Social isolation causers mortality by disrupting energy homeostrasis in ants

Social deprivation can have negative effects on the lives of social animals, including humans, yet little is known about the mechanisms by which social withdrawal affects animal health. Here we show that in the carpenter ant Camponotus fellah, socially isolated workers have a greatly reduced life span relative to ants kept in groups of ten individuals. By using a new tracking system, we found that social isolation resulted in important behavioral changes and greatly increased locomotor activity. The higher activity of single ants and their increased propensity to leave the nest to move along the walls suggested that the increased mortality of isolated ants might stem from an imbalance of energy income and expenditure. This view was supported by the finding that while isolated ants ingested the same amount of food as grouped ants, they retained food in the crop, hence preventing its use as an energy source. Moreover, the difference in life span between single and grouped individuals vanished when ants were not fed. This study thus underlines the role of social interactions as key regulators of energy balance, which ultimately affects aging and health in a highly social organism.

Le nombre de reines chez les fourmis et sa conséquence sur l'organisations sociale

Nearly half of all ant species form polygyne societies (cohabitation of more than a single egg-laying queen). These queens are generally smaller and store fewer fat reserves than queens from monogyne colonies. Most queens in polygyne colonies (70-100 pour 100) are inseminated, although this proportion varies among species, and even among populations of the same species. They exhibit mutual tolerance and they all contribute to the reproductive effort of the colony. Nevertheless, their individual fecundity is considerably reduced compared with that of queens from monogyne colonies. This reduction in fecundity seems to be due to some form of mutual inhibition, in some cases the secretion by each female of a substance suppressing egg production in other queens has been implicated. In a few species, queens are organized into a hierarchy such that certain queens lay more eggs than others or even monopolize egg-laying (functional monogyny). Polygyny is linked to a particular life history. It rarely results from the association of several foundresses (primary polygyny). Usually, it is due to the adoption of young queens by an established nest just after a nuptial flight. This secondary polygyny means that the dispersal of the species is limited and is achieved by the budding of a mother nest. Thus colony founding is dependent; with workers accompanying young queens in establishing new colonies. Observation of closely related species exhibiting different social organizations, some monogyne and others polygyne, shows a possible link between queen number and ecological conditions: polygyne forms are more frequent in unstable habitats susceptible to rapid change, such as that caused by human activity. The existence of polygyne societies is an intriguing evolutionary mystery. Research into the origin and maintenance of polygyny focuses on patterns of speciation in relation to queen number and the different theories put forth for the evolution of eusociality, mainly kin selection and mutualism.

Coloration signals the ability to cope with elevated stress hormones: effects of corticosterone on growth of barn owls are associated with melanism.

Stressful situations during development can shape the phenotype for life by provoking a trade-off between development and survival. Stress hormones, mainly glucocorticoids, play an important orchestrating role in this trade-off. Hence, how stress sensitive an animal is critically determines the phenotype and ultimately fitness. In several species, darker eumelanic individuals are less sensitive to stressful conditions than less eumelanic conspecifics, which may be due to the pleiotropic effects of genes affecting both coloration and physiological traits. We experimentally tested whether the degree of melanin-based coloration is associated with the sensitivity to an endocrine response to stressful situations in the barn owl. We artificially administered the mediator of a hormonal stress response, corticosterone, to nestlings to examine the prediction that corticosterone-induced reduction in growth rate is more pronounced in light eumelanic nestlings than in darker nest mates. To examine whether such an effect may be genetically determined, we swapped hatchlings between randomly chosen pairs of nests. We first showed that corticosterone affects growth and, thus, shapes the phenotype. Second, we found that under corticosterone administration, nestlings with large black spots grew better than nestlings with small black spots. As in the barn owl the expression of eumelanin-based coloration is heritable and not sensitive to environmental conditions, it is therefore a reliable, genetically based sign of the ability to cope with an increase in blood corticosterone level.

Stay or drift? Queen acceptance in the ant Formica paralugubris

The acceptance of new queens in ant colonies has profound effects on colony kin structure and inclusive fitness of workers. Therefore, it is important to study the recognition and discrimination behaviour of workers towards reproductive individuals entering established colonies. We examined the acceptance rate of queens in populations of the highly polygynous ant F. paralugubris, where the genetic differentiation among nests and discrimination ability among workers suggest that workers might reject foreign queens. We experimentally introduced young queens in their natal nest and in foreign nests. Surprisingly, the survival rate of mated queens did not differ significantly when introduced in a foreign male-producing nest, a foreign female-producing nest, or the natal nest. Moreover, the survival of virgin queens in their natal nest was twice the one of mated queens, suggesting that mating status plays an important role for acceptance. The results indicate that other factors than queen discrimination by workers are implicated in the limited long-distance gene flow between nests in these populations.

Schizotrypanids: the occurence of dermatitis in immunodeficiency animals infected with Trypanosoma cruzi

Congenitally athymic nude Balb/c (nu/nu) and their phenothypically normal adult and neonate littermates (nu/+), the C3H/HeN as well, were intraperitoneally infected with two strains (Y or CL) of Trypanossoma cruzi. The nude mice and the neonates developed a severe parasitaemia, the susceptible C3H/HeN also presented high level and adult Balb/c mice presented parasitaemia similar to that observed in outbred mice. Erythematous skin lesions were observed initially in infected athymic nude and neonates, being charactherized by nests of amastigotes in the dermis; in C3H/HeN infected mice no nest of parasite was observed but a low-grade inflammatory reaction was seen. In adult Balb/c or OF1 outbred mice nest was found but discreet inflammatory reaction was observed in severe infections.

Interfície gràfica pel simulador científic de nanoestructures BITLLES

L’emergent indústria nanoelectrònica necessita de nous simuladors de dispositius nanoelectrònics. Des del departament d’Enginyeria Electrònica de la UAB se n’està desenvolupant un anomenat BITLLES. Malgrat el seu avançat estat de desenvolupament els manca d’una interfície gràfica que faciliti l’entrada de dades al simulador. Aquest projecte final de carrera s’encarregarà de confeccionar aquesta peça clau per tal de assolir una aplicació prou madura per la seva comercialització. A partir de les tecnologies existents per a la realització d’interfícies es farà una selecció de les eines més adequades pels nostres objectius i seguidament es dissenyarà la interfície gràfica adaptant-la a les necessitats i objectius dels desenvolupadors del projecte BITLLES i dels possibles futurs usuaris.

No experimental evidence that sibling competition induces young to switch nests in the colonial Alpine swift, Apus melba

Adoption is frequent in colonial animals where opportunities for dependent young to receive care from nonbiological parents are high. The departure of dependent young from their original family to seek adoption in neighbouring families is thought to be induced by sibling competition for access to limited resources provided by poor-quality parents. We tested this hypothesis in the colonial Alpine swift by manipulating the number of young reared per brood, with the prediction that offspring from enlarged broods switch nests more frequently than those from reduced broods. Although nestling swifts hatch with little locomotor activity, from 20 days until their first flight at 50-70 days they frequently move out of their nests to seek adoption in neighbouring families. Although nestlings reared in experimentally enlarged broods were lighter and their body mass at day 20 after hatching was more variable than in nestlings reared in reduced broods, there was no difference between the two treatments in the frequency of nests switching and in the age when nestlings switched nests for the first time. However, consistent with other evidence that nest switching by nestling swifts evolved as a strategy to reduce ectoparasite load, young from broods with naturally high numbers of the ectoparasitic louse fly Crataerina melbae were more prone to switch nests. This shows that ectoparasitism rather than sibling competition is a key proximate factor promoting the evolution of nest switching in the colonial Alpine swift. (c) 2006 The Association for the Study of Animal Behaviour Published by Elsevier Ltd. All rights reserved.

Habitat, breeding performance, diet and individual age in Swiss barn owls (Tyto alba)

Intensification of farming over the past 50 years has homogenised the landscape structure and contributed to the decline of bird populations in Europe. To better target the conservation of the Barn Owl Tyto alba, we assessed the influence of the landscape structure on breeding performance in western Switzerland. The analyses considered a 23-year data set of breeding parameters collected in an area dominated by intensive agriculture. Using a Geographic Information System approach, landscape characteristics were described around 194 nest sites. Our analyses showed that nest-box occupancy, laying date, clutch and brood size, egg volume and probability of producing a second annual clutch were not significantly associated with any of the eight principal landscape variables (agricultural land, woodland, urban area, hedgerows, cereals, sugar beet, maize and meadow). Nevertheless, the probability that a breeding pair occupied a nest-box decreased the more roads there were surrounding the nest-box. The absence of strong associations between habitat features and breeding parameters suggests that prey availability may be relatively similar between the different breeding sites. In our study area Barn Owls can always find suitable foraging habitats around most nest-boxes.

Wild birds as hosts of Amblyomma cajennense (Fabricius, 1787) (Acari: Ixodidae)

We evaluated the prevalence, mean intensity and relative density of ticks in 467 wild birds of 67 species (12 families) from forest and cerrado habitats at two protected areas of Minas Gerais, between March and September 1997. Ticks collected (n=177) were identified as larvae and nymphs of Amblyomma cajennense and four other species of Amblyomma. We report for the first time 28 bird species as hosts of the immature stages of A. cajennense, demonstrating the lack of host specificity of the larvae and nymphs. A. cajennense had 15% prevalence on birds, with a mean infestation intensity of 0.37 ticks per host sampled, and 2.5 ticks per infested bird. Prevalence varied in relation to host species, diet and between birds from forests at two successional stages. There were no differences in relation to host forest dependence, participation in mixed flocks of birds, and nest type constructed. A. cajennense is a species of medical and veterinary importance, occurring on domestic animals but is known little of its occurrence on wildlife.

The vigilance components of begging and sibling competition

The conflict between siblings over how parental resources are divided has promoted the evolution of specific behaviour to outcompete each other. Young animals look out for parents' arrival in order to start begging as quickly as possible, since a rapid begging reaction increases the likelihood of being fed before nestmates. If the young can physically intercept the parents, selection might be operating on the offspring ability to monitor parent arrival (vigilance towards parents) and any sudden modifications in siblings' behaviour (vigilance towards siblings). To investigate the adaptive value of nestling vigilance in the context of family interactions, we recorded which direction barn owl Tyto alba siblings were facing in 89 two-chick broods before the first parental feeding visit of the night. Nestlings were more vigilant towards nest entrance than expected by chance suggesting that vigilance towards parents is an important component of sibling competition. When positioned near the nest-box entrance where parents predictably deliver food, the younger individual (i.e. junior) looked more towards the entrance than its older sibling. Thus, when the likelihood of obtaining a food item is relatively high, juniors are more vigilant than seniors to detect the incoming parent. When positioned at the back of the nest, the senior looked relatively more frequently towards its sibling than the junior did in the same situation. This suggests that when the likelihood of obtaining a food item is relatively low, seniors are more vigilant than juniors to observe their sibling. Because vigilance was not related to hunger level and prey obtaining, we propose the hypothesis that vigilance towards parents and siblings only indirectly influences the outcome of sibling competition.

Evaluation of two minimally invasive techniques for electroencephalogram recording in wild or freely behaving animals.

Insight into the function of sleep may be gained by studying animals in the ecological context in which sleep evolved. Until recently, technological constraints prevented electroencephalogram (EEG) studies of animals sleeping in the wild. However, the recent development of a small recorder (Neurologger 2) that animals can carry on their head permitted the first recordings of sleep in nature. To facilitate sleep studies in the field and to improve the welfare of experimental animals, herein, we test the feasibility of using minimally invasive surface and subcutaneous electrodes to record the EEG in barn owls. The EEG and behaviour of four adult owls in captivity and of four chicks in a nest box in the field were recorded. We scored a 24-h period for each adult bird for wakefulness, slow-wave sleep (SWS), and rapid-eye movement (REM) sleep using 4 s epochs. Although the quality and stability of the EEG signals recorded via subcutaneous electrodes were higher when compared to surface electrodes, the owls' state was readily identifiable using either electrode type. On average, the four adult owls spent 13.28 h awake, 9.64 h in SWS, and 1.05 h in REM sleep. We demonstrate that minimally invasive methods can be used to measure EEG-defined wakefulness, SWS, and REM sleep in owls and probably other animals.

Impact of helpers on colony productivity in a primitively eusocial bee

Small societies of totipotent individuals are good systems in which to study the costs and benefits of group living that are central to the origin and maintenance of eusociality. For instance, in eusocial halictid bees, some females remain in their natal nest to help rear the next brood. Why do helpers stay in the nest? Do they really help, and if yes, is their contribution large enough to voluntarily forfeit direct reproduction? Here, we estimate the impact of helpers on colony survival and productivity in the sweat bee Halictus scabiosae. The number of helpers was positively associated with colony survival and productivity. Colonies from which we experimentally removed one helper produced significantly fewer offspring. However, the effect of helper removal was very small, on average. From the removal experiment, we estimated that one helper increased colony productivity by 0.72 additional offspring in colonies with one to three helpers, while the increase was smaller and not statistically significant in larger colonies. We conclude that helpers do actually help in this primitively eusocial bee, particularly in small colonies. However, the resulting increase in colony productivity is low, which suggests that helpers may be constrained in their role or may attempt to reproduce.

Protecció i detecció preventiva de la violència masclista a Terrassa

La violència que pateixen les dones esdevé un fenomen que afecta totes les cultures, grups socials i edats d’arreu del món i, per tant, Catalunya no n’està exempta. Es tracta d’un fenomen universal que, fruit del sistema patriarcal, és present a gairebé totes les cultures i a tots els nivells socials i econòmics i està vinculat a les mancances de les nostres societats pel que fa a les cotes d’igualtat. La violència contra les dones és el resultat més greu d’unes relacions socials basades en la discriminació per raó de sexe. Si la violència masclista és una greu vulneració dels drets humans bàsics de les dones i la definició actual de “seguretat pública” és aquella que la presenta com a les “actuacions dels poders públics adreçades a la protecció de les persones i béns davant possibles agressions d’origen humà o natural i que comprèn les mesures de prevenció i protecció eficaces en l’assegurament dels drets i llibertats dels ciutadans ide les ciutadanes”, la violència masclista, doncs, esdevé un objectiu prioritari per a les polítiques públiques de seguretat en un Estat de dret. Així doncs, en el cas de Terrassa estan sent eficaces i eficients les polítiques públiques implementades per reduir i minimitzar la violència masclista?

Immunocompetence and nestling survival in the house martin: the tasty chick hypothesis

In altricial birds post-fledging survival is usually positively related to nestling body mass. A large number of studies have shown that the latest hatched chick is the more likely to die, even if food is abundant. Here we suggest that ectoparasites may be a key factor in the evolution and the maintenance of the establishment of weight hierarchies within broods. We prepose the hypothesis that weight hierarchies within broods may be adaptive if the chick in poor condition is the one with the least efficient immune system within a nest. In this case parasites would preferentially feed on such a "tasty chick", because it would allow high reproductive rates for the parasites, without negatively affecting the survival of the other nestlings. This could prevent entire nest failure of the brood or allow the other chicks to grow more efficiently. This hypothesis was investigated in a colony of house martins Delichon urbica. We predicted that immunocompetence was positively correlated with body condition, and that nestlings dying before hedging should have lower immune responses when challenged with an antigen. T-cell immune response to an experimentally injected antigen was strongly positively related to body condition. Non-surviving chicks had low body condition and a weak immune response. The implications of these results are discussed in the context of the adaptive significance of hatching asynchrony.

Ant queens (Hymenoptera: Formicidae) are attracted to fungal pathogens during the initial stage of colony founding

Ant queens that attempt to disperse and found new colonies independently face high mortality risks. The exposure of queens to soil entomopathogens during claustral colony founding may be particularly harmful, as founding queens lack the protection conferred by mature colonies. Here, we tested the hypotheses that founding queens (I) detect and avoid nest sites that are contaminated by fungal pathogens, and (II) tend to associate with other queens to benefit from social immunity when nest sites are contaminated. Surprisingly, in nest choice assays, young Formica selysi BONDROIT, 1918 queens had an initial preference for nest sites contaminated by two common soil entomopathogenic fungi, Beauveria bassiana and Metarhizium brunneum. Founding queens showed a similar preference for the related but non-entomopathogenic fungus Fusarium graminearum. In contrast, founding queens had no significant preference for the more distantly related nonentomopathogenic fungus Petromyces alliaceus, nor for heat-killed spores of B. bassiana. Finally, founding queens did not increase the rate of queen association in presence of B. bassiana. The surprising preference of founding queens for nest sites contaminated by live entomopathogenic fungi suggests that parasites manipulate their hosts or that the presence of specific fungi is a cue associated with suitable nesting sites.