| 1. |
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| 2. |
- Arnadottir, Anna, et al.
(författare)
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The Meridian S03E04 : Finding the way using starlight
- 2023
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Astronomers, such as Nic and Rebecca, are not the only ones orienting themselves using the stars. Animals, big and small, also navigate by starlight. In this last episode of the third season we invited Prof. Marie Dacke from the Department of Biology over to tell us about her research on the subject.In this third season we are also including some Cosmic Curiosities. These are some ideas, events or trivia from astronomic history that Ross, Victor and Lucian feel are worth bringing out of obscurity for one more look.
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| 3. |
- Baird, Emily, et al.
(författare)
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Bearing selection in ball-rolling dung beetles: is it constant?
- 2010
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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. ; 196, s. 801-806
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Tidskriftsartikel (refereegranskat)abstract
- Ball rolling in dung beetles is thought to have evolved as a means to escape intense inter- and intra-specific competition at the dung pile. Accordingly, dung beetles typically roll along a straight-line path away from the pile, this being the most effective escape strategy for transporting dung to a suitable burial site. In this study, we investigate how individual diurnal dung beetles, Scarabaeus (Kheper) nigroaeneus, select the compass bearing of their straight-line rolls. In particular, we examine whether roll bearings are constant with respect to geographic cues, celestial cues, or other environmental cues (such as wind direction). Our results reveal that the roll bearings taken by individual beetles are not constant with respect to geographic or celestial references. Environmental cues appear to have some influence over bearing selection, although the relationship is not strong. Furthermore, the variance in roll bearing that we observe is not affected by the presence or absence of other beetles. Thus, rather than being constant for individual beetles, bearing selection varies each time a beetle makes a ball and rolls it away from the dung pile. This strategy allows beetles to make an efficient escape from the dung pile while minimizing the chance of encountering competition.
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| 4. |
- Baird, Emily, et al.
(författare)
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Finding the gap : A brightness-based strategy for guidance in cluttered environments
- 2016
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 0962-8452. ; 283:1828
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Tidskriftsartikel (refereegranskat)abstract
- The ability to move safely between obstacles is critical for animals that fly rapidly through cluttered environments but surprisingly little is known about how they achieve this. Do they reactively avoid obstacles or do they instead fly towards the gaps between them? If they aim towards gaps, what information do they use to detect and fly through them? Here, we aim to answer these questions by presenting orchid bees with different apertures. When negotiating gaps, orchid bees locate and fly close to the point that gives themgreatest clearance from the edges. The cue that they use to pinpoint this spot is the brightness gradient formed across the aperture. Furthermore, we find that orchid bees also rely on brightness cues to locate gaps that are sufficiently large to negotiate safely. The advantage of using brightness for locating and negotiating gaps in a cluttered environment is that it provides information about the safest path through obstacles, at least in a forest environment. This brightness-based guidance strategy for gap detection and negotiation represents a fast, computationally simple and efficient mechanism to identify the clearest path through a forest and is, therefore, likely to represent a more general mechanism used by other animals.
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| 5. |
- Baird, Emily, et al.
(författare)
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Minimum viewing angle for visually guided ground speed control in bumblebees.
- 2010
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 213:10, s. 1625-1632
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Tidskriftsartikel (refereegranskat)abstract
- To control flight, flying insects extract information from the pattern of visual motion generated during flight, known as optic flow. To regulate their ground speed, insects such as honeybees and Drosophila hold the rate of optic flow in the axial direction (front-to-back) constant. A consequence of this strategy is that its performance varies with the minimum viewing angle (the deviation from the frontal direction of the longitudinal axis of the insect) at which changes in axial optic flow are detected. The greater this angle, the later changes in the rate of optic flow, caused by changes in the density of the environment, will be detected. The aim of the present study is to examine the mechanisms of ground speed control in bumblebees and to identify the extent of the visual range over which optic flow for ground speed control is measured. Bumblebees were trained to fly through an experimental tunnel consisting of parallel vertical walls. Flights were recorded when (1) the distance between the tunnel walls was either 15 or 30 cm, (2) the visual texture on the tunnel walls provided either strong or weak optic flow cues and (3) the distance between the walls changed abruptly halfway along the tunnel's length. The results reveal that bumblebees regulate ground speed using optic flow cues and that changes in the rate of optic flow are detected at a minimum viewing angle of 23-30 deg., with a visual field that extends to approximately 155 deg. By measuring optic flow over a visual field that has a low minimum viewing angle, bumblebees are able to detect and respond to changes in the proximity of the environment well before they are encountered.
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| 6. |
- Baird, Emily, et al.
(författare)
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Nocturnal insects use optic flow for flight control.
- 2011
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Ingår i: Biology letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 7, s. 499-501
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Tidskriftsartikel (refereegranskat)abstract
- To avoid collisions when navigating through cluttered environments, flying insects must control their flight so that their sensory systems have time to detect obstacles and avoid them. To do this, day-active insects rely primarily on the pattern of apparent motion generated on the retina during flight (optic flow). However, many flying insects are active at night, when obtaining reliable visual information for flight control presents much more of a challenge. To assess whether nocturnal flying insects also rely on optic flow cues to control flight in dim light, we recorded flights of the nocturnal neotropical sweat bee, Megalopta genalis, flying along an experimental tunnel when: (i) the visual texture on each wall generated strong horizontal (front-to-back) optic flow cues, (ii) the texture on only one wall generated these cues, and (iii) horizontal optic flow cues were removed from both walls. We find that Megalopta increase their groundspeed when horizontal motion cues in the tunnel are reduced (conditions (ii) and (iii)). However, differences in the amount of horizontal optic flow on each wall of the tunnel (condition (ii)) do not affect the centred position of the bee within the flight tunnel. To better understand the behavioural response of Megalopta, we repeated the experiments on day-active bumble-bees (Bombus terrestris). Overall, our findings demonstrate that despite the limitations imposed by dim light, Megalopta-like their day-active relatives-rely heavily on vision to control flight, but that they use visual cues in a different manner from diurnal insects.
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| 7. |
- Baird, Emily, et al.
(författare)
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The dung beetle dance: an orientation behaviour?
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- An interesting feature of dung beetle behaviour is that once they have formed a piece of dung into a ball, they roll it along a straight path away from the dung pile. This straight-line orientation ensures that the beetles depart along the most direct route, guaranteeing that they will not return to the intense competition (from other beetles) that occurs near the dung pile. Before rolling a new ball away from the dung pile, dung beetles perform a characteristic "dance," in which they climb on top of the ball and rotate about their vertical axis. This dance behaviour can also be observed during the beetles' straight-line departure from the dung pile. The aim of the present study is to investigate the purpose of the dung beetle dance. To do this, we explored the circumstances that elicit dance behaviour in the diurnal ball-rolling dung beetle, Scarabaeus (Kheper) nigroaeneus. Our results reveal that dances are elicited when the beetles lose control of their ball or lose contact with it altogether. We also find that dances can be elicited by both active and passive deviations of course and by changes in visual cues alone. In light of these results, we hypothesise that the dung beetle dance is a visually mediated mechanism that facilitates straight-line orientation in ball-rolling dung beetles by allowing them to 1) establish a roll bearing and 2) return to this chosen bearing after experiencing a disturbance to the roll path.
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| 8. |
- Baird, Emily, et al.
(författare)
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Visual flight control in naturalistic and artificial environments.
- 2012
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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. ; 198:12, s. 869-876
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Tidskriftsartikel (refereegranskat)abstract
- Although the visual flight control strategies of flying insects have evolved to cope with the complexity of the natural world, studies investigating this behaviour have typically been performed indoors using simplified two-dimensional artificial visual stimuli. How well do the results from these studies reflect the natural behaviour of flying insects considering the radical differences in contrast, spatial composition, colour and dimensionality between these visual environments? Here, we aim to answer this question by investigating the effect of three- and two-dimensional naturalistic and artificial scenes on bumblebee flight control in an outdoor setting and compare the results with those of similar experiments performed in an indoor setting. In particular, we focus on investigating the effect of axial (front-to-back) visual motion cues on ground speed and centring behaviour. Our results suggest that, in general, ground speed control and centring behaviour in bumblebees is not affected by whether the visual scene is two- or three dimensional, naturalistic or artificial, or whether the experiment is conducted indoors or outdoors. The only effect that we observe between naturalistic and artificial scenes on flight control is that when the visual scene is three-dimensional and the visual information on the floor is minimised, bumblebees fly further from the midline of the tunnel. The findings presented here have implications not only for understanding the mechanisms of visual flight control in bumblebees, but also for the results of past and future investigations into visually guided flight control in other insects.
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| 9. |
- Balkenius, Anna, et al.
(författare)
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Learning of Multi-Modal Stimuli in Hawkmoths
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The hawkmoth, Manduca sexta, uses both colour and odour to find flowers when foraging for nectar. In the present study we investigated how vision and olfaction interact during learning. Manduca sexta were equally attracted to a scented blue coloured feeding target (multimodal stimulus) as to one that does not carry any scent (unimodal stimulus; visual) or to an invisible scented target (unimodal stimulus; odour). This naive attraction to multimodal as well as to unimodal stimuli could be manipulated through training. Moths trained to feed from a blue, scented multimodal feeding target will, when tested in a set-up containing all three feeding targets, select the multimodal target as well as the scented, unimodal target, but ignore the visual target. Interestingly, moths trained to feed from a blue, unimodal visual feeding target will select the visual target as well as the scented, multimodal target, but ignore the unimodal odour target. Our results indicate that a multimodal target is perceived as two separate modalities, colour and odour, rather than as a unique fused target. These findings differ from earlier studies of desert ants that perceive combined visual and odour signals as a unique fused stimulus following learning trials.
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| 10. |
- Balkenius, Anna, et al.
(författare)
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The Approach Behaviour of the Hawkmoth Manduca sexta toward Multi-modal Stimuli: A Simulation Model
- 2010
-
Ingår i: From Animals to Animats 11 : 11th International Conference on Simulation of Adaptive Behavior, SAB 2010, Paris - Clos Lucé, France, August 25-28, 2010. Proceedings - 11th International Conference on Simulation of Adaptive Behavior, SAB 2010, Paris - Clos Lucé, France, August 25-28, 2010. Proceedings. - 9783642151927 - 9783642151934 ; 6226, s. 232-241
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Konferensbidrag (refereegranskat)
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| 11. |
- Bijma, Nienke N., et al.
(författare)
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The effect of surface topography on the ball-rolling ability of Kheper lamarcki (Scarabaeidae)
- 2024
-
Ingår i: The Journal of experimental biology. - 1477-9145 .- 0022-0949. ; 227:1
-
Tidskriftsartikel (refereegranskat)abstract
- The most effective way to avoid intense inter- and intra-specific competition at the dung source, and to increase the distance to the other competitors, is to follow a single straight bearing. While ball-rolling dung beetles manage to roll their dung balls along nearly perfect straight paths when traversing flat terrain, the paths that they take when traversing more complex (natural) terrain are not well understood. In this study, we investigate the effect of complex surface topographies on the ball-rolling ability of Kheper lamarcki. Our results reveal that ball-rolling trajectories are strongly influenced by the characteristic scale of the surface structure. Surfaces with an increasing similarity between the average distance of elevations and the ball radius cause progressively more difficulties during ball transportation. The most important factor causing difficulties in ball transportation appears to be the slope of the substrate. Our results show that, on surfaces with a slope of 7.5 deg, more than 60% of the dung beetles lose control of their ball. Although dung beetles still successfully roll their dung ball against the slope on such inclinations, their ability to roll the dung ball sideways diminishes. However, dung beetles do not seem to adapt their path on inclines such that they roll their ball in the direction against the slope. We conclude that dung beetles strive for a straight trajectory away from the dung pile, and that their actual path is the result of adaptations to particular surface topographies.
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| 12. |
- Byrne, M, et al.
(författare)
-
Visual cues used by ball-rolling dung beetles for orientation
- 2003
-
Ingår i: Journal of Comparative Physiology A. - : Springer Science and Business Media LLC. - 1432-1351. ; 189:6, s. 411-418
-
Tidskriftsartikel (refereegranskat)abstract
- Ball rolling by dung beetles is considered to be a derived behaviour that evolved under pressure for space, and from competitors at the dung pat. Straight-line orientation away from the pat using a celestial cue should be the most successful rolling strategy to move dung to an unknown burial site. We tested this hypothesis in the field and the laboratory by presenting five species of ball-rolling beetles with different orientation tasks, involving reaction to obstacles as well as to reflected sunlight and artificial light sources. Beetles were found to consistently orientate along a chosen route, usually in the direction of the sun. Beetles rolling dung balls successfully negotiated barriers and returned to the original path as did beetles falling from ramps, or rotated about a fixed point while rolling a ball. The sun was found to be the main orientation cue, which could be substituted by reflected or artificial light. However, beetles reoriented themselves less accurately in response to lights in the laboratory, than they did to the reflected sun in the field. It is probable that phototactic orientation using the sun, which is widespread amongst arthropods, has been incorporated in the straight-line foraging behaviour that has evolved in ball-rolling dung beetles.
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| 13. |
- Chaib, Sandra, et al.
(författare)
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Dorsal landmark navigation in a Neotropical nocturnal bee
- 2021
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 31:16, s. 3-3605
-
Tidskriftsartikel (refereegranskat)abstract
- Bees, ants, and wasps are well known to visually navigate when traveling between their nests and foraging sites. When leaving their nest, landmarks in the vicinity are memorized and used upon return to locate the nest entrance.1,2 The Neotropical nocturnal sweat bee Megalopta genalis navigates under the forest canopy at light intensities ten times dimmer than starlight.3 Despite these dim conditions, Megalopta is able to memorize visual landmarks around the nest entrance in the frontal visual field.4 Even though frontal landmarks can clearly be discerned by Megalopta, the visual feature of greatest contrast in the rainforest at night is actually the dark dorsal silhouette of the distant canopy against the brighter night sky. Several species of ants,5–10 as well as a subsocial shield bug,11 use bright open gaps in the canopy as dorsal landmarks to navigate home while walking. Here we show that Megalopta is also able to distinguish dorsal landmarks during homing, the first flying insect known with this capacity. Megalopta is able to discriminate between differently oriented dorsal black striped patterns, or an “artificial canopy” of black circles, and to use this information to locate its nest entrance. These results suggest that the local foliage patterns created by the canopy against the brighter sky could potentially provide the bee with reliable landmark information for navigation during foraging and homing at night. Video Abstract: [Figure presented]
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| 14. |
- Chakravarthi, Aravin, et al.
(författare)
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Differences in spatial resolution and contrast sensitivity of flight control in the honeybees Apis cerana and Apis mellifera
- 2018
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 221:20
-
Tidskriftsartikel (refereegranskat)abstract
- Visually guided behaviour is constrained by the capacity of the visual system to resolve detail. This, in turn, is limited by the spatial resolution and contrast sensitivity of the underlying visual system. Because these properties are interdependent and vary nonuniformly, it is only possible to fully understand the limits of a specific visually guided behaviour when they are investigated in combination. To understand the visual limits of flight control in bees, which rely heavily on vision to control flight, and to explore whether they vary between species, we tested how changes in spatial resolution and contrast sensitivity affect the speed and position control of the Asian and European honeybees (Apis cerana and Apis mellifera). Despite the apparent similarity of these species, we found some interesting and surprising differences between their visual limits. While the effect of spatial frequency and contrast on position control is similar between the species, ground speed is differently affected by these variables. A comparison with published data from the bumblebee Bombus terrestris revealed further differences. The visual resolution that limits the detection and use of optic flow for flight control in both species of honeybee is lower than the previously anatomically determined resolution and differs from object detection limits of A. mellifera, providing evidence that the limits of spatial resolution and contrast sensitivity are highly tuned to the particular behavioural task of a species.
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| 15. |
- Chakravarthi, Aravin, et al.
(författare)
-
High contrast sensitivity for visually guided flight control in bumblebees
- 2017
-
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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| 16. |
- Chakravarthi, Aravin, et al.
(författare)
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How well can bees see the world?
- 2016
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Ingår i: Navigation News. - 0268-6317. ; MAR/APR 2016, s. 10-10
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 17. |
- Chakravarthi, Aravin, et al.
(författare)
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Spatial Vision in Bombus terrestris.
- 2016
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Ingår i: Frontiers in Behavioral Neuroscience. - : Frontiers Media SA. - 1662-5153. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- Bombus terrestris is one of the most commonly used insect models to investigate visually guided behavior and spatial vision in particular. Two fundamental measures of spatial vision are spatial resolution and contrast sensitivity. In this study, we report the threshold of spatial resolution in B. terrestris and characterize the contrast sensitivity function of the bumblebee visual system for a dual choice discrimination task. We trained bumblebees in a Y-maze experimental set-up to associate a vertical sinusoidal grating with a sucrose reward, and a horizontal grating with absence of a reward. Using a logistic psychometric function, we estimated a resolution threshold of 0.21 cycles deg(-1) of visual angle. This resolution is in the same range but slightly lower than that found in honeybees (Apis mellifera and A. cerana) and another bumblebee species (B. impatiens). We also found that the contrast sensitivity of B. terrestris was 1.57 for the spatial frequency 0.090 cycles deg(-1) and 1.26 for 0.18 cycles deg(-1).
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| 18. |
- Dacke, Marie, et al.
(författare)
-
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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| 19. |
- Dacke, Marie, et al.
(författare)
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A specialized dorsal rim area for polarized light detection in the compound eye of the scarab beetle Pachysoma striatum.
- 2002
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Ingår i: Journal of Comparative Physiology A. - : Springer Science and Business Media LLC. - 1432-1351. ; 188:3, s. 211-216
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Tidskriftsartikel (refereegranskat)abstract
- Many animals have been shown to use the pattern of polarized light in the sky as an optical compass. Specialised photoreceptors are used to analyse this pattern. We here present evidence for an eye design suitable for polarized skylight navigation in the flightless desert scarab Pachysoma striatum. Morphological and electrophysiological studies show that an extensive part of the dorsal eye is equivalent to the dorsal rim area used for polarized light navigation in other insects. A polarization-sensitivity of 12.8 (average) can be recorded from cells sensitive to the ultraviolet spectrum of light. Features commonly known to increase the visual fields of polarization-sensitive photoreceptors, or to decrease their spatial resolution, are not found in the eye of this beetle. We argue that in this insect an optically unspecialised area for polarized light detection allows it not be used exclusively for polarized light navigation.
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| 20. |
- Dacke, Marie
(författare)
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Celestial Orientation in Dim Light
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The polarization pattern of skylight offers many animals a reference for visual compass orientation. In those cases when this optical compass is identified, the receptors involved are often confined to a small part of an eye built predominantly for other visual tasks. This thesis reports the discovery of a unique compass organ in the spider Drassodes cupreus, where a pair of specialised secondary eyes co-operate to analyse skylight polarisation. These eyes have no refracting lens and thus can not form images. Moreover, the eyes use a built-in polariser to precisely determine the direction of polarisation. The spiders become active around sunset and use polarisation cues to find their way back to their nests after foraging trips. Measurements using a model eye indicate that the compass organ is best suited for navigation at twilight. The lack of a lens makes it possible for each receptor of the eye to collect light from a large region of the sky. This makes the compass organ well adapted to polarised light detection at low light levels. A comparative study of the eyes of several spider families suggests that this compass organ may not be an isolated phenomenon. The dung beetle Scarabaeus zambesianus also starts to forage around sunset. After locating a source of fresh animal droppings it forms a ball of dung and rolls off at high speed along a straight path to escape competition at and around the dung pile. Behavioural experiments in the field and in the laboratory, clearly show that the beetle is able to roll straight by orientating to the polarised light pattern of a twilight sky, as well as to the polarisation of a moon-lit sky. This is the first report of an animal using the polarisation pattern of the moon for orientation. The nocturnal polarised light pattern shows no significant difference in its structure from that of the pattern of polarised light formed around the sun. The two patterns do, however, differ in intensity by about one million times. The nocturnal polarised light detection system of this beetle is also similar to that of day-active insects, but with an increased sensitivity to light. Large rhabdoms, a reflecting tracheal sheet and a lack of screening pigments make the dung beetle eye well adapted for polarised light detection at low light levels.
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| 21. |
- Dacke, Marie, et al.
(författare)
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Dung beetles ignore landmarks for straight-line orientation
- 2012
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Ingår i: Journal of Comparative Physiology A. - : Springer Science and Business Media LLC. - 1432-1351 .- 0340-7594. ; 199, s. 17-23
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Tidskriftsartikel (refereegranskat)abstract
- Upon locating a suitable dung pile, ball-rolling dung beetles shape a piece of dung into a ball and roll it away in a straight line. This guarantees that they will not return to the dung pile, where they risk having their ball stolen by other beetles. Dung beetles are known to use celestial compass cues such as the sun, the moon and the pattern of polarised light formed around these light sources to roll their balls of dung along straight paths. Here, we investigate whether terrestrial landmarks have any influence on straight-line orientation in dung beetles. We find that the removal or re-arrangement of landmarks has no effect on the beetle’s orientation precision. Celestial compass cues dominate straight-line orientation in dung beetles so strongly that, under heavily overcast conditions or when prevented from seeing the sky, the beetles can no longer orient along straight paths. To our knowledge, this is the only animal with a visual compass system that ignores the extra orientation precision that landmarks can offer.
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| 22. |
- Dacke, Marie, et al.
(författare)
-
Dung Beetles Use the Milky Way for Orientation
- 2013
-
Ingår i: Current Biology. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 23:4, s. 298-300
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Tidskriftsartikel (refereegranskat)abstract
- When the moon is absent from the night sky, stars remain as celestial visual cues. Nonetheless, only birds [1, 2], seals [3], and humans [4] are known to use stars for orientation. African ball-rolling dung beetles exploit the sun, the moon, and the celestial polarization pattern to move along straight paths, away from the intense competition at the dung pile [5-9]. Even on clear moonless nights, many beetles still manage to orientate along straight paths [5]. This led us to hypothesize that dung beetles exploit the starry sky for orientation, a feat that has, to our knowledge, never been demonstrated in an insect. Here, we show that dung beetles transport their dung balls along straight paths under a starlit sky but lose this ability under overcast conditions. In a planetarium, the beetles orientate equally well when rolling under a full starlit sky as when only the Milky Way is present. The use of this bidirectional celestial cue for orientation has been proposed for vertebrates [10], spiders [11], and insects [5, 12], but never proven. This finding represents the first convincing demonstration for the use of the starry sky for orientation in insects and provides the first documented use of the Milky Way for orientation in the animal kingdom.
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| 23. |
- Dacke, Marie, et al.
(författare)
-
Evidence for counting in insects
- 2008
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Ingår i: Animal Cognition. - : Springer Science and Business Media LLC. - 1435-9456 .- 1435-9448. ; 11:4, s. 683-689
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Tidskriftsartikel (refereegranskat)abstract
- Here we investigate the counting ability in honeybees by training them to receive a food reward after they have passed a specific number of landmarks. The distance to the food reward is varied frequently and randomly, whilst keeping the number of intervening landmarks constant. Thus, the bees cannot identify the food reward in terms of its distance from the hive. We find that bees can count up to four objects, when they are encountered sequentially during flight. Furthermore, bees trained in this way are able count novel objects, which they have never previously encountered, thus demonstrating that they are capable of object-independent counting. A further experiment reveals that the counting ability that the bees display in our experiments is primarily sequential in nature. It appears that bees can navigate to food sources by maintaining a running count of prominent landmarks that are passed en route, provided this number does not exceed four.
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| 24. |
- Dacke, Marie, et al.
(författare)
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How dim is dim? Precision of the celestial compass in moonlight and sunlight.
- 2011
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Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2970 .- 0962-8436. ; 366:1565, s. 697-702
-
Tidskriftsartikel (refereegranskat)abstract
- Prominent in the sky, but not visible to humans, is a pattern of polarized skylight formed around both the Sun and the Moon. Dung beetles are, at present, the only animal group known to use the much dimmer polarization pattern formed around the Moon as a compass cue for maintaining travel direction. However, the Moon is not visible every night and the intensity of the celestial polarization pattern gradually declines as the Moon wanes. Therefore, for nocturnal orientation on all moonlit nights, the absolute sensitivity of the dung beetle's polarization detector may limit the precision of this behaviour. To test this, we studied the straight-line foraging behaviour of the nocturnal ball-rolling dung beetle Scarabaeus satyrus to establish when the Moon is too dim-and the polarization pattern too weak-to provide a reliable cue for orientation. Our results show that celestial orientation is as accurate during crescent Moon as it is during full Moon. Moreover, this orientation accuracy is equal to that measured for diurnal species that orient under the 100 million times brighter polarization pattern formed around the Sun. This indicates that, in nocturnal species, the sensitivity of the optical polarization compass can be greatly increased without any loss of precision.
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| 25. |
- Dacke, Marie, et al.
(författare)
-
How Dung Beetles Steer Straight
- 2021
-
Ingår i: Annual Review of Entomology. - : Annual Reviews. - 0066-4170 .- 1545-4487. ; 66, s. 243-256
-
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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| 26. |
- Dacke, Marie, et al.
(författare)
-
Insect orientation to polarized moonlight
- 2003
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 424:6944, s. 33-33
-
Tidskriftsartikel (refereegranskat)
|
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| 27. |
- Dacke, Marie, et al.
(författare)
-
Lunar orientation in a beetle
- 2004
-
Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 271:1537, s. 361-365
-
Tidskriftsartikel (refereegranskat)abstract
- Many animals use the sun's polarization pattern to orientate, but the dung beetle Scarabaeus zambesianus is the only animal so far known to orientate using the million times dimmer polarization pattern of the moonlit sky. We demonstrate the relative roles of the moon and the nocturnal polarized-light pattern for orientation. We find that artificially changing the position of the moon, or hiding the moon's disc from the beetle's field of view, generally did not influence its orientation performance. We thus conclude that the moon does not serve as the primary cue for orientation. The effective cue is the polarization pattern formed around the moon, which is more reliable for orientation. Polarization sensitivity ratios in two photoreceptors in the dorsal eye were found to be 7.7 and 12.9, similar to values recorded in diurnal navigators. These results agree with earlier results suggesting that the detection and analysis of polarized skylight is similar in diurnal and nocturnal insects.
|
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| 28. |
- Dacke, Marie
(författare)
-
Marie Dacke
- 2014
-
Ingår i: Current Biology. - 1879-0445. ; 24:12, s. 546-547
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 29. |
- Dacke, Marie, et al.
(författare)
-
Multimodal cue integration in the dung beetle compass
- 2019
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 116:28, s. 14248-14253
-
Tidskriftsartikel (refereegranskat)abstract
- South African ball-rolling dung beetles exhibit a unique orientation behavior to avoid competition for food: after forming a piece of dung into a ball, they efficiently escape with it from the dung pile along a straight-line path. To keep track of their heading, these animals use celestial cues, such as the sun, as an orientation reference. Here we show that wind can also be used as a guiding cue for the ball-rolling beetles. We demonstrate that this mechanosensory compass cue is only used when skylight cues are difficult to read, i.e., when the sun is close to the zenith. This raises the question of how the beetles combine multimodal orientation input to obtain a robust heading estimate. To study this, we performed behavioral experiments in a tightly controlled indoor arena. This revealed that the beetles register directional information provided by the sun and the wind and can use them in a weighted manner. Moreover, the directional information can be transferred between these 2 sensory modalities, suggesting that they are combined in the spatial memory network in the beetle's brain. This flexible use of compass cue preferences relative to the prevailing visual and mechanosensory scenery provides a simple, yet effective, mechanism for enabling precise compass orientation at any time of the day.
|
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| 30. |
- Dacke, Marie, et al.
(författare)
-
The Dung Beetle Compass
- 2018
-
Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 28:17, s. 993-997
-
Forskningsöversikt (refereegranskat)abstract
- What do a burly rower, a backstroke swimmer and a hard-working South African dung beetle all have in common? The answer is: they all benefit from moving along a straight path, and do so moving backwards. This, however, is where the similarity ends. While the rower has solved this navigational challenge by handing the task of steering to the coxswain, who faces the direction of travel, and the swimmer is guided down her lane by colourful ropes, the beetle puts its faith in the sky. From here, it utilises a larger repertoire of celestial compass cues than is known to be used by any other animal studied to date. A robust internal compass, designed to interpret directional information, has evolved under the selective pressure of shifting today's lunch efficiently out of reach of competitors, also drawn to the common buffet. While this is a goal that beetles might share with the hungry athletes, they reach it with drastically different brain powers; the brain of the beetle is several times smaller than a match head, containing fewer than a million neurons. In this Primer, Marie Dacke and Basil el Jundi examine the behavioural and neuronal mechanisms of the dung beetle's celestial compass underlying straight-line orientation.
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| 31. |
- Dacke, Marie, et al.
(författare)
-
The role of the sun in the celestial compass of dung beetles.
- 2014
-
Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2970 .- 0962-8436. ; 369:1636
-
Tidskriftsartikel (refereegranskat)abstract
- Recent research has focused on the different types of compass cues available to ball-rolling beetles for orientation, but little is known about the relative precision of each of these cues and how they interact. In this study, we find that the absolute orientation error of the celestial compass of the day-active dung beetle Scarabaeus lamarcki doubles from 16° at solar elevations below 60° to an error of 29° at solar elevations above 75°. As ball-rolling dung beetles rely solely on celestial compass cues for their orientation, these insects experience a large decrease in orientation precision towards the middle of the day. We also find that in the compass system of dung beetles, the solar cues and the skylight cues are used together and share the control of orientation behaviour. Finally, we demonstrate that the relative influence of the azimuthal position of the sun for straight-line orientation decreases as the sun draws closer to the horizon. In conclusion, ball-rolling dung beetles possess a dynamic celestial compass system in which the orientation precision and the relative influence of the solar compass cues change over the course of the day.
|
|
| 32. |
- Dacke, Marie, et al.
(författare)
-
Twilight orientation to polarised light in the crepuscular dung beetle Scarabaeus zambesianus
- 2003
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 206:9, s. 1535-1543
-
Tidskriftsartikel (refereegranskat)abstract
- The polarisation pattern of skylight offers many arthropods a reference for visual compass orientation. The dung beetle Scarabaeus zambesianus starts foraging at around sunset. After locating a source of fresh droppings, it forms a ball of dung and rolls it off at high speed to escape competition at and around the dung pile. Using behavioural experiments in the field and in the laboratory, we show that the beetle is able to roll along a straight path by using the polarised light pattern of evening skylight. The receptors used to detect this skylight cue can be found in the ommatidia of the dorsal rim area of the eye, whose structures differ from the regular ommatidia in the rest of the eye. The dorsal rim ommatidia are characterised by rhabdoms with microvilli oriented at only two orthogonal orientations. Together with the finding that the receptors do not twist along the length of the rhabdom, this indicates that the photoreceptors of the dorsal rim area are polarisation sensitive. Large rhabdoms, a reflecting tracheal sheath and a lack of screening pigments make this area of the eye well adapted for polarised light detection at low light levels. The fan-shaped arrangement of receptors over the dorsal rim area was previously believed to be an adaptation to polarised light analysis, but here we argue that it is simply a consequence of the way that the eye is built.
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| 33. |
- Dacke, Marie, et al.
(författare)
-
Two odometers in honeybees?
- 2008
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 211:20, s. 3281-3286
-
Tidskriftsartikel (refereegranskat)abstract
- Although several studies have examined how honeybees gauge and report the distance and direction of a food source to their nestmates, relatively little is known about how this information is combined to obtain a representation of the position of the food source. In this study we manipulate the amount of celestial compass information available to the bee during flight, and analyse the encoding of spatial information in the waggle dance as well as in the navigation of the foraging bee. We find that the waggle dance encodes information about the total distance flown to the food source, even when celestial compass cues are available only for a part of the journey. This stands in contrast to how a bee gauges distance flown when it navigates back to a food source that it already knows. When bees were trained to find a feeder placed at a fixed distance in a tunnel in which celestial cues were partially occluded and then tested in a tunnel that was fully open to the sky, they searched for the feeder at a distance that corresponds closely to the distance that was flown under the open sky during the training. Thus, when navigating back to a food source, information about distance travelled is disregarded when there is no concurrent input from the celestial compass. We suggest that bees may possess two different odometers - a 'community' odometer that is used to provide information to nestmates via the dance, and a 'personal' odometer that is used by an experienced individual to return to a previously visited source.
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| 34. |
- El Jundi, Basil, et al.
(författare)
-
A snapshot-based mechanism for celestial orientation
- 2016
-
Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 26
-
Tidskriftsartikel (refereegranskat)abstract
- n order to protect their food from competitors, ball-rolling dung beetles detach a piece of dung from a pile, shape it into a ball, and roll it away along a straight path [1]. They appear to rely exclusively on celestial compass cues to maintain their bearing [2, 3, 4, 5, 6, 7 and 8], but the mechanism that enables them to use these cues for orientation remains unknown. Here, we describe the orientation strategy that allows dung beetles to use celestial cues in a dynamic fashion. We tested the underlying orientation mechanism by presenting beetles with a combination of simulated celestial cues (sun, polarized light, and spectral cues). We show that these animals do not rely on an innate prediction of the natural geographical relationship between celestial cues, as other navigating insects seem to [9 and 10]. Instead, they appear to form an internal representation of the prevailing celestial scene, a “celestial snapshot,” even if that scene represents a physical impossibility for the real sky. We also find that the beetles are able to maintain their bearing with respect to the presented cues only if the cues are visible when the snapshot is taken. This happens during the “dance,” a behavior in which the beetle climbs on top of its ball and rotates about its vertical axis [11]. This strategy for reading celestial signals is a simple but efficient mechanism for straight-line orientation.
|
|
| 35. |
- el Jundi, Basil, et al.
(författare)
-
Diurnal dung beetles use the intensity gradient and the polarization pattern of the sky for orientation.
- 2014
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 217:13, s. 2422-2429
-
Tidskriftsartikel (refereegranskat)abstract
- To escape competition at the dung pile, a ball-rolling dung beetle forms a piece of dung into a ball and rolls it away. To ensure an their efficient escape from the dung pile, the beetles rely on a celestial compass to move along a straight paths. Here, we analyzed the reliability of different skylight cues for this compass and found that dung beetles rely not only on the sun, but also on the skylight polarization pattern. Moreover, we show the first evidence of an insect using the celestial light intensity gradient for orientation. Using a polarizer, we manipulated skylight so that the polarization pattern appeared to turn by 90°. The beetles then changed their bearing close to the expected 90°. This behavior was abolished if the sun was visible to the beetle, suggesting that polarized light is hierarchically subordinate to the sun. If the sky was depolarized and the sun was invisible, the beetles could still move along straight paths. We therefore analyzed the use of the celestial intensity gradient for orientation. Artificially rotating the intensity pattern by 180° caused beetles to orient in the opposite direction. The intensity cue was also found to be subordinate to the sun, and could play a role in disambiguating the polarization signal, especially at low sun elevations.
|
|
| 36. |
- el Jundi, Basil, et al.
(författare)
-
Neural coding underlying the cue preference for celestial orientation
- 2015
-
Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 112:36, s. 11395-11400
-
Tidskriftsartikel (refereegranskat)abstract
- Diurnal and nocturnal African dung beetles use celestial cues, such as the sun, the moon, and the polarization pattern, to roll dung balls along straight paths across the savanna. Although nocturnal beetles move in the same manner through the same environment as their diurnal relatives, they do so when light conditions are at least 1 million-fold dimmer. Here, we show, for the first time to our knowledge, that the celestial cue preference differs between nocturnal and diurnal beetles in a manner that reflects their contrasting visual ecologies. We also demonstrate how these cue preferences are reflected in the activity of compass neurons in the brain. At night, polarized skylight is the dominant orientation cue for nocturnal beetles. However, if we coerce them to roll during the day, they instead use a celestial body (the sun) as their primary orientation cue. Diurnal beetles, however, persist in using a celestial body for their compass, day or night. Compass neurons in the central complex of diurnal beetles are tuned only to the sun, whereas the same neurons in the nocturnal species switch exclusively to polarized light at lunar light intensities. Thus, these neurons encode the preferences for particular celestial cues and alter their weighting according to ambient light conditions. This flexible encoding of celestial cue preferences relative to the prevailing visual scenery provides a simple, yet effective, mechanism for enabling visual orientation at any light intensity.
|
|
| 37. |
- el Jundi, Basil, et al.
(författare)
-
Neuroarchitecture of the dung beetle central complex
- 2018
-
Ingår i: Journal of Comparative Neurology. - : Wiley. - 0021-9967. ; 526:16, s. 2612-2630
-
Tidskriftsartikel (refereegranskat)abstract
- Despite their tiny brains, insects show impressive abilities when navigating over short distances during path integration or during migration over thousands of kilometers across entire continents. Celestial compass cues often play an important role as references during navigation. In contrast to many other insects, South African dung beetles rely exclusively on celestial cues for visual reference during orientation. After finding a dung pile, these animals cut off a piece of dung from the pat, shape it into a ball and roll it away along a straight path until a suitable place for underground consumption is found. To maintain a constant bearing, a brain region in the beetle's brain, called the central complex, is crucially involved in the processing of skylight cues, similar to what has already been shown for path-integrating and migrating insects. In this study, we characterized the neuroanatomy of the sky-compass network and the central complex in the dung beetle brain in detail. Using tracer injections, combined with imaging and 3D modeling, we describe the anatomy of the possible sky-compass network in the central brain. We used a quantitative approach to study the central-complex network and found that several types of neuron exhibit a highly organized connectivity pattern. The architecture of the sky-compass network and central complex is similar to that described in insects that perform path integration or are migratory. This suggests that, despite their different orientation behaviors, this neural circuitry for compass orientation is highly conserved among the insects.
|
|
| 38. |
- el Jundi, Basil, et al.
(författare)
-
Spectral information as an orientation cue in dung beetles
- 2015
-
Ingår i: Biology letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 11:11
-
Tidskriftsartikel (refereegranskat)abstract
- During the day, a non-uniform distribution of long and short wavelength light generates a colour gradient across the sky. This gradient could be used as a compass cue, particularly by animals such as dung beetles that rely primarily on celestial cues for orientation. Here, we tested if dung beetles can use spectral cues for orientation by presenting them with monochromatic (green and UV) light spots in an indoor arena. Beetles kept their original bearing when presented with a single light cue, green or UV, or when presented with both light cues set 180° apart. When either the UV or the green light was turned off after the beetles had set their bearing in the presence of both cues, they were still able to maintain their original bearing to the remaining light. However, if the beetles were presented with two identical green light spots set 180° apart, their ability to maintain their original bearing was impaired. In summary, our data show that ball-rolling beetles could potentially use the celestial chromatic gradient as a reference for orientation.
|
|
| 39. |
- El Jundi, Basil, et al.
(författare)
-
The brain behind straight-line orientation in dung beetles
- 2019
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 222
-
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.
|
|
| 40. |
- Evangelista, C., et al.
(författare)
-
Honeybee navigation: critically examining the role of the polarization compass
- 2014
-
Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2970 .- 0962-8436. ; 369:1636
-
Tidskriftsartikel (refereegranskat)abstract
- Although it is widely accepted that honeybees use the polarized-light pattern of the sky as a compass for navigation, there is little direct evidence that this information is actually sensed during flight. Here, we ask whether flying bees can obtain compass cues derived purely from polarized light, and communicate this information to their nest-mates through the 'waggle dance'. Bees, from an observation hive with vertically oriented honeycombs, were trained to fly to a food source at the end of a tunnel, which provided overhead illumination that was polarized either parallel to the axis of the tunnel, or perpendicular to it. When the illumination was transversely polarized, bees danced in a predominantly vertical direction with waggles occurring equally frequently in the upward or the downward direction. They were thus using the polarized-light information to signal the two possible directions in which they could have flown in natural outdoor flight: either directly towards the sun, or directly away from it. When the illumination was axially polarized, the bees danced in a predominantly horizontal direction with waggles directed either to the left or the right, indicating that they could have flown in an azimuthal direction that was 90 degrees to the right or to the left of the sun, respectively. When the first half of the tunnel provided axial illumination and the second half transverse illumination, bees danced along all of the four principal diagonal directions, which represent four equally likely locations of the food source based on the polarized-light information that they had acquired during their journey. We conclude that flying bees are capable of obtaining and signalling compass information that is derived purely from polarized light. Furthermore, they deal with the directional ambiguity that is inherent in polarized light by signalling all of the possible locations of the food source in their dances, thus maximizing the chances of recruitment to it.
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| 41. |
- Evangelista, C., et al.
(författare)
-
The moment before touchdown: landing manoeuvres of the honeybee Apis mellifera
- 2010
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 213:2, s. 262-270
-
Tidskriftsartikel (refereegranskat)abstract
- Although landing is a crucial part of insect flight, it has attracted relatively little study. Here, we investigate, for the first time, the final moments of a honeybee's (Apis mellifera) landing manoeuvre. Using high-speed video recordings, we analyse the behaviour of bees as they approach and land on surfaces of various orientations. The bees enter a stable hover phase, immediately prior to touchdown. We have quantified behaviour during this hover phase and examined whether it changes as the tilt of the landing surface is varied from horizontal (floor), through sloped (uphill) and vertical (wall), to inverted (ceiling). The bees hover at a remarkably constant distance from the surface, irrespective of its tilt. Body inclination increases progressively as the tilt of the surface is increased, and is accompanied by an elevation of the antennae. The tight correlation between the tilt of the surface, and the orientation of the body and the antennae, indicates that the bee's visual system is capable of inferring the tilt of the surface, and pointing the antennae toward it. Touchdown is initiated by extending the appendage closest to the surface, namely, the hind legs when landing on horizontal or sloping surfaces, and the front legs or antennae when landing on vertical surfaces. Touchdown on inverted surfaces is most likely triggered by a mechanosensory signal from the antennae. Evidently, bees use a landing strategy that is flexibly tailored to the varying topography of the terrain.
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| 42. |
- Foster, James J., et al.
(författare)
-
How animals follow the stars
- 2018
-
Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 285:1871
-
Forskningsöversikt (refereegranskat)abstract
- Throughout history, the stars have provided humans with ever more information about our world, enabling increasingly accurate systems of navigation in addition to fuelling some of the greatest scientific controversies. What information animals have evolved to extract from a starry sky and how they do so, is a topic of study that combines the practical and theoretical challenges faced by both astronomers and field biologists. While a number of animal species have been demonstrated to use the stars as a source of directional information, the strategies that these animals use to convert this complex and variable pattern of dim-light points into a reliable ‘stellar orientation’ cue have been more difficult to ascertain. In this review, we assess the stars as a visual stimulus that conveys directional information, and compare the bodies of evidence available for the different stellar orientation strategies proposed to date. In this context, we also introduce new technologies that may aid in the study of stellar orientation, and suggest how field experiments may be used to characterize the mechanisms underlying stellar orientation.
|
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| 43. |
- Foster, James J., et al.
(författare)
-
Light pollution forces a change in dung beetle orientation behavior
- 2021
-
Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 31:17, s. 3-3942
-
Tidskriftsartikel (refereegranskat)abstract
- Increasing global light pollution1,2 threatens the night-time darkness to which most animals are adapted. Light pollution can have detrimental effects on behavior,3–5 including by disrupting the journeys of migratory birds,5,6 sand hoppers,7–9 and moths.10 This is particularly concerning, since many night-active species rely on compass information in the sky, including the moon,11,12 the skylight polarization pattern,13,14 and the stars,15 to hold their course. Even animals not directly exposed to streetlights and illuminated buildings may still experience indirect light pollution in the form of skyglow,3,4 which can extend far beyond urban areas.1,2 While some recent research used simulated light pollution to estimate how skyglow may affect orientation behavior,7–9 the consequences of authentic light pollution for celestial orientation have so far been neglected. Here, we present the results of behavioral experiments at light-polluted and dark-sky sites paired with photographic measurements of each environment. We find that light pollution obscures natural celestial cues and induces dramatic changes in dung beetle orientation behavior, forcing them to rely on bright earthbound beacons in place of their celestial compass. This change in behavior results in attraction toward artificial lights, thereby increasing inter-individual competition and reducing dispersal efficiency. For the many other species of insect, bird, and mammal that rely on the night sky for orientation and migration, these effects could dramatically hinder their vital night-time journeys.
|
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| 44. |
- Foster, James J., et al.
(författare)
-
Orienting to polarized light at night - matching lunar skylight to performance in a nocturnal beetle
- 2019
-
Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 222
-
Tidskriftsartikel (refereegranskat)abstract
- For polarized light to inform behaviour, the typical range of degrees of polarization observable in the animal's natural environment must be above the threshold for detection and interpretation. Here, we present the first investigation of the degree of linear polarization threshold for orientation behaviour in a nocturnal species, with specific reference to the range of degrees of polarization measured in the night sky. An effect of lunar phase on the degree of polarization of skylight was found, with smaller illuminated fractions of the moon's surface corresponding to lower degrees of polarization in the night sky. We found that the South African dung beetle Escarabaeus satyrus can orient to polarized light for a range of degrees of polarization similar to that observed in diurnal insects, reaching a lower threshold between 0.04 and 0.32, possibly as low as 0.11. For degrees of polarization lower than 0.23, as measured on a crescent moon night, orientation performance was considerably weaker than that observed for completely linearly polarized stimuli, but was nonetheless stronger than in the absence of polarized light.
|
|
| 45. |
- Foster, James J., et al.
(författare)
-
Stellar performance : Mechanisms underlying milky way orientation in dung beetles
- 2017
-
Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 372:1717
-
Tidskriftsartikel (refereegranskat)abstract
- Nocturnal dung beetles (Scarabaeus satyrus) are currently the only animals that have been demonstrated to use the Milky Way for reliable orientation. In this study, we tested the capacity of S. satyrus to orient under a range of artificial celestial cues, and compared the properties of these cues with images of the Milky Way simulated for a beetle’s visual system. We find that the mechanism that permits accurate stellar orientation under the Milky Way is based on an intensity comparison between different regions of the Milky Way. We determined the beetles’ contrast sensitivity for this task in behavioural experiments in the laboratory, and found that the resulting threshold of 13% is sufficient to detect the contrast between the southern and northern arms of the Milky Way under natural conditions. This mechanism should be effective under extremely dim conditions and on nights when the Milky Way forms a near symmetrical band that crosses the zenith. These findings are discussed in the context of studies of stellar orientation in migratory birds and itinerant seals.
|
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| 46. |
- Gislén, Anna, et al.
(författare)
-
Superior underwater vision in a human population of sea gypsies
- 2003
-
Ingår i: Current Biology. - 1879-0445. ; 13:10, s. 833-836
-
Tidskriftsartikel (refereegranskat)abstract
- Humans are poorly adapted for underwater vision. In air, the curved corneal surface accounts for two-thirds of the eye's refractive power, and this is lost when air is replaced by water [1]. Despite this, some tribes of sea gypsies in Southeast Asia live off the sea, and the children collect food from the sea floor without the use of visual aids [2]. This is a remarkable feat when one considers that the human eye is not focused underwater and small objects should remain unresolved. We have measured the visual acuity of children in a sea gypsy population, the Moken, and found that the children see much better underwater than one might expect. Their underwater acuity (6.06 cycles/degree) is more than twice as good as that of European children (2.95 cycles/degree). Our investigations show that the Moken children achieve their superior underwater vision by maximally constricting the pupil (1.96 mm compared to 2.50 mm in European children) and by accommodating to the known limit of human performance (15-16 D) [3]. This extreme reaction-which is routine in Moken children-is completely absent in European children. Because they are completely dependent on the sea, the Moken are very likely to derive great benefit from this strategy.
|
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| 47. |
- Gislén, Anna, et al.
(författare)
-
Visual training improves underwater vision in children
- 2006
-
Ingår i: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 46:20, s. 3443-3450
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Tidskriftsartikel (refereegranskat)abstract
- Children in a tribe of sea-gypsies from South-East Asia have been found to have superior underwater vision compared to European children. In this study, we show that the improved underwater vision of these Moken children is not due to better contrast sensitivity in general. We also show that European children can achieve the same underwater acuity as the Moken children. After I month of underwater training (I I sessions) followed by 4 months with no underwater activities, European children showed improved underwater vision and distinct bursts of pupil constriction. When tested 8 months after the last training session in an outdoor pool in bright sunlight-comparable to light environments in South-East Asia-the children had attained the same underwater acuity as the sea-gypsy children. The achieved performance can be explained by the combined effect of pupil constriction and strong accommodation. (c) 2006 Elsevier Ltd. All rights reserved.
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| 48. |
- Greiner, Birgit, et al.
(författare)
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Eye structure correlates with distinct foraging-bout timing in primitive ants
- 2007
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Ingår i: Current Biology. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 17:20, s. 879-880
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Social insects have evolved remarkable physiological adaptations and behavioural strategies that enable them to access new temporal foraging niches (for example [1]). Here we report striking correlations between the timing of foraging bouts and the modification of eye structure in four species of ants belonging to the primitive genus Myrmecia. Most noteworthy, photoreceptor diameters progressively increase from 1.3 μm in strictly day-active species, to 5.9 μm in predominantly night-active species.
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| 49. |
- 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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| 50. |
- 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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