Cataglyphis Research Articles

Does social thermal regulation constrain individual thermal tolerance in an ant species?

In ants, social thermal regulation is the collective maintenance of a nest temperature that is optimal for individual colony members. In the thermophilic ant Aphaenogaster iberica, two key behaviours regulate nest temperature: seasonal nest relocation and variable nest depth. Outside the nest, foragers must adapt their activity to avoid temperatures that exceed their thermal limits. It has been suggested that social thermal regulation constrains physiological and morphological thermal adaptations at the individual level. We tested this hypothesis by examining the foraging rhythms of six populations of A. iberica, which were found at different elevations (from 100 to 2,000m) in the Sierra Nevada mountain range of southern Spain. We tested the thermal resistance of individuals from these populations under controlled conditions. Janzen's climatic variability hypothesis (CVH) states that greater climatic variability should select for organisms with broader temperature tolerances. We found that the A. iberica population at 1,300m experienced the most extreme temperatures and that ants from this population had the highest heat tolerance (LT50=57.55°C). These results support CVH's validity at microclimatic scales, such as the one represented by the elevational gradient in this study. Aphaenogaster iberica maintains colony food intake levels across different elevations and mean daily temperatures by shifting its rhythm of activity. This efficient colony-level thermal regulation and the significant differences in individual heat tolerance that we observed among the populations suggest that behaviourally controlled thermal regulation does not constrain individual physiological adaptations for coping with extreme temperatures.

Multimodal influences on learning walks in desert ants (Cataglyphis fortis)

Ants are excellent navigators using multimodal information for navigation. To accurately localise the nest at the end of a foraging journey, visual cues, wind direction and also olfactory cues need to be learnt. Learning walks are performed at the start of an ant’s foraging career or when the appearance of the nest surrounding has changed. We investigated here whether the structure of such learning walks in the desert ant Cataglyphis fortis takes into account wind direction in conjunction with the learning of new visual information. Ants learnt to travel back and forth between their nest and a feeder, and we then introduced a black cylinder near their nest to induce learning walks in regular foragers. By doing this across days with different wind directions, we were able to probe how ants balance different sensory modalities. We found that (1) the ants’ outwards headings are influenced by the wind direction with their routes deflected such that they will arrive downwind of their target, (2) a novel object along the route induces learning walks in experienced ants and (3) the structure of learning walks is shaped by the wind direction rather than the position of the visual cue.

Limitation of Rayleigh sky model for bioinspired polarized skylight navigation in three-dimensional attitude determination

Insects such as desert ants and drosophilae can sense polarized skylight for navigation. Inspired by insects, many researchers have begun to study how to use skylight polarization patterns for attitude determination. The Rayleigh sky model has become the most widely used skylight polarization model for bioinspired polarized skylight navigation due to its simplicity and practicality. However, this is an ideal model considering only single Rayleigh scatter events, and the limitation of this model in bio-inspired attitude determination has not been paid much attention and lacks strict inference proof. To address this problem, the rotational and plane symmetry of the Rayleigh sky model are analyzed in detail, and it is theoretically proved that this model contains only single solar vector information, which contains only two independent scalar pieces of attitude information, so it is impossible to determine three Euler angles simultaneously in real-time. To further verify this conclusion, based on a designed hypothetical polarization camera, we discuss what conditions different three-dimensional attitudes must satisfy so that the polarization images taken at different 3D attitudes are the same; this indicates that multiple solutions will appear when only using the Rayleigh sky model to determine 3D attitude. In conclusion, due to its single solar vector information and the existence of multiple solutions, it is fully proved that 3D attitude cannot be determined in real time based only upon the Rayleigh sky model. Code is available at: https://github.com/HuajuLiang/HypotheticalPolarizationCamera

Navigation: How the Recent Past Shapes Future Routes in Desert Ants.

When falling into a trap, desert ants remember the last views preceding this event and avoid them on future foraging journeys. This association of images with negative experience might be responsible for the establishment of stable routes through complex environments.

Rapid Aversive and Memory Trace Learning during Route Navigation in Desert Ants.

The ability of bees and ants to learn long visually guided routes in complex environments is perhaps one of the most spectacular pieces of evidence for the impressive power of their small brains. Whereas flying bees can visit flowers in an optimized sequence over kilometers, walking solitary foraging ants can precisely recapitulate routes of up to 100m in complex environments [1]. It is clear that route following depends largely on learned visual information and we have a good idea of how visual memories can guide individuals along them [2-6], as well as how this is implemented in the insect brain [7, 8]. However, little is known about the mechanisms that control route learning and development. Here we show that ants (Melophorus bagoti and Cataglyphis fortis) navigating in their natural environments can actively learn a route detour to avoid a pit trap. This adaptive flexibility depends on a mechanism of aversive learning based on memory traces of recently encountered stimuli, reflecting the laboratory paradigm of trace conditioning. The views experienced before falling into the trap become associated with the ensuing negative outcome and thus trigger salutary turns on the subsequent trip. This drives the ants to orient away from the goal direction and avoid the trap. If the pit trap is avoided, the novel views experienced during the detour become positively reinforced and the new route crystallizes. We discuss how such an interplay between appetitive and aversive memories might be implemented in insect neural circuitry.

Accuracy and spread of nest search behaviour in the Saharan silver ant, Cataglyphis bombycina, and in the salt pan species, Cataglyphis fortis

Desert ants of the genus Cataglyphis are renowned for their navigation abilities, especially for their beeline homing after meandering foraging excursions reaching several hundreds of meters in length. A spiralling nest search is performed when an ant misses the nest entrance upon completing its homebound travel. We examined the nest search behaviours of two desert ant species dwelling in different habitats—Cataglyphis bombycina living in the dunes of the Sahara and Cataglyphis fortis found in the salt pans of North Africa. The two species show distinct differences in walking behaviour. C. bombycina performs a strict tripod gait with pronounced aerial phases, high stride frequencies, and extremely brief ground contact times. In view of these peculiarities and the yielding sand dune substrate, we hypothesised that homing accuracy, and namely distance measurement by stride integration, should be lower in C. bombycina, compared to the well-studied C. fortis with less specialised walking behaviour. We tested this hypothesis in ants’ homebound runs from a feeding site in a linear channel setup. Surprisingly, the accuracies of nest searches were similar in the two ant species, and search accuracy was also independent of the walking substrate, soft dune sand or a hard floor. The spread of the nest search, by contrast, differed significantly between the two species, C. bombycina exhibiting a larger search spread. This may be interpreted as an increased path integration uncertainty due to the above locomotor specialisations, or as a compensation strategy accounting for the silver ants’ particular environmental and behavioural situation.

Bio-inspired attitude measurement method using a polarization skylight and a gravitational field.

High precision and reliability attitude measurement play an important role in autonomous unmanned navigation. Finding inspiration from desert ants, known as highly efficient navigators who can find their way after foraging for hundreds of meters from their home in hostile environments, we propose an attitude measurement method using polarization skylight and gravitational field. Contrary to the previous method, we utilize three-dimensional polarization vectors and any one-dimensional output of the accelerometers to calculate attitudes. In addition, we designed an accelerometer component selection algorithm, which is to select the one-dimensional component with the minimum motion acceleration from the output of the three-dimensional accelerometer. With this method, even if the carriers remain in a maneuvering state, the motion acceleration of the vehicle will have less impact on the accuracy of attitude measurement. To evaluate the performance of our method, the outdoor experiment was carried out to compare our method with existing traditional methods. Comparison results show that our method has higher measurement accuracy than others and is still applicable in the case of carriers maneuvering in practice under a clear sky.

The effect of spatially restricted experience on extrapolating learned views in desert ants, Melophorus bagoti.

Desert ants are known for learning walks at the beginning of their foraging life, during which they learn terrestrial cues of the panorama and surrounding landmarks around their nest. Foragers retain memories of the visual cues of the nest panorama learned during the pre-foraging trials. When away from the nest, they can compare these stored views with their current vision to return to their nest. In this study we investigated whether spatially restricted foraging ants can extrapolate their memory of visual cues to unexperienced sites. We carried out two conditions to examine whether desert ants extrapolate learned views. In the first condition, naïve ants of Melophorus bagoti were restricted to a nest arena 1m in radius with a 10cm high wall (wall condition) for 3days, then released at distant locations on the fourth day and focal individuals return trips were recorded. In the second condition, a 10cm sunken metallic barrier was constructed around the nest (moat condition) and the restricted foragers that viewed the unrestricted visual panorama around the 1m-radius nest arena were then displaced away from the nest as in the wall condition. In the wall condition, most of the ants were unable to orient in the correct heading towards the home direction. In the moat condition ants were able to correctly orient to the nest from displacement sites up to 8m from the nest. We conclude that while travelling to unfamiliar sites, M. bagoti ants can extrapolate views learned from foraging in a restricted area when given unrestricted views.

Cataglyphis meets Drosophila

In Cataglyphis and Drosophila – in desert ants and fruit flies – research on visually guided behavior took different paths. While work in Cataglyphis started in the field and covered the animal’s wide navigational repertoire, in Drosophila the initial focus was on a particular kind of visual control behavior scrutinized within the confines of the laboratory arena, before research concentrated on more advanced behaviors. In recent times, these multi-pronged approaches in flies and ants increasingly converge, both conceptually and methodologically, and thus lay the ground for combined neuroethological efforts. In spite of the obvious differences in the behavioral repertoire of these two groups of insects, likely commonalities in the navigational processes and underlying neuronal circuitries are increasingly coming to the fore.

A Combination Orientation Compass Based on the Information of Polarized Skylight/Geomagnetic/MIMU

The aim of this present is to design a new kind of compass which can be used during the absence of satellite signals. It is a development trend to enhance the reliability and environmental adaptability of navigation system to enable the vehicle-borne system to have the ability of navigation and orientation without satellite signals. So far, the geomagnetic/micro inertial measurement unit(MIMU) orientation method which has been commonly used in orientation mode is vulnerable to environmental interference and has weak reliabilities. Through the research of bionic navigation at home and abroad, it has been found that some insects such as desert ants, bees, etc. can find orientation by sensing atmospheric polarization information. In this paper, by using array polarization vision sensor to get the polarization information of the local zenith, the heading angle of polarization information can be calculated, and then by using Kalman filter, the heading angle of polarization information can be fused with the results of geomagnetic/MIMU, so as to achieve better optimal heading estimation. The environmental adaptability and effectiveness of the compass have been verified by theoretical analysis and vehicle experiments.

SWARM OPTIMIZATION ALGORITHM BASED ON THE ANT COLONY LIFE CYCLE

Optimization is very important to the success of any business. One technique for solving optimization is swarm intelligence; it has been successfully applied to solve a wide range of optimization problems. We devised a new swarm intelligence optimization algorithm based on the cooperative behavior of three different kinds of ants in a colony. Our algorithm consists of both exploration and exploitation processes to achieve better search performance. A new local search, inspired by the foraging of desert ants, was introduced to help the search move away from the local optima. Performance was evaluated on 23 standard benchmark functions of varying complexity. Our algorithm was able to find the global optima in more than 80 percent of the test functions, whereas the second-place algorithm only found around 10 percent of the functions tested.

Repeated evolution of queen parthenogenesis and social hybridogenesis in Cataglyphis desert ants.

Over the last decade, genetic studies on social insects have revealed a remarkable diversity of unusual reproductive strategies, such as male clonality, female clonality, and social hybridogenesis. In this context, Cataglyphis desert ants are useful models because of their unique reproductive systems. In several species, queens conditionally use sexual reproduction and parthenogenesis to produce sterile workers and reproductive queens, respectively. In social hybridogenesis, two distinct genetic lineages coexist within a population, and workers result from mating between partners of different lineages; in contrast, queens and males are both produced asexually by parthenogenesis. Consequently, nonreproductive workers are all interlineage hybrids, whereas reproductives are all pure lineage individuals. Here, we characterized the reproductive systems of 11 species to investigate the distribution of the conditional use of sex and social hybridogenesis in Cataglyphis. We identified one new case in which sexual reproduction was conditionally used in the absence of dependent-lineage reproduction. We also discovered five new instances of social hybridogenesis. Based on our phylogenetic analyses, we inferred that both the conditional use of sex and social hybridogenesis independently evolved multiple times in the genus Cataglyphis.

World's fastest ant even outpaces larger cousin

According to Noël Coward, mad dogs and Englishmen are the only creatures that go out in the midday sun, but Harald Wolf from the University of Ulm, Germany, would add another animal: Saharan silver ants (Cataglyphis bombycina). Venturing from their nests to scavenge the corpses of less-fortunate creatures at the peak of the day – when the sand can reach 60°C – these resilient ants had always fascinated Wolf. ‘Even among desert ants, the silver ants are special’, he says, explaining that the insects were reputed to hit speeds approaching 1 m s−1. But little was known about how the ants scamper at such blistering speeds across the sand. During an earlier trip to the salt pans of Tunisia – to study the silver ant's cousin, Cataglyphis fortis – Wolf, Sarah Pfeffer, Verena Wahl and Matthias Wittlinger had taken a detour to Douz to search for the enigmatic desert dwellers. After finding silver ants thriving in the dunes, the team returned in 2015 to film them in action.Pfeffer recalls that locating the inconspicuous nests was far from easy: ‘We had to look for digging ants or follow a foraging ant back home’, she explains. However, once the team had located a nest, it was simply a matter of connecting an aluminium channel to the entrance and placing a feeder at the end to lure the ants out. ‘After the ants have found the food – they love mealworms – they shuttle back and forth in the channel and we mounted our camera to film them from the top’, smiles Pfeffer. In addition, the team excavated a nest, returning with it to Germany, to record the insects running more slowly at cooler temperatures.Calculating the insects’ top speeds, Pfeffer and Wahl were impressed to find the animals hit an extraordinary 0.855 m s−1 (that is, 855 mm s−1 or 108 times their own body length per second) during the hottest part of the desert day, falling to 0.057 m s−1 at 10°C in the lab. In contrast, larger Cataglyphis fortis only get up to 0.62 m s−1 (only 50 body lengths s−1), making C. bombycina the world's fastest ant and placing them close to the top of the list of world record-breaking creatures, alongside Australian tiger beetles (171 body lengths s−1) and California coastal mites (377 body lengths s−1).The scientists also compared the leg lengths of the two species and it was evident that the swift silver ants are doing something remarkable. Their limbs are almost 20% shorter than those of their leggier cousins. Wondering how the smaller ants outstrip their larger Cataglyphis relatives, the team focused on the ants’ footwork.Analysing the silver ant's manoeuvres, the team realised that the insects were swinging their 4.3–6.8 mm long legs at speeds of up to 1200 mm s−1, taking up to 47 strides s−1 – around a third faster than their larger relatives. And when they scrutinised the ants’ stride lengths, they quadrupled from 4.7 mm to 20.8 mm as the ants shifted up through the gears. The team also discovered that instead of simply running, the ants switched to a gallop, with all six feet off the ground simultaneously at speeds above 0.35 m s−1. In addition, they analysed the ants’ coordination and were impressed by how well the ants synchronised their feet – tightly coordinating the movements of the three legs that work together forming tripods as they walk – while each foot only contacted the ground for as little as 7 ms before initiating the next stride.‘These features may be related to the sand dune habitat’, says Wolf, adding, ‘[they] could prevent the animal's feet from sinking too deeply into the soft sand’. He is also keen to find out more about how these desert dwellers pull off their high-speed feats, which he suspects must require muscle contraction speeds close to physiological limits.

Same but different: Socially foraging ants backtrack like individually foraging ants but use different mechanisms

Diverse species may adopt behaviourally identical solutions to similar environmental challenges. However, the underlying mechanisms dictating these responses may be quite different and are often associated with the specific ecology or habitat of these species. Foraging desert ants use multiple strategies in order to successfully navigate. In individually foraging ants, these strategies are largely visually-based; this includes path integration and learned panorama cues, with systematic search and backtracking acting as backup mechanisms. Backtracking is believed to be controlled, at least in solitary foraging species, by three criteria: 1) foragers must have recent exposure to the nest panorama, 2) the path integrator must be near zero, and 3) the ant must be displaced to an unfamiliar location. Instead of searching for the nest, under these conditions, foragers head in the opposite compass direction of the one in which they were recently travelling. Here, we explore backtracking in the socially foraging desert harvester ant (Veromessor pergandei), which exhibits a foraging ecology consisting of a combination of social and individual cues in a column and fan structure. We find that backtracking in V. pergandei, similar to solitary foraging species, is dependent on celestial cues, and in particular on the sun’s position. However, unlike solitary foraging species, backtracking in V. pergandei is not mediated by the same criteria. Instead the expression of this behaviour is dependent on the presence of the social cues of the column and the proportion of the column that foragers have completed prior to displacement.

Vector calibration in Australian desert ants, Melophorus bagoti: Effects of a delay after the acquisition of vector information

AbstractDesert ants navigate by using two chief strategies: path integration, keeping track of the straight‐line distance and direction to the starting point as they travel, and landmark guidance, orientation based on the visual panorama. Both Cataglyphis ants in North Africa and Melophorus bagoti in Central Australia are known to adjust their vectors derived from path integration to compensate for mismatches between their outbound direction of travel and (the reverse of) the inbound direction of travel that takes them home, a process known as vector calibration. We created mismatches of 90° between the outbound vector and the homebound direction by displacing ants from a feeder before their homebound run. We examined temporal factors in vector calibration by varying the delay (0, 1 or 3 hr) between the outbound run to the feeder and the homebound run from the displacement site. According to the temporal weighting rule, such a delay should decrease the weight given to the vector information obtained from the outbound run. This in turn should favour reliance on the visual panorama and thus speed up calibration. Results did not support this prediction. At the displacement site, a delay had little effect on the extent of calibration or the speed of calibration (the number of trials to reach maximum calibration). Just before being displaced, ants were also tested in a test ring surrounded by high walls that obliterated the visual scenery. In the test ring, a delay made the ants less likely to rely on their vector: ants were often not oriented as a group. Otherwise, the ants in the test ring also did not calibrate any more or any faster.

Destruction of Spiderwebs and Rescue of Ensnared Nestmates by a Granivorous Desert Ant (Veromessor pergandei).

Prey species rarely seek out and dismantle traps constructed by their predators. In the current study, we report an instance of targeted trap destruction by an invertebrate and a novel context for rescue behavior. We found that foragers of the granivorous desert ant (Veromessor pergandei) identify and cooperatively dismantle spiderwebs (Araneae: Theridiidae, Steatoda spp., and Asagena sp.) During group foraging, workers ensnared in webs are recovered by sisters, which transport them to the nest and groom away their silk bindings. The presence of an ensnared nestmate and chemical alarm signal significantly increased the probability of web removal and nestmate retrieval. A subset of larger-bodied foragers participated in web removal, and 6.3% became tangled or were captured by spiders. Most animals that perform rescue behavior live in small groups, but V. pergandei colonies include tens of thousands of short-lived workers. To maintain their size, large colonies must collect enough seeds to produce 650 new ants each day. We hypothesize that the removal of spiderwebs allows for an unimpeded income of seeds on a single foraging path during a brief daily temperature window. Despite the cost to individuals, webs are recognized and removed only when workers are captured in them.

A desert ant as inspiration for a paint-like material that could keep buildings cool

A desert ant as inspiration for a paint-like material that could keep buildings cool

Ocellar structure of African and Australian desert ants.

Few walking insects possess simple eyes known as the ocelli. The role of the ocelli in walking insects such as ants has been less explored. Physiological and behavioural evidence in the desert ant, Cataglyphis bicolor, indicates that ocellar receptors are polarisation sensitive and are used to derive compass information from the pattern of polarised skylight. The ability to detect polarised skylight can also be inferred from the structure and the organisation of the ocellar retina. However, the functional anatomy of the desert ant ocelli has not been investigated. Here we characterised the anatomical organisation of the ocelli in three species of desert ants. The two congeneric species of Cataglyphis we studied had a fused rhabdom, but differed in their organisation of the retina. In Cataglyphis bicolor, each retinula cell contributed microvilli in one orientation enabling them to compare e-vector intensities. In Cataglyphis fortis, some retinula cells contributed microvilli in more than one orientation, indicating that not all cells are polarisation sensitive. The desert ant Melophorus bagoti had an unusual ocellar retina with a hexagonal or pentagonal rhabdomere arrangement forming an open rhabdom. Each retinula cell contributed microvilli in more than one orientation, making them unlikely to be polarisation detectors.

The Interplay between Incipient Species and Social Polymorphism in the Desert Ant Cataglyphis

In social insects, due to considerable polyphenism as well as high level of hybridization, the delimitation of species can be challenging. The genus Cataglyphis presents a high level of diversification, making it an excellent model with which to study evolutionary paths. Israel appears to be a “hot spot” for recent speciation in this genus. Although previous studies have described multiple species of Cataglyphis in Israel, a recent genetic study has questioned the existence of some of these historically described species. The present study focuses on an apparent species complex, the C. niger species complex which includes C. niger, C. savigyi, and C. drusus that are distinguishable by their mitochondrial DNA (and therefore named mitotypes) but not by their nuclear DNA. Using a multi-method approach (genetics, chemistry and behavior), we show that these mitotypes also differ in their social structures and are readily distinguishable by their cuticular hydrocarbons profiles. While most populations of the different mitotypes are allopatric, at our study site they are sympatric, but nonetheless maintain the observed differences between them. This raises the evolutionary question: Are these incipient species that have diverged with gene flow, or is this a case of social and chemical polymorphism that is maintained within a single species? Unveiling the interplay between social polyphenism and species segregation is at the core of evolutionary biology.

Path integration: how details of the honeybee waggle dance and the foraging strategies of desert ants might help in understanding its mechanisms.

Path integration is a navigational strategy that gives an animal an estimate of its position relative to some starting point. For many decades, ingenious and probing behavioural experiments have been the only window onto the operation of path integration in arthropods. New methods have now made it possible to visualise the activity of neural circuits in Drosophila while they fly or walk in virtual reality. Studies of this kind, as well as electrophysiological recordings from single neurons in the brains of other insects, are revealing details of the neural mechanisms that control an insect's direction of travel and other aspects of path integration. The aim here is first to review the major features of path integration in foraging desert ants and honeybees, the current champion path integrators of the insect world, and second consider how the elaborate behaviour of these insects might be accommodated within the framework of the newly understood neural circuits. The discussion focuses particularly on the ability of ants and honeybees to use a celestial compass to give direction in Earth-based coordinates, and of honeybees to use a landscape panorama to provide directional guidance for path integration. The possibility is raised that well-ordered behaviour might in some cases substitute for complex circuitry.