State‐dependent cooperation in burying beetles: parents adjust their contribution towards care based on both their own and their partner's size

Handicapping experiments on species with biparental care show that a focal parent increases its contribution when its partner is handicapped. Such results are interpreted as evidence for negotiation, whereby each parent adjusts its amount of care to that of its partner. However, it is currently unclear whether the focal parent responds to a change in its handicapped partner's behaviour or state. To address this gap, we conducted an experiment on the burying beetle Nicrophorus vespilloides where we first generated different‐sized males and females by varying the duration of larval development. We then used a 2 × 2 factorial design in which a small or large male was paired with a small or large female. Small females provided less direct care (food provisioning and interactions with larvae) than large females, and both males and females provided less direct care when paired with a small partner. Thus, the focal parent adjusted its contribution towards care based on both its own state and that of its partner. There was also evidence for negotiation between the two parents as the focal parent adjusted its contribution based on the amount of care by its partner. However, there was no evidence that negotiation accounted for how the focal parent responded to its partner's size. Our results have important implications for our understanding of biparental cooperation as they show that each parent adjusts its contribution not only based on the amount of care provided by its partner but also based on its own state and its partner's state.     

Minimum Sample Size Ensuring Validity of Classical Confidence Intervals for Means of Skewed and Platykurtic Distributions

COCHRAN (1953) and BARTCH (1957) gave formulae for the magnitude of the sample size (n) ensuring the validity of the limiting normal distribution of the sample mean x(ⁿ) obtained from a non-normal distribution with marked asymmetry and kurtosis. These formulae have been checked empirically in this paper using (a) simulated data with given asymmetry and kurtosis and (b) real data gathered from a coronary heart disease study. We find that our results are in general agreement with Bartch's formula. However, in a number of cases, the asymptotic normal distribution is attained for smaller sample size than that required by Bartch's formula.     

No Evidence for Audience Effects in Reciprocal Cooperation of Norway Rats

Norway rats (Rattus norvegicus) cooperate according to indirect reciprocity, which implies the involvement of a reputation mechanism. Here, we test whether the rats employ such mechanism in repeated cooperative interactions. Focal subjects were first trained individually to pull food towards a social partner. During the experiment, the focal rats were confronted with two types of trained social partners: one always cooperated and the other one always defected, either in the presence or in the absence of an audience. Based on the hypotheses that the rats possess a reputation mechanism involving image scoring, we predicted them to be more helpful in the presence of an audience, independently of the partner's cooperative behaviour. If, in contrast, reputation involved a standing strategy, we predicted the rats to distinguish more between cooperators and defectors in the presence of an audience than in its absence. The rats helped cooperative partners more than defectors, but against both predictions the presence or absence of an audience did not influence their helping propensity. This indicates that either reputation is not included in the decision of rats to help an individual that has helped others, or that reputation is neither involving image scoring nor a standing strategy. Although the rats have been shown to modulate their decision to help a social partner based on its helpful behaviour towards others, they do not seem to adjust their behaviour strategically to the presence of an audience.     

Mutual ornamentation and the parental behaviour of male and female Collared Flycatchers Ficedula albicollis during incubation

One of the benefits of mate choice based on sexually selected traits is the greater investment of more ornamented individuals in parental care. The choosy individual can also adjust its parental investment to the sexual signals of its partner. Incubation is an important stage of avian reproduction, but the relationship between behaviour during incubation and mutual ornamentation is unclear. Studying a population of Collared Flycatchers Ficedula albicollis, we monitored the behaviour of both sexes during incubation in relation to their own and their partner's plumage traits, including plumage‐level reflectance attributes and white patch sizes. There was a marginally positive relationship between male feeding rate during incubation and female incubation rate. Female but not male behavioural traits were associated with the laying date of the first egg and clutch size. The behaviour of the two sexes jointly determined the relative hatching speed of clutches and the hatching success of eggs. Females with larger white wing patches spent less time incubating eggs and left the nestbox more frequently. Males with larger white wing patches fed females less frequently, whereas males with brighter white plumage areas visited the nestbox more regularly without feeding. Females tended to leave the nest less often when mated to males with larger wing patches, and females spent less time incubating when males had more UV chromatic plumage. The behaviour of both partners during incubation therefore predicted hatching patterns and was correlated with their own and sometimes with their partner's plumage ornamentation. These results call for further studies of mutual ornamentation and reproductive effort during incubation.     

Exogenous selection rather than cytonuclear incompatibilities shapes asymmetrical fitness of reciprocal Arabidopsis hybrids

Reciprocal crosses between species often display an asymmetry in the fitness of F₁ hybrids. This pattern, referred to as isolation asymmetry or Darwin's corollary to Haldane's rule, is a general feature of reproductive isolation in plants, yet factors determining its magnitude and direction remain unclear. We evaluated reciprocal species crosses between two naturally hybridizing diploid species of Arabidopsis to assess the degree of isolation asymmetry at different postmating life stages. We found that pollen from Arabidopsis arenosa will usually fertilize ovules from Arabidopsis lyrata; the reverse receptivity being less complete. Maternal A. lyrata parents set more F₁ hybrid seed, but germinate at lower frequency, reversing the asymmetry. As predicted by theory, A. lyrata (the maternal parent with lower seed viability in crosses) exhibited accelerated chloroplast evolution, indicating that cytonuclear incompatibilities may play a role in reproductive isolation. However, this direction of asymmetrical reproductive isolation is not replicated in natural suture zones, where delayed hybrid breakdown of fertility at later developmental stages, or later‐acting selection against A. arenosa maternal hybrids (unrelated to hybrid fertility, e.g., substrate adaptation) may be responsible for an excess of A. lyrata maternal hybrids. Exogenous selection rather than cytonuclear incompatibilities thus shapes the asymmetrical postmating isolation in nature.     

Encystment in the Hypotrichous Ciliate Paraurostyla weissei: Ultrastructure and Cytochemistry1

The cyst wall of Paraurostyla weissei consists of four morphologically distinct layers. It shows an ultrastructure and composition similar to that of the previously described kinetosome-resorbing cysts, and its cytoplasm displays characteristics of “urostylid-type” cysts. Therefore it is possible to consider it a “transition ciliate” between Stichotrichina and Sporadotrichina.     

How to reject Benatar's asymmetry argument

In this article I reconsider David Benatar's primary argument for anti‐natalism—the asymmetry argument—and outline a three‐step process for rejecting it. I begin in Part 2 by reconstructing the asymmetry argument into three main premises. I then turn in Parts 3–5 to explain how each of these premises is in fact false. Finally, I conclude in Part 6 by considering the relationship between the asymmetry argument and the quality of life argument in Benatar's overall case for anti‐natalism and argue that it is the latter argument that is actually doing the work. In this sense, the asymmetry argument is not only unsuccessful in generating Benatar's anti‐natalist conclusion, it is also unnecessary as well.     

Reciprocity and communication of partner quality

In a cooperative exchange, the size of a partner''s contribution is likely to depend both on the partner''s ability to supply help and on the partner''s need for help in return. Referring to such needs and abilities as aspects of partner quality, it follows that variation in the amount of help offered in a relationship could transmit information about partner quality. A plausible behaviour might then be to vary the investment in a partner according to available information about partner quality and to invest little in a partner who offers little in return. Thus, regulation of a relationship through communication of partner quality would tend to follow the principle of reciprocity. In an analysis of an iterated game where players have private information about their needs and abilities, I verify this possibility by describing an evolutionarily stable state space strategy, referred to as ''state-dependent reciprocity'', entailing communication of partner quality. Although the evolution of cooperation has been studied in great detail, there has been no previous analysis of communication of needs and abilities in a relationship. It may well be that such communication is of major importance for the evolution of cooperative behaviour in nature.     

Reevaluation of the ‘well-known’ Paraurostyla weissei complex,with notes on the ontogenesis of a new Paraurostyla species (Ciliophora,Hypotrichia)

Two hypotrichous ciliates, Paraurostyla wuhanensis nov. spec. from Wuhan (China) and a new North American population of the Paraurostyla weissei complex, were studied based on live observations and protargol impregnation. Paraurostyla wuhanensis nov. spec. differs from the congeners by the combined features of having six or seven frontal cirri, 2–4 frontoventral cirri, 5–7 ventral rows, and yellow-greenish cortical granules. Ontogenesis proceeds as in the type species, except that fewer frontoventral cirri are formed in the new species. The morphology of the new population of the Paraurostyla weissei complex corresponds well with other American populations. In the phylogenetic trees based on the 18S rRNA gene, Paraurostyla sequences nest in a large clade together with Apoamphisiella and Notohymena. Monophyly of Paraurostyla is rejected by the results of the approximately unbiased test analyses. Morphological, morphogenetic, and phylogenetic analyses show a close relationship between the North American populations of the Paraurostyla weissei complex and Apoamphisiella, indicating that the taxonomic position of the former needs to be reassigned. A new combination, viz. Apoamphisiella polymicronucleata (Merriman, 1937) comb. nov., a reevaluation of the Paraurostyla weissei complex, and emended diagnoses of Paraurostyla and Apoamphisiella, are provided.     

Ecophenotypic asymmetry in the middle Danian brachiopod Obliquorhynchia flustracea caused by adaptation to attachment on the coral Dendrophyllia candelabrum

The rhynchonellid brachiopod Obliquorhynchia flustracea from the middle Danian (Paleocene) cool‐water coral mounds of the Faxe Formation, Denmark, exhibits commissural asymmetry, a rare feature in articulate brachiopods. It has been much discussed whether the underlying reasons for this asymmetry were species specific caused by pedicle attachment in the limited space between the branches of the scleractinian Dendrophyllia candelabrum. The two species are always found together, and the brachiopod is essentially missing outside facies characterized by D. candelabrum. Based on morphological analyses and statistical tests, we suggest that ecophenotypic variation is the main reason for the variability in the external shell morphology and development of commissural asymmetry. Conditions such as sexual dimorphism and defects can be dismissed as a facilitating reason of phenotypic variation. This is a rare case where it is possible to directly link commissural asymmetry to mode of attachment on a specific host.     

MITOCHONDRIAL GENOTYPES HAVE NO DETECTABLE EFFECTS ON MERISTIC TRAITS IN CUTTHROAT TROUT HYBRID SWARMS

Efforts to detect effects of cytoplasmic genes are confounded by the problem of partitioning nuclear and cytoplasmic effects. In this study we test for effects of mtDNA haplotype on development in hybrid populations of cutthroat trout (Oncorhynchus clarki) with randomly associated nuclear and mtDNA genotypes. We have previously described several intraspecific hybrid swarms formed by interbreeding of westslope cutthroat trout (O. c. lewisi) and Yellowstone cutthroat trout (O. c. bouvieri). Genetic distance between these subspecies is high (Nei's D = 0.30; mtDNA P = 0.02), and diagnostic alleles at multiple nuclear loci and two distinct mtDNA haplotypes are present in the hybrids. Historical associations between alleles at nuclear loci and between cytotypes and nuclear alleles have largely decayed. We test for differences in meristic characters between fish with alternate mtDNA haplotypes. Counts and fluctuating bilateral asymmetry for these characters have been previously shown to be sensitive indicators of genetic differences that affect development. No differences were found between mtDNA types in meristic counts or fluctuating asymmetry. Therefore, the alternate mtDNA haplotypes had no detectable effect on development as measured by meristic counts in these hybrid populations. However, diagnostic alleles at one nuclear allozyme locus (CK-CI) were associated with several fin ray counts.     

Differences in offspring size predict the direction of isolation asymmetry between populations of a placental fish

Crosses between populations or species often display an asymmetry in the fitness of reciprocal F₁ hybrids. This pattern, referred to as isolation asymmetry or Darwin''s Corollary to Haldane''s Rule, has been observed in taxa from plants to vertebrates, yet we still know little about which factors determine its magnitude and direction. Here, we show that differences in offspring size predict the direction of isolation asymmetry observed in crosses between populations of a placental fish, Heterandria formosa. In crosses between populations with differences in offspring size, high rates of hybrid inviability occur only when the mother is from a population characterized by small offspring. Crosses between populations that display similarly sized offspring, whether large or small, do not result in high levels of hybrid inviability in either direction. We suggest this asymmetric pattern of reproductive isolation is due to a disruption of parent–offspring coadaptation that emerges from selection for differently sized offspring in different populations.     

Spermatophore expulsion in the carrion beetle Silpha perforata (Coleoptera: Silphidae)

Silphinae (Coleoptera: Silphidae) is an abundant decomposer that plays important roles in the ecosystem. However, there is little information about the life history of this taxon. We found sperm displacement behavior in carrion beetle Silpha perforata. Copulating males bit the female's antenna strongly and inserted the penis into the partner's genital organ more than once. We found a white substance on the tip of penis during copulation. We examined whether this white substance is a previous male's spermatophore, which was removed from the mating partner. When females were dissected just after mating, the same substance that often presents on the penis of mating males was found in the bursa copulatrix of females, although the bursa copulatrix of virgin females was empty. Male behavior during copulation with females of different mating history was also observed to confirm that the removal of spermatophores was observed only in copulation with females that have the spermatophores of previous males. Consequently, we estimated that S. perforata males removed spermatophores of previous males from mating partners. In addition, we dissected the males frozen during copulation, and inspected the penis morphology. This observation revealed that the apical part of the penis was usually hidden in the basal part of penis, but expanded and appeared during insertion. This apical part had many spines, which play an important role in sperm displacement and sexual conflict in some species. These results indicate that there is the sperm competition in S. perforata. This is the first report on sperm competition in Silphinae.     

海南霸王岭陆均松空间分布格局及其与微生境异质性的关系

应用地统计学及限制性排序分析方法,对海南霸王岭陆均松(Dacrydium pectinatum)幼苗、幼树、成树及其微生境因子的空间分布特征进行分析。结果表明:1)陆均松不同生活史阶段空间分布格局存在明显差异,幼苗阶段表现为聚集性分布,具有显著的空间自相关结构,聚集强度随年龄增长呈逐渐减弱趋势;2)RDA分析表明,陆均松空间分布格局与微生境因子的关系在不同生活史阶段存在差异,生境过滤的影响会随着生活史阶段的不同而有所差别;3)微生境变量对陆均松幼苗、幼树、成树空间变异的总解释量分别为78.4%、41.2%、33.6%,微生境因素对陆均松分布的限制作用主要集中在幼苗阶段;4)在大尺度条件下,PCNM变量与微生境变量具有较大的共同解释量(22.2%),存在典型的"诱导空间变差"现象,微生境变量空间变化引起响应变量即陆均松幼苗、幼树、成树的分布产生类似的空间结构。研究结果证实了微生境因子与不同生活史阶段陆均松分布的关联性,为深入理解陆均松种群维持机制、空间分布格局、更新动态与生境的关系提供科学依据。     

Smoking during pregnancy and offspring fat and lean mass in childhood

Objective: Maternal smoking during pregnancy has been shown to be associated with obesity in the offspring, but findings have been based mainly on BMI, which is derived from height and weight. This study examined the association between maternal and partner smoking during pregnancy and offspring total fat, truncal fat, and lean mass in childhood. Research Methods and Procedures: Analysis was based on 5689 white singletons born in 1991–1992 and enrolled in the Avon Longitudinal Study of Parents and Children, with maternal smoking data recorded for at least one trimester in pregnancy and their own body composition assessed by DXA at mean age 9.9 years. Results: Smoking at any time during pregnancy was associated with higher offspring BMI [0.18 (95% confidence interval, 0.12 to 0.25) standard deviation units] and total fat mass [0.17 (95% confidence interval, 0.12 to 0.23) standard deviation units], after adjustment for age, sex, height, and height squared for total fat mass. These associations were not attenuated by adjustment for the confounding factors that were measured. Maternal smoking was also associated with lean mass and, to a lesser extent, truncal fat mass. Associations with partner's smoking were in the same direction but weaker than those of the mother's for all outcomes. Discussion: Maternal smoking at any time during pregnancy is associated with higher offspring total fat mass at mean age 9.9 years. However, as the associations with partner smoking were only a little weaker than those with maternal smoking, confounding by social factors rather than a direct effect of maternal smoking is a possible explanation.     

Upside-down spiders build upside-down orb webs: web asymmetry,spider orientation and running speed in Cyclosa

Almost all spiders building vertical orb webs face downwards when sitting on the hubs of their webs, and their webs exhibit an up–down size asymmetry, with the lower part of the capture area being larger than the upper. However, spiders of the genus Cyclosa, which all build vertical orb webs, exhibit inter- and intraspecific variation in orientation. In particular, Cyclosa ginnaga and C. argenteoalba always face upwards, and C. octotuberculata always face downwards, whereas some C. confusa face upwards and others face downwards or even sideways. These spiders provide a unique opportunity to examine why most spiders face downwards and have asymmetrical webs. We found that upward-facing spiders had upside-down webs with larger upper parts, downward-facing spiders had normal webs with larger lower parts and sideways-facing spiders had more symmetrical webs. Downward-facing C. confusa spiders were larger than upward- and sideways-facing individuals. We also found that during prey attacks, downward-facing spiders ran significantly faster downwards than upwards, which was not the case in upward-facing spiders. These results suggest that the spider''s orientation at the hub and web asymmetry enhance its foraging efficiency by minimizing the time to reach prey trapped in the web.     

Duboscquella cachoni N. Sp., a Parasitic Dinoflagellate Lethal to Its Tintinnine Host Eutintinnus pectinis1

The parasitic dinoflagellate Duboscquella cachoni n. sp. is described from infestations of the tintinnine ciliate Eutintinnus pectinis collected from the Chesapeake Bay, a major North American estuary located on the east coast of the United States. Examination of parasite life history, morphology, and developmental processes reveals that D. cachoni differs from other members of the genus by the structure of the trophont, the pattern of sporogenesis, and spore morphology. Sporogenesis results in the production of either biflagellated macrospores, microspores with a single flagellum, or a cyst-like stage. The number of spores formed per infestation and their survival outside the host vary with spore type. Infested ciliates are apparently unable to reproduce, and infestations are always fatal to E. pectinis. Aspects of parasite biology and observations of a natural host-parasite assemblage suggest that D. cachoni may have a significant impact on its host's population dynamics.     

Sex‐biased dispersal,kin selection and the evolution of sexual conflict

There is growing interest in resolving the curious disconnect between the fields of kin selection and sexual selection. Rankin's (2011, J. Evol. Biol. 24 , 71–81) theoretical study of the impact of kin selection on the evolution of sexual conflict in viscous populations has been particularly valuable in stimulating empirical research in this area. An important goal of that study was to understand the impact of sex‐specific rates of dispersal upon the coevolution of male‐harm and female‐resistance behaviours. But the fitness functions derived in Rankin's study do not flow from his model's assumptions and, in particular, are not consistent with sex‐biased dispersal. Here, we develop new fitness functions that do logically flow from the model's assumptions, to determine the impact of sex‐specific patterns of dispersal on the evolution of sexual conflict. Although Rankin's study suggested that increasing male dispersal always promotes the evolution of male harm and that increasing female dispersal always inhibits the evolution of male harm, we find that the opposite can also be true, depending upon parameter values.     

Effects of two seminal fluid transcripts on post‐mating behaviour in the simultaneously hermaphroditic flatworm Macrostomum lignano

The seminal fluid proteins (SFPs) transferred to mating partners along with sperm often play crucial roles in mediating post‐mating sexual selection. One way in which sperm donors can maximize their own reproductive success is by modifying the partner's (sperm recipient's) post‐copulatory behaviour to prevent or delay re‐mating, thereby decreasing the likelihood or intensity of sperm competition. Here, we adopted a quantitative genetic approach combining gene expression and behavioural data to identify candidates that could mediate such a response in the simultaneously hermaphroditic flatworm Macrostomum lignano. We identified two putative SFPs—Mlig‐pro46 and Mlig‐pro63—linked to both mating frequency and ‘suck’ frequency, a distinctive behaviour, in which, upon ejaculate receipt, the worm places its pharynx over its female genital opening and apparently attempts to remove the received ejaculate. We, therefore, performed a manipulative experiment using RNA interference‐induced knockdown to ask how the loss of Mlig‐pro46 and Mlig‐pro63 expression, singly and in combination, affects mating frequency, partner suck propensity and sperm competitive ability. None of the knockdown treatments impacted strongly on the mating frequency or sperm competitive ability, but knockdown of Mlig‐pro63 resulted in a significantly decreased suck propensity of mating partners. This suggests that Mlig‐pro63 may normally act as a cue in the ejaculate to trigger recipient suck behaviour and—given that other proteins in the ejaculate have the opposite effect—could be one component of an ongoing arms race between donors and recipients over the control of ejaculate fate. However, the adaptive significance of Mlig‐pro46 and Mlig‐pro63 from a donor perspective remains enigmatic.     

诺如病毒感染宿主免疫应答机制及疫苗研究进展

诺如病毒是引起人类急性胃肠炎的重要食源性病原之一。由于体外复制系统和感染模型的缺乏,研究人员对其宿主保护性免疫的理解始终有限,导致控制病毒感染方面的研究也受到较大阻碍。近年来,随着病毒衣壳蛋白外源表达、替代病毒的使用、志愿者实验的开展,尤其是细胞培养模型的突破,使得体液免疫和细胞免疫的研究取得较大进展。因此,本文针对诺如病毒感染宿主的先天性免疫、体液免疫和细胞免疫应答机制等进行了综述,并对后续其在诺如病毒候选疫苗研制等领域的应用进行了展望。