Solar Elevation Triggers Foraging Activity in a Thermophilic Ant

Nycthemeral rhythm is an important biological trait that allows animals to escape predation and competition and, conversely, to coincide with mutualists. Although laboratory studies have shown that the rhythm depends on both endogenous factors and cyclic environmental cues, the latter is often poorly understood, particularly in the wild. Because insects are mostly ectothermal organisms, their activity rhythm is often thought to depend directly on ground temperature. In Mediterranean habitats, Cataglyphis ants are well known for their unusual thermoresistance, allowing them to forage in summer at the central hours of the day when the ground reaches temperatures that are lethal to their competitors. However, we show that the rhythm of Cataglyphis floricola in south‐western Spain is governed by light cues rather than by temperature. First, variations in ant traffic at the nest entrance were better explained by solar elevation angle than by ground temperature on both seasonal and daily scales. Second, if ants waited for the ground to reach a threshold temperature to start their activity, we would expect similar temperatures regardless of the opening hour. However, we found a significant increase in ground temperature as opening hour got later in the day. Third, by using a simple experimental set‐up that increased the apparent solar elevation over the nest entrance, we provoked a delay of nest closure time. We discuss the relevance of these results with respect to the life history of Cataglyphis species and their possible consequences in relation to global warming.     

Spatial Heterogeneity and Nestmate Encounters Affect Locomotion and Foraging Success in the Ant Dorymyrmex goetschi

The spatial structure of habitats contains physical barriers that restrict the performance of diverse behavioural tasks. In heterogeneous habitats, information acquisition may allow animals to improve the performance of diverse activities such as foraging and locomotion. Nonetheless, changes in locomotion performance and their effects on the foraging success of animals have been scarcely studied. We examined these relationships in the harvester ant Dorymyrmex goetschi (subfamily Dolichoderinae) under laboratory conditions. In an experimental arena, we offered a food patch located at a fixed distance from the nest entrance. Landscape heterogeneity was created using wooden cubes arranged in different types of spatial distribution. We video recorded the behaviour of different colonies and quantified the number of active foragers, number of head contacts per capita per inbound trip, path length by workers that transported a food load from the resource patch to the nest, time invested in inbound travels, and the number of prey captured per colony. During the initial phase of patch exploitation, the number of foragers and prey captured were significantly lower than during the half and final phases of the experiment. Landscapes with greater spatial heterogeneity increased travel time and diminished locomotion velocity. A multiple regression analysis revealed that greater antennal contacts and locomotion velocities increased prey removal. Therefore, in this study, we documented a formal link between variables that characterize the movement paths of individuals and the foraging success of a colony. Information transfer between individuals generated a collective work with a concomitant improvement of food exploitation.     

Tasks Performed by Different Groups of Foragers and Regulation of Foraging Activity in the Mediterranean Harvest Ant Messor wasmanni (Hymenoptera,Formicidae)

Journal of Insect Behavior - The moment-to-moment tasks performed by an individual can change in response to a shift of internal, e.g. body size or age, and external conditions, e.g. the number of...     

The Role of Colony Size on Tunnel Branching Morphogenesis in Ant Nests

Many ant species excavate nests that are made up of chambers and interconnecting tunnels. There is a general trend of an increase in nest complexity with increasing population size. This complexity reflects a higher ramification and anastomosis of tunnels that can be estimated by the meshedness coefficient of the tunnelling networks. It has long been observed that meshedness increases with colony size within and across species, but no explanation has been provided so far. Since colony size is a strong factor controlling collective digging, a high value of the meshedness could simply be a side effect of a larger number of workers. To test this hypothesis, we study the digging dynamics in different group size of ants Messor sancta. We build a model of collective digging that is calibrated from the experimental data. Model''s predictions successfully reproduce the topological properties of tunnelling networks observed in experiments, including the increase of the meshedness with group size. We then use the model to investigate situations in which collective digging progresses outward from a centre corresponding to the way tunnelling behaviour occurs in field conditions. Our model predicts that, when all other parameters are kept constant, an increase of the number of workers leads to a higher value of the meshedness and a transition from tree-like structures to highly meshed networks. Therefore we conclude that colony size is a key factor determining tunnelling network complexity in ant colonies.     

The Dynamics of Foraging Trails in the Tropical Arboreal Ant Cephalotes goniodontus

The foraging behavior of the arboreal turtle ant, Cephalotes goniodontus, was studied in the tropical dry forest of western Mexico. The ants collected mostly plant-derived food, including nectar and fluids collected from the edges of wounds on leaves, as well as caterpillar frass and lichen. Foraging trails are on small pieces of ephemeral vegetation, and persist in exactly the same place for 4–8 days, indicating that food sources may be used until they are depleted. The species is polydomous, occupying many nests which are abandoned cavities or ends of broken branches in dead wood. Foraging trails extend from trees with nests to trees with food sources. Observations of marked individuals show that each trail is travelled by a distinct group of foragers. This makes the entire foraging circuit more resilient if a path becomes impassable, since foraging in one trail can continue while a different group of ants forms a new trail. The colony’s trails move around the forest from month to month; from one year to the next, only one colony out of five was found in the same location. There is continual searching in the vicinity of trails: ants recruited to bait within 3 bifurcations of a main foraging trail within 4 hours. When bait was offered on one trail, to which ants recruited, foraging activity increased on a different trail, with no bait, connected to the same nest. This suggests that the allocation of foragers to different trails is regulated by interactions at the nest.     

Seasonal Activity and Foraging Preferences of the Leaf-Cutting Ant Atta sexdens piriventris (Santschi) (Hymenoptera: Formicidae)

Leaf-cutting ants are known for their habit of foraging. These habits can be influenced by several factors, including variations in topography, soil, and climate among others. The objective of this research was to study the seasonal activity and foraging preferences of the leaf-cutting ant Atta sexdens piriventris (Santschi). The study was carried out from January to October of 2007 in grasslands of the state of Santa Catarina, Brazil. Nests of A. sexdens piriventris were randomly selected and the forager’s activities were recorded. Damaged plant species, soil fertility, and climatic conditions were recorded. The maximum foraging activity in the summer was recorded during periods of darkness or low light (between 7 p.m. and 5 a.m.). In autumn and spring, foraging was the highest in the morning, but during winter time the foraging activity was high in the afternoon. Fourteen plant species were frequently visited during our study with the lowest foraging activity being recorded at very low (1 to 4°C) or very high temperatures (above 26°C). The number of exploited plant species was higher in winter (13) than in summer (9). Baccharis trimera (Asteraceae) (43%) and Paspalum spp. (Poaceae) (33%) were the most exploited plants among the identified species.     

癌基因ras对β-1,4-半乳糖基转移酶活性的调节

 研究癌基因ras对细胞表面的 β 1,4 半乳糖基转移酶活性的调节 构建Ha ras表达载体并转染NIH 3T3细胞株 ,测定细胞表面和细胞内 β 1,4 半乳糖基转移酶活性和其mRNA的水平 结果发现ras使NIH 3T3细胞表面的 β 1,4 半乳糖基转移酶活性降低 ,而高尔基体内的活性不变 此外用Northern印迹检测后发现 ,ras不能改变细胞内 β 1,4 半乳糖基转移酶的mRNA水平 这说明癌基因ras能够调节细胞表面β 1,4 半乳糖基转移酶活性 ,但不能改变其转录水平     

The Effect of Moonlight on Scopoli's Shearwater Calonectris diomedea Colony Attendance Patterns and Nocturnal Foraging: A Test of the Foraging Efficiency Hypothesis

Moonlight is known to affect the nocturnal behaviour and activity rhythms of many organisms. For instance, predators active at night may take advantage from increased visibility afforded by the moon, while prey might regulate their activity patterns to become less detectable. Many species of pelagic seabirds attend their colony only at night, in complete darkness, avoiding approaching their nest sites under moonlight. This behaviour has been most often interpreted as an antipredator adaptation (‘predation avoidance’ hypothesis). However, it may also reflect a lower foraging efficiency during moonlit nights (‘foraging efficiency’ hypothesis). Indeed, moonlight may reduce prey availability because preferred seabird prey is known to occur at higher depths in moonlit nights. Using high‐accuracy behavioural information from data loggers, we investigated the effect of moonlight on colony attendance and at‐sea nocturnal foraging in breeding Scopoli's shearwaters Calonectris diomedea. We found that birds departing for self‐feeding trips around the full moon performed longer trips than those departing around the new moon. On nights when the moon was present only partly, nest burrow entrances took place largely in the moonless portion of the night. Moreover, contrary to predictions from the ‘foraging efficiency’ hypothesis, nocturnal foraging activity increased according to moonlight intensity, suggesting that birds increased their foraging activity when prey became more detectable. This study strengthens the idea that colony attendance behaviour is strictly controlled by moonlight in shearwaters, which is possibly related to the perception of a predation risk.     

The Model Identification for Small Unmanned Aerial Rotorcraft Based on Adaptive Ant Colony Algorithm

This paper proposes a model identification method to get high performance dynamic model of a small unmanned aerial rotorcraft.With the analysis of flight characteristics,a linear dynamic model is constructed by the small perturbation theory.Using the micro guidance navigation and control module,the system can record the control signals of servos,the state information of attitude and velocity information in sequence.After the data preprocessing,an adaptive ant colony algorithm is proposed to get optimal parameters of the dynamic model.With the adaptive adjustment of the pheromone in the selection process,the proposed model identification method can escape from local minima traps and get the optimal solution quickly.Performance analysis and experiments are conducted to validate the effectiveness of the identified dynamic model.Compared with real flight data,the identified model generated by the proposed method has a better performance than the model generated by the adaptive genetic algorithm.Based on the identified dynamic model,the small unmanned aerial rotorcraft can generate suitable control parameters to realize stable hovering,turning,and straight flight.     

Regulation of Brood-Care Behavior in the Dimorphic Castes of the Ant Pheidole morrisi (Hymenoptera: Formicidae): Effects of Caste Ratio, Colony Size, and Colony Needs

This study examines the social stimuli that regulate brood-care behavior in the two physical castes of the ant Pheidole morrisi. By increasing the proportion of major workers in a colony, brood-care behavior could be induced in individuals of this caste, which do not normally care for brood. Minor and major worker brood-care rates increased with the proportion of majors in the colony or as the need for brood care increased. Changes in colony size did not significantly affect the rate of either minor or major brood care. Major workers began to care for brood when the caste ratio reached a critical threshold but did not appear to be as efficient at rearing larvae as minor workers, which normally perform this task. After a perturbation that skewed the caste ratio toward majors, minor workers increased their rate of brood care, apparently to compensate for the inefficiency of brood care provided by majors. These results suggest that caste plasticity involves a social mechanism of ldquo;coupled compensation that maintains the efficiency of labor by ensuring that tasks are completed.     

Activity Time Budget during Foraging Trips of Emperor Penguins

We developed an automated method using depth and one axis of body acceleration data recorded by animal-borne data loggers to identify activities of penguins over long-term deployments. Using this technique, we evaluated the activity time budget of emperor penguins (n = 10) both in water and on sea ice during foraging trips in chick-rearing season. During the foraging trips, emperor penguins alternated dive bouts (4.8±4.5 h) and rest periods on sea ice (2.5±2.3 h). After recorder deployment and release near the colony, the birds spent 17.9±8.4% of their time traveling until they reached the ice edge. Once at the ice edge, they stayed there more than 4 hours before the first dive. After the first dive, the mean proportions of time spent on the ice and in water were 30.8±7.4% and 69.2±7.4%, respectively. When in the water, they spent 67.9±3.1% of time making dives deeper than 5 m. Dive activity had no typical diurnal pattern for individual birds. While in the water between dives, the birds had short resting periods (1.2±1.7 min) and periods of swimming at depths shallower than 5 m (0.25±0.38 min). When the birds were on the ice, they primarily used time for resting (90.3±4.1% of time) and spent only 9.7±4.1% of time traveling. Thus, it appears that, during foraging trips at sea, emperor penguins traveled during dives >5 m depth, and that sea ice was primarily used for resting. Sea ice probably provides refuge from natural predators such as leopard seals. We also suggest that 24 hours of sunlight and the cycling of dive bouts with short rest periods on sea ice allow emperor penguins to dive continuously throughout the day during foraging trips to sea.     

植物水通道蛋白活性的调节机制

植物水通道蛋白的活性主要由磷酸化作用、蛋白质异聚化、pH值、Ca2 浓度、环境胁迫、胞内渗透压、温度等因素调节。该文主要从分子生物学角度介绍了与上述因子有关的水通道蛋白活性的调节机制。     

钙蛋白酶的结构及活性调节

钙蛋白酶广泛存在于各组织,广泛表达的钙蛋白酶有两种,钙蛋白酶Ⅰ和钙蛋白酶Ⅱ,它们激活所需的Ca^2＋浓度不同.这两种酶都有大、小两个亚基,分子质量分别为80 ku和30 ku.大亚基有4个结构域,小亚基由2个结构域构成.新近还发现了几种组织特异表达的钙蛋白酶.钙蛋白酶抑制蛋白是钙蛋白酶的内源抑制蛋白,它由5个结构域组成,其中4个为重复序列,均具有独立抑制钙蛋白酶活性的功能.体内钙蛋白酶活性受到严格调控,贴膜反应可以降低钙蛋白酶对Ca^2＋的依赖性,膜磷脂头部所带的磷酸基团与激活作用有关,自溶也可以降低对Ca^2＋的依赖,而钙蛋白酶抑制蛋白则起专一的抑制作用.     

Spatial and Temporal Variations in the Occurrence and Foraging Activity of Coastal Dolphins in Menai Bay,Zanzibar, Tanzania

Understanding temporal patterns in distribution, occurrence and behaviour is vital for the effective conservation of cetaceans. This study used cetacean click detectors (C-PODs) to investigate spatial and temporal variation in occurrence and foraging activity of the Indo-Pacific bottlenose (Tursiops aduncus) and Indian Ocean humpback (Sousa plumbea) dolphins resident in the Menai Bay Conservation Area (MBCA), Zanzibar, Tanzania. Occurrence was measured using detection positive minutes. Inter-click intervals were used to identify terminal buzz vocalisations, allowing for analysis of foraging activity. Data were analysed in relation to spatial (location) and temporal (monsoon season, diel phase and tidal phase) variables. Results showed significantly increased occurrence and foraging activity of dolphins in southern areas and during hours of darkness. Higher occurrence at night was not explained by diel variation in echolocation rate and so were considered representative of occurrence patterns. Both tidal phase and monsoon season influenced occurrence but results varied among sites, with no general patterns found. Foraging activity was greatest during hours of darkness, High water and Flood tidal phases. Comparisons of echolocation data among sites suggested differences in the broadband click spectra of MBCA dolphins, possibly indicative of species differences. These dolphin populations are threatened by unsustainable fisheries bycatch and tourism activities. The spatial and temporal patterns identified in this study have implications for future conservation and management actions with regards to these two threats. Further, the results indicate future potential for using passive acoustics to identify and monitor the occurrence of these two species in areas where they co-exist.     

The Influence of Relatedness, Neighbourhood and Overall Distance on Colony Mate Recognition in a Polydomous Ant

The ‘dear enemy phenomenon’ predicts that territorial animals respond less aggressively towards more familiar neighbours than towards unfamiliar conspecifics if potential losses to strangers are more costly than potential losses to neighbours. Conversely, territorial animals should respond more aggressively to neighbours, if potential losses to them are more costly than potential losses to strangers. In social insects the question of how colony members distinguish neighbours from strangers, however, is intertwined with the more general question of how colony members discriminate themselves from non‐colony members; both genetic and spatial distance can correlate with levels of inter‐colonial aggression. In this paper I disentangle the role of experience, genetic and spatial distance on inter‐colonial aggression in a polydomous population of Iridomyrmex purpureus. In I. purpureus, aggression is related to the spatial distance between colonies irrespective of genetic similarity. Spatial distance affected aggression in two different ways. First, workers were more likely to exhibit aggression towards alien conspecifics of adjoining rather than non‐adjoining territories, suggesting the opposite of the dear enemy phenomenon. Second, workers were more often aggressive towards conspecifics of more distant colonies, implying that environmental cues play a role in the recognition system of I. purpureus.     

Chuck Vocalizations of Wild Female Squirrel Monkeys (Saimiri sciureus) Contain Information on Caller Identity and Foraging Activity

Analysis of the acoustic signal of the chuck vocalizations of adult female squirrel monkeys (Saimiri sciureus) in Parque Nacional de Manu, Peru, revealed consistent differences within and between individuals. We quantified four peak frequency parameters: (a) the peak frequency of single chucks, (b) the first and (c) the second peak frequencies of double chucks, and (d) the peak difference: the difference between the first and the second double chuck peaks. One-way ANOVAs and a posteriori comparisons of these variables revealed that each distinguished more than 70% of all possible pairs of females. When all double chuck measures were included in a discriminant analysis, 57% of double chucks were correctly assigned to the caller. Another category of information potentially encoded in the acoustic structure of chuck vocalizations is foraging activity. When the chucks of squirrel monkeys during foraging and nonforaging activities were compared, the single chuck peak frequency, and the first peak frequency and the peak difference of double chucks, were significantly reduced during foraging contexts. Previously Boinski and Mitchell (1992) concluded that chucks facilitate group cohesion among widely dispersed troop members by providing information of the location of callers; the rate of chucks produced by an adult female increases as she becomes more spatially and visually separated from other adult females. The additional information potentially conveyed by chucks on caller identity and foraging activity documented in these new analyses further emphasizes the role chucks serve to enhance group coordination and cohesion.     

The Relationship between Canopy Cover and Colony Size of the Wood Ant Formica lugubris - Implications for the Thermal Effects on a Keystone Ant Species

Climate change may affect ecosystems and biodiversity through the impacts of rising temperature on species’ body size. In terms of physiology and genetics, the colony is the unit of selection for ants so colony size can be considered the body size of a colony. For polydomous ant species, a colony is spread across several nests. This study aims to clarify how climate change may influence an ecologically significant ant species group by investigating thermal effects on wood ant colony size. The strong link between canopy cover and the local temperatures of wood ant’s nesting location provides a feasible approach for our study. Our results showed that nests were larger in shadier areas where the thermal environment was colder and more stable compared to open areas. Colonies (sum of nests in a polydomous colony) also tended to be larger in shadier areas than in open areas. In addition to temperature, our results supported that food resource availability may be an additional factor mediating the relationship between canopy cover and nest size. The effects of canopy cover on total colony size may act at the nest level because of the positive relationship between total colony size and mean nest size, rather than at the colony level due to lack of link between canopy cover and number of nests per colony. Causal relationships between the environment and the life-history characteristics may suggest possible future impacts of climate change on these species.     

神经型一氧化氮合酶的活性调控

一氧化氮是重要的信使分子,在生物体内参与众多生理及病理过程。生物体内存在着复杂的一氧化氮合酶活性调控机制以精确调控一氧化氮的生成。在神经系统中,一氧化氮主要由神经型一氧化氮合酶催化生成。神经型一氧化氮合酶的活性主要受到翻译后水平上钙离子和钙调蛋白的调控,其调控方式包括二聚化、多位点的磷酸化和去磷酸化,以及主要由PDZ结构域介导的蛋白质-蛋白质相互作用。一氧化氮本身对其合酶的活性具有负反馈调控作用。近年来的研究提示,细胞质膜上的脂筏微区在神经性一氧化氮合酶的活性调控中也起到重要的调节作用。     

Blackboard Mechanism Based Ant Colony Theory for Dynamic Deployment of Mobile Sensor Networks

A novel bionic swarm intelligence algorithm, called ant colony algorithm based on a blackboard mechanism, is proposed to solve the autonomy and dynamic deployment of mobiles sensor networks effectively. A blackboard mechanism is introduced into the system for making pheromone and completing the algorithm. Every node, which can be looked as an ant, makes one information zone in its memory for communicating with other nodes and leaves pheromone, which is created by ant itself in naalre. Then ant colony theory is used to find the optimization scheme for path planning and deployment of mobile Wireless Sensor Network （WSN）. We test the algorithm in a dynamic and unconfigurable environment. The results indicate that the algorithm can reduce the power consumption by 13% averagely, enhance the efficiency of path planning and deployment of mobile WSN by 15% averagely.