Length of index and ring fingers differentially influence sexual attractiveness of men’s and women’s hands

Humans show intra- and intersexual variation in second (2D) relative to fourth (4D) finger length, men having smaller 2D:4D ratio, possibly because of differential exposure to sex hormones during fetal life. The relations between 2D:4D and phenotypic traits including fitness components reported by several studies may originate from the organizational effects that sex hormones have on diverse organs and their concomitant effect on 2D:4D. Evolutionary theory posits that sexual preferences are adaptations whereby choosy individuals obtain direct or genetic indirect benefits by choosing a particular mate. Since sex hormones influence both fitness and 2D:4D, hand sexual attractiveness should depend on 2D:4D, a hypothesis tested only in one correlational study so far. We first presented hand computer images to undergraduates and found that opposite-sex hands with long 2D and 4D were considered more sexually attractive. When we experimentally manipulated hand images by increasing or decreasing 2D and/or 4D length, women preferred opposite-sex hands that had been masculinized by elongating 4D, whereas men avoided masculinized opposite-sex right hands with shortened 2D. Hence, consensus exists about which hands are attractive among different opposite-sex judges. Finger length may signal desirable sex hormone-dependent traits or genetic quality of potential mates. Psychological mechanisms mediating hand attractiveness judgments may thus reflect adaptations functioning to provide direct or indirect benefits to choosy individuals. Because the genetic mechanisms that link digit development to sex hormones may be mediated by Hox genes which are conserved in vertebrates, present results have broad implications for sexual selection studies also in nonhuman taxa.     

A predator’s preference for egg-carrying prey: a novel cost of parental care

Using a subsocial spitting spider (Scytodes pallida) as the prey and a spider-eating jumping spider (Portia labiata) as the predator, the cost of parental care is investigated. Our findings suggest that being singled out as preferred prey by P. labiata is, for egg-carrying females of S. pallida, an important cost of parental care. In survival tests, during which P. labiata was given access to egg-carrying and eggless S. pallida females, egg-carrying females were preyed on more often than eggless females. In preference tests, motionless lures instead of living S. pallida were used. The lures were made by mounting dead egg-carrying and dead eggless S. pallida females in lifelike posture in webs. In these tests, P. labiata detected and identified, by vision alone, both kinds of prey (egg-carrying and eggless), and singled out egg-carrying females as preferred prey.Communicated by M.A. Elgar     

Mating behavior of female rock shrimp Rhynchocinetes typus (Decapoda: Caridea)—indication for convenience polyandry and cryptic female choice

While studies on a wide diversity of organisms have demonstrated the importance of female behavior during matings, in crustacean studies, a strong bias towards male mating behavior prevails. Reproductively mature rock shrimp (Rhynchocinetes typus) exist as several ontogenetic stages that differ in their morphological and physiological capacities. In natural populations, the majority of males are in early ontogenetic stages (termed typus), many are in intermediate stages (intermedius), and few are in the terminal molt stage (robustus). Dominant robustus males, which have already demonstrated their biological fitness by surviving to this stage, have previously been shown to have a higher potential than subordinate typus males to defend receptive females against other males, and fertilize the entire clutch of a female. While females should thus show a preference for robustus males, they nevertheless frequently receive sperm from typus males. These observations suggested that females might have mechanisms to discriminate against sperm from subordinate males. In laboratory experiments, we observed that females avoided being seized by typus males for longer time periods in the absence of robustus males than in their presence. Following seizure, females that were initially held by typus males, required more time to initiate spawning than those held by robustus males. Many typus males transferred spermatophores to females before these started to spawn while robustus males waited until females began to spawn before they transferred spermatophores. Females manipulated spermatophores received from typus males for long time periods (minutes), but not those they received from robustus males. By accepting sperm from subordinate typus males, females may avoid further harassment (convenience polyandry), but they subsequently may discriminate against these subordinate males by delaying spawning and removing their sperm. These observations suggest that female behavior influences the outcome of matings, favoring fertilization of eggs by sperm from dominant males. Convenience polyandry and cryptic female choice may be common in other crustaceans as well.Electronic Supplementary Material Supplementary material is available in the online version of this article at .Communicated by T. Czeschlik     

Males in the shade: habitat use and sexual segregation in the Galápagos sea lion (Zalophus californianus wollebaeki)

In many sexually dimorphic species adult sexes tend to segregate socially, spatially, or in habitat use. Several hypotheses have been formulated regarding underlying mechanisms. We investigated terrestrial habitat use and sexual segregation in a tropical otariid, the Galápagos sea lion (Zalophus californianus wollebaeki), where most of the hypotheses can be ruled out a priori. Factors relating to thermoregulation and costs of locomotion were of prime importance for habitat use. Habitats directly adjacent to the sea, with simple structured flat surfaces, shade, and tide pools were most frequented, but sexes and age classes differed in their usage patterns. Sexual segregation, both spatial and by habitat was pronounced in the reproductive period (RP), but remained high during the nonreproductive period (NRP). A GLM model of habitat use showed that in both seasons adult males frequented habitat types that adult females and other age classes used much less. Males were most abundant in suboptimal inland habitats, which offered only shade for cooling. Females with newborns differed in habitat use from females with older offspring and lone females. Spatial and habitat segregation are explained most parsimoniously as by-products of social processes, primarily intrasexual competition and female avoidance of male harassment, linked to the polygynous mating system.Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Multiple sexual advertisements honestly reflect health status in peacocks (Pavo cristatus)

The evolution of multiple sexual traits remains controversial and poorly understood in evolutionary biology. In many bird species, males exhibit complex courtships involving feather ornaments and behavioral display. Multiple traits may convey information on the genetic and phenotypic quality of males. In particular, fixed characters, such as feather ornaments (produced once a year during the annual molt in many bird species) might convey information about past male condition (at the time of trait development); whereas flexible traits such as behavioral displays should be sensitive to present condition. Here we show that both flexible behavioral displays and fixed feather ornaments of peacocks, used by females to choose a mate, honestly reflect health status. Correlative data showed that peacocks with high display rate (the number of behavioral displays per hour) and a large number of tail eyespots had low levels of circulating heterophils, suggesting better health status. Experimental activation of the immune system, through LPS injection, significantly reduced display rate compared to a control group. However, the sensitivity of a male display rate to the immune challenge was dependent on the number of tail eyespots: males with higher number of tail eyespots were better able to cope with the experimental immune challenge, and maintained their display rate at levels closer to the levels performed before the immune activation. These results are consistent with the idea that multiple signaling might enhance information reliability.     

Sequential male mate choice in a fish,the Pacific blue-eye<Emphasis Type="Italic"> Pseudomugil signifer</Emphasis>

Mate choice is not just a female preoccupation. Under some circumstances, males may also be choosy. However, studies of male mate choice have generally been confined to situations where males can make direct comparisons between potential partners. In contrast, sequential male mate choice has largely been overlooked despite its biologically importance, especially if current investment in mate attraction diminishes a males future mating opportunities. Using the Pacific blue-eye fish Pseudomugil signifer, we show that males are capable of exercising sequential mate choice. When presented sequentially with large and small females, males spent more effort courting the former. However, males did not appear to modify the time spent courting a given female based on the size of the female encountered previously. We suggest that greater attention to the sequential choice problem in males may help illuminate similarities and differences between the sexes when it comes to mating decisions.Communicated by T. Czeschlik     

Optimal divorce and re-mating strategies for monogamous female birds: a simulation model

Although the extensive variation in divorce rates among monogamous bird species has stimulated several theoretical accounts, the mechanisms underlying divorce strategies remain poorly understood. Here, we use an individual-based simulation model to investigate the adaptiveness of mechanisms of mate choice in the context of remating. Our model compares the fitness of females that choose a mate during each breeding season using one of two different decision rules; best-of-n females sample n potential partners and then select the male with the highest quality, whereas better option females choose a mate whose quality is maximal among the non-mated individuals they sampled the season before. It is assumed in the model that best-of-n females have no a priori information about the quality of potential partners and systematically decide to divorce at the beginning of each breeding season before searching for a new mate. Conversely, better option females use the information they gained the season before, and may retain their previous partner if they have no opportunity to mate with an individual of better quality. Results from simulations indicate that the best-of-n decision rule should be favoured when there is a large variation in male quality and low costs of mate sampling. On the other hand, the probability that the better option rule may invade the population is predicted to increase with male survival rate. However, changes in male mortality had no marked influence on the expected proportion of divorcing pairs, contrary to previous theoretical expectations.Communicated by H. Kokko     

抽压混合式通风除尘系统布置方式的选择和技术参数的确定

根据我国双鸭山、徐州、大同等矿区通风除尘技术发展实践经验和系统的理论研究,对目前国内外煤矿常用的“长抽长压”、“长抽短压”、“长压短抽”、“单机前抽后压”、“独立式负压除尘”系统的布置方式、适用条件、技术特征、安全效益及优缺点进行综合评价分析,提出优化系统设计必须遵循多指标综合分析的选型为依据的原则,同时重点阐述了直接影响系统通风除尘效果的“工作面风量”、“除尘器处理风量”,巷道不同阶段“风速”等重要参数的确定方法和理论计算公式。对煤矿安全生产和通风除尘设计具有普遍意义。     

区域特性分析在广东烟气脱硫工艺优选中的应用

电厂优选烟气脱硫工艺时必须进行切合实际的区域特性分析。石灰石—石膏湿法烟气脱硫工艺成熟、稳定、高效，且具有适应广东区域特点的诸多优势，故存在着广阔的发展前景。     

凤凰城旅游景区转让后的效应评价

在我国经济市场化改革的大背景下，转让景区经营权、实行企业化运作成为一些风景名胜区经营管理改革过程中的一种制度创新模式。地处西部大开发战略图中的湘西凤凰县由于在旅游开发中受到了资金缺口和管理瓶颈的双重制约，于2001年底将其辖域内的八大景区（点）的50年经营权转让给了湖南黄龙洞投资股份有限公司。景区经营权转让是一个十分复杂而敏感的话题。本文避开关于景区经营权转让的各种是非争论，基于对旅游地社区各利益主体以及旅游者的实地调查和访谈记录分析，对凤凰景区企业化运作三年来的绩效与影响作了较为客观的评估，并就如何完善景区企业化运作模式、规避经营管理风险和负面影响等提出了相关理论思考和政策建议。