GSM 900 MHz radiation inhibits ants' association between food sites and encountered cues

The kinetics of the acquisition and loss of the use of olfactory and visual cues were previously obtained in six experimental colonies of the ant Myrmica sabuleti meinert 1861, under normal conditions. In the present work, the same experiments were conducted on six other naive identical colonies of M. sabuleti, under electromagnetic radiation similar to those surrounding GSM and communication masts. In this situation, no association between food and either olfactory or visual cues occurred. After a recovery period, the ants were able to make such an association but never reached the expected score. Such ants having acquired a weaker olfactory or visual score and still undergoing olfactory or visual training were again submitted to electromagnetic waves. Not only did they lose all that they had memorized, but also they lost it in a few hours instead of in a few days (as under normal conditions when no longer trained). They kept no visual memory at all (instead of keeping 10% of it as they normally do). The impact of GSM 900?MHz radiation was greater on the visual memory than on the olfactory one. These communication waves may have such a disastrous impact on a wide range of insects using olfactory and/or visual memory, i.e., on bees.     

Food collection and response to pheromones in an ant species exposed to electromagnetic radiation

We used the ant species Myrmica sabuleti as a model to study the impact of electromagnetic waves on social insects' response to their pheromones and their food collection. We quantified M. sabuleti workers' response to their trail, area marking and alarm pheromone under normal conditions. Then, we quantified the same responses while under the influence of electromagnetic waves. Under such an influence, ants followed trails for only short distances, no longer arrived at marked areas and no longer orientated themselves to a source of alarm pheromone. Also when exposed to electromagnetic waves, ants became unable to return to their nest and recruit congeners; therefore, the number of ants collecting food increases only slightly and slowly. After 180 h of exposure, their colonies deteriorated. Electromagnetic radiation obviously affects social insects' behavior and physiology.     

Sensu stricto individual conditioning,and imitation,in the ant Myrmica sabuleti (Hymenoptera: Formicidae)

Summary

Conditioning of isolated ants was attempted in the ant Myrmica sabuleti. Isolated ants did not die and could be visually as well as olfactorily conditioned. They acquired and kept ? or partly lost ? their visual ? or their olfactory ? conditioned responses as do ants living in a colony. Each individual of an ant colony is thus able to learn and memorize by itself. Any collective conditioning, learning and memory actually reflect the individuals’ performance. Naive workers paired with isolated previously conditioned ants apparently acquired olfactory conditioning in a shorter time than isolated ants, reaching a conditioning score identical to that of isolated ants. But they lost their apparent conditioning as soon as the olfactory cue was removed. Thus, imitation of nestmates exists in ants but does not lead, by itself, to learning sensu stricto since nothing of what has been imitated is retained.     

Memory and chemical communication in the orientation of two mass-recruiting ant species

Summary The relative contribution of visual and chemical components in the orientation ofLasius niger andIridomyrmex humilis (Argentine ant) workers during mass recruitment to newly discovered food sources is analyzed over short time intervals. While both species orient in response to the trail pheromone, a large number ofL. niger foragers rapidly switch to a more individual orientation, based on their memory of environmental cues.I. humilis workers, on the other hand, predominantly use collective chemical cues. The effect of the number of reinforcements on visual learning and its interference with chemical communication show that olfactory cues always prevail in the Argentine ant. InL. niger, the proportion of ants orienting to visual cues is independent of the trail concentration. Detailed observations of the trail-laying behavior of individually marked foragers show that nearly all theI. humilis workers initially lay a trail, whereas only half theL. niger foragers do so. This proportion decreases considerably with the number of trips performed byL. niger workers, while remaining constant for the Argentine ants. These results are interpreted with respect to the species' behavioral ecology.     

Effect of Short-Term GSM Radiation at Representative Levels in Society on a Biological Model: The Ant Myrmica sabuleti

Well-controlled electromagnetic exposure conditions were set up at a representative societal GSM radiation intensity level, 1.5 V/m, which is the legally allowed level in Brussels. Two nests of the ant species Myrmica sabuleti were repeatedly irradiated during 10 min. before their behavior was observed, based on the analysis of the ant trajectories. Under these exposure conditions, behavioral effects were detected. The ants’ locomotion slightly changed. The ants’ orientation towards their attractive alarm pheromone statistically became of lower quality. The ants still presented their trail following behavior but less efficiently. In this controversial issue, ants could be considered as possible bioindicators.     

Comparative outlook over physiological and ecological characteristics of three closely-related Myrmica species

This paper summarizes our findings on the eye morphology, visual perception, learning abilities, navigation system and recruitment strategy of three Myrmica species, pointing out the agreement between each species’ morphological, physiological and behavioral characters as well as the accordance between these characters and each species’ environmental preferences. We also draw biological generalities and report other similar studies. Myrmica sabuleti workers have small eyes, perceive the dimension, number of basic elements and orientation of a visual cue but do not distinguish shapes from one another. They see the colors, perceive UV light and the perspective, and adapt their vision to the light intensity. They learn odors better than visual cues and essentially use odors to navigate. Myrmica ruginodis workers have large eyes, distinguish shapes, small see-through forms as well as patterns of luminous points located above them. They have no olfactory memory but a very long lasting visual one. They exclusively use visual cues located above them while travelling, relying on odors only when they no longer see. Myrmica rubra workers have eyes of middle size and distinguish filled shapes but not hollow forms. Their olfactory and visual conditioning lead to equivalent learning in the course of time and they use all available olfactory and visual elements for navigating.     

A desert ant's memory of recent visual experience and the control of route guidance

Insects such as desert ants learn stereotyped visual routes between their nests and reliable food sites. Studies here reveal an important control element for ensuring that the route memories are used appropriately. They find that visual route memories can be disengaged, so that they do not provide guidance, even when all appropriate visual cues are present and when there are no competing guidance cues. Ants were trained along a simple route dominated by a single isolated landmark. If returning ants were caught just before entering the nest and replaced at the feeder, then they often interrupted the recapitulation of their homeward route with a period of apparent confusion during which the route memories were ignored. A series of experiments showed that this confusion occurred in response to the repetition of the route, and that the ants must therefore maintain some kind of a memory of their visual experience on the current trip home. A conceptual model of route guidance is offered to explain the results here. It proposes how the memory might act and suggests a general role for disengagement in regulating route guidance.     

Visual discrimination of cues differing as for their number of elements, their shape or their orientation, by the ant Myrmica sabuleti

Using operant conditioning as a method, we study if Myrmica sabuleti workers can discriminate figures made of different numbers of the same element, different filled shapes or hollow forms and elements differently oriented. The ants effectively discriminate figures containing different numbers of the same element but without counting the elements: their distinguishing is based on the global aspect (dimensions, area) of the figures. They distinguish filled shapes as well as hollow forms when these look different if seen with convexity. For instance, they differentiate well between concave filled shapes or concave hollow forms. They see distinctly an element and the same one rotated if this element, seen with convexity, looks different after its rotation. They perceive until a 30° rotation of a vertical segment and until a 15° rotation of a horizontal segment. In conclusion, M. sabuleti workers are sensitive to the number of elements, dimension, shape, form and orientation of visual cues with the restriction that they probably see them with convexity.     

Memory of Location and Site Recognition in the Ant Formica uralensis (Hymenoptera: Formicidae)

Spatial recognition cues used in site fidelity in the ant Formica uralensis Ruzsky were studied using outdoor and laboratory arenas. Ant workers visiting symmetrically spaced feeders were colour-marked corresponding to the initial feeder visited during sampling. The effect of manipulating environmental cues on the mean 'spatial specialization' of the population was measured. Site recognition appears to be based on visual landmark/canopy cues. However, ants maintained some fidelity when shielded from these cues, suggesting the involvement of additional cues. When ridding our experimental device of olfactory deposits and shielding visual cues, site fidelity was lost. Idiothetic and/or geomagnetic cues are thought to provide spatial references to visual or olfactory landmarks. Altering nest position relative to the arena and changing the geomagnetic field within the arena in our study, however, did nothing to the site fidelity of visually deprived and non-deprived foragers.
We conclude that site fidelity is developed in a visually structured environment but supplemented by an olfactory backup system that is probably based on discrete home range markings rather than radial odour trails. We demonstrate furthermore that the visual component involved in site location can be stored in the memory of individual F. uralensis foragers during a 6-month hibernation period.     

Visual Navigation during Colony Emigration by the Ant Temnothorax rugatulus

Many ants rely on both visual cues and self-generated chemical signals for navigation, but their relative importance varies across species and context. We evaluated the roles of both modalities during colony emigration by Temnothorax rugatulus. Colonies were induced to move from an old nest in the center of an arena to a new nest at the arena edge. In the midst of the emigration the arena floor was rotated 60°around the old nest entrance, thus displacing any substrate-bound odor cues while leaving visual cues unchanged. This manipulation had no effect on orientation, suggesting little influence of substrate cues on navigation. When this rotation was accompanied by the blocking of most visual cues, the ants became highly disoriented, suggesting that they did not fall back on substrate cues even when deprived of visual information. Finally, when the substrate was left in place but the visual surround was rotated, the ants'' subsequent headings were strongly rotated in the same direction, showing a clear role for visual navigation. Combined with earlier studies, these results suggest that chemical signals deposited by Temnothorax ants serve more for marking of familiar territory than for orientation. The ants instead navigate visually, showing the importance of this modality even for species with small eyes and coarse visual acuity.     

Oviposition preferences in Grapholita molesta: the relative importance of visual and olfactory cues

The oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), is a major pest of fruit trees worldwide. Females oviposit on the young leaves of peach [Prunus persica (L.) Batsch (Rosaceae)] shoots at twilight, when light intensity changes markedly. Previous researches have shown that the oviposition response of this moth is guided particularly by visual and olfactory cues from host plants. However, the relative importance of visual and olfactory cues in their oviposition preference is largely unknown. As a crepuscular moth, how do choices change as light intensity drops rapidly from day to night? In the present study, through two‐choice behavioural experiments, the oviposition responses of G. molesta to visual and olfactory cues (alone or in combination) from peach shoots were tested at four light intensities ranging from daylight to starlight. Grapholita molesta showed similar oviposition responses to plant cues under 1 000, 100, 1 and 0.01 mW m^?2 illumination. Olfactory cues from peach shoots attracted significantly more oviposition than the negative control, whereas visual cues alone did not. Furthermore, olfactory cues were more attractive than visual cues, and no significant interaction was observed between the responses to the two cues. Our findings indicate that G. molesta females mainly rely on olfactory cues to recognize oviposition sites, regardless of differences in light intensity. These results do not provide evidence for attraction to visual cues, but the possibility that the brightness of leaves might be used to guide oviposition is discussed.     

Olfactory and visual plant cues as drivers of selective herbivory

Food quality is an important consideration in the foraging strategy of all animals, including herbivores. Those that can detect and assess the nutritional value of plants from afar, using senses such as smell and sight, can forage more efficiently than those that must assess food quality by taste alone. Selective foraging not only affects herbivore fitness but can influence the structure and composition of plant communities, yet little is known about how olfactory and visual cues help herbivores to find preferred plants. We tested the ability of a free‐ranging, generalist mammalian browser, the swamp wallaby Wallabia bicolor, to use olfactory and visual plant cues to find and/or browse differentially on Eucalyptus pilularis seedlings grown under different nutrient conditions. Low‐nutrient seedlings differed from high‐nutrient seedlings, having lighter coloured leaves, red stems and lower biomass and nitrogen content. In the absence of visual cues, wallabies used odour to differentiate vials containing cut seedlings. They visited and investigated patches with high‐nutrient seedling odour most, followed by patches with low‐nutrient seedling odour, and patches with no added odour least. However, when visual and olfactory cues of seedlings were present, wallabies reversed their foraging response and were more likely to browse low‐ than high‐nutrient seedlings. This browsing difference, in turn, disappeared when long‐range visual cues were reduced by pinning seedlings horizontal to the ground. We suggest that visual cues overrode the effects of olfactory cues on browsing patterns of intact seedlings. Our study shows that herbivores can respond to odours of higher nutrient plants but in ecologically realistic scenarios they use a variety of visual and olfactory cues, with a context‐dependent outcome that is not always selection of high nutrient food. Our results demonstrate the importance of testing the sensory abilities of herbivores in realistic multi‐sensory settings to understand their function in selective foraging.     

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.     

Visual and Chemical Cues Used in Host Location and Acceptance by a Dipteran Parasitoid

Locating potential hosts for egg laying is a critical challenge in the life history of many insects. Female insects in several orders have evolved mechanisms to find hosts by using olfactory and visual signals derived from their hosts. We describe visual and chemical cues used by the dipteran parasitoid Apocephalus paraponerae (Diptera: Phoridae) in the location and acceptance of its host ant Paraponera clavata (Hymenoptera: Formicidae: Ponerinae). Our results show that A. paraponerae uses the visual cue of ant body size when locating hosts at short range and that these flies lay more eggs in ants that retain their surface chemicals than in ants with these chemicals removed. We compare the cues used by A. paraponerae with cues used by tephritid fruit flies in location and acceptance of their hosts, and we suggest further avenues for the study of host location, acceptance, and host discrimination of A. paraponerae and other parasitoids of ants.     

Ontogenesis of visual and olfactory kin recognition,in the ant Myrmica sabuleti (Hymenoptera: Formicidae)

In the present work, firstly, ant emergence was observed: it is a long, stereotyped, precarious event which may require the help of congeners. Then, our experiments on Myrmica sabuleti Meinert 1861 callow ants emerging apart from or inside their colony showed the following points. 1. Newly emerged workers, even if having never olfactorily perceived nestmates, are attracted by congeners’ odor. They can distinguish such an odor from that of another species of Myrmica as well as somewhat from that of alien workers of the same species. So, they might have acquired, at least partly, the knowledge of their congeners’ odor during their larval life. 2. Callow ants having visually perceived congeners at their emergence move towards a presented congener’s washed corpse. Callow ants having emerged without seeing any congeners do not move towards such a corpse. Callow ants having emerged beside a piece of thyme moved towards a non-odorous (solvent-washed) piece of thyme. So, ants may acquire, at least partly, the knowledge of the visual aspect of their species just at their emergence, probably by imprinting. 3. Very young workers confronted with their congeners’ odor on one hand and their congeners’ visual aspect on the other hand, somewhat prefer the odor, even if these young ants belong to a species which exclusively uses its vision for navigating. So, for very young ants, whatever the species, odors are more important and better known than visual characters.     

Use of learned visual cues during habitat location by Brachymeria intermedia

Like many other parasitoids, Brachymeria intermedia (Hymenoptera: Chalcididae) uses olfactory cues to find its host, but in addition it appears to use learned visual cues to focus its searching efforts at the macrohabitat level. In laboratory experiments, females were held in cages where Lymantria dispar pupae were hidden either in a vertical, tree-like structure or on the floor. After four days females had learned to search for hosts in the structure in which they previously had found pupae. Such training was reversible. During similar tests in a semi-natural situation, in which pupae were hung from a tree trunk or were hidden under leaf litter, females also tailored their subsequent searching to favour the macrohabitat where hosts previously had been found. This parasitoid most likely uses a combination of visual and olfactory cues during host searching.     

Cognitive impairment in rats after long-term exposure to GSM-900 mobile phone radiation

Considering the frequent use of mobile phones, we have directed attention to possible implications on cognitive functions. In this study we investigated in a rat model the long-term effects of protracted exposure to Global System for Mobile Communication-900 MHz (GSM-900) radiation. Out of a total of 56 rats, 32 were exposed for 2 h each week for 55 weeks to radio-frequency electromagnetic radiation at different SAR levels (0.6 and 60 mW/kg at the initiation of the experimental period) emitted by a (GSM-900) test phone. Sixteen animals were sham exposed and eight animals were cage controls, which never left the animal house. After this protracted exposure, GSM-900 exposed rats were compared to sham exposed controls. Effects on exploratory behaviour were evaluated in the open-field test, in which no difference was seen. Effects on cognitive functions were evaluated in the episodic-like memory test. In our study, GSM exposed rats had impaired memory for objects and their temporal order of presentation, compared to sham exposed controls (P = 0.02). Detecting the place in which an object was presented was not affected by GSM exposure. Our results suggest significantly reduced memory functions in rats after GSM microwave exposure (P = 0.02).     

Garden ant homing behavior in a maze task based on local visual cues

Although it has been shown that visual cues play an essential role in navigation by the garden ant Lasius niger, no previous studies have addressed the way in which information from local visual cues is acquired and utilized in navigation. We found that in the absence of pheromone trails, ants whose homing motivation was triggered by feeding returned to the nest following local visual cues. In our experiments, the ants travelled through a maze to reach a feeder. They explored the maze and sometimes became trapped in its dead ends. We found that the ants more effectively used visual cues during their homeward journey if they experienced a dead end during their outward journey. This result suggested that the ants used the information acquired from visual cues during the outward journey to avoid a dead end on their return journey.     

Cues Used for Localizing Food by the Gray Squirrel (Sciurus carolinensis)

We compared the use of olfactory, visual, and spatial cues for learning the location of stored food by gray squirrels (Sciurus carolinensis). All experimental cues were extrinsic, that is, they originated from the environment around the food rather than from the food itself. In training trials, artificial caches with one of two odors, one of two colors, and six of 12 spatial locations contained sunflower seeds. In experimental trials, the odors, colors, and sets of spatial locations associated with food were reversed one at a time, so that only two of the three training cues gave evidence of the food rewards. Consequent declines in food localization by the squirrels revealed differential use of particular cue modalities. The data show that squirrels used visual cues the most and olfactory cues the least with this design. These results, along with other evidence, suggest that gray squirrels use spatial memory in food recovery.     

Effects of exposure to electromagnetic fields emitted by GSM 900 and WCDMA mobile phones on cognitive function in young male subjects

Results of studies on the possible effects of electromagnetic fields emitted by mobile phones on cognitive functions are contradictory, therefore, possible effects of long‐term (7 h 15 min) electromagnetic field (EMF) exposure to handset‐like signals of Global System for Mobile Communications (GSM) 900 and Wideband Code‐Division Multiple Access (WCDMA) on attention and working memory were studied. The sample comprised 30 healthy male subjects (mean ± SD: 25.3 ± 2.6 years), who were tested on nine study days in which they were exposed to three exposure conditions (sham, GSM 900 and WCDMA) in a randomly assigned and balanced order. All tests were presented twice (morning and afternoon) on each study day within a fixed timeframe. Univariate comparisons revealed significant changes when subjects were exposed to GSM 900 compared to sham, only in the vigilance test. In the WCDMA exposure condition, one parameter in the vigilance and one in the test on divided attention were altered compared to sham. Performance in the selective attention test and the n‐back task was not affected by GSM 900 or WCDMA exposure. Time‐of‐day effects were evident for the tests on divided and selective attention, as well as for working memory. After correction for multiple testing, only time‐of‐day effects remained significant in two tests, resulting in faster reactions in the afternoon trials. The results of the present study do not provide any evidence of an EMF effect on human cognition, but they underline the necessity to control for time of day. Bioelectromagnetics 32:179–190, 2011. © 2010 Wiley‐Liss, Inc.