Predator exposure alters female mate choice in the green swordtail

Female green swordtails, Xiphophorus helleri, show a matingpreference for males with brightly colored, elongated swords.This preference is thought to be due to a preexisting receiverbias favoring longer sworded males. In this study, we examinedvariation in the expression of this sword bias in females. Specifically,we tested the hypothesis that an increase in perceived predationrisk will decrease female response to males with longer swords.We used a video playback experiment to evaluate female choicebetween two recordings of a displaying male that differed onlyin sword length. We scored responses of females to these recordingsimmediately before and after they had been exposed to a videorecording of a predation event between a cichlid and a malepossessing a long sword. We found that prior to exposure tothis predation event, females preferred the male with the longersword. However, after exposure to the predator, females alteredtheir mating response, preferring the male with the sword removed.Exposure to the predator also caused an increase in the frequencywith which females moved from potential mating positions toa neutral zone. The results presented here suggest that thefemale preference for males with longer swords can be modulatedbased on the perceived risk of predation.     

Influence of repeated exposure of male rats to oestrous odour on their subsequent sexual behaviour

Adult and sexually naive male rats were individually, in repeated sessions, put into a box the floor of which had beforehand been scent-marked by oestrous females. The males of the control group were put into a box which had not been scent-marked. Although the males exposed to scent-marks showed, in two performed tests, significantly more precopulatory activities towards the passively receptive female, they were not able to initiating copulation with her. They initiated copulatory behaviour only in the test when their partner was a female exhibiting ritualized dartings.     

Impaired discrimination of and aversion to parasitized male odors by female oxytocin knockout mice

A major cost of social behavior is the increased risk of exposure to parasites, with animals utilizing social information to recognize and avoid infected conspecifics. In mice, females can discriminate between infected and uninfected males on the basis of social cues, displaying aversive responses to the odors of infected males. In the present study, using female mice whose gene for oxytocin (OT) has been selectively deleted (OT knockout mice (OTKO)), we show that at least one normal allele for OT is required for the mediation of the recognition and avoidance of parasitized males. Female wild type (OTWT) and heterozygous (OTHZ) mice distinguished between the odors of individual males infected with the louse, Polyplax serrata , and uninfected males while the KO mice did not. Exposure to the odors of infected males induced analgesia in OTWT and OTHZ females, with OTKO females displaying attenuated analgesia. OTWT and OTHZ females, but not the OTKO females, also distinguished between the odors of novel and familiar infected males and modulated their analgesic responses on the basis of prior familiarity. In an odor choice test, OTWT and OTHZ females displayed a marked initial choice for the odors of uninfected males, whereas the OTKO females showed no consistent choice. This impairment was specific to the odors of infected males. OTKO females displayed normal analgesic responses to another aversive social odor, that of a stressed male, and an aversive non-social odor, that of a cat. The OTKOs had normal non-social olfactory memory, but were impaired in their social odor memory. These findings indicate that a normal OT gene comprises an essential part of the central recognition mechanism whereby females can both reduce the transmission of parasites to themselves and select for parasite-free males.     

To mate or not to mate,and subsequent host search by a haplodiploid female parasitoid wasp

Mated females of haplodiploid species can vary the sex ratio of their offspring, but virgin or sperm‐depleted females can produce only males. Depending on the costs and benefits, the theory of constrained sex allocation states that female haplodiploids may vary in their propensity to mate, with important implications for the populations’ sex ratio. Unmated female parasitoid wasps Alabagrus texanus (Braconidae) have been observed to reject matings with males, even under highly confined spatial conditions. We performed field trials to determine whether unmated female A. texanus would mate. We then compared the preferences of the resulting unmated (constrained) and mated (unconstrained) female wasps for shelters constructed and occupied by their hosts, fern moth caterpillars Herpetogramma theseusalis (Crambidae) on fern fronds. We presented the wasps with pairs of shelters collected from the field that differed in size, as well as freshness, fern species, and presence or absence of caterpillars. Unconstrained females searched small shelters more frequently than did constrained females and tended to favor senesced (old) shelters over fresher ones. They did not differ in choice between shelters on marsh and sensitive ferns or between shelters containing caterpillars and empty shelters. The preference for small shelters by the unconstrained wasps may enhance their rate of contacting favorable hosts, but the foraging regime of the constrained females should expose them to caterpillars at sites infrequently searched by the unconstrained females.     

Developmental exposure to environmental estrogens alters anxiety and spatial memory in female mice

Humans and wildlife are exposed to numerous anthropogenic drugs and pollutants. Many of these compounds are hormonally active, and recent evidence suggests that the presence of these endocrine disruptors permanently alters normal development and physiology in a variety of vertebrate species. Here, we report on the effects of developmental exposure to two common estrogenic pollutants, bisphenol A and ethinyl estradiol on sexually dimorphic, non-reproductive behavior. Mice (Mus musculus domesticus) were exposed to environmentally relevant levels of these chemicals (2 and 200 microg/kg/day for bisphenol A and 5 microg/kg/day for ethinyl estradiol) throughout prenatal and early postnatal development. As adults, the animals were observed in a variety of tests measuring sexually dimorphic behaviors including short-term spatial memory (in a radial-arm maze and a Barnes maze) and anxiety (in an elevated-plus maze and a light/dark preference chamber). Developmental exposure to ethinyl estradiol was found to masculinize behavior in all of the assays used. Bisphenol A increased anxious behavior in a dose-dependent fashion but had no effect on spatial memory. These results indicate that non-reproductive, sexually dimorphic behavior is sensitive to endocrine disruption. In addition, these experiments suggest that both humans and wildlife are being exposed to levels of these endocrine disrupting compounds that are sufficient to disrupt the development of the nervous system and that may have permanent consequences on sexually dimorphic behaviors.     

Hormonal responses to female conspecifics in hyperprolactinemic male rats and mice

Exposure to a female results in an acute release of LH and testosterone (T) in normal male rats and mice. This study was conducted to determine whether these hormonal responses are altered in hyperprolactinemic (hyperPRL) male rats in which copulatory behavior is known to be suppressed and in hyperPRL male mice in which it is not. Adult male CDF (F-344) rats were made hyperPRL either by grafting of three anterior pituitaries under the kidney capsule or by treatment with diethylstilbestrol (DES). Exposure of control males to receptive females for 10-15 min produced the expected two- to fourfold statistically significant elevations in plasma LH levels. In contrast, plasma LH levels in pituitary grafted or DES-treated males were not altered by female exposure. Male mice were pituitary grafted (two pituitaries per recipient) or sham-operated and housed individually with a female for 1 week. The resident females were then replaced with novel females in half of the cages and blood samples were taken from the males after 5 min exposure for determination of LH levels or after 45-60 min exposure for T levels. Female-induced LH and T elevations occurred in both hyperPRL and control groups. Failure of hyperPRL male rats to experience an increase in plasma LH levels in response to a female suggests abnormality of mechanisms controlling LHRH release. Suppression of LHRH release may be involved also in the induction of deficits of sexual behavior in these animals.     

Vomeronasal neuroepithelium and forebrain Fos responses to male pheromones in male and female mice

Male urinary pheromones modulate behavioral and neuroendocrine function in mice after being detected by sensory neurons in the vomeronasal organ (VNO) neuroepithelium. We used nuclear Fos protein immunoreactivity (Fos-IR) as a marker of changes in neuronal activity to examine the processing of male pheromones throughout the VNO projection pathway to the hypothalamus. Sexually naive male and female Balb/c mice were gonadectomized and treated daily with estradiol benzoate (EB) or oil vehicle for 3 weeks. Subjects were then exposed to soiled bedding from gonadally intact Balb/c males or to clean bedding for 90 min prior to sacrifice and processing of their VNOs and forebrains for Fos-IR. Male pheromones induced similar numbers of Fos-IR cells in the VNO neuroepithelium of oil-treated male and female subjects; however, EB-treated females had significantly more Fos-IR neurons in the VNO than any other group. There was an equivalent neuronal Fos response to male odors in the mitral and granule cells of the anterior and posterior accessory olfactory bulb of males and females, regardless of hormone treatment. In central portions of the VNO projection pathway (i.e., bed nucleus of the stria terminalis, medial preoptic area) neuronal Fos responses to male pheromones were present in female but absent in male subjects, regardless of hormone treatment. In a separate experiment, mating induced neuronal Fos-IR in these brain regions at levels in gonadally intact male subjects which were equal to or greater than those seen in ovariectomized females primed with estrogen and progesterone. This suggests that neurons in the central portions of the male's VNO pathway are capable of expressing Fos. Our results suggest that sexually dimorphic central responses to pheromones exist in mice that may begin in the VNO neuroepithelium.     

Adaptation to short-term extreme fat consumption alters intestinal lipid handling in male and female mice

The small intestine is a highly adaptable organ serving as both a barrier to the external environment and a conduit for nutrient absorption. Enterocytes package dietary triglycerides (TG) into chylomicrons for transport into circulation; the remaining TGs are stored in cytosolic lipid droplets (CLDs). The current study aimed to characterize the impact of diet composition on intestinal lipid handling in male and female wild-type mice. Mice were continued on their grain-based diet (GBD) and switched to either a high-fat, high cholesterol Western-style diet (WD) or a ketogenic diet (KD) for 3 or 5 weeks. KD-fed mice displayed significantly higher plasma TG levels in response to an olive oil gavage than WD- and GBD-fed mice; TG levels were ~2-fold higher in male KD-fed mice than female KD-fed mice. Poloxamer-407 experiments revealed enhanced intestinal-TG secretion rates in male mice fed a KD upon olive oil gavage, whereas secretion rates were unchanged in female mice. Surprisingly, jejunal CLD size and TG mass after oil gavage were similar among the groups. At fasting, TG mass was significantly higher in the jejunum of male KD-fed mice and the duodenum of female KD-fed mice, providing increased substrate for chylomicron formation. In addition to greater fasting intestinal TG stores, KD-fed male mice displayed longer small intestinal lengths, while female mice displayed markedly longer jejunal villi lengths. After 5 weeks of diet, 12 h fasting-2 h refeeding experiments revealed jejunal TG levels were similar between diet groups in male mice; however, in female mice, jejunal TG mass was significantly higher in KD-fed mice compared to GBD- and WD-fed mice. These experiments reveal that KD feeding promotes distinct morphological and functional changes to the murine small intestine compared to the WD diet. Moreover, changes to intestinal lipid handling in response to carbohydrate and protein restriction manifest differently in male and female mice.     

Influences of alcohol on the social responses of male resident mice to anosmic female intruders

The effects of acutely administered ethanol (0, 0.5, 1.0 or 2.0 g/kg, i.p.) were studied in individually-housed male Swiss mice in dyadic encounters with anosmic, group-housed female intruders. The procedure was designed to suppress levels of attack in isolates. Videotape analysis of 500-second encounters, using both simplified and complex ethological techniques, revealed that alcohol did not potentiate aggression at any dose tested. At the highest alcohol dose there were marked increases in total time spent in timid-defensive and non-social behaviours, with concomitant decreases in aggressive and social/sexual activities. The postural analysis showed increases and decreases in elements of non-social behaviour and social investigatory elements, together with marked increases in certain timid-defensive activities and a decrease in tail-rattling. Comparison with previous work on inter-male paradigms shows that the type of opponent not only modifies the behaviour of saline-treated controls, but markedly influences the behavioural responses to alcohol treatment.     

Prenatal exposure to androgen influences morphology and aggressive behavior of male and female mice

To assess the effects of prenatal exposure to androgen on adult aggressiveness in mice, pregnant mice were given injections of 1.5 mg testosterone propionate (TP) or oil from Days 12 to 16 of pregnancy. All offspring were gonadectomized on the day of birth. Neonatal treatment occurred on the day following birth and consisted of one-half of the animals from each prenatal treatment group being injected with 100 μg TP while the other half were injected with oil, yielding four Prenatal/Neonatal treatment groups for each sex. On postnatal Day 60, all offspring were given subcutaneous implants of encapsulated testosterone (T) and tested for 10 min every other day against a male opponent until aggression was observed. Female offspring of TP-treated mothers were indistinguishable from males on external examination at birth. The duration of exposure to T required to induce aggression provides an index of the sensitivity of the neural substrate to T. When arranged from the most sensitive to the least sensitive to the aggression inducing action of T, the four Prenatal/Neonatal treatment groups of females were significantly different from each other: Group TP/TP > Group OIL/TP > Group TP/OIL > Group OIL/OIL. A similar pattern was observed for the male offspring. There were no differences in the proportion of animals per group that exhibited aggression (virtually all animals fought) or the intensity of aggression once exhibited. The results demonstrate that morphological and behavioral masculinization can occur in response to exposure to androgen during prenatal as well as neonatal life in mice.     

Early exposure to a nonhygienic environment alters pulmonary immunity and allergic responses

The hygiene hypothesis suggests that early life exposure to a nonhygienic environment that contains endotoxin reduces the risk of developing allergic diseases. The mechanisms underlying the hygiene hypothesis are unclear and may involve subtle immune system interactions that occur during maturation. Experimental objectives of this study were to use a novel animal model to test the hygiene hypothesis and to characterize early life immune system responses to a nonhygienic environment. Mice were reared in corn dust, a grain-processing byproduct with a high-endotoxin content and microbial products or in a low-endotoxin environment. The influence of early or later life exposure to corn dust on a subsequent allergen stimulus (ovalbumin) was assessed by bronchoalveolar lavage (BAL) cell analysis, lung histology, serum IgE, and BAL cytokine measurements. The influence of the corn dust environment on the developing pulmonary immune system was assessed by BAL cell analysis and immunostaining of lung tissue. The corn dust environment contained significantly more endotoxin (P < 0.001), and the dust exposures attenuated the cellular inflammatory response to ovalbumin in the adult mouse (P < 0.01) but did not reduce serum IgE levels or alter baseline BAL fluid proinflammatory cytokine levels. The corn dust environment did not induce significant neutrophilia in lavage fluid but significantly increased the number of antigen-presenting cells in alveolar walls early in life by approximately 37%. In conclusion, exposure to a nonhygienic environment did not induce significant airway neutrophilia, yet altered the population of immunologically active cells in the lung and reduced subsequent allergic inflammation.     

Prior exposure to male phenotypes influences mate choice in the guppy, Poecilia reticulata

This study examined the effect of experience on the patternof mate choice in female guppies. Females from some naturalpopulations are known to discriminate among males on the basisof the relative area of orange in the color pattern. We exposedmaturing female guppies to groups of males that differed inphenotvpic distribution of orange coloration (high orange, loworange, and mixed) and tested their subsequent mating preferences.Females that had been exposed to high-orange or low-orange malegroups showed no discrimination in choice tests, but femalesexposed to mixed male groups favored high-orange males overlow-orange males. These results demonstrate that mating preferencesof females can be modified depending on prior experience. Femalesmay be able to adjust their pattern of mate choice dependingon the degree to which choice cues permit effective discriminationamong males. This potential for short-term modification of matechoice patterns could affect the evolutionary outcome of sexualselection     

Bioassay approaches to observing behavioural responses of adult female Cydia molesta to host plant odour

Abstract:  Three different olfactometers were evaluated in order to develop a bioassay procedure testing for the olfactory responses of Cydia molesta . Females were tested individually using a linear and a Y-tube olfactometer, and in groups using a dual-choice arena. Room temperature, relative humidity, light intensity, airflow, age of the moths and odour source were kept constant during experiments. The odour source tested was a green shoot of peach excised 10 min before experiments started. Cydia molesta females showed a significant response to this plant odour in all olfactometers. A number of qualitative aspects were found to be in favour of the dual choice arena as a tool for screening potentially attractive odour sources. It allowed for a differentiation of the response of mated and virgin females. Experimental conditions allowed the circadian rhythm of insects to be mimicked. Manipulation of individuals is reduced and flight is not precluded.     

Darcin: a male pheromone that stimulates female memory and sexual attraction to an individual male's odour

Background

Among invertebrates, specific pheromones elicit inherent (fixed) behavioural responses to coordinate social behaviours such as sexual recognition and attraction. By contrast, the much more complex social odours of mammals provide a broad range of information about the individual owner and stimulate individual-specific responses that are modulated by learning. How do mammals use such odours to coordinate important social interactions such as sexual attraction while allowing for individual-specific choice? We hypothesized that male mouse urine contains a specific pheromonal component that invokes inherent sexual attraction to the scent and which also stimulates female memory and conditions sexual attraction to the airborne odours of an individual scent owner associated with this pheromone.

Results

Using wild-stock house mice to ensure natural responses that generalize across individual genomes, we identify a single atypical male-specific major urinary protein (MUP) of mass 18893Da that invokes a female's inherent sexual attraction to male compared to female urinary scent. Attraction to this protein pheromone, which we named darcin, was as strong as the attraction to intact male urine. Importantly, contact with darcin also stimulated a strong learned attraction to the associated airborne urinary odour of an individual male, such that, subsequently, females were attracted to the airborne scent of that specific individual but not to that of other males.

Conclusions

This involatile protein is a mammalian male sex pheromone that stimulates a flexible response to individual-specific odours through associative learning and memory, allowing female sexual attraction to be inherent but selective towards particular males. This 'darcin effect' offers a new system to investigate the neural basis of individual-specific memories in the brain and give new insights into the regulation of behaviour in complex social mammals.See associated Commentary http://www.biomedcentral.com/1741-7007/8/71

     

花生幼苗对重复干旱胁迫的生理响应

防雨棚内设盆栽试验,设置对照(Control,75%田间持水量)、干旱胁迫(D,35%)、重复干旱胁迫(D_D,35%)3个处理,探讨花生幼苗对预干旱胁迫的适应和记忆响应,分析预干旱对缓解重复干旱胁迫危害的生理作用。结果表明,与干旱胁迫处理相比,重复干旱胁迫提高了叶片的相对含水量,减少脯氨酸的积累,降低MDA和O·_2~-含量;抗氧化酶SOD、CAT活性降低,其中POD活性降低最为明显,并在复水后恢复到与对照相同水平或低于对照。与正常水分的对照相比,干旱胁迫显著降低叶片光合速率(P_N)、最大光合势能(P_C)、最大光量子产量(Y_Q),但重复干旱处理在重复干旱胁迫时期和复水后P_N、P_C和Y_Q均高于干旱处理。预干旱胁迫导致光合和气孔导度滞后面积、滞后率(H_P和H_g)增加,经过预干旱胁迫后,重复干旱显著降低光合和气孔导度滞后面积和滞后率。预干旱胁迫提高植株在重复干旱胁迫下叶片含水量,减轻重复干旱对植株造成的生理伤害,在光合作用上提高对重复干旱的抵御能力,并在复水后快速恢复到正常水分条件下植株生长水平,减少干旱对植株的不利影响。因此,预干旱胁迫促使花生幼苗具备适应或可记忆初始胁迫的能力,重复干旱胁迫时表现更为迅速和强烈的生理防御和快速的生理恢复机制。     

Tetrachlorodibenzo-p-dioxin exposure alters radial arm maze performance and hippocampal morphology in female AhR mice

Perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been reported to alter spatial learning in rats tested on a radial arm maze (RAM). TCDD is believed to exert most of its effects through binding to the aryl hydrocarbon receptor (AhR). To determine whether the AhR mediates TCDD-induced alterations in spatial learning, we tested male and female AhR-knockout (AhR-/-), heterozygous (AhR+/-) and wild-type (AhR+/+) mice on the RAM. AhR+/- male and female mice were time mated, and treated dams were dosed with 5 microg TCDD/kg body weight on day 13 of gestation. When offspring reached adulthood, male and female AhR+/+, AhR+/- and AhR-/- mice from TCDD-exposed and unexposed litters were tested on the eight-arm RAM. After testing, we examined hippocampal morphology as visualized by the Timm's silver sulfide stain. TCDD-exposed female AhR+/- mice made more errors than their respective controls on the RAM and exhibited a decrease in the size of the intra- and infrapyramidal mossy fiber (IIP-MF) field of the hippocampus. None of the other TCDD-exposed groups differed from their respective control groups with regard to maze performance or hippocampal morphology. The reduction of IIP-MF field indicates a possible morphological basis for the learning deficit that was observed in the female AhR+/- mice. It is hypothesized that the effect of TCDD exposure is AhR dependent and that TCDD may alter GABAergic activity in the hippocampus of female mice during development.     

Neonatal exposure to oestrogens alters the protein profiles and gene expression in the genital tract of adult male mice.

After neonatal administration of supraphysiological doses of oestradiol, the concentration of tissue proteins, in adult mice, was significantly reduced by 39, 45 and 56% in epididymis, vas deferens and seminal vesicle respectively. The protein profiles showed persistent alterations. In epididymis, 4 protein bands were differentially increased (14.4, 43 and 67 kDa) or reduced (24 kDa) in oestrogenized males. In vas deferens, 4 proteins were increased (14.4, 49,67 and 76 kDa) and one (34 kDa) virtually absent. In seminal vesicle, about 20 proteins of varying molecular weights (12-140 kDa) were differentially increased or decreased. Testosterone substitution, at adulthood, was unable to reverse these effects. Treatments with oestradiol during adult life induced persistent alterations in the protein profiles of the 3 organs but, in contrast to neonatal treatment, these alterations could be reversed by androgen therapy. A cDNA library has been constructed with RNA prepared from adult seminal vesicle and screened by differential hybridization. Neonatal oestrogenization strongly reduced the abundance of some mRNA species. Eleven recombinants containing putative oestrogen-sensitive sequences were isolated. Two of them, having an insert of about 500 base pairs, were used for dot-blot hybridization. Results showed that the two clones contained sequences which were differently regulated by androgens.     

Does the time spent near a male predict female mate choice in a Malawian cichlid?

Gravid female Malawian Pseudotropheus cichlids spent significantly more time with males that they subsequently chose as mates, indicating that time spent near a male is a valid and accurate method of measuring female preference. Furthermore, females preferred to mate with males that had longer pelvic fins and a larger number of eggspots on their anal fins. In some instances, females chose to mate with both of the males with which they were presented, possibly because they were unable to discriminate between them.