Orientation to shorelines by the supratidal amphipod Talorchestia longicornis: Wavelength specific behavior during sun compass orientation

If released in water or on sand the supratidal amphipod Talorchestia longicornis Say amphipods moves in the onshore direction. The present study was designed to determine whether this species uses the sun as a cue for orientation and if so, which visual pigment in the compound eyes is involved. When tested in an apparatus with a view of only the sun and sky amphipods were disoriented when the sun was obscured by clouds. However, when the sun was visible, they oriented in the onshore direction of their home beach in both water and air during both the morning and afternoon. Resetting the time of their circadian rhythm in activity with either an altered light:dark or diel temperature cycle also reset the chronometric mechanism associated with sun compass. orientation. T. longicornis has two visual pigments with absorption maxima near 420 nm and 520 nm. Only the 420 nm pigment is used for sun compass orientation, which may be an adaptation for increasing the contrast between the sun and background scattered skylight or for detecting the radiance distribution of skylight. Irradiating the 520 nm absorbing pigment alone induced positive phototaxis to the sun but not onshore orientation. Thus, T. longicornis shows wavelength specific behavior by using only one of its visual pigments for sun compass orientation.     

Y-axis orientation in the South American freshwater snail species Chilina patagonica (Gastropoda: Chilinidae)

Y-axis orientation, a movement perpendicular to the shore or coastline, enables aquatic animals to stay in a preferred zone in generally unstable habitats. Such behaviour is a widespread phenomenon in many freshwater and intertidal animal taxa. In the present study, an arena approach was used to test the orientation response of pulmonate freshwater snails. Using this experimental design, Y-axis orientation was shown for the first time in a freshwater snail species, the riverine Chilina patagonica. Some cues, potentially mediating Y-axis orientation, appeared to play no role in the shown orientation behaviour, such as chemical, gravity and humidity cues or a sun compass. Magnetic cues, however, could not be excluded. Since no significant differences in orientation were detected between different size classes in C. patagonica, orientation behaviour may not vary substantially throughout the snail's life history. In contrast to C. patagonica, no consistent orientation response was seen in the related lacustrine species Chilina llanquihuensis. The adaptation of C. patagonica to exhibit orientation along the Y-axis may be driven by the avoidance of high velocities in deeper water.     

The role of the sun in the celestial compass of dung beetles

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.     

Adaptive Visually-Directed Orientation in Uca pugilator

Sand fiddler crabs are ill-equipped to inhabit either the terrestrialor permanently submerged littoral zones. They are obligate inhabitantsof the intertidal region in which, at any point, extremes ofconditions continually fluctuate. The crabs must constantlymove about to specific areas in order to carry out life-supportingprocesses while avoiding detrimental physical conditons. Forthis reason, directional orientation is basic to their existence. The typical activities of adult sand fiddlers during diurnallow tides have charateristic directional components. Some directedmovements have immediate survival value under conditions ofstress, such as the approach of a predator. For example, crabson the lower beach (well away from their burrow area) oftenrun landward and enter burrows or vegetation, thereby obtainingrefuge. Those which are chased offshore or inland are able toreorient to the beach. Experiments conducted both in the field and under controlledconditions indicate that these adaptive oriented movements areguided primarily by visual mechanisms. Adult crabs exhibit atime-compensated, menotactic orientation to the sun and polarizedsky-light that enables them to maintain a heading coincidentwith the landward compass bearing of their particular shoreline.New directional preferences can be induced by holding crabsin simulated habitats with specific shore-water spatial configurations. The crabs also exhibit a telotaxis toward gross landmarks, suchas mangroves or clumps of beach grass, that stand in opticalcontrast to the background. This orientation occurs in mostindividuals if celestial cues are obscured or if the animalsbecome desiccated. Upon reaching the object, crabs enter suitableinterstices affording refuge. Since they can orient by eithercelestial cues or landmarks, or both, there are probably fewtimes in nature when they are disoriented from lack of guidance-stimuli.     

Orientation of the sand-beach amphipod, Orchestoidea corniculata

Laboratory experiments demonstrated that Orchestoidea corniculata, a sand-beach amphipod, can orient to slopes of only 3°. Studies suggest they reach the upper interdial zone where they burrow by moving up a wet slope or down a dry slope. When they emerge from the sand at night, however, they either reverse this response or show no response to slope. This behaviour, enhanced by a preference for wet, surface sand, would account for the initial seaward movement observed in the field. Behavioural variations among differing segments of the population were investigated. Three additional beach inhabitants oriented to slope, thus indicating the mechanism of slope orientation as a possible generalization in the beach habitat.     

昆虫定向机制研究进展

许多昆虫具有定向运动的行为。对部分社会性昆虫和迁飞性昆虫定向行为的大量研究已经初步阐明太阳、地磁场、天体、风及地面标志物等都可能成为昆虫返巢和迁飞定向的线索。社会性昆虫具有对不同定向线索进行整合而实现精确导航的能力。日间迁飞性昆虫利用时间补偿太阳罗盘进行定向的机制亦已明确,但夜间迁飞昆虫的定向机制尚需深入研究。迁飞性害虫定向机制的明确将有助于判断害虫迁飞路径及降落区域,为迁飞害虫的准确预测提供科学依据。本文对昆虫的定向机制研究进展进行了综述。     

The orientation of the sandhopper <Emphasis Type="Italic">Talitrus saltator</Emphasis> during a partial solar eclipse

To acquire more information about the identification and use of the sun and other celestial cues in the sea–land orientation of the sandhopper Talitrus saltator, we carried out releases in a confined environment during a partial solar eclipse and at sunset. The sandhoppers were unable to identify the sun (86% covered) during the eclipse nor to use other celestial compass factors of orientation. This was probably due to the low level of light intensity (close to the minimum level for orientation recorded at sunset) and to the variations in intensity and pattern of skylight polarization.     

Nocturnal orientation in the black carpenter antCamponotus pennsylvanicus (DeGeer) (Hymenoptera: Formicidae)

Summary The black carpenter antCamponotus pennsylvanicus (DeGeer), a predominantly nocturnal Formicine ant, responds to a hierarchy of visual and tactile cues when orienting along odor trails at night. Under illumination from moonlight or artificial light, workers rely upon these beacons to mediate phototactic orientation. In the absence of moonlight or artificial lights, ants were able to orient visually to terrestrial landmarks. In the absence of all landmarks, save for overhanging tree branches, ants could negotiate shortcuts or make directional changes in response to visual landmarks presented within the tree canopy on a moonless night. When experimental manipulations placed the ants in total darkness, they could no longer negotiate shortcuts and would resort to thigmotactic orientation along structural guidelines to reach a food source. The hierachical organization of these diverse cues in a foraging strategy is discussed, as well as their adaptive significance toC. pennsyhanicus.     

Dung beetles ignore landmarks for straight-line orientation

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.     

Keynote papers on sandhopper orientation and navigation

This article analyses the relevant studies that have made sandhoppers a model subject for the study of orientation, and traces the development of the paradigm through innovative hypotheses and empirical evidence. Sandhoppers are able to maintain their direction without sensorial contact with the goal, which is their burrowing zone extended along the beach, but very narrow across it. They actively determine the direction of their movements, according to their internal state and the environmental features encountered. Each population shows an 'innate directional tendency' adapted to the shoreline of origin, and the inexpert laboratory-born young behave in a similar way to the adults. Genetic differences have been demonstrated between, as well as within natural populations. The question of the calibration of the sun compass to orientation on a particular shoreline implies a redundancy of mechanisms of orientation. Orientation mechanisms may involve environmental cues perceived through diverse sensory modalities, and range from simple orientation reflexes to sun compass navigational systems. These include scototaxis and geotaxis, and the response to the silhouette of the dune, in addition to sun and moon orientation, which is dependent on the time of the day and orientates daily migrations on the beach. Different modalities of orientation may operate singly, or in conjunction with each other, and their ecological significance may vary according to the habitat and lifestyle of the animals. Taken collectively, the orientation behaviour of the group appears to be a most accommodating phenotype, with considerable adaptive potential. The evidence from comparative studies of different populations promotes consideration of behavioural plasticity as an adaptation to changing coastlines.     

Sun compass orientation in seed-caching scrub jays (Aphelocoma coerulescens)

Summary In their natural environment, scrub jays harvest pinyon pine seeds and store them in subterranean caches. In our tests, the birds performed this behavior in an octagonal outdoor aviary with sand-filled cups inserted in the floor. For caching, only 12 such cups in a 90° sector were available, while for the recovery session 4 to 6 days later all 48 cups in the entire aviary were open. In control tests, the birds concentrated their search in the sector where the seeds had been cached. When the internal clock of the birds was shifted 6 h between caching and recovery, they preferentially probed in the adjacent 90° sector. This indicated that they used sun compass information to relocate their caches, largely ignoring visual cues from surrounding landmarks.The dominant role of the sun compass which has a parallel in the orientation of homing pigeons, may reflect a general tendency to prefer compass information in spatial orientation tasks; it is in agreement with the model that birds generally have a directionally oriented view of space.Abbreviations OR Original caches - SH shifted caches     

Multiple sources of celestial compass information in the Central Australian desert ant Melophorus bagoti

The Central Australian desert ant Melophorus bagoti is known to use celestial cues for compass orientation. We manipulated the available celestial cues for compass orientation for ants that had arrived at a feeder, were captured and then released at a distant test site that had no useful terrestrial panoramic cues. When tested in an enclosed transparent box that blocked some or most of the ultraviolet light, the ants were still well oriented homewards. The ants were again significantly oriented homewards when most of the ultraviolet light as well as the sun was blocked, or when the box was covered with tracing paper that eliminated the pattern of polarised light, although in the latter case, their headings were more scattered than in control (full-cue) conditions. When the position of the sun was reflected 180° by a mirror, the ants headed off in an intermediate direction between the dictates of the sun and the dictates of unrotated cues. We conclude that M. bagoti uses all available celestial compass cues, including the pattern of polarised light, the position of the sun, and spectral and intensity gradients. They average multiple cues in a weighted fashion when these cues conflict.     

Target-directed Orientation in Displaced Honeybees

Under sunny weather conditions, displaced honeybees (Apis mellifera) usually fly into the celestial compass direction and thus may be misled from their goal, or they are disorientated. Under cloudy conditions, they may determine the celestial compass direction from prominent landmarks. They may also fly directly toward their goal from a release site. In two experiments, we investigated the orientation of displaced bees when a landmark (target) was close to the goal under different weather conditions. It is shown that in sunny conditions, the celestial compass will override target orientation under most conditions. Under 100% cloud cover, the celestial compass direction retrieved from landmarks modulates target-orientated behaviour but is not by itself a primary orientation factor. The bees will fly toward a previously encountered landmark that signals the target, and in case of several similar landmarks which are visible to the bees, they will choose the one in the direction nearest the celestial compass direction. The results indicate that honeybee orientation is the result of a set of context-specific interdependent orientation mechanisms.     

Kompass im Kopf

Ant compass – how desert ants learn to navigate Successful spatial orientation is a daily challenge for many animals. Cataglyphis desert ants are famous for their navigational performances. They return to the nest after extensive foraging trips without any problems. How do ants take their navigational systems into operation? After conducting different tasks in the dark nest for several weeks, they become foragers under bright sun light. This transition requires both a drastic switch in behavior and neuronal changes in the brain. Experienced foragers mainly rely on visual cues. They use a celestial compass and landmark panoramas. For that reason, naïve ants perform stereotype learning walks to calibrate their compass systems and acquire information about the nest's surroundings. During their learning walks, the ants frequently look back to the nest entrance to learn the homing direction. For aligning their gazes, they use the earth's magnetic field as a compass reference. This magnetic compass in Cataglyphis ants was previously unknown.     

Orientation and navigation in Amphibia

Aquatic and terrestrial amphibians integrate acoustic, magnetic, mechanical, olfactory and visual directional information into a redundant-multisensory orientation system. The sensory information is processed to accomplish homing following active or passive displacement by either path integration, beaconing, pilotage, compass orientation or true navigation. There is evidence for two independent compass systems, a time-compensated compass based on celestial cues and a light-dependent magnetic inclination compass. Beaconing along acoustic or olfactory gradients emanating from the home site, as well as pilotage along fixed visual landmarks also form an important part in the behaviour of many species. True navigation has been shown in only one species, the aquatic salamander Notophthalmus viridescens. Evidence on the nature of the navigational map obtained so far is compatible with the magnetic map hypothesis.     

Orientation by magnetic field in leaf-cutter ants, Atta colombica (Hymenoptera: Formicidae)

Leaf‐cutter ants (Atta colombica) use trail following to travel between foraging sites and the home nest. However, this combination of pheromone and visual cues is likely to be complemented by a directional reference system such as a compass, used not only when foraging but also during colony formation, where foraging trails degrade or where ants become displaced. One candidate system is the magnetic polarity compass. We tested the orientation of leaf‐cutter ants under a magnetic field of reversed‐polarity, with the prediction that the ants would show 180° deflection compared with control ants in an unchanged geomagnetic field. When the sun's disc was unobstructed by clouds, orientation was the same as that of control ants, implying that magnetic cues were not used to orient. However, when the sky was overcast, ants in the experimental treatment significantly shifted their mean orientation both in comparison with controls and reversed‐polarity ants under the sun. Although a total reversal in orientation was not induced, the results demonstrate that Atta respond to magnetic reversal in the absence of sunlight cues, and suggest a role for magnetic cues in determining direction during orientation.     

Compass Orientation During Dispersal of Freshwater Hatchling Snapping Turtles (Chelydra serpentina) and Blanding's Turtles (Emydoidea blandingii)

Freshwater turtle hatchlings primarily use visual cues for orientation while dispersing from nests; however, hatchlings rapidly develop a relationship between a sun or geomagnetic compass and a dispersal target that allows them to maintain an established direction of movement when target habitats are not visible. We examined dispersal patterns of hatchling snapping turtles (Chelydra serpentina) and Blanding's turtles (Emydoidea blandingii) dispersing in large arenas in a mowed field and in dense corn. The dispersal of three categories of hatchlings were examined: (1) naïve individuals (no previous dispersal experience), (2) arena‐experienced (limited dispersal experience in arenas in natural habitat), and (3) natural‐experienced hatchling Blanding's turtles (captured after extensive experience dispersing W in natural habitats toward wetlands). Experienced hatchlings were assigned to treatments consisting of having a magnet or a non‐magnetic aluminum sham or nothing glued to their anterior carapace before release in the corn arena. Dispersal patterns of naïve hatchlings of both species were strongly directional in the field arena with visible target horizons and primarily random in the corn arena where typical target horizons were blocked. When released in corn, dispersal patterns were similar for arena‐experienced hatchlings with magnets or shams attached and differed from their prior dispersal headings in the field arena as naïve hatchlings. Natural‐experienced hatchling Blanding's turtles with and without magnets were able to accurately maintain their prior headings to the WNW while dispersing in the field or corn arenas (i.e., the presence of a magnet did not disrupt their ability to maintain their prior heading). Based on the assumption that no other type of compass exists in hatchlings, we conclude that they were not using a geomagnetic compass, but by default were using sun compass orientation to maintain dispersal headings in dense corn where no typical target habitats were visible.     

Mechanisms of dance orientation in the Asian honey beeApis florea L.

Summary Early studies of dance communication inApis florea had shown that waggle dances are not performed on a vertical plane and oriented to gravity, as in the other species ofApis, but instead take place on the flattened top of the exposed comb and are oriented to celestial cues directly. More recent experiments showed thatA. florea can dance in the absence of a view of the sun or blue sky, but did not establish what mechanism permitted this orientation. I now report that dances can be oriented directly to landmarks visible from the nest, the first evidence of an environmental feature other than celestial cues or gravity being involved in dance orientation. Landmarks near the nest are probably used to refer to celestial cues, in a fashion analogous to the use of broad features of the landscape by honeybees in order to learn the sun's course, which permits them to determine their flight angle on overcast days or at night, and to compensate accurately for solar movement.Apis florea may therefore be able to learn the sun's course with respect to two sets of landmarks.In other experiments I have examined the influence of slope onA. florea's dance orientation to visual references. In the first extensive observations of its dances on a vertical plane, I have amply confirmed that this species cannot transpose light and gravity in setting its dance angle, as the other species ofApis can. Nor do dancers orient so as to match visual information seen during the dance with that remembered from the flight. Patterns in the data when the same patch of sky was presented from different angles suggest instead thatA. florea continues to orient to projections of celestial cues onto the horizontal plane even when dancing on a steep slope. This compensation for slope may involve an ability to detect gravity and factor it out in aligning the dance to celestial cues.These insights suggest thatA. florea's dance orientation system has been adapted to requirements imposed by its nesting behavior, and has diverged sharply from the system shared by the other species ofApis.     

Involvement of the sun and the magnetic compass of domestic fowl in its spatial orientation

Domestic chicks are able to find a food goal at different times of day, with the sun as the only consistent visual cue. This suggests that domestic chickens may use the sun as a time-compensated compass, rather than as a beacon. An alternative explanation is that the birds might use the earth's magnetic field. In this study, we investigated the role of the sun compass in a spatial orientation task using a clock-shift procedure. Furthermore, we investigated whether domestic chickens use magnetic compass information when tested under sunny conditions.Ten ISA Brown chicks were housed in outdoor pens. A separate test arena comprised an open-topped, opaque-sided, wooden octagonal maze. Eight goal boxes with food pots were attached one to each of the arena sides. A barrier inside each goal box prevented the birds from seeing the food pot before entering. After habituation, we tested in five daily 5-min trials whether chicks were able to find food in an systematically allocated goal direction. We controlled for the use of olfactory cues and intra-maze cues. No external landmarks were visible. All tests were done under sunny conditions. Circular statistics showed that nine chicks significantly oriented goalwards using the sun as the only consistent visual cue during directional testing. Next, these nine chicks were subjected to a clock-shift procedure to test for the role of sun-compass information. The chicks were housed indoors for 6 days on a light-schedule that was 6 h ahead of the natural light–dark schedule. After clock-shifting, the birds were tested again and all birds except one were disrupted in their goalward orientation. For the second experiment, six birds were re-trained and fitted with a tiny, powerful magnet on the head to disrupt their magnetic sense. The magnets did not affect the chicks’ goalward orientation.In conclusion, although the strongest prediction of the sun-compass hypothesis (significant re-orientation after clock-shifting) was neither confirmed nor refuted, our results suggest that domestic chicks use the sun as a compass rather than as a beacon. These findings suggest that hens housed indoors in large non-cage systems may experience difficulties in orientation if adequate alternative cues are unavailable. Further research should elucidate how hens kept in non-cage systems orient in space in relation to available resources.     

Experimental Change of the Orientation of Two Populations of Talitrus saltator (Crustacea Amphipoda Talitridae) from Cap Bon (North‐Eastern Tunisia)

The orientation of sandhopper populations is adapted to the direction of the shoreline of the sandy beaches where they live; this behaviour was shown to be inherited in some Mediterranean populations. The question was open whether this behaviour could be adaptively modified in case of changing shoreline or passive transfer to a new differently oriented shoreline. The Cap Bon beaches in north‐eastern Tunisia are particularly interesting because they belong to two different Mediterranean Basins, the central and the eastern one, and their supra‐tidal populations do not come together. This work verified the effect of experimental change of the shoreline direction in two populations of Talitrus saltator from Cap Bon (north‐eastern Tunisia) through a displacement experiment. We transferred samples of T. saltator from two different localities (Korba and Ratiba) from their original beach to the familiar one and tested their solar and landscape orientation on the new beach that had an almost opposite direction with respect to the previous one. The comparisons of the results on the home beach and the new one confirmed the use of the solar compass in both populations, as well as the importance of landscape view and optical local sky factor in adjusting the escape direction. In both populations, an increase of scatter was observed on the new beach, especially when individuals could see the landscape. Also, a clear behavioural difference between the two populations was recorded, being Ratiba population not significantly oriented to the shoreline when tested on the unfamiliar beach, while Korba population maintained its home direction also on the new beach.