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1.	Beetz, M. Jerome, et al. (author) Flight-induced compass representation in the monarch butterfly heading network 2022 In: Current Biology. - : Elsevier BV. - 0960-9822. ; 32:2, s. 5-349 Journal article (peer-reviewed)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.
2.	Beetz, M Jerome, et al. (author) Topographic organization and possible function of the posterior optic tubercles in the brain of the desert locust Schistocerca gregaria 2015 In: Journal of Comparative Neurology. - : Wiley. - 1096-9861 .- 0021-9967. ; 523:11, s. 1589-1607 Journal article (peer-reviewed)abstract Migrating desert locusts, Schistocerca gregaria, are able to use the skylight polarization pattern for navigation. They detect polarized light with a specialized dorsal rim area in their compound eye. After multistage processing, polarization signals are transferred to the central complex, a midline-spanning brain area involved in locomotor control. Polarization-sensitive tangential neurons (TB-neurons) of the protocerebral bridge, a part of the central complex, give rise to a topographic arrangement of preferred polarization angles in the bridge, suggesting that the central complex acts as an internal sky compass. TB-neurons connect the protocerebral bridge with two adjacent brain areas, the posterior optic tubercles. To analyze the polarotopic organization of the central complex further, we investigated the number and morphologies of TB-neurons and the presence and colocalization of three neuroactive substances in these neurons. Triple immunostaining with antisera against Diploptera punctata allatostatin (Dip-AST), Manduca sexta allatotropin (Mas-AT), and serotonin (5HT) raised in the same host species revealed three spatially distinct TB-neuron clusters, each consisting of 10 neurons per hemisphere: cluster 1 and 3 showed Dip-AST/5HT immunostaining, whereas cluster 2 showed Dip-AST/Mas-AT immunostaining. Five subtypes of TB-neuron could be distinguished based on ramification patterns. Corresponding to ramification domains in the protocerebral bridge, the neurons invaded distinct but overlapping layers within the posterior optic tubercle. Similarly, neurons interconnecting the tubercles of the two hemispheres also targeted distinct layers of these neuropils. From these data we propose a neuronal circuit that may be suited to stabilize the internal sky compass in the central complex of the locust
3.	Dacke, Marie, et al. (author) A dung beetle that path integrates without the use of landmarks 2020 In: Animal Cognition. - : Springer Science and Business Media LLC. - 1435-9448 .- 1435-9456. ; 23, s. 1161-1175 Journal article (peer-reviewed)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.
4.	Dacke, Marie, et al. (author) How Dung Beetles Steer Straight 2021 In: Annual Review of Entomology. - : Annual Reviews. - 0066-4170 .- 1545-4487. ; 66, s. 243-256 Journal article (peer-reviewed)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.
5.	Dacke, Marie, et al. (author) Multimodal cue integration in the dung beetle compass 2019 In: 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 Journal article (peer-reviewed)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.
6.	Dacke, Marie, et al. (author) The Dung Beetle Compass 2018 In: Current Biology. - : Elsevier BV. - 0960-9822. ; 28:17, s. 993-997 Research review (peer-reviewed)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.
7.	Dacke, Marie, et al. (author) The role of the sun in the celestial compass of dung beetles. 2014 In: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2970 .- 0962-8436. ; 369:1636 Journal article (peer-reviewed)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.
8.	Dreyer, David, et al. (author) Evidence for a southward autumn migration of nocturnal noctuid moths in central Europe 2018 In: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 221 Journal article (peer-reviewed)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.
9.	El Jundi, Basil, et al. (author) A snapshot-based mechanism for celestial orientation 2016 In: Current Biology. - : Elsevier BV. - 0960-9822. ; 26 Journal article (peer-reviewed)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.
10.	el Jundi, Basil, et al. (author) Diurnal dung beetles use the intensity gradient and the polarization pattern of the sky for orientation. 2014 In: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 217:13, s. 2422-2429 Journal article (peer-reviewed)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.
11.	el Jundi, Basil, et al. (author) Integration of polarization and chromatic cues in the insect sky compass. 2014 In: Journal of Comparative Physiology A. - : Springer Science and Business Media LLC. - 1432-1351 .- 0340-7594. ; 200:6, s. 575-589 Research review (peer-reviewed)abstract Animals relying on a celestial compass for spatial orientation may use the position of the sun, the chromatic or intensity gradient of the sky, the polarization pattern of the sky, or a combination of these cues as compass signals. Behavioral experiments in bees and ants, indeed, showed that direct sunlight and sky polarization play a role in sky compass orientation, but the relative importance of these cues are species-specific. Intracellular recordings from polarization-sensitive interneurons in the desert locust and monarch butterfly suggest that inputs from different eye regions, including polarized-light input through the dorsal rim area of the eye and chromatic/intensity gradient input from the main eye, are combined at the level of the medulla to create a robust compass signal. Conflicting input from the polarization and chromatic/intensity channel, resulting from eccentric receptive fields, is eliminated at the level of the anterior optic tubercle and central complex through internal compensation for changing solar elevations, which requires input from a circadian clock. Across several species, the central complex likely serves as an internal sky compass, combining E-vector information with other celestial cues. Descending neurons, likewise, respond both to zenithal polarization and to unpolarized cues in an azimuth-dependent way.
12.	el Jundi, Basil, et al. (author) Neural coding underlying the cue preference for celestial orientation 2015 In: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 112:36, s. 11395-11400 Journal article (peer-reviewed)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.
13.	el Jundi, Basil, et al. (author) Neuroarchitecture of the dung beetle central complex 2018 In: Journal of Comparative Neurology. - : Wiley. - 0021-9967. ; 526:16, s. 2612-2630 Journal article (peer-reviewed)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.
14.	el Jundi, Basil, et al. (author) Spectral information as an orientation cue in dung beetles 2015 In: Biology letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 11:11 Journal article (peer-reviewed)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.
15.	El Jundi, Basil, et al. (author) The brain behind straight-line orientation in dung beetles 2019 In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 222 Research review (peer-reviewed)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.
16.	el Jundi, Basil, et al. (author) Three-dimensional atlases of insect brains 2020 In: Neurohistology and Imaging Techniques. - New York, NY : Springer US. - 1940-6045 .- 0893-2336. ; 153, s. 73-124 Book chapter (peer-reviewed)abstract The morphological structure of the nervous system is ultimately the basis of its function. Analyses of the anatomical layout of brain areas, single neuron morphologies, and the synaptic connectivity of neurons are therefore essential for a comprehensive understanding of the computational processes implemented in neuronal networks. Insect brains have long served as models to examine neuronal circuits that process sensory information, provide the substrates for learning and memory, or generate motor patterns that drive well-studied behavior. The relatively small number of neurons these brains are composed of (up to one million) and their small overall size make them easily accessible for physiological and anatomical research. To aid the comparison of results within and across species, and thus make it possible to relate function to anatomical structure, printed brain atlases have been used as a common frame of reference for many decades. In recent years, digital, three-dimensional atlases were generated to provide geometrical as well as conceptual reference systems for the brains of several insect species. In this review we compare the different approaches for generating such three-dimensional atlases. We highlight the key problems that must be overcome during this process and the solutions that have been found to achieve this. The advantages and limitations of the different strategies are discussed, and the applications that have so far resulted from the implementation of these atlases are described.
17.	Foster, James J., et al. (author) Orienting to polarized light at night - matching lunar skylight to performance in a nocturnal beetle 2019 In: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 222 Journal article (peer-reviewed)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.
18.	Foster, James J., et al. (author) Stellar performance : Mechanisms underlying milky way orientation in dung beetles 2017 In: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 372:1717 Journal article (peer-reviewed)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.
19.	Franzke, Myriam, et al. (author) Spatial orientation based on multiple visual cues in non-migratory monarch butterflies 2020 In: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 223 Journal article (peer-reviewed)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.
20.	Franzke, Myriam, et al. (author) Stimulus-dependent orientation strategies in monarch butterflies 2022 In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 225:3 Journal article (peer-reviewed)abstract Insects are well known for their ability to keep track of their heading direction based on a combination of skylight cues and visual landmarks. This allows them to navigate back to their nest, disperse throughout unfamiliar environments, as well as migrate over large distances between their breeding and non-breeding habitats. The monarch butterfly (Danaus plexippus), for instance, is known for its annual southward migration from North America to certain trees in Central Mexico. To maintain a constant flight route, these butterflies use a time-compensated sun compass, which is processed in a region in the brain, termed the central complex. However, to successfully complete their journey, the butterflies' brain must generate a multitude of orientation strategies, allowing them to dynamically switch from sun-compass orientation to a tactic behavior toward a certain target. To study whether monarch butterflies exhibit different orientation modes and if they can switch between them, we observed the orientation behavior of tethered flying butterflies in a flight simulator while presenting different visual cues to them. We found that the butterflies' behavior depended on the presented visual stimulus. Thus, while a dark stripe was used for flight stabilization, a bright stripe was fixated by the butterflies in their frontal visual field. If we replaced a bright stripe with a simulated sun stimulus, the butterflies switched their behavior and exhibited compass orientation. Taken together, our data show that monarch butterflies rely on and switch between different orientation modes, allowing the animal to adjust orientation to its actual behavioral demands.
21.	Heinze, Stanley, et al. (author) A unified platform to manage, share, and archive morphological and functional data in insect neuroscience 2021 In: eLife. - 2050-084X. ; 10 Journal article (peer-reviewed)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.
22.	Heinze, Stanley, et al. (author) Anatomical basis of sun compass navigation II: The neuronal composition of the central complex of the monarch butterfly 2013 In: Journal of Comparative Neurology. - : Wiley. - 1096-9861 .- 0021-9967. ; 521:2, s. 267-298 Journal article (peer-reviewed)abstract Each fall, eastern North American monarch butterflies in their northern range undergo a long-distance migration south to their overwintering grounds in Mexico. Migrants use a time-compensated sun compass to determine directionality during the migration. This compass system uses information extracted from sun-derived skylight cues that is compensated for time of day and ultimately transformed into the appropriate motor commands. The central complex (CX) is likely the site of the actual sun compass, because neurons in this brain region are tuned to specific skylight cues. To help illuminate the neural basis of sun compass navigation, we examined the neuronal composition of the CX and its associated brain regions. We generated a standardized version of the sun compass neuropils, providing reference volumes, as well as a common frame of reference for the registration of neuron morphologies. Volumetric comparisons between migratory and nonmigratory monarchs substantiated the proposed involvement of the CX and related brain areas in migratory behavior. Through registration of more than 55 neurons of 34 cell types, we were able to delineate the major input pathways to the CX, output pathways, and intrinsic neurons. Comparison of these neural elements with those of other species, especially the desert locust, revealed a surprising degree of conservation. From these interspecies data, we have established key components of a conserved core network of the CX, likely complemented by species-specific neurons, which together may comprise the neural substrates underlying the computations performed by the CX. J. Comp. Neurol. 521:267298, 2013. (c) 2012 Wiley Periodicals, Inc.
23.	Immonen, Esa Ville, et al. (author) Anatomical organization of the brain of a diurnal and a nocturnal dung beetle 2017 In: Journal of Comparative Neurology. - : Wiley. - 0021-9967. ; 525:8, s. 1879-1908 Journal article (peer-reviewed)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.
24.	Jundi, Basil el, et al. (author) Insect Orientation : The Drosophila Wind Compass Pathway 2021 In: Current Biology. - : Elsevier BV. - 0960-9822. ; 31:2, s. 83-85 Journal article (peer-reviewed)abstract Wind can act as an external cue to control an animal's heading. A new study reveals the neural mechanisms behind the wind information pathway in the insect brain.
25.	Kelber, Almut, et al. (author) Linking brain and behaviour in animal navigation : navigation from genes to maps 2019 In: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 222:Suppl 1 Journal article (other academic/artistic)
26.	Selcho, Mareike, et al. (author) The Role of octopamine and tyramine in Drosophila larval locomotion 2012 In: Journal of Comparative Neurology. - : Wiley. - 1096-9861 .- 0021-9967. ; 520:16, s. 3764-3785 Journal article (peer-reviewed)abstract The characteristic crawling behavior of Drosophila larvae consists of a series of rhythmic waves of peristalsis and episodes of head swinging and turning. The two biogenic amines octopamine and tyramine have recently been shown to modulate various parameters of locomotion, such as muscle contraction, the time spent in pausing or forward locomotion, and the initiation and maintenance of rhythmic motor patterns. By using mutants having altered octopamine and tyramine levels and by genetic interference with both systems we confirm that signaling of these two amines is necessary for larval locomotion. We show that a small set of about 40 octopaminergic/tyraminergic neurons within the ventral nerve cord is sufficient to trigger proper larval locomotion. Using single-cell clones, we describe the morphology of these neurons individually. Given various potential roles of octopamine and tyramine in the larval brain, such as locomotion, learning and memory, stress-induced behaviors or the regulation of the energy state, functions that are often not easy to discriminate, we dissect here for the first time a subset of this complex circuit that modulates specifically larval locomotion. Thus, these data will help to understandfor a given neuronal modulatorhow specific behavioral functions are executed within distinct subcircuits of a complex neuronal network. J. Comp. Neurol. 520:37643785, 2012. (C) 2012 Wiley Periodicals, Inc.
27.	Smolka, Jochen, et al. (author) Dung beetles use their dung ball as a mobile thermal refuge 2012 In: Current Biology. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 22:20, s. 863-864 Journal article (peer-reviewed)abstract At midday, surface temperatures in the desert often exceed 60°C. To be active at this time, animals need extraordinary behavioural or physiological adaptations. Desert ants, for instance, spend up to 75% of their foraging time cooling down on elevated thermal refuges such as grass stalks [1]. Ball-rolling dung beetles work under similar thermal conditions in South African savannahs. After landing at a fresh dung pile, a beetle quickly forms a dung ball and rolls it away in a straight line, head down, walking backwards [2]. Earlier studies have shown that some dung beetles maintain an elevated body temperature to gain a competitive advantage [3], [4] and [5], and that heat shunting may prevent overheating during flight [6] and [7]. However, we know little about the behavioural strategies beetles might employ to mitigate heat stress while rolling their dung balls. Using infrared thermography and behavioural experiments, we show here that dung beetles use their dung ball as a mobile thermal refuge onto which they climb to cool down while rolling across hot soil. We further demonstrate that the moist ball functions not only as a portable platform, but also as a heat sink, which effectively cools the beetle as it rolls or climbs onto it.
28.	Smolka, Jochen, et al. (author) Night sky orientation with diurnal and nocturnal eyes: dim-light adaptations are critical when the moon is out of sight 2016 In: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 111, s. 127-146 Journal article (peer-reviewed)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.
29.	Stöckl, Anna, et al. (author) Differential investment in visual and olfactory brain areas reflects behavioural choices in hawk moths 2016 In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6 Journal article (peer-reviewed)abstract Nervous tissue is one of the most metabolically expensive animal tissues, thus evolutionary investments that result in enlarged brain regions should also result in improved behavioural performance. Indeed, large-scale comparative studies in vertebrates and invertebrates have successfully linked differences in brain anatomy to differences in ecology and behaviour, but their precision can be limited by the detail of the anatomical measurements, or by only measuring behaviour indirectly. Therefore, detailed case studies are valuable complements to these investigations, and have provided important evidence linking brain structure to function in a range of higher-order behavioural traits, such as foraging experience or aggressive behaviour. Here, we show that differences in the size of both lower and higher-order sensory brain areas reflect differences in the relative importance of these senses in the foraging choices of hawk moths, as suggested by previous anatomical work in Lepidopterans. To this end we combined anatomical and behavioural quantifications of the relative importance of vision and olfaction in two closely related hawk moth species. We conclude that differences in sensory brain volume in these hawk moths can indeed be interpreted as differences in the importance of these senses for the animal's behaviour.
30.	Yilmaz, Ayse, et al. (author) Mechanisms of spectral orientation in a diurnal dung beetle 2022 In: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : Royal Society Publishing. - 0962-8436 .- 1471-2970. ; 377:1862 Journal article (peer-reviewed)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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