The formation of collective silk balls in the spider mite Tetranychus urticae Koch

Tetranychus urticae is a phytophagous mite that forms colonies of several thousand individuals. These mites construct a common web to protect the colony. When plants become overcrowded and food resources become scarce, individuals gather at the plant apex to form a ball composed of mites and their silk threads. This ball is a structure facilitating group dispersal by wind or animal transport. Until now, no quantitative study had been done on this collective form of migration. This is the first attempt to understand the mechanisms that underlie the emergence and growth of the ball. We studied this collective behaviour under laboratory conditions on standardized infested plants. Our results show that the collective displacement and the formation of balls result from a recruitment process: by depositing silk threads on their way up to the plant apex, mites favour and amplify the recruitment toward the balls. A critical threshold (quorum response) in the cumulative flow of mites must be reached to observe the emergence of a ball. At the beginning of the balls formation, mites form an aggregate. After 24 hours, the aggregated mites are trapped inside the silk balls by the complex network of silk threads and finally die, except for recently arrived individuals. The balls are mainly composed of immature stages. Our study reconstructs the key events that lead to the formation of silk balls. They suggest that the interplay between mites' density, plant morphology and plant density lead to different modes of dispersions (individual or collective) and under what conditions populations might adopt a collective strategy rather than one that is individually oriented. Moreover, our results lead to discuss two aspects of the cooperation and altruism: the importance of Allee effects during colonization of new plants and the importance of the size of a founding group.     

Conflict management by hamadryas baboons (Papio hamadryas hamadryas) during crowding: a tension-reduction strategy

Primates change a variety of behavioral responses during short-term exposure to crowding. Under crowded conditions, rates of aggression, submissive behavior, and affiliative behavior may increase or decrease. Different patterns of change among these three categories of response have been interpreted as various coping "strategies" for managing the increased risk of conflict under crowded conditions. Grooming is of particular interest because this behavior is known to have a calming influence on the recipient and could be used to manage conflict under tense situations. A captive group of nine hamadryas baboons (Papio hamadryas hamadryas) composed of two harems was observed under short-term crowding to determine whether this species adopts conflict-management strategies similar to those described in other primates. The aggression, submission, affiliation, and displacement activities of the six adults in the group (two males and four females) were recorded, and behaviors in their small indoor quarters was compared with baseline behaviors in the outdoor section of their enclosure, which had over 10 times more space. Repeated-measures analysis of variance (ANOVA) was used to compare behavioral rates during crowding with baseline rates recorded immediately after crowding and during matched controls collected at the same time of day as the crowding sessions. Aggression and submission rates did not change significantly across conditions. Huddling together and proximity increased during crowding, and females increased grooming of their harem male during crowding. Displacement activities (e.g., pacing and self-grooming) increased during crowding, but scratching, an indicator of anxiety in primates, did not. The pattern of behavior exhibited by this group conforms to an active "tension-reduction" strategy in which animals successfully reduce the higher risk of aggression during crowding.     

Effect of Ninjin-yoei-to (Rensheng-Yangrong-Tang) on olfactory behavior after olfactory nerve transection

Ninjin-yoei-to (NYT), a Japanese traditional medicine, is used to treat athrepsia due to surgery, anorexia, cold constitution, and anemia. There are reports of the effects of NYT on the nervous system; however, there have been no behavioral studies of the effect of NYT on olfactory function. The olfactory system undergoes continuous replacement of sensory neurons. Morphologic and behavioral studies have shown that the olfactory system recovers after bilateral olfactory nerve transection (BNX). However, in the humans, olfactory function does not always recover. In this study, we examined the effect of oral NYT on behavioral recovery after BNX. Fourteen mice were subjected to BNX. The regular diet was mixed with 2% NYT (NYT diet). Mice were separated into two groups; seven mice were fed the regular diet (control group), and seven mice were fed the NYT diet (NYT group). NYT was administered beginning 7 days prior to BNX and continuing for 35 days after BNX. Mice in both groups had free access to food and water. Olfactory function was evaluated by testing each mouse's ability to avoid cotton balls treated with acetic acid. After BNX, mice lost their ability to avoid cotton balls treated with acetic acid. In the control group, the time for behavioral recovery after BNX was 28 days. In the NYT group, the time for behavioral recovery after BNX was 21 days. NYT hastened behavioral recovery after BNX. NYT may have therapeutic benefits for patients with olfactory disorders.     

Comportements maternels chez la souris: Telle mere telle fille?

Relations between mother' and daughter' maternal behaviour were surched by continuous recording of locomotor activity and time spent in the nest during the first six days postpartum in two isogenic generations of mice. The first generation was composed of either heterozygous Fl or inbred C57BL/6 (=B6) dams, both giving birth after ovarian graft to B6 pups. In each litter the maternal behaviour of a female was studied in the same conditions as for her mother. Even in developing in quite different environments, both groups of B6 daughters did not differ for the behavioural patterns under study. Links between mother' and daughter' activity during the nursing period were shown in one group by important negative correlations suggesting a feedbak regulation mechanism. This illustrate a possible way of passive hereditary transmission of acquired behavioural characteristics.     

GDP and carboxyatractylate inhibit 4-hydroxynonenal-activated proton conductance to differing degrees in mitochondria from skeletal muscle and heart

The lipid peroxidation product 4-hydroxynonenal (HNE) increases the proton conductance of the inner mitochondrial membrane through effects on uncoupling proteins (UCPs) and the adenine nucleotide translocase (ANT); however, the relative contribution of the two carriers to these effects is unclear. To clarify this we isolated mitochondria from skeletal muscle and heart of wild-type and Ucp3 knockout (Ucp3KO) mice. To increase UCP3 expression, some mice were i.p. injected with LPS (12 mg/kg body weight). In spite of the increased UCP3 expression levels, basal proton conductance did not change. HNE increased the proton conductance of skeletal muscle and heart mitochondria. In skeletal muscle, this increase was lower in Ucp3KO mice and higher in LPS-treated wild-type mice, and was partially abolished by GDP (UCPs inhibitor) and completely abolished by carboxyatractylate (ANT inhibitor) or addition of both inhibitors. GDP had no effect on HNE-induced conductance in heart mitochondria, but carboxyatractylate or administration of both inhibitors had a partial effect. GDP-mediated inhibition of HNE-activated proton conductance in skeletal muscle mitochondria was not observed in Ucp3KO mice, indicating that GDP is specific for UCP3, at least in muscle. Carboxyatractylate was able to inhibit UCP3, probably through an indirect mechanism. Our results are consistent with the conclusion that, in skeletal muscle, HNE-induced increase in proton conductance is mediated by UCP3 (30%) and ANT, whereas in the heart the increase is mediated by ANT and other carriers, possibly including UCP3.     

A qualitative investigation of major urinary proteins in relation to the onset of aggressive behavior and dispersive motivation in male wild house mice (<Emphasis Type="Italic">Mus musculus domesticus</Emphasis>)

The physiological basis for population differentiation of dispersal timing during individual development in male wild house mice is still unknown. As major urinary proteins (MUPs) are known to convey information about competitive ability in male mice, we examined individual MUP profiles defined by isoelectric-focusing (IEF) patterns in relation to developmental timing of dispersive motivation. As an experimental paradigm marking the development of the dispersal propensity, we used agonistic onset between litter mate brothers when kept in pairs under laboratory conditions. Agonistic onset is known to reflect the initiation of dispersive motivation. Hence, we compared individual MUP IEF patterns between fraternal pairs that did or did not develop agonistic relationships before the age of 2 months. Urine was collected on the day of weaning and at the beginning of adulthood. We investigated whether there was a significant co-occurrence of particular MUP IEF patterns with the agonistic onset in male mice. We assumed that, based on this co-occurrence, particular MUP IEF patterns and/or a particular dynamic of MUP IEF expression from weaning to adulthood may be considered a physiological predictor of a specific behavioral strategy in male mice (i.e. submissive-philopatric or agonistic-dispersive strategy). We found that agonistic males expressed more MUP IEF bands than amicable ones at weaning, but these differences disappeared later on. The presence of two particular IEF bands at weaning was significantly associated with early agonistic onset. Our study suggests that MUPs could have a predictive value for the onset of aggressive behavior and dispersal tendency in male wild house mice.     

Group personality during collective decision-making: a multi-level approach

Collective decision-making processes emerge from social feedback networks within a group. Many studies on collective behaviour underestimate the role of individual personality and, as a result, personality is rarely analysed in the context of collective dynamics. Here, we show evidence of sheltering behaviour personality in a gregarious insect (Periplaneta americana), which is characterized by a collective personality at the group level. We also highlight that the individuals within groups exhibited consistent personality traits in their probability of sheltering and total time sheltered during the three trials over one week. Moreover, the group personality, which arises from the synergy between the distribution of behaviour profiles in the group and social amplifications, affected the sheltering dynamics. However, owing to its robustness, personality did not affect the group probability of reaching a consensus. Finally, to prove social interactions, we developed a new statistical method that will be helpful for future research on personality traits and group behaviour. This approach will help to identify the circumstances under which particular group compositions may improve the fitness of individuals in gregarious species.     

Environmental modification and agonistic behavior in NIH/S male mice: nesting material enhances fighting but shelters prevent it

Outbred NIH/S male mice were housed from weaning in groups of 4 without enrichment (control) or with nesting material (nest), nesting material and a box (nest-and-box), or nesting material and a tube (nest-and-tube) as environmental modification. The aim of the study was to investigate effects of widely recommended nesting material and additional shelters on male mice. The aggressiveness of the mice in their home cages clearly increased in the nest group, as assessed by the number of wounds. In the nest group, fighting was a stressful situation for the mice, leading to changes in weight gain and in the weights of the thymus, adrenals, spleen, and epididymal adipose tissue. Moreover, the agonistic behavior of these mice toward an intruder was increased both in individual tests (an intruder with the individual mouse) and group tests (an intruder with a group of mice). The provision of a box or tube as a shelter, in addition to nesting material, prevented intracage fighting and did not lead to alterations in the weight gain or organ weights of the mice. However, the agonistic behavior of mice with shelters was slightly increased in behavioral tests. Anxiety in the elevated plus-maze was not affected by any of the housing systems. In conclusion, the agonistic behavior of NIH/S mice, an aggressive strain, seemed to be easily enhanced by these environmental modifications. The suitability of any enrichment should be carefully evaluated, especially when highly aggressive mice are used.     

Swelling behavior of poly(vinyl alcohol) cryogels employed as matrices for cell immobilization

Poly(vinyl alcohol) cryogels are prepared from aqueous solutions of the polymer by freezing and thawing and are employed as matrices for cell immobilization. The swelling behavior of these macroporous gel carriers in pure water and in solutions of certain compounds (salts, amino acids, and glucose) was studied to elucidate the osmotic properties of the cryogels during long-term exposure to aqueous media. It was shown that after the initial sol fraction was washed out, the residual gel matrix possessed high stability even at extreme pH conditions (acid or alkali concentration up to 1.0 mol l⁻¹) or in the presence of strong chaotropic salts such as sodium rhodanide. Although the macroporous supermolecular structure of the carriers under consideration underwent certain changes as a result of aging processes during prolonged washing of the gel, the high porous morphology of the material was retained.     

Interleukin-17 acts independently of TNF-alpha under arthritic conditions

The proinflammatory T cell cytokine IL-17 is a potent inducer of other cytokines such as IL-1 and TNF-alpha. The contribution of TNF in IL-17-induced joint inflammation is unclear. In this work we demonstrate using TNF-alpha-deficient mice that TNF-alpha is required in IL-17-induced joint pathology under naive conditions in vivo. However, overexpression of IL-17 aggravated K/BxN serum transfer arthritis to a similar degree in TNF-alpha-deficient mice and their wild-type counterparts, indicating that the TNF dependency of IL-17-induced pathology is lost under arthritic conditions. Also, during the course of the streptococcal cell wall-induced arthritis model, IL-17 was able to enhance inflammation and cartilage damage in the absence of TNF. Additional blocking of IL-1 during IL-17-enhanced streptococcal cell wall-induced arthritis did not reduce joint pathology in TNF-deficient mice, indicating that IL-1 is not responsible for this loss of TNF dependency. These data provide further understanding of the cytokine interplay during inflammation and demonstrate that, despite a strong TNF dependency under naive conditions, IL-17 acts independently of TNF under arthritic conditions.     

The female pheromone 2,5-dimethylpyrazine induces sperm head abnormalities in male CBA mice

The effect of the house mouse female pheromone 2,5-dimethylpyrazine (2,5-DMP) on sperm differentiation in male CBA mice has been studied. For this purpose, mature males were treated with a 0.01% aqueous solution of the pheromone for six days. Control mice were similarly treated with physiologic saline. The mice were sacrificed 23 days after the treatment, and material for the analysis of sperm-head abnormalities was sampled from the caudal portion of the epididymis. Analysis of the frequency of abnormal sperms has demonstrated that the pheromonal treatment significantly increases the frequencies of various sperm-head abnormalities. Apparently, this results from disturbances in sex-cell differentiation germline cells caused by the induction of genetic damage at stages immediately preceding meiosis, as well as during the first and second meiotic divisions. The relationship between the effect of 2,5-DMP and the decrease in the fertility of male CBA mice that was earlier observed after a similar treatment is discussed.     

The Female Pheromone 2,5-Dimethylpyrazine Induces Sperm-Head Abnormalities in Male CBA Mice

The effect of the house mouse female pheromone 2,5-dimethylpyrazine (2,5-DMP) on sperm differentiation in male CBA mice has been studied. For this purpose, mature males were treated with a 0.01% aqueous solution of the pheromone for six days. Control mice were similarly treated with physiologic saline. The mice were sacrificed 23 days after the treatment, and material for the analysis of sperm-head abnormalities was sampled from the caudal portion of the epididymis. Analysis of the frequency of abnormal sperms has demonstrated that the pheromonal treatment significantly increases the frequencies of various sperm-head abnormalities. Apparently, this results from disturbances in germ cell differentiation caused by the induction of genetic damage at stages immediately preceding meiosis, as well as during the first and second meiotic divisions. The relationship between the effect of 2,5-DMP and the decrease in the fertility of male CBA mice that was earlier observed after a similar treatment is discussed.     

Behavioral Plasticity and Variation in Pit Construction of Antlion Larvae in Substrates with Different Particle Sizes

Behavioral plasticity allows animals to maximize their fitness in a variety of environmental conditions. Trap‐building predators represent case studies in such plasticity as the characteristics of their traps are dependent upon the substrate available. We investigated the effect of sand particle size on pit construction in antlions (Euroleon nostras), sand‐dwelling insect larvae that build pitfall traps to capture prey. The pit construction behavior of the species comprises six stages. When antlions were exposed to different sand particle sizes, their behavior differed in terms of the occurrence and duration of particular stages and in the frequency of jerks produced during sand tossing. Jerk frequency was negatively correlated with sand particle size and also changed during pit construction. Furthermore, at larger particle sizes, individuals occasionally constructed irregular traps with a figure of eight shape, and they crossed the center of the truncated cone during deepening. In the largest substrate, particle size of antlions did not construct pits. Our results demonstrate that variation in traps under differing environmental conditions stems directly from behavioral plasticity in this species.     

Planar Cell Polarity Signaling in Collective Cell Movements During Morphogenesis and Disease

Collective and directed cell movements are crucial for diverse developmental processes in the animal kingdom, but they are also involved in wound repair and disease. During these processes groups of cells are oriented within the tissue plane, which is referred to as planar cell polarity (PCP). This requires a tight regulation that is in part conducted by the PCP pathway. Although this pathway was initially characterized in flies, subsequent studies in vertebrates revealed a set of conserved core factors but also effector molecules and signal modulators, which build the fundamental PCP machinery. The PCP pathway in Drosophila regulates several developmental processes involving collective cell movements such as border cell migration during oogenesis, ommatidial rotation during eye development, and embryonic dorsal closure. During vertebrate embryogenesis, PCP signaling also controls collective and directed cell movements including convergent extension during gastrulation, neural tube closure, neural crest cell migration, or heart morphogenesis. Similarly, PCP signaling is linked to processes such as wound repair, and cancer invasion and metastasis in adults. As a consequence, disruption of PCP signaling leads to pathological conditions. In this review, we will summarize recent findings about the role of PCP signaling in collective cell movements in flies and vertebrates. In addition, we will focus on how studies in Drosophila have been relevant to our understanding of the PCP molecular machinery and will describe several developmental defects and human disorders in which PCP signaling is compromised. Therefore, new discoveries about the contribution of this pathway to collective cell movements could provide new potential diagnostic and therapeutic targets for these disorders.     

High zooxanthella density shortens the survival time of coral cell aggregates under thermal stress

To investigate bleaching mechanisms in coral-zooxanthella symbiotic systems, it is important to study the cellular- or tissue-level responses of corals to stress. We established an experimental system to study the stress responses of coral cells using coral cell aggregates. Dissociated coral cells aggregate to form spherical bodies, which rotate by ciliary movement. These spherical bodies (tissue balls) stop rotating and disintegrate when exposed to a thermal stress. Tissue balls prepared from dissociated cells of Fungia sp. and Pavona divaricata were exposed to either elevated temperature (31 °C, with 25 °C as the control) or elevated temperature in the presence of exogenous antioxidants (ascorbic acid and catalase, or mannitol). The survival curves of tissue balls were markedly different between 31 and 25 °C. At 31 °C, most tissue balls disintegrated within 24 h, whereas at 25 °C, most tissue balls survived for more than 24 h. There was a negative correlation between survival time and the zooxanthella density of tissue balls at 31 °C, but no significant relationship was found at 25 °C. Antioxidants extended the survival time of tissue balls at high temperature, suggesting that zooxanthellae produce reactive oxygen species under stress. These results indicate that zooxanthellae produce harmful substances and damage coral cells under high-temperature stress. Tissue balls provide a good experimental system with which to study the effects of stress and various chemical reagents on corals cells.     

Comparison of the stability of morphometric and nonmetric skeletal characteristics of inbred mice with regard to environmental exposure in prenatal development

The influence of some environmental factors on size and shape of mandible in BALB/cJLacSto inbred mice was studied during prenatal development by multivariate morphometric methods. The factors under study were: introduction of methylthiouracil into the diet of pregnant females; injections of pregnant females with adrenocorticotropic or parathyroid hormones; keeping the females at low temperatures (two regimes). It was established that the changes of mandible shape caused by the changes of conditions of prenatal development did not achieve the level of differences between strains, and mouse strain identification was possible under various conditions of animal's keeping. It has been shown by comparison of these results with preceding data that the nonmetric skeletal traits were more stable to the influence of the same factors than morphometric ones. This gives us the foundations to consider the method of evaluation of phenetic distances between natural groups of animals for the set of non-metric threshold skeletal traits more suitable for detection of genetical differentiation of wild populations.     

The role of EGF in testosterone-induced reproductive tract differentiation

EGF is known to modulate a variety of cellular functions including differentiation. The aim of this investigation was to determine the role of EGF in androgen-induced masculine differentiation. Accordingly, a series of experiments were designed and the results are summarized as described below. (1) We found that the specific deprivation of EGF using anti-EGF serum during the period of masculine differentiation in an organ culture bioassay system resulted in the disintegration of the Wolffian system in a dose-dependent manner. (2) Exogenous EGF supplemented in the above experiment corrected the anti-EGF effect, suggesting a specific role of EGF. (3) Anti-EGF serum was also found to disrupt the differentiation even in the presence of exogenous testosterone, suggesting an effect independent of testosterone synthesis. (4) EGF was found to have a direct masculinizing effect both in vivo and in vitro; however, it was not able to mimic all masculinizing effects of testosterone. The mesonephric segment of the Wolffian duct was retained by EGF in the female fetal tract under in vitro conditions, and under in vivo conditions EGF was able to increase anogenital distance and to induce epididymis in some female fetal mice. (5) We were able to detect an EGF-like material in the fetal genital tract during differentiation and found that the level of this material increased with advancement of differentiation. Thus, it appears from the above results that EGF plays a role in testosterone-induced reproductive tract differentiation.     

Immunopathological Changes in the Brain of Immunosuppressed Mice Experimentally Infected with Toxocara canis

Toxocariasis is a soil-transmitted helminthozoonosis due to infection of humans by larvae of Toxocara canis. The disease could produce cognitive and behavioral disturbances especially in children. Meanwhile, in our modern era, the incidence of immunosuppression has been progressively increasing due to increased incidence of malignancy as well as increased use of immunosuppressive agents. The present study aimed at comparing some of the pathological and immunological alterations in the brain of normal and immunosuppressed mice experimentally infected with T. canis. Therefore, 180 Swiss albino mice were divided into 4 groups including normal (control) group, immunocompetent T. canis-infected group, immunosuppressed group (control), and immunosuppressed infected group. Infected mice were subjected to larval counts in the brain, and the brains from all mice were assessed for histopathological changes, astrogliosis, and IL-5 mRNA expression levels in brain tissues. The results showed that under immunosuppression, there were significant increase in brain larval counts, significant enhancement of reactive gliosis, and significant reduction in IL-5 mRNA expression. All these changes were maximal in the chronic stage of infection. In conclusion, the immunopathological alterations in the brains of infected animals were progressive over time, and were exaggerated under the effect of immunosuppression as did the intensity of cerebral infection.