Circadian oscillatory patterns of oxygen uptake in individual workers of the ant Camponotus rufipes

Abstract. Respiratory rates of individual workers of Camponotus rufipes Fabricius (Hymenoptera: Formicidae) were measured at 25C and LD 12:12 h (lights on 06.00 hours), DL 12:12h (lights on 18.00 hours), LL (850 lux) and DD (red light, 20–30 lux), using the micro-Warburg technique. Worker ants were collected from natural nest during the winter of 1987 in a woodland park in the region of Rio Claro, Sāo Paulo, Brazil. The respiration of ants showed a circadian rhythm with acrophase ranging from 20 h 41 min to O1 h 18 min and from 10 h 32 min to 12 h 22 min at LD and DD, respectively. In constant darkness the rhythmometric variables were similar to those presented by ants kept at LD 12:12 h. Under constant light no circadian rhythm in the respiration rates was found. A reduction in the amplitude was observed, indicating an inhibitory effect of this light regime on the respiration process.     

Rice phytochrome A controls apical hook opening after a single light pulse in transgenic tobacco seedlings

Apical hook opening in tobacco seedlings can be induced by a single red light pulse and this induction can be reverted by a subsequent far-red light pulse. The slow hook opening kinetics and the reversibility of an inductive light pulse even after 8 h of darkness indicate the involvement of stable phytochrome. Compared with wild-type, transgenic BN1 seedlings which overexpress rice phytochrome A exhibit a higher sensitivity to low irradiance red light pulses. Moreover, in BN1 seedlings an inductive red light pulse is only partially reversible even after 30 min, whereas wild-type tobacco seedlings show complete reversibility during the entire hook opening process. The data found show that rice phytochrome A is active in transgenic tobacco seedlings in controlling hook opening and that the introduced rice phytochrome A and the endogenous stable phytochrome behave differently in this response.     

A duplex retina and the electroretinogram in the nocturnal Perodicticus potto.

The presence of cones in potto's retina has been proved beyond doubt although they are very restricted in number (1 cone for 300 rods). Morphologically, speaking there is no point in calling these cones "rudimentary" except for their slender outer segment. There are red sensitive elements in that retina at wavelengths beyond the spectral sensitivity of visual purple and it is tempting to assume that these elements are cones. The ERG evoked from these elements by red light differs from that in response to white and blue light. They dark-adapt faster than the receptors sensitive to blue and white flashes. However in some of their properties, for example fusion frequency, these cones behave like rods in other species. As these few cones seem to activate the bipolar cells nearly as effectively as the numerous rods, it is suggested that these cones may be responsible for day vision in the potto.     

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.     

Does substrate coarseness matter for foraging ants? An experiment with Lasius niger (Hymenoptera; Formicidae)

We investigated whether workers of the ant species Lasius niger are able to sense and discriminate the coarseness of the substrate on which they walk. First, we studied the way in which substrate coarseness affects the ants' locomotory behaviour. Second, we investigated the spontaneous preference of ants for substrates of different coarseness. And third, we tested with a differential conditioning procedure the ants' capacity to learn to associate a given coarseness with a food reward. The locomotory behaviour of ants differed according to substrate coarseness: ants moved significantly faster and had more sinuous trajectories on a fine than on a coarse substrate. No spontaneous preference for a substrate of a given coarseness was observed and, even after 20 successive conditioning trials, there was little evidence of the effect of experience on substrate coarseness discrimination. Overall however, ants trained on fine sand made significantly more correct choice than those trained on coarse sand. We discuss these results and argue that in L. niger substrate coarseness may be more important at the collective level, by interacting with the chemical properties of the pheromone trail used in mass recruitment to food source, than at the individual level.     

Possible Evidence for Shift Work Schedules in the Media Workers of the Ant Species Camponotus compressus

The locomotor activity rhythm of the media workers of the ant species Camponotus compressus was monitored under constant conditions of the laboratory to understand the role of circadian clocks in social organization. The locomotor activity rhythm of most ants entrained to a 24 h light/dark (12:12 h; LD) cycle and free-ran under constant darkness (DD) with circadian periodicities. Under entrained conditions about 75% of media workers displayed nocturnal activity patterns, and the rest showed diurnal activity patterns. In free-running conditions these ants displayed three types of activity patterns (turn-around). The free-running period (τ) of the locomotor activity rhythm of some ants (10 out of 21) showed period lengthening, and those of a few (6 out of 21) showed period shortening, whereas the locomotor activity rhythm of the rest of the ants (5 out of 21) underwent large phase shifts. Interestingly, the pre-turn-around τ of those ants that showed nocturnal activity patterns during earlier LD entrainment was shorter than 24 h, which became greater than 24 h after 6–9 days of free-run in DD. On the other hand, the pre-turn-around τ of those ants, which exhibited diurnal patterns during earlier LD entrainment, was greater than 24 h, which became shorter than 24 h after 6–9 days of free-run in DD. The patterns of activity under LD cycles and the turn-around of activity patterns in DD regime suggest that these ants are shift workers in their respective colonies, and they probably use their circadian clocks for this purpose. Circadian plasticity thus appears to be a general strategy of the media workers of the ant species C. compressus to cope with the challenges arising due to their roles in the colony constantly exposed to a fluctuating environment.     

Effect of social and environmental factors on ant aggregation: a general response?

In social species, the interactions that occur between individuals and also between individuals and their environment can lead to various spatial distributions. Our goal was to understand how both factors (social and environmental) can affect such spatial distribution of individuals. Aggregation experiments were conducted on the ant Crematogaster scutellaris: the level of inter-attraction between individuals was characterized and the influence of an environmental factor (light intensity) was studied. Two ethological castes (brood-tenders and foragers) were tested, showing a strong and similar aggregation pattern—although faster for foragers. This difference could be explained by a higher degree of inter-attraction for brood-tenders, resulting in longer interaction time and therefore a slower aggregation rate. We also showed the influence of light conditions by carrying out experiments in total darkness and under red light. C. scutellaris appeared highly sensitive to the red light, aggregating just underneath it. Nevertheless, the level of aggregation is not affected by the luminosity condition. These results are discussed in relation to the ecology of the species, and are compared with results obtained in another ant species, Lasius niger, which exhibits a similar response to aggregation. We propose, therefore, a general link between the level/pattern of aggregation and polyethism in ants.     

Possible evidence for shift work schedules in the media workers of the ant species Camponotus compressus

The locomotor activity rhythm of the media workers of the ant species Camponotus compressus was monitored under constant conditions of the laboratory to understand the role of circadian clocks in social organization. The locomotor activity rhythm of most ants entrained to a 24 h light/dark (12:12 h; LD) cycle and free-ran under constant darkness (DD) with circadian periodicities. Under entrained conditions about 75% of media workers displayed nocturnal activity patterns, and the rest showed diurnal activity patterns. In free-running conditions these ants displayed three types of activity patterns (turn-around). The free-running period (τ) of the locomotor activity rhythm of some ants (10 out of 21) showed period lengthening, and those of a few (6 out of 21) showed period shortening, whereas the locomotor activity rhythm of the rest of the ants (5 out of 21) underwent large phase shifts. Interestingly, the pre-turn-around τ of those ants that showed nocturnal activity patterns during earlier LD entrainment was shorter than 24 h, which became greater than 24 h after 6-9 days of free-run in DD. On the other hand, the pre-turn-around τ of those ants, which exhibited diurnal patterns during earlier LD entrainment, was greater than 24 h, which became shorter than 24 h after 6-9 days of free-run in DD. The patterns of activity under LD cycles and the turn-around of activity patterns in DD regime suggest that these ants are shift workers in their respective colonies, and they probably use their circadian clocks for this purpose. Circadian plasticity thus appears to be a general strategy of the media workers of the ant species C. compressus to cope with the challenges arising due to their roles in the colony constantly exposed to a fluctuating environment.     

Preliminary assessment of metabolic costs of the nematode Myrmeconema neotropicum on its host, the tropical ant Cephalotes atratus

The parasitic nematode Myrmeconema neotropicum infects workers of the neotropical arboreal ant Cephalotes atratus. Infected ants exhibit altered behavior, e.g., reduced aggression and slower tempo, as well as physical traits, e.g., gaster changes from shiny black to bright red. These changes are thought to induce fruit mimicry and attract frugivorous birds, which are the presumed paratenic hosts for the nematodes. We used respirometry to measure the energetic costs of nematode infection, testing the prediction of higher metabolic rates for infected workers maintaining both ant and nematode biomass. Contrary to this prediction, infected workers had lower mass-specific metabolic rates than uninfected workers. Parasites are limited to the gasters (abdomens) of adult ants, and infected gasters had 57% more mass, but 37% lower metabolic rates, compared to uninfected gasters. These results use a metabolic currency to measure, in vivo, the energetic costs of parasitism, and they shed light on the complex co-evolutionary relationship between host and parasite.     

蓝光促进黑曲霉分生孢子发育和产糖化酶的研究

以黑暗为对照 ,研究了不同光质对黑曲霉产糖化酶及生长发育的影响。持续蓝光作用下 ,孢子萌发后菌丝较粗 ,菌丝细胞顶端膨大显著 ,菌丝细胞膜的通透性增加 ,残糖消耗快 ,孢子和孢子穗增大。在 3(4d时 ,蓝光下菌丝产糖化酶活力最高达 6 6 0 (30U mL ,比黑暗高出了 15. 4 % ,生物量增加了 4 9. 4 8% ,菌丝细胞可溶性蛋白含量提高了10 0. 5 6 % ,尤其是在开始产孢子的阶段 ,蓝光下黑曲霉产糖化酶活力、生物量有很大提高。研究表明 ,蓝光明显促进黑曲霉分生孢子发育和产孢阶段包括糖化酶在内的多种淀粉酶活力的迅速增加。     

Task-specific expression of the foraging gene in harvester ants

In social insects, groups of workers perform various tasks such as brood care and foraging. Transitions in workers from one task to another are important in the organization and ecological success of colonies. Regulation of genetic pathways can lead to plasticity in social insect task behaviour. The colony organization of advanced eusocial insects evolved independently in ants, bees, and wasps and it is not known whether the genetic mechanisms that influence behavioural plasticity are conserved across species. Here we show that a gene associated with foraging behaviour is conserved across social insect species, but the expression patterns of this gene are not. We cloned the red harvester ant (Pogonomyrmex barbatus) ortholog (Pbfor) to foraging, one of few genes implicated in social organization, and found that foraging behaviour in harvester ants is associated with the expression of this gene; young (callow) worker brains have significantly higher levels of Pbfor mRNA than foragers. Levels of Pbfor mRNA in other worker task groups vary among harvester ant colonies. However, foragers always have the lowest expression levels compared to other task groups. The association between foraging behaviour and the foraging gene is conserved across social insects but ants and bees have an inverse relationship between foraging expression and behaviour.     

The Influence of Light Wavelength on Phase-Dependent Responsiveness of the Photoperiodic Clock in Migratory Blackheaded Bunting

We investigated the phase-dependent effects of light wavelength on photoperiodic clock in the migratory blackheaded bunting. Two experiments were performed, employing a skeleton paradigm (6 hours light : 6 hours darkness : 1 hour light : 11 hours darkness; 6L : 6D : 1L : 11D) at 37 ± 2 lux intensity. In the experiment 1, both 6 and 1 h light pulses were given at the same wavelength, 500 nm (green) or 650 nm (red). A group exposed to both pulses of white light served as control. In the experi-ment 2, the two light pulses were given at two different wavelengths, 6 h at 500 nm (green) and 1 h at 640 nm (red) in one group or vice-versa in the other. There was almost no photoinduction when both light pulses in experiment 1, or 1 h light pulse in experiment 2, were green. On the other hand, birds fattened and testes recrudesced when both the light pulses in experiment 1, or 1 h light pulse in experiment 2, were red. Birds receiving both pulses of white light in experiment 1 showed an intermediate response. Taken together, these results indicate that the photoperiodic clock in buntings is differentially responsive at its various circadian phases to different light wavelengths.     

Spectral preference and temporal modulation of photic orientation by Colorado potato beetle on a servosphere

The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), is a diurnal insect that strongly relies on visual cues to guide its walk. In the present study, we investigated the orientation behavior of non‐diapausing walking CPB in response to emissive colors produced by light emitting diodes (LEDs) in a dual choice arena adapted to a servosphere, where the only illumination available came from the photo‐stimuli. Our results demonstrate that CPB show positive phototactic behavior when stimulated with different wavelengths of light; they preferred to orient towards white (420–775 nm), ultraviolet (UV) (351 nm), blue (472 nm), green (570 nm), yellow (585 nm), orange (590 nm), and red (660 nm) over darkness when both alternatives were offered, but no orientation responses were elicited by infrared (940 nm). Both males and females preferred yellow and green over other colors, but did not show any particular preference between them, thus correlating with their preference for wavelengths reflected by vegetation. Sexual differences were noted in that male CPB preferred white over either red or UV, whereas female CPB did not show any preferences when offered these colors. Female CPB preferred UV and blue over red, whereas males showed no preferences when these colors were offered. Colorado potato beetles turned at higher angles and performed more tortuous walks in complete darkness and when infrared vs. darkness were offered compared with the rest of the colored lights. Both sexes preferred continuous over pulsed yellow light. Colorado potato beetles subjected to pulsed yellow light showed a temporal alteration of their walking performance by walking less, slower, and turning at a higher rate. The results are discussed with regard to the role of color in the CPB attraction to host plants and conspecifics as well as the role of intermittent photic stimuli in their orientation behavior. The information provided here provides a basis for the improvement of trapping devices for detection and survey of incipient or invasive CPB, and development of alternate control strategies for this important pest of potatoes and other solanaceous crops.     

Behavioral dissection of Drosophila larval phototaxis

A behavior generally comprises multiple processes. Analyzing these processes helps to reveal more characteristics of the behavior. In this report, light/dark choice-based Drosophila larval phototaxis is analyzed with a simplistic mathematical model to reveal a fast phase and a slow phase response that are involved. Larvae of the strain w¹¹¹⁸, which is photophobic in phototaxis tests, prefer darkness to light in an immediate light/dark boundary passing test and demonstrate a significant reduction in motility in the dark condition during phototaxis tests. For tim⁰¹ larvae, which show neutral performance in phototaxis tests, larvae unexpectedly prefer light to darkness in the immediate light/dark boundary passing test and demonstrate no significant motility alteration in the dark condition. It is proposed that Drosophila larval phototaxis is determined by a fast phase immediate light/dark choice and an independent slow phase light/dark-induced motility alteration that follows.     

The Influence of Light Wavelength on Phase-Dependent Responsiveness of the Photoperiodic Clock in Migratory Blackheaded Bunting

We investigated the phase-dependent effects of light wavelength on photoperiodic clock in the migratory blackheaded bunting. Two experiments were performed, employing a skeleton paradigm (6 hours light : 6 hours darkness : 1 hour light : 11 hours darkness; 6L : 6D : 1L : 11D) at 37 ± 2 lux intensity. In the experiment 1, both 6 and 1 h light pulses were given at the same wavelength, 500 nm (green) or 650 nm (red). A group exposed to both pulses of white light served as control. In the experi-ment 2, the two light pulses were given at two different wavelengths, 6 h at 500 nm (green) and 1 h at 640 nm (red) in one group or vice-versa in the other. There was almost no photoinduction when both light pulses in experiment 1, or 1 h light pulse in experiment 2, were green. On the other hand, birds fattened and testes recrudesced when both the light pulses in experiment 1, or 1 h light pulse in experiment 2, were red. Birds receiving both pulses of white light in experiment 1 showed an intermediate response. Taken together, these results indicate that the photoperiodic clock in buntings is differentially responsive at its various circadian phases to different light wavelengths.     

Testing the adjustable threshold model for intruder recognition on Myrmica ants in the context of a social parasite

Social insect colonies are like fortresses, well protected and rich in shared stored resources. This makes them ideal targets for exploitation by predators, parasites and competitors. Colonies of Myrmica rubra ants are sometimes exploited by the parasitic butterfly Maculinea alcon. Maculinea alcon gains access to the ants' nests by mimicking their cuticular hydrocarbon recognition cues, which allows the parasites to blend in with their host ants. Myrmica rubra may be particularly susceptible to exploitation in this fashion as it has large, polydomous colonies with many queens and a very viscous population structure. We studied the mutual aggressive behaviour of My. rubra colonies based on predictions for recognition effectiveness. Three hypotheses were tested: first, that aggression increases with distance (geographical, genetic and chemical); second, that the more queens present in a colony and therefore the less-related workers within a colony, the less aggressively they will behave; and that colonies facing parasitism will be more aggressive than colonies experiencing less parasite pressure. Our results confirm all these predictions, supporting flexible aggression behaviour in Myrmica ants depending on context.     

Orientation and foraging movements in a patchy environment by the ant Serrastruma lujae (formicidae-myrmicinae)

Serrastruma lujae ants individually search for collembolans in the leaf litter of humid tropical forests. During the dry season, collembolans aggregate in wet patches randomly scattered in the dry litter where numerous single workers come hunting from their nest. We simulated this situation in the laboratory, and observed that workers seem to be able to use the humidity gradient direction to efficiently orient themselves towards a wet patch. Once the patch has been reached, they exhibit area-concentrated searching,consisting, in particular, of adopting a high sinuosity and a low speed. After capturing a collembolan, the ants return to their nest along nearly straight paths. This ability may rely on a spatial memory of the nest location by means of a path-integration process. In the absence of prey, however, various behaviours were observed after an unsuccessful search. Comparisons between these data and the results obtained with a homogeneously wet environment simulating the rainy season situation showed that these ants do not simply respond to the humidity level but are also sensitive to the degree of patchiness of their environment. They can therefore be said to be able to adapt suitably to the considerable climatic changes they encounter during the year.     

Light Stimulation of Active Transport in Hydrodictyon africanum

The mechanism of light stimulation of active K and Cl influx and active Na efflux, in Hydrodictyon africanum has been investigated using different wavelengths of red light and different gas mixtures, and the inhibitors DCMU and CCCP. The active Cl influx requires photosystem 2, since its relative quantal efficiency falls with increasing wavelength of red light, and it is as sensitive to the inhibitor DCMU as is photosynthesis; it is relatively insensitive to the uncoupler CCCP. The active K influx and active Na efflux are inhibited by CCCP, but the relative quantal efficiency of these processes increases with increasing wavelength of red light, and they are relatively insensitive to DCMU. These cation fluxes can be supported by cyclic photophosphorylation, whereas Cl influx needs photosystem 2 but probably not ATP.     

红火蚁工蚁对颜色信号的选择与利用

为探明红火蚁Solenopsis invicta工蚁对颜色信号的选择与利用,本研究测定了不同颜色色卡对工蚁的趋向行为以及不同颜色饵料对工蚁觅食行为的影响,以期为红火蚁的高效监测与防控提供重要基础。结果表明颜色显著影响了红火蚁工蚁的趋向行为,黑色对工蚁的引诱率最高,可达32%;黄色对工蚁的引诱率最低,仅为7%。研究也发现不同颜色的饵料显著影响了红火蚁工蚁的觅食。在5 min时间内,工蚁在黄色、绿色以及蓝色饵料上觅食的数量最多,显著高于在紫色和黑色上饵料的觅食工蚁数;工蚁对红色、橙色、黄色、绿色、蓝色饵料的搬运量最大,显著高于紫色与黑色的饵料。综上,红火蚁工蚁可以识别与利用颜色信号,在制备红火蚁监测与防控饵剂时,可以考虑将饵剂染色红、橙、黄、绿、蓝等反射波长较长的颜色,以便工蚁能快速定位到饵剂并搬运更多的饵剂到蚁巢中。     

Photoperiodic and light spectral conditions which inhibit circulating concentrations of thyroxine in the male hamster

Adult male Syrian hamsters were exposed daily for 12 weeks to 11 h/day of cool white fluorescent light (350 +/- 50 microW/cm2) followed by an additional 3 h of near ultraviolet (339-317 nm), blue (435-500 nm), green (515-550 nm), yellow (558-636 nm) or red (653-668 nm) light at an irradiance of 0.2 microW/cm2 or to total darkness. Animals exposed to the wavelengths between 558-668 nm (yellow or red half peak bandwidths) or those receiving a total of 13 h of darkness/day had suppressed circulating levels of thyroxine (T4), a depressed free T4 index (FT4I) and a higher T3/T4 ratio compared to animals receiving a total of 14 h of white light (350 +/- 50 microW/cm2). These results suggest that specific wavelengths of light can affect the neuroendocrine-thyroid axis.