Marie Trabalon

Chemical Communication and Contact Cuticular Compounds in Spiders

We review here spider social contact pheromones. Spider contact pheromones are typically associated with the silk, draglines or substrate, and body cuticle. The chemical composition of the cuticle, especially the lipid layer, can be used for information transfer. These substances act as releaser pheromones and are identified by the spider after contact with another animal. Behavioural observations demonstrate that chemical contact compounds are able to inhibit aggressive behaviour between conspecifics (prevent cannibalism). Different studies have shown that qualitative and/or quantitative changes in cuticular lipids could play a role in intra- and interspecific relationships in spiders. Knowledge of the function and mode of action of cuticular compounds is only fragmentary in arachnid groups. The endocrine regulation of contact pheromone synthesis is not known.

Mares prefer the voices of highly fertile stallions.

We investigated the possibility that stallion whinnies, known to encode caller size, also encoded information about caller arousal and fertility, and the reactions of mares in relation to type of voice. Voice acoustic features are correlated with arousal and reproduction success, the lower-pitched the stallion’s voice, the slower his heart beat and the higher his fertility. Females from three study groups preferred playbacks of low-pitched voices. Hence, females are attracted by frequencies encoding for large male size, calmness and high fertility. More work is needed to explore the relative importance of morpho-physiological features. Assortative mating may be involved as large females preferred voices of larger stallions. Our study contributes to basic and applied ongoing research on mammal reproduction, and questions the mechanisms used by females to detect males’ fertility.

Early experience and social performance in spiderlings

The social context experienced during early ontogeny can have lifelong consequences on the expression of social skills, and social isolation during development frequently impairs social competence. In this study, we used spiders as a model to investigate whether early social experience shapes social performance later in life. In spiders, the juveniles of all species show a transient gregarious phase that extends after their emergence from the maternal cocoon and ends with the initiation of agonistic interactions and cannibalism. Most studies that investigated social interactions in spiderlings focused on kin recognition. However, the potential mechanisms shaping recognition and discrimination, and particularly the role of early social experience, received little attention. Therefore, we examined to what extent early social isolation can influence the expression of social behaviours. We also investigated the influence of familiarity and kinship, and of their interaction with social experience on the expression of cannibalism. Our results showed that social isolation of spiderlings of Agelena labyrinthica since the egg stage did not influence social performance after emergence. Our study advocates for the existence of a species-specific chemical signature inhibiting cannibalistic tendencies in spiderlings.

Cannibalism in spiderlings is not only about starvation

Many species show a transient group life, and dispersal often coincides with the onset of agonistic behaviors. Changes in the nature of interactions among conspecifics can rely on a variation in the production of communication cues and/or on a switch in the processing of social information. The relative contribution of each process on the initiation of aggression still remains to be investigated. Spiders constitute relevant models to address this issue since all solitary species undergo a transient gregarious phase prior dispersal. In this study, we developed a combination of behavioral and physiological assays to examine the mechanisms accompanying the onset of agonistic interactions in spiderlings of the solitary species Agelena labyrinthica. Juveniles of different developmental stages were supplied with diets differing in prey availability. We showed that unfed spiderlings never molted, retained their cuticular lipid signature, and did not behave aggressively. This contrasted with fed individuals that molted, changed their cuticular profiles, and displayed agonistic interactions and cannibalism. We demonstrated that depletion in lipid stores was not sufficient to elicit aggression or cannibalism. Our analysis also revealed that major shifts in cuticular profiles only occurred after the first molt outside the cocoon. The lack of agonistic interactions in unfed spiderlings suggests an absence of behavioral plasticity in response to food shortage at the earliest developmental stages. We propose that the initiation of aggression relies more on a shift in the production of cuticular cues accompanying molting rather than on changes in information processing depending on the physiological state of individuals.Significance statementMost species of spiders display a transient gregarious phase preceding the initiation of agonistic interactions and dispersal. We examined what factors are associated with the onset of aggression in gregarious juveniles and we showed that pre-dispersing spiderlings despite low energetic stores never cannibalized conspecifics. This contrasts with later instars that displayed increased levels of aggression. The initiation of agonistic interactions coincided with major changes in the profiles of cuticular lipids, which are used in spiders to regulate social interactions. Our study suggests that depletion of lipid stores is not sufficient to trigger aggression but that it likely requires changes in communication cues associated with molting. We propose that the absence of behavioral plasticity of pre-dispersing juveniles in response to starvation allows spiderlings to maintain social cohesion and to benefit from the potential advantages granted by gregariousness, irrespective of environmental fluctuations.

Sexual odor discrimination and physiological profiles in adult male rats after a neonatal, short term, reversible nasal obstruction.

The present study was designed to examine behavioral responses (interpreted as preferences) to olfactory cues (nest bedding odor and odors of estrous and anestrus females) in adult male rats after they had a short term reversible, bilateral, nasal obstruction (RbNO) as developing rat pups. These results were compared to behavior of control (untreated) and sham operated male littermates. Behavioral tests and physiological parameters were analyzed 90 days after recovery of nasal breathing. Experiments investigated the time spent in arms or the center of a maze of male rats in response to odors from the nest bedding or from adult females. There were no differences in responses between untreated, sham and RbNO adult male rats to fresh and nest bedding odors. RbNO males spent more time in the center of the maze when given a choice of estrus or anestrus female odors, or bedding odors from untreated or sham operated female rats. In contrast untreated and sham male rats preferred the odors of estrous females and of untreated or sham females. Plasma corticosterone levels in the males increased during the behavioral tests. Plasma testosterone levels were significantly lower in RbNO males compared to untreated males and did not increase during the behavioral tests compared to sham operated males. Males from all groups had similar preferences for the odor of bedding from adult RbNO females. Plasma levels of cholesterol and triglycerides were increased in RbNO adults. In conclusion, short term nasal obstruction in males while juvenile has long term consequences on hormones and behavioral preferences, thus potential partner selection when adult.

Chronic dehydration is associated with obstructive sleep apnoea syndrome.

We were interested to read the recent review article in Clinical Science concerning OSA (obstructive sleep apnoea) and its connections to obesity, diabetes and hypertension [1]. That article looked into the evidence supporting the association of OSA with hypertension, and described the different associated health problems of obesity, hypoxia and cardiovascular disease and the difficulty in finding successful treatments, even using animal models. Similar points have been laid out recently in an editorial published in the New England Journal … We were interested to read the recent review article in Clinical Science concerning OSA (obstructive sleep apnoea) and its connections to obesity, diabetes and hypertension [1]. That article looked into the evidence supporting the association of OSA with hypertension, and described the different associated health problems of obesity, hypoxia and cardiovascular disease and the difficulty in finding successful treatments, even using animal models. Similar points have been laid out recently in an editorial published in the New England Journal …

Distinct physiological, biochemical and morphometric adjustments in the malaria vectors Anopheles gambiae and A. coluzzii as means to survive dry season conditions in Burkina Faso

ABSTRACT Aestivation and dispersive migration are the two strategies evoked in the literature to explain the way in which malaria vectors Anopheles coluzzii and A. gambiae survive the harsh climatic conditions of the dry season in sub-Saharan Africa. However, the physiological mechanisms regulating these two strategies are unknown. In the present study, mosquito species were exposed to controlled environmental conditions mimicking the rainy and dry seasons of south western Burkina Faso. Survival strategies were studied through morphometric (wing length), ecophysiological (respiratory gas exchanges), biochemical (cuticular hydrocarbons composition) and molecular (AKH mRNA expression levels) parameters, variations of which are usually considered to be hallmarks of aestivation and dispersion mechanisms in various insects. Our results showed that ecophysiological and morphometric adjustments are made in both species to prevent water losses during the dry season. However, the usual metabolic rate modifications expected as signatures of aestivation and migration were not observed, highlighting specific and original physiological mechanisms sustaining survival in malaria mosquitoes during the dry season. Differences in epicuticular hydrocarbon composition and AKH levels of expression were found between the permanent and temporary A. coluzzii populations, illustrating the great phenotypic plasticity of this mosquito species. Altogether, our work underlines the diverse and complex pattern of changes occurring in the two mosquito species and at the population level to cope with the dry season and highlights potential targets of future control tools. Summary: A diverse and complex pattern of physiological mechanisms occurs in the Anopheles gambiae s.l. mosquito species and at the population level to cope with the harsh dry season.

Effects of prolonged exposure to CO

Atmospheric CO2 concentrations increased significantly over the last century and continuing increases are expected to have significant effects on current ecosystems. This study evaluated the behavioural and physiological (hormone status, muscle structure) effects of prolonged CO2 exposure in young female Wistar rats exposed at 700ppm of CO2 during 6h a day for 15days. Prolonged CO2 exposure, though not continuous, produced significant disturbances in behaviour with an increase in drinking, grooming and resting, and a reduction in rearing, jumping-play and locomotor activity. Furthermore, CO2 exposure was accompanied by increased plasma levels of corticosterone, suggesting that prolonged exposure to CO2 was stressful. The muscular structure can also be modified also when respiratory working conditions change. The expression of myosin heavy chain was significantly affected in the diaphragm and oral respiratory muscles: Masseter Superficialis and Anterior Digastric. Modified behaviour and hormonal changes both appear to be at the origin of the observed muscular adaptation.

_2

This study presents the first characterisation of the silk lipids of the cocoons of a wolf spider (Pardosa saltans). Wolf spiders’ maternal behaviour is complex and involves guarding a cocoon for several weeks, and so cocoons must emit cues to ensure their care and the development of juveniles. We investigated cues associated with the cocoon silk. We assessed qualitative changes of the lipid contents and the composition of cocoon silk in relation to the development of P. saltans wolf spider juveniles. Gas chromatography–mass spectrometry of P. saltans’ cocoon silk revealed 62 different lipid compounds. The compounds were aliphatic alcohols, glycerides, fatty acids and their methylesters containing 13–29 carbon atoms. We reveal for the first time the presence of ethanolamides and phytosterol on cocoon silk. Qualitative and quantitative changes occur during the embryonic period, as some polar compounds, such as diglycerides and ethanolamides, disappeared while hydrocarbons emerge, and fatty acids disappeared later during the post-embryonic period. Qualitative and/or quantitative changes could play a role in tactochemical communication between mothers and their cocoon. However, mothers do not modify their behaviour in relation to the developmental stage of their cocoon. Mothers’ behaviour appears to be linked to both internal (physiological state) and external mechanisms (signals from the cocoon).

on behaviour, hormone secretion and respiratory muscles in young female rats

Introduction: Nasal obstruction is a risk factor in sleep-disordered breathing with a negative Methods: The rats were killed at specific time points after surgery. Plasma samples were taken for biochemical analyses, and histological measurements were performed. Shortly after nasal obstruction, the volumes of external plexiform (CPE), internal plexiform (CGI), and granule cell (CGr) was measured in both sexes of test rats compared with controls. Results and Conclusion: Reversible nasal obstruction was further associated with reduced dimensions of the volumes of CPE (male: 55%; female: 37%), CGI (male: 49%; female: 34%) and CGr (male: 70%; female: 47%). Basal corticosterone levels had increased in female rats, however, we observed the lower level of thyroid hormone, especially in male experimental group.