雌雄罗氏沼虾应对低氧胁迫的行为生理响应

为查明雌雄罗氏沼虾应对低氧胁迫的行为生理响应,设置6.46(对照)、4.48和3.27 mg·L^-13种溶解氧水平,研究了雌、雄个体在胁迫6 d后肝胰脏和肌肉能量代谢酶活性及游泳和弹跳速度。结果表明: 溶解氧从6.46 mg·L^-1降至4.48 mg·L^-1,雌雄个体肌肉有氧代谢酶活性及游泳速度均显著下降,且雄性下降幅度小于雌性,厌氧代谢酶活性并无显著变化;溶解氧继续降至3.27 mg·L^-1,雌雄个体肌肉有氧代谢酶和厌氧代谢酶活性均显著下降,肝胰脏厌氧代谢酶中的乳酸脱氢酶(LDH)活性及弹跳速度显著下降,且雌性肝胰脏LDH活性下降幅度小于雄性。雌雄罗氏沼虾游泳速度与游泳足肌肉有氧代谢酶活性呈显著正相关,弹跳速度则与腹部肌肉厌氧代谢酶活性呈显著正相关。表明罗氏沼虾可以通过降低能量代谢水平应对低氧胁迫,但这种生理调节会导致运动能力下降,雄性优先将能量分配于肌肉以满足运动,雌性则优先保障肝胰脏能量供应。     

Consistent sex ratio bias of individual female dragon lizards

Sex ratio evolution relies on genetic variation in either the phenotypic traits that influence sex ratios or sex-determining mechanisms. However, consistent variation among females in offspring sex ratio is rarely investigated. Here, we show that female painted dragons (Ctenophorus pictus) have highly repeatable sex ratios among clutches within years. A consistent effect of female identity could represent stable phenotypic differences among females or genetic variation in sex-determining mechanisms. Sex ratios were not correlated with female size, body condition or coloration. Furthermore, sex ratios were not influenced by incubation temperature. However, the variation among females resulted in female-biased mean population sex ratios at hatching both within and among years.     

Behavioral responses to physical vs. social novelty in male and female laboratory rats

Most behavioral tests used with laboratory rodents involve measuring behavioral responses to physical novelty. However, laboratory rodents are often derived from highly social species for which novel social stimuli may induce different levels of fear or curiosity compared to novel physical objects. We hypothesized that behavioral responses will differ in response to novel physical vs. social cues, and that females may show more exploration of social novelty, based on prior studies indicating that females more actively seek social support during duress compared to males. We compared young (55-day-old) Sprague-Dawley rats’ responses to an arena filled with novel objects (“physical”) or a novel same-sex caged conspecific (“social”). Rats were more active and spent twice as much time in contact with the novel social stimulus compared to novel physical stimuli. Although females were more active than males, females were not particularly more exploratory in the social arena compared to males. The results indicate that a novel social partner (even a caged one with limited ability to interact) elicits more exploration than novel objects for both male and female rats.     

Wolbachia, sex ratio bias and apparent male killing in the harlequin beetle riding pseudoscorpion

Bacterial endosymbionts that manipulate host reproduction are now known to be widespread in insects and other arthropods. Since they inhabit the cytoplasm and are maternally inherited, these microorganisms can enhance their fitness by biasing host sex ratio in favour of females. At its most extreme, sex ratio manipulation may be achieved by killing male embryos, as occurs in a number of insect species. Here, we provide evidence for the first case of male killing by a tetracycline-sensitive microbe in pseudoscorpions. Using a combination of inheritance studies, antibiotic treatment and molecular assays, we show that a new strain of Wolbachia is associated with extreme female bias in the pseudoscorpion, Cordylochernes scorpioides. In a highly female-biased line, sex ratio distortion was maternally inherited, and occurred in conjunction with a high rate of spontaneous abortion and low reproductive success. Antibiotic treatment cured females of the Wolbachia infection, restored offspring sex ratio to 1:1, and significantly enhanced female reproductive success. The discovery of apparent male-killing in C. scorpioides is of interest because pseudoscorpions are viviparous. Theory predicts that male killing should be favoured, if male death enhances the fitness of infected female siblings. In a live-bearing host, reallocation of maternal resources from dead male embryos to their sisters provides a direct, physiological mechanism through which fitness compensation could favour male killing by cellular endosymbionts. Our results suggest, however, that fitness compensation and the spread of male-killing endosymbionts may be undermined by a high rate of spontaneous abortion in infected females of this viviparous arthropod.     

Behavioral and physiological responses to experimentally elevated testosterone in female dark-eyed juncos (Junco hyemalis carolinensis)

Testosterone mediates the expression of many fitness-related traits in male vertebrates and is thought to account for numerous sex differences in trait expression. Testosterone is also secreted by females; however, far less is known regarding its effects on female physiology and behavior. Using a bird species in which the effects of testosterone on males are well characterized, the dark-eyed junco (Junco hyemalis), we tested whether an increase in exogenous testosterone in females would alter the phenotypic expression of a suite of behavioral and physiological traits. We found that increased testosterone levels in female dark-eyed juncos led to decreased cell-mediated immune function and increased intrasexual aggression, hypothalamo-pituitary-adrenal (HPA) axis responsiveness, baseline corticosterone and corticosterone-binding globulin (CBG) levels. Furthermore, immunosuppression following testosterone implantation was negatively correlated with total and free testosterone but did not appear to be related to either total or free corticosterone. These results demonstrate that the phenotypic impact of elevated testosterone is not confined to males in dark-eyed juncos, and that the impact in adults can be similar in males and females. We discuss these results in the context of potential endocrine-immune interactions and the evolution of sexual dimorphism.     

Birds bias offspring sex ratio in response to livestock grazing

Livestock grazing, which has a large influence on habitat structure, is associated with the widespread decline of various bird species across the world, yet there are few experimental studies that investigate how grazing pressure influences avian reproduction. We manipulated grazing pressure using a replicated field experiment, and found that the offspring sex ratio of a common upland passerine, the meadow pipit Anthus pratensis, varied significantly between grazing treatments. The proportion of sons was lowest in the ungrazed and intensively grazed treatments and highest in treatments grazed at low intensity (by sheep, or a mixture of sheep and cattle). This response was not related to maternal body condition. These results demonstrate the sensitivity of avian reproductive biology to variation in local conditions, and support growing evidence that too much grazing, or the complete removal of livestock from upland areas, is detrimental for common breeding birds.     

Behavioral responses of male lobsters to Ecdysones

Four ecdysones with molting hormone activity, β‐ecdysone, inokosterone, ponasterone A, and cyasterone were tested for their capacity to elicit behavioral responses, especially sexual responses in the male lobster (Homarus americanus). Of these ecdysones, only β‐ecdysone elicited a low key alerting response. However, no particular type of behavior, such as feeding, aggressive or sexual behavior could be observed. A role of β‐ecdysone as a crustacean sex pheromone is not supported by these experiments and the general validity of this notion is discussed.     

Behavioral and physiological responses of Diaeretiella rapae to semiochemicals

Diaeretiella rapae (M'Intosh) (Hymenoptera: Braconidae) parasitizes many aphid species, including cabbage aphids on cruciferous crops and Russian wheat aphids on cereal crops. We investigated the olfactory perception of D. rapae to semiochemicals that may be encountered in these two environments while searching for hosts or for mates. We conducted electroantennogram and flight-tunnel experiments on male and female D. rapae and found marked differences between sexes. Cruciferous volatiles elicited physiological and behavioral responses by females but not by males. Males and females responded similarly to (Z)-3-hexen-1-ol, a component of green-leaf volatiles, in both electroantennogram and flight-tunnel assays. Female wasps responded similarly regardless of prior oviposition experience or population origin. Likewise, mating history and aphid presence did not increase responsiveness toward these semiochemicals.     

Nestling sex ratio is associated with both male and female attractiveness in rock sparrows

According to theory, in species in which male variance in reproductive success exceeds that of the females, sons are more costly to produce; females mated with high quality males or those in better condition should produce more sons. In monogamous species, however, the variance in the reproductive success of the two sexes is often similar and mate choice is often mutual, making predictions regarding sex allocation more difficult. In the rock sparrow Petronia petronia, both males and females have a sexually selected yellow patch on the breast, whose size correlates with individual body condition. We investigated whether the brood sex ratio co‐varies with the size of the yellow patch of the father and the mother in a sample of 173 broods (818 chicks) over 8 breeding seasons. While the size of the yellow patch of the mother and the father did not predict per se a deviation from the expected 1:1 sex ratio, brood sex ratios were predicted by the interaction of male and female yellow patch size. This result is surprising, as the ornament is sexually selected by both males and females as an indicator of quality in both sexes and should therefore be inherited by all offspring irrespective of their sex. It indirectly suggests that other sex‐specific traits associated with patch size (e.g. polygyny in males and fecundity in females) may explain the sex allocation bias observed in rock sparrows. Thus, female individual quality alone, as expressed through the size of the yellow patch, was not associated with the biases in sex ratios reported in this study. Our results rather suggest that sex allocation occurs in response to male attractiveness in interaction with female attractiveness. In other words, females tend to preferentially allocate towards the sex of the parent with more developed ornament within the pair.     

Reconciling direct and indirect estimates of functional connectivity in a Mediterranean pond-breeding amphibian

Conservation Genetics - Understanding demographic dynamics and functional connectivity among demes is essential to prevent, identify and reverse amphibian population declines. Attempts to...     

Rare male advantage and sex ratio

Relative success of mutant white and wild-type CS Drosophila melanogaster males is frequency-dependent, if sex ratio is 1:1. If the number of females is constant, this success depends on the ratio between the mutant and wild-type males. The sex ratio changes strongly affect the male mating activity of both genotypes.Emphasis is placed on the general interest of the Ayala equation and the Wattiaux-Lichtenberger equation in frequency-dependence and sex ratio dependence analysis.     

Serial monogamy and sex ratio bias in Nazca boobies

Biased operational sex ratios (OSRs) can drive sexual selection on members of the over-represented sex via competition for mates, causing higher variance and skew in reproductive success (RS) among them if an individual's quality is a persistent characteristic. Alternatively, costs of reproduction may degrade breeding performance, creating the opportunity for members of the limiting sex to switch mates adaptively, effectively homogenizing variance and skew in RS among the sex in excess. We tested these two contrasting models in a male-biased population of the Nazca booby (Sula granti) with demonstrated costs of reproduction with data on total RS over a 14-year period. Variances and skews in RS were similar, and males changed from breeder to non-breeder more frequently than females. Under the persistent individual quality model, females should mate only with high quality males, and non-breeding males should seldom enter the breeding pool, yet 45% of non-breeding males (re)entered the breeding pool each year on average. Many Nazca booby females apparently exchange a depleted male for a new mate from the pool of current non-breeder males. Our evidence linking serial monogamy to costs of reproduction is novel and suggests selection on female mating preferences based on an interaction between at least two life-history components (OSR and reproductive effort).     

Behavioral and reproductive responses of female opossums to volatile and nonvolatile components of male suprasternal gland secretion

Female gray short-tailed opossums (Monodelphis domestica) lack an estrous cycle and are induced into estrus by exposure to a pheromone in male scent marks. Behavioral and physiological responses of females to the volatile and nonvolatile components of scent marks were examined in two experiments. Young females (n = 9) were tested prior to and during their first estrus for behavioral responses to scent marks, collected on a 7-ml glass vial rubbed over the suprasternal gland of a mature male. The response to volatile components of the scent mark, recorded when marked and unmarked vials were covered with a perforated shield, was compared to the response to these vials when unshielded. Estrous females nuzzled the shields over marked vials (55.8 ± 8.5 nuzzles/10 min) more than the shielded clean vial (10.9 ± 2.4) (P < 0.05); a similar response was observed in anestrous females. Nuzzling of unshielded, scent-marked vials was higher (P < 0.05) during anestrus than in the same females when in estrus. The role of nonvolatile pheromones in reproductive activation was tested in adult females (n = 11) exposed for up to 14 days to a shielded, marked vial or to an unshielded, marked vial in a crossover design. All females exposed to unshielded vials expressed estrus, and 10 copulated. Only 2 females expressed estrus (significantly fewer, P < 0.05), when exposed to shielded marked vials, and neither copulated. These results demonstrate that females detect and respond behaviorally to both volatile and nonvolatile components of male suprasternal gland secretion, but the estrus-inducing pheromone in these secretions is nonvolatile.     

Behavioral and reproductive responses of female opossums to volatile and nonvolatile components of male suprasternal gland secretion

Female gray short-tailed opossums (Monodelphis domestica) lack an estrous cycle and are induced into estrus by exposure to a pheromone in male scent marks. Behavioral and physiological responses of females to the volatile and nonvolatile components of scent marks were examined in two experiments. Young females (n = 9) were tested prior to and during their first estrus for behavioral responses to scent marks, collected on a 7-ml glass vial rubbed over the suprasternal gland of a mature male. The response to volatile components of the scent mark, recorded when marked and unmarked vials were covered with a perforated shield, was compared to the response to these vials when unshielded. Estrous females nuzzled the shields over marked vials (55.8 ± 8.5 nuzzles/10 min) more than the shielded clean vial (10.9 ± 2.4) (P < 0.05); a similar response was observed in anestrous females. Nuzzling of unshielded, scent-marked vials was higher (P < 0.05) during anestrus than in the same females when in estrus. The role of nonvolatile pheromones in reproductive activation was tested in adult females (n = 11) exposed for up to 14 days to a shielded, marked vial or to an unshielded, marked vial in a crossover design. All females exposed to unshielded vials expressed estrus, and 10 copulated. Only 2 females expressed estrus (significantly fewer, P < 0.05), when exposed to shielded marked vials, and neither copulated. These results demonstrate that females detect and respond behaviorally to both volatile and nonvolatile components of male suprasternal gland secretion, but the estrus-inducing pheromone in these secretions is nonvolatile.     

Behavioral responses of male elk to hunting risk

Prey respond to predation risk with a range of behavioral tactics that can vary based on space use and hunting mode of the predator. Unlike other predators, human hunters are often more spatially and temporally restricted, which creates a period of short-duration, high-intensity predation risk for prey. Consequently, identifying the roles different hunting modes (i.e., archery and rifle), hunts for targeted and non-targeted species, and landscape features play in altering spatial and temporal responses of prey to predation risk by humans is important for effective management of harvested populations. From 2009 to 2016, we used a large-scale experiment including 50 animal-years of location data from 38 unique male elk (Cervus canadensis) to quantify changes in movement and resource selection in response to hunters during 3 separate 5-day controlled hunts for antlered males (elk archery, deer [Odocoileus spp.] rifle, and elk rifle) at the Starkey Experimental Forest and Range in northeast Oregon, USA. We evaluated competing hypotheses regarding elk responses to varying levels of prey risk posed by the different hunt types. We predicted that the strength of elk behavioral responses would increase with perceived hunter lethality (i.e., weak response to elk archery but similar response to elk and deer rifle hunts) and that prey response would be closely associated with hunter activity within the diel cycle (greater during diurnal than nocturnal hours) and across hunting seasons. Elk responses were strongest during diurnal hours when hunters were active on the landscape and were generally more pronounced during both rifle hunts than during the archery hunt (supporting our perceived lethality hypothesis). Male elk avoided open roads across all periods except during nocturnal hours of the breeding season and alternated between avoidance of areas with high canopy cover during nocturnal hours and selection during diurnal hours. In combination these patterns led to distinct distributional changes of male elk from pre-hunt to hunt periods. Patterns of male elk selection highlight the importance of managing for heterogeneous landscapes to meet a variety of habitat, harvest, hunter satisfaction, and escapement objectives.     

Behavioral responses of male lobsters to ecdysone metabolites

A molting hormone metabolite of crustecdysone 4,4‐dimethylbutyrolactone, 4, and six structurally related compounds were tested for their capacity to elicit behavioral responses, especially sexual responses, in the male lobster (Homarus americanus). Of these compounds, 6, 7, 8, and especially 9 provoked alert responses. Moreover, compounds 7 and 9 startled the lobsters, which responded with defensive and perhaps aggressive postures. No feeding or sexual behavior was observed. These results do not support the hypothesis that metabolites of molting hormones act as sex pheromones in the lobster. A comparison of chemical structure with behavioral response between the most active compound 9 and the inactive compound 10 is made.     

Behavioral and hormonal responses of male zebra finches to antiandrogens

After it was shown that the sexual behavioral patterns of male zebra finches are dependent on testosterone, the effects of treatment with two antiandrogens were investigated. The antiandrogens cyproterone (Cy) and cyproterone acetate (CyA) were used in this study. The results show that injections of CyA depress the sexual activity of the birds as measured by the amount of courtship song. The undirected song, too, is negatively influenced by a higher dosage of CyA. With the same dosage of Cy neither of these effects is observed. Radioimmunoassay for plasma testosterone showed that birds treated with CyA had lower, and birds treated with Cy had higher, testosterone levels in comparison with control animals. CyA is described as an antiandrogen with gestagenic side effects while Cy acts as a pure antiandrogen without side effects. Presumably the gestagenic side effects of CyA stop the production of testosterone by negative feedback mechanisms. This negative feedback combined with the antiandrogenic activity seems to account for the effects of CyA on behavior. Cy has no gestagenic side effect but is antiandrogenic with respect to blocking of androgen receptors. The organism tries to compensate for this deficit by increasing the testosterone production. The antiandrogenic activity of Cy probably is neutralized by this stimulated testosterone production.     

Evaluating the reproductive cost of migration for females in a partially migrating pond-breeding amphibian

Populations of animals with resident and migratory individuals provide an ideal system for addressing questions concerning the evolution of migration. Partially migratory populations may persist because residents and migrants have equal fitness or because migration is based on conditional asymmetries. Studies measuring the costs and benefits of migration provide empirical data to test hypotheses concerning the maintenance of partial migration within a population. In this study, we measured the reproductive differences between resident and migrant females in a pond-breeding amphibian, the red-spotted newt Notophthalmus viridescens . We used large field enclosures to repeatedly sample egg laying over the prolonged breeding season of this species. Resident females did not lay a greater number of eggs or begin laying eggs earlier, despite beginning the breeding season earlier and having a higher mass than migrant newts. The only difference in reproduction we detected was that the eggs of resident females hatched into larger larvae compared with the larvae of migrant females. We discuss this result in the context of other potential trade-offs between residency and migration. This study illustrates the phenology of egg laying of N. viridescens and our results contribute to understanding the population dynamics of partially migratory species.