Can Wolf Spider Mothers Detect Insecticides in the Environment? Does the Silk of the Egg-Sac Protect Juveniles from Insecticides?

The use of pesticides for plague control in agroecosystems generates a threat to wildlife and a major problem for human health. Pesticide compounds are also an important source of water and atmosphere contamination. Although insecticides are effective on their target organisms, they often affect organisms that are not their target. The aim of the present study was to research the effects of 3 types of neurotoxic insecticides-a pyrethroid (cypermethrin), a neonicotinoid (imidacloprid), and an organophosphate (chlorpyrifos)-on behavioral and physiological parameters of Pardosa saltans spider (Lycosidae). Our study analyzed for the first time the exploratory behavior of the spider mothers in the presence of these 3 insecticides on their egg-sacs and also on the ground. We also evaluated the oxidative stress effects on the juveniles hatched in the egg-sac protected by silk in relation to variations in detoxification enzymes (catalase, glutathione reductase, superoxide dismutase, glutathione-S-transferase, and glutathione peroxidase) and lipid peroxidation (reactive oxygen species [ROS]). The results show that these insecticides are repellents for mothers (cypermethrin is the most repellent), and maternal behavior is modified after detection of an insecticide on their egg-sac but mothers do not abandon their egg-sacs. These neurotoxic insecticides affect the juveniles inside their egg-sac. Cypermethrin and chlorpyrifos caused more oxidative stress in juveniles than did imidacloprid. The ROS generated by these insecticides seemed to be adequately eliminated by the juveniles' antioxidant systems. Environ Toxicol Chem 2021;40:2861-2873. © 2021 SETAC.

Residual vitellus and energetic state of wolf spiderlings Pardosa saltans after emergence from egg-sac until first predation

The aim of this study was to evaluate energetic source used by juveniles of a terrestrial oviparous invertebrate during the earliest periods of their life. Growth, behavioural activities and energy contents of Pardosa saltans spiderlings' residual vitellus were monitored during 8 days after their emergence from their egg-sac until they disperse autonomously. The life-cycle of juvenile after emergence can be divided into three periods: a gregarious while juveniles are aggregated on their mother, dismounting off their mother's back and dispersion. We present the first biochemical study of residual vitellus and energy expenditure during these three periods. At emergence, the mean weight of juveniles was 0.59 mg and energy stock from residual vitellus averaged 51 cal/g wet mass. During gregarious period, the weight of the juveniles aggregated on their mother did not vary significantly and juveniles utilized only 1 cal/day from their residual vitellus. During the period from dismounting until their first exogenous feed, juveniles lost weight and used 30% of their residual vitellus stock. Proteins from the residual vitellus contributed principally to their energy expenditure during this period: 1.5 µg protein/day. Juveniles' first exogenous feeding was observed 7-8 days after emergence, when 70% of residual vitellus energy had been utilized. Juveniles dispersed after eating, reconstituting an energy stock comparable to that observed at emergence from egg-sac (50 cal/g wet mass). This new energy stock contains mainly lipids unlike the energy stock from the residual vitellus.

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

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.

Effects of prolonged exposure to CO2 on behaviour, hormone secretion and respiratory muscles in young female rats

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.

Myosin heavy chain expression and muscle adaptation to chronic oral breathing in rat

The purpose of this study was to establish if early chronic oral breathing could induce an ultra-structural adaptation of the diaphragm and orofacial muscles related to oral or nasal breathing. Therefore, we performed a bilateral nasal obstruction at day 8 on rat pups and the myosin heavy chain (MHC) composition of the muscles was analyzed at day 21. Nasal obstruction and the related switch to chronic oral breathing were associated with impaired growth, atrophy of olfactory bulbs, hypertrophy of adrenal glands and reduced muscle growth for all muscles studied except the diaphragm. Furthermore, we detected a smaller decrease of MHC 2b compared to MHC 2a and 2x in levator nasolabialis, a muscle involved with nasal breathing. In masseter superficialis and anterior digastric involved with oral breathing, we observed a smaller decrease of MHC 2a compared to MHC 2b or 2x, respectively. No difference was detected in the diaphragm MHC expression of oral breathing animals. Since the relative expression of fatigue resistant MHC fiber types increased in muscles involved with oral breathing, orofacial muscles seem to present a profile in MHC adapted to the transition from nasal to oral breathing, facilitating respiration.

Mild, non-lesioning transient hypoxia in the newborn rat induces delayed brain neurogenesis associated with improved memory scores

Although neonatal hypoxia can lead to brain damage, mild hypoxic episodes may be beneficial, as illustrated by tolerance induction by preconditioning, a process that might involve neurogenesis. To examine if brief hypoxia in newborn rats could stimulate the generation of neurons, pups were exposed for 5 min to 100% N2. Cell density and apoptosis were monitored in various brain regions and cell proliferation was studied by the incorporation of bromodeoxyuridine. Hypoxia did not result in detectable cell death but promoted cell proliferation in the ensuing three weeks in the subventricular zone and hippocampal dentate gyrus, with increased cell density in hippocampus CA1 pyramidal cells and granular layer of the dentate gyrus. Newly generated cells expressed neuronal markers (NeuroD or neuronal nuclear antigen) and were able to migrate from germinative zones to specific sites, in particular from the subventricular zone to the CA1 layer along the posterior periventricle. Neurogenesis was associated with an early activation of the extracellular regulated kinase 1/2 pathway, and pre-hypoxic administration of U0126, an inhibitor of mitogen-activated protein kinase kinase, impaired hypoxia effect on cell proliferation. Neurobehavioral capacities of hypoxic rats paralleled those of controls, but early exposure to hypoxia was associated with significantly improved memory retrieval scores at 40 days. In conclusion, brief neonatal hypoxia may trigger delayed generation of potentially functional neurons without concomitant cell death. This may constitute an interesting model for studying cell key events involved in the induction of neurogenesis.

Modification of morphological characters and cuticular compounds in worker ants Leptothorax nylanderi induced by endoparasites Anomotaenia brevis

Anomotaenia brevis (Cestoda, Cyclophyllidea) induces major changes in the morphological characters of the host ant, Leptothorax nylanderi (Hymenoptera, Formicidae): alteration of pigmentation, lowering of adult mean size, reduction of legs, eyes and head, enlargement of petiole. The presence of parasites in adult ants also modifies the quantity of cuticular compounds but not their quality. The parasite induces some changes in the synthesis/release of 13 cuticular hydrocarbons. The higher the number of parasites within a worker, the larger the quantitative changes in four cuticular hydrocarbons in comparison with normal ants. Such modifications (morphology, chemistry, behaviour) may explain the partial intolerance exerted by normal workers against the parasitized ants.

Relationships among food and contact signals in experimental group-living young of tegenaria atrica

Relationships between the quantity of diet, and group vs. individual rearing toward ontogenesis on degree of cannibalism and cuticular lipid profile of young Tegenaria atrica Araneae, Agelenidae were studied. Ad libitum diet increases the development rate and decreases cannibalism between conspecifics compared to a reduced diet. Individually reared young on the two diets showed no quantitative differences in cuticular lipid profile, but differences were observed in individual vs. group rearing modes. The ad libitum-fed grouped young spiders had notably increased quantities of palmitic acid, 13,17-,11,17-, and 9,17-dimethylhentriacontane, methyl oleate, and n-heptatriacontane over the reduced diet, cannibalistic group. Arch. Copyright 1999 Wiley-Liss, Inc.

Ovarian development and correlated changes in hemolymphatic ecdysteroid levels in two spiders, Coelotes terrestris and Tegenaria domestica (Araneae, Agelenidae)

Oocyte development during the first vitellogenic cycle of Coelotes terrestris and Tegenaria domestica is described. Under the present conditions, this development took about 40 days during which the oocytes went through six stages of maturation. For the first time presence of ecdysteroids is reported in adult females of spiders. Hemolymphatic ecdysteroid peaks were observed in both species at the transition between previtellogenesis and vitellogenesis. 20-Hydroxyecdysone and ecdysone were present in slightly different ratios in C. terrestris as well as T. domestica. These data largely agree with current views of ovarian development in Arthropods.

Cuticular hydrocarbons of Calliphora vomitoria (Diptera): relation to age and sex

Changes in epicuticular hydrocarbon content and composition were examined from 3 to 120 hr postemergence in both sexes of Calliphora vomitoria. n-Alkanes and mono- and dimethylalkanes with 20 to 31 carbon atoms were the major hydrocarbons detected. Alkenes were only detected in the females. Males had fewer hydrocarbons (40 versus 49 for the females). In males this number remained constant from 3 to 120 hr, whereas in females the number increased progressively from 3 to 48 hr. The males had a greater total of hydrocarbons than the females (x6 versus x3.5). They had significantly more hydrocarbons by 48 hr, the time of sexual maturation, while in females, the hydrocarbon content increased between 6 and 24 hr postemergence, just before the onset of previtellogenesis. Hydrocarbon synthesis continued up to 120 hr in males, but remained constant in the females after 24 hr. Hydrocarbon composition differed in males and females and between the young (3 and 6 hr) and the older animals (24 to 120 hr). The young animals were characterized by the presence of monomethylalkanes with chain lengths over 25C and the older animals by monomethylalkanes with chain lengths less than 25C. Alkenes were found only in females. The males were characterized by the presence of di- and monomethylalkanes with 23, 24, and 26 carbon atoms.

Relationships among hormonal changes, cuticular hydrocarbons, and attractiveness during the first gonadotropic cycle of the female Calliphora vomitoria (Diptera)

Attractiveness in adult females of Calliphora vomitoria is correlated with ovarian development and there is a marked increase during the previtellogenic and vitellogenic periods. The development of attractiveness may result from the combined actions of ecdysteroids and juvenile hormone. A rise in total hydrocarbons parallels the first increase in levels of these hormones during the previtellogenic stage. Cuticular hydrocarbons subsequently fall, along with the disappearance of hemolymphatic ecdysteroids, and then rise again during the vitellogenic phase of JH production. Increasing and decreasing of some cuticular hydrocarbons, some hydrocarbons implicated in the attractiveness, are correlated with variation of the titer of these hormones, especially JH III.