brain is thus a prerequisite to understand the neuronal network that underlies celestial compass orientation. Here, we describe and compare the brains of a day-active and a night-active dung beetle species based on immunostainings against synapsin and serotonin. We also provide 3D reconstructions for all brain areas and many of the fiber bundles in the brain of the day-active dung beetle. Comparison of neuropil structures between the two dung beetle species revealed differences that reflect adaptations to different light conditions. Altogether, our results provide a reference framework for future studies on the neuroethology of insects in general and dung beetles in particular.
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| 9. |
- Heinze, Stanley, et al.
(författare)
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A unified platform to manage, share, and archive morphological and functional data in insect neuroscience
- 2021
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Ingår i: eLife. - 2050-084X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Insect neuroscience generates vast amounts of highly diverse data, of which only a small fraction are findable, accessible and reusable. To promote an open data culture, we have therefore developed the InsectBrainDatabase (IBdb), a free online platform for insect neuroanatomical and functional data. The IBdb facilitates biological insight by enabling effective cross-species comparisons, by linking neural structure with function, and by serving as general information hub for insect neuroscience. The IBdb allows users to not only effectively locate and visualize data, but to make them widely available for easy, automated reuse via an application programming interface. A unique private mode of the database expands the IBdb functionality beyond public data deposition, additionally providing the means for managing, visualizing, and sharing of unpublished data. This dual function creates an incentive for data contribution early in data management workflows and eliminates the additional effort normally associated with publicly depositing research data.
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| 10. |
- Beetz, M. Jerome, et al.
(författare)
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Flight-induced compass representation in the monarch butterfly heading network
- 2022
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 32:2, s. 5-349
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Tidskriftsartikel (refereegranskat)abstract
- For navigation, animals use a robust internal compass. Compass navigation is crucial for long-distance migrating animals like monarch butterflies, which use the sun to navigate over 4,000 km to their overwintering sites every fall. Sun-compass neurons of the central complex have only been recorded in immobile butterflies, and experimental evidence for encoding the animal's heading in these neurons is still missing. Although the activity of central-complex neurons exhibits a locomotor-dependent modulation in many insects, the function of such modulations remains unexplored. Here, we developed tetrode recordings from tethered flying monarch butterflies to reveal how flight modulates heading representation. We found that, during flight, heading-direction neurons change their tuning, transforming the central-complex network to function as a global compass. This compass is characterized by the dominance of processing steering feedback and allows for robust heading representation even under unreliable visual scenarios, an ideal strategy for maintaining a migratory heading over enormous distances.
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