Comportement d'approvisionnement des fourmis coupeuses de feuilles : de la piste chimique à la piste physique

Les fourmis coupeuses de feuilles, du fait de la relation symbiotique qu'elles entretiennent avec leur champignon, possèdent certainement l'organisation la plus complexe de toutes les espèces de fourmis. Ce travail de thèse a eu pour but d'étudier le comportement d'approvisionnement de ces fourmis, en appréhendant les multiples aspects de ce comportement par une combinaison d'expériences réalisées au laboratoire et sur le terrain. Nous nous sommes intéressés aux infrastructures mises en place par les fourmis et qui sont impliquées dans l'activité de récolte (pistes physiques et tunnels de fourragement), à la modulation des différents signaux impliqués dans le recrutement (piste chimique et contacts entre ouvrières), et enfin aux choix des substrats récoltés, pour proposer un pattern global de l'activité de récolte des fourmis coupeuses de feuilles en conditions naturelles.Leaf cutting ants, with their symbiotic fungus, exhibit certainly the most complex organization of all ant species. The aim of this thesis was to study the foraging behavior of these ants, by a combination of laboratory and field experiments. We investigated the role of the structures built by ants outside the nest (trunk trails and foraging tunnels), the modulation of different types of communication involved in the recruitment to the resource exploited (chemical trail and contacts between workers), and finally the mechanisms underlying the choice of the harvested substrate, to suggest a general pattern of the foraging strategy used by these ants in natural conditions

Appetitive olfactory learning and memory in the honeybee depend on sugar reward identity

One of the most important tasks of the brain is to learn and remember information associated with food. Studies in mice and Drosophila have shown that sugar rewards must be metabolisable to form lasting memories, but few other animals have been studied. Here, we trained adult, worker honeybees (Apis mellifera) in two olfactory tasks (massed and spaced conditioning) known to affect memory formation to test how the schedule of reinforcement and the nature of a sugar reward affected learning and memory. The antennae and mouthparts of honeybees were most sensitive to sucrose but glucose and fructose were equally phagostimulatory. Whether or not bees could learn the tasks depended on sugar identity and concentration. However, only bees rewarded with glucose or sucrose formed robust long-term memory. This was true for bees trained in both the massed and spaced conditioning tasks. Honeybees fed with glucose or fructose exhibited a surge in haemolymph sugar of greater than 120. mM within 30. s that remained elevated for as long as 20. min after a single feeding event. For bees fed with sucrose, this change in haemolymph glucose and fructose occurred with a 30. s delay. Our data showed that olfactory learning in honeybees was affected by sugar identity and concentration, but that olfactory memory was most strongly affected by sugar identity. Taken together, these data suggest that the neural mechanisms involved in memory formation sense rapid changes in haemolymph glucose that occur during and after conditioning

Foraging behavior of leaf-cutting ants : from chemical to physical trail

Les fourmis coupeuses de feuilles, du fait de la relation symbiotique qu'elles entretiennent avec leur champignon, possèdent certainement l'organisation la plus complexe de toutes les espèces de fourmis. Ce travail de thèse a eu pour but d'étudier le comportement d'approvisionnement de ces fourmis, en appréhendant les multiples aspects de ce comportement par une combinaison d'expériences réalisées au laboratoire et sur le terrain. Nous nous sommes intéressés aux infrastructures mises en place par les fourmis et qui sont impliquées dans l'activité de récolte (pistes physiques et tunnels de fourragement), à la modulation des différents signaux impliqués dans le recrutement (piste chimique et contacts entre ouvrières), et enfin aux choix des substrats récoltés, pour proposer un pattern global de l'activité de récolte des fourmis coupeuses de feuilles en conditions naturelles.Leaf cutting ants, with their symbiotic fungus, exhibit certainly the most complex organization of all ant species. The aim of this thesis was to study the foraging behavior of these ants, by a combination of laboratory and field experiments. We investigated the role of the structures built by ants outside the nest (trunk trails and foraging tunnels), the modulation of different types of communication involved in the recruitment to the resource exploited (chemical trail and contacts between workers), and finally the mechanisms underlying the choice of the harvested substrate, to suggest a general pattern of the foraging strategy used by these ants in natural conditions

Nutrient Utilization during Male Maturation and Protein Digestion in the Oriental Hornet

Males of social Hymenoptera spend the first days following eclosion inside the nest before dispersing to find a young queen to mate with. During this period, they must acquire enough nutrients to enable their sexual maturation and store energy to sustain them through their nuptial journey. It was previously argued that adult hornets are unable to process dietary proteins and rely on the larvae to supply them with free amino acids and carbohydrates that they secrete via trophallaxis. Using isotopically enriched diets, we examined nutrient allocation and protein turnover in newly-emerged males of the Oriental hornet during their maturation period and tested the protein digestion capability in the presence and absence of larvae in both males and worker hornets. The results indicated that protein turnover in males occurs during the first days following eclosion, while carbohydrates are incorporated into body tissues at higher rates towards the end of the maturation period. Additionally, we found that males cannot digest protein and depend on larval secretions as a source of nutrition, while workers, in contrast to previous reports, can metabolize protein independently. Our findings demonstrate the contribution of adult male nutrition and larval secretions to colony fitness

Total number of matings.

<p>We observed 131 females mating with six types of males: a dominant sibling, a dominant non-sibling, a no-status sibling, a no-status non-sibling, a subordinate sibling or a subordinate non-sibling. Overall, females mated more often with dominant males than with subordinate males irrespective of kinship.</p

Multi-model selection procedure.

<p>We compared generalised linear mixed effects models (GLMM) with triad_ID nested in male type as random effect and the following combination of fixed effects: male dominance status (Dominance), kinship (Kin), male body size (Body Size), interaction between male dominance status and kinship, interaction between male body size and kinship, interaction between male body size and male dominant status. Number of parameters retained (K), Akaike information criterion weighted for small sample size (AICc), differences between AICc (Δ AICc) and normalized Akaike weights (wi) for each model are shown. Data are showed for sexual display and mate choice analyses.</p

Succession of behavioural acts during mate choice in <i>Nauphoeta cinerea</i>.

<p>In this example, a virgin female (green dot on the pronotum) is given a choice between two males (blue and red). (A) After having initiated antennal contacts with the female, the courting male (blue) turns around in front of the female and raises its wings so that the female can mount on the male’s abdomen. (B) The female licks the abdominal secretions from the male’s tergal glands while the male pushes his abdomen further back to grasp the female’s genitalia. (C) Copulation lasts for approximately 15 minutes during which the male and the female remain paired in straight-line opposite position, allowing for the formation and transfer of a spermatophore into the female’s genital tract. In this example, the non-copulating male (red) initiates antennal contacts with the female during mating. Photographs by SB.</p

Sex-Specific Effect of the Dietary Protein to Carbohydrate Ratio on Personality in the Dubia Cockroach

Animal personality, defined by behavioral variations among individuals consistent over contexts or time, is shaped by genetic and environmental factors. Among these factors, nutrition can play an important role. The Geometric Framework of Nutrition has promoted a better understanding of the role of the macronutrient proportion in animal development, survival, reproduction, and behavior, and can help to disentangle its modulatory effect on animal personality. In this study, we investigated the effects of protein to carbohydrate (P:C) ratio in the personality of the cockroach Blaptica dubia. Newly emerged adults were fed over a period of eight weeks on five different diets varying in their P:C ratio and their diet consumption, mass variation, survival, exploratory behavior, and mobility were assessed. We found that females, unlike males, were able to regulate their nutrient intake and preferred carbohydrate-rich diets. Females also gained more body mass and lived longer compared to males. In addition, their behavior and mobility were not affected by the diet. In males, however, high-protein diets induced a bolder personality. We suggest that the sex-specific effects observed on both survival and behavior are related to the nutrient intake regulation capacity and might improve the species’ fitness in adverse nutritional conditions.publishe