Extraordinary flux in sex ratio

The ratio of males to females in a species is often considered to be relatively constant, at least over ecological time. Hamilton noted that the spread of "selfish" sex ratio-distorting elements could be rapid and produce a switch to highly biased population sex ratios. Selection against a highly skewed sex ratio should promote the spread of mutations that suppress the sex ratio distortion. We show that in the butterfly Hypolimnas bolina the suppression of sex biases occurs extremely fast, with a switch from a 100:1 population sex ratio to 1:1 occurring in fewer than 10 generations.     

性比对非繁殖期圈养白鹇行为的影响

[目的]为了探讨性比对个体行为的影响。[方法]2007年9~11月在广东象头山国家级自然保护区采用随机取样法和瞬时扫描取样法开展了3种性比圈养白鹇的行为学研究。[结果]不同性比的白鹇都具有明显的日节律:取食高峰出现在16:00~17:00,休息高峰在12:00~13:00。在时间分配上,同一性比的雄性与雌性间存在差异:性比为2∶2时,雄性与雌性在游走和休息上的差异极显著(P<0.01);性比为3∶1时,雄性与雌性在取食和游走的差异极显著(P<0.01)。不同性比的同性间仍存在差异∶雄性在性比为2∶2与3∶1时游走的差异极显著(P<0.01);雌性在性比为2∶2与3∶1时取食和游走的差异极显著(P<0.01),并在性比为3∶1与3∶0时取食和游走的差异极显著(P<0.01)。不同性比的白鹇个体之间亲疏关系不同,但总有2只雌性个体关系密切。[结论]性比对白鹇圈养白鹇的行为时间分配有影响,而且雌性个体更趋于集群活动,雄性则趋于单个活动。     

Sex ratio and local resource competition in a prosimian primate

Competition between female kin for local limiting resources may explain a male-biased secondary sex ratio in the prosimian Galago crassicaudatus. Data demonstrating the skewed sex ratio, a brief summary of field observations on the species, and a simple mathematical statement of the hypothesis are presented. Local resource competition may influence sex ratio in other mammals.     

影响布氏潜蝇茧蜂子代性比的因素

布氏潜蝇茧蜂可以寄生不同龄期的橘小实蝇幼虫,寄生蜂子代雌蜂率随寄主龄期的增加而升高,寄生4日龄寄主时,其子代雌蜂率为58.27%,而寄生1日龄寄主时,其子代雌蜂率仅为15.29%。在不同寄生蜂密度条件下,雌蜂比率随寄生蜂密度的增加不断下降,20只寄生蜂存在时,其子代雌蜂率只有24.32%,而供1只寄生蜂寄生时,其子代雌蜂率可达53.65%。寄生蜂在羽化后5 d产卵寄生时,其子代雌蜂率为31.97%,10 d时雌蜂率为44.39%,随着寄生蜂龄期的增加雌蜂率逐渐升高,10-30 d子代雌蜂率无显著差异。寄生蜂在35℃时产卵会影响其子代雌蜂比率,15℃条件下产卵与正常温度相比子代性比无显著差异。供给寄生蜂不同食物,不影响寄生蜂子代的雌性比率。     

Analysis of the Offspring Sex Ratio of Chicken by Using Molecular Sexing

The overall sex ratio of offspring （dead embryos and hatch chicks） from all the fertilized eggs of 140 hens collected for 30 days was studied using duplex PCR of certain fragments of sex chromosomes. Additional 894 dead embryos over a period of 21 days of incubation were also investigated to verify the sex ratio of the dead embryos. The sex of the early dead embryos was identified using this molecular sexing technique. The sex ratio of the hatch chicks and the total offspring of the hens investigated in this experiment did not differ from the expected sex ratio （i.e., 1：1）., However, the number of female dead embryos was significantly more than that of males. The data indicated that the different physiologic function of males and females contributed to female-biased mortality during incubation. It was also found by further analysis that the sex ratios of the offspring of some hens were significantly biased to female or male over the period investigated, which suggested that the sex ratio of offspring might be influenced by the maternal condition to some degrees.     

Haplodiploidy and the evolution of facultative sex ratios in a primitively eusocial bee

In eusocial Hymenoptera, the haplodiploid system of sex determination creates relatedness asymmetries such that workers are more closely related on average to their sisters than to their brothers. For such societies, kin-selection theory and sex-ratio theory predict that workers maximize their inclusive fitness by biasing the investment sex ratio toward females. To test the prediction of sex-ratio biasing, relatedness asymmetries were experimentally manipulated in colonies of the primitively eusocial bee Augochlorella striata (Halictidae: Hymenoptera) by removing or not removing foundress queens. Queenright colonies (relatedness asymmetry present) produced a more female-biased sex ratio than did queenless colonies (relatedness asymmetry absent). Worker reproduction and unmated replacement queens can be discounted as alternative explanations. Workers therefore facultatively adjusted their colony's sex ratio and, in the presence of a relatedness asymmetry, biased the investment sex ratio toward their more closely related sisters and away from their more distantly related brothers.     

二点委夜蛾的交配行为与产卵量

为了对二点委夜蛾性信息素田间应用的可能性提供理论依据,在温度（26±1）℃、相对湿度50%±10%、光周期14 h∶10 h（L∶D）条件下对二点委夜蛾的交配行为和能力进行了研究,并对性信息素应用以及二点委夜蛾暴发为害性及其成虫防控技术进行了综合分析。结果表明：成虫一般在羽化后1 d进行交配和产卵。雄蛾和雌蛾均可以多次交配,交配能力和产卵量均受性比影响。雌蛾交配能力与产卵量呈显著正相关,雌雄比为1∶5时单雌平均产卵量为501头;雄蛾交配能力则与雌蛾产卵量呈显著负相关,雌雄比为5∶1时单雌平均产卵量降低为227头。应用性诱剂诱杀二点委夜蛾雄蛾可以降低雌蛾的产卵量,但由于雌蛾产卵量大,因此仍需结合其他措施同时降低雌雄蛾数量才能达到更好的防治效果。     

橘小实蝇遗传性别品系性比与单雌有效卵量的关系

为进一步优化橘小实蝇遗传性别品系大量饲养技术,对其性比与有效卵量的关系进行了研究.结果表明:在一定种群密度下,当性比(♀∶♂)为1∶2、1∶1、2∶1、4∶1时,单雌有效卵量间没有显著差异;对性比(X)和单雄有效卵量(Y)间的关系进行拟合,得到方程Y=0.747X3-36.408X2+887.368X-102.805,由方程可知,在一定种群密度下,1.5∶1♀∶♂2∶1的性比最适宜橘小实蝇遗传性别品系的人工繁育.     

Sex ratio adaptations to local mate competition in a parasitic wasp

Females of the parasitic wasp Nasonia vitripennis adjust the sex ratio of their broods according to whether they are a first or second wasp to parasitize a host. The first wasp produces a strong daughter bias. The second wasp adjusts the prorportion of sons to the relative level of local mate competition, as predicted by a natural selection model. The results provide a quantitative test of sex ratio theory.     

绵山天幕毛虫求偶和交配行为研究(摘要)(英文)

[目的]研究绵山天幕毛虫求偶和交配行为,为发展利用性信息素防控绵山天幕毛虫提供理论依据。[方法]通过室内和野外观察,研究绵山天幕毛虫成虫求偶行为的发生过程、求偶周期、不同雌雄比及种群密度对绵山天幕毛虫交配率的影响。[结果]虫卵越冬次年4月下旬幼虫开始孵化,5月上旬为孵化盛期,5月中旬孵化结束全部进入幼虫期,幼虫期大约70d,共6～7龄。幼虫老熟后于7月上旬开始下树,7月中下旬为化蛹盛期,蛹期约20d。7月下旬开始羽化,羽化时间一般为11:00～18:00,9月中旬产卵结束,进入滞育越冬状态。室内饲养绵山天幕毛虫成虫最早在7月中旬出现,比自然羽化时间提前,可能是由于室内平均温度较野外高。室内饲养的绵山天幕毛虫雌雄比约为1∶1.8,比野外雌雄比例有所减少,可能是由于室内的环境条件所致。自然界中绵山天幕毛虫雌雄比为1∶1.2,实验室饲养的绵山天幕毛虫雌雄比则为1∶1.8。在自然条件下,雌虫求偶最早出现在18:00,从19:00以后雌虫求偶率明显上升,19:00～21:00达到高峰,以后求偶率逐渐下降。雌虫求偶行为主要发生在羽化后的第1和第2天,第1天的求偶率达90%,第2天求偶率明显下降。不同比例及种群密度对雌雄蛾交配行为影响较大,且种群密度过高不利于其繁殖;绵山天幕毛虫雌、雄蛾一生均只交配1次。[结论]利用性信息素防治绵山天幕毛虫具有较好的应用前景。     

遗传和温度因素对鱼类性别分化相关基因表达及性别比例的影响

鱼类的性别决定机制较为复杂,是遗传和环境共同作用的结果,具有很大的可塑性。随着分子生物技术的不断更新,对鱼类性别决定及分化相关基因的鉴定和研究有了新的进展,环境因子如温度、光照、p H、低氧、水压等均能影响大多数鱼类的性别决定和分化过程。本研究中,阐述了鱼类遗传型性别决定(GSD)和温度依赖型性别决定(TSD)方式,并对TSD与遗传型性别加温度影响(GSD+TE)性别决定机制下,性别决定相关基因在雌雄异型中的表达及结合温度诱导性逆转进行概述,分析了温度对鱼类性别比例的影响,并提出今后应加强对性别决定基因的鉴定、解析和基因功能研究,为科学制定鱼类繁殖计划提供指导。     

微尾鼩年龄分布与性比研究

[目的]探究微尾鼩的年龄分布与性比,为进行种群数量预测奠定基础。[方法]将捕获于四川南充市郊的929只微尾鼩(434♂,495♀)分为4个年龄组,分析了12个月的微尾鼩性比、年龄组成及其季节动态。[结果]12月至次年2月为低数量期,种群中以亚成体组(Ⅰ)为主;4～9月为高数量期,雌、雄性都以成体二组(Ⅲ)为主。除亚成体组(Ⅰ)雄性略多于雌性以外,捕获的雌性个体多于雄性(♂/♀为0.88),但经过卡方检验各组性比均符合1∶1的比例。在调查期间,各月的性比♂/♀值在0.64～2.00,9月捕获的雌性个体比雄性多46.67%,差异显著。[结论]微尾鼩越冬个体以亚成体组(Ⅰ)为主,各年龄组性比为1∶1。     

蜜蜂性比研究进展

蜜蜂性比是指蜂群中雌性蜜蜂与雄性蜜蜂的比例。本文对蜜蜂性比由谁操纵(蜂王还是工蜂)、影响蜜蜂性比的因素以及蜜蜂性比对蜂群生产力及生物学特性的影响进行了论述，并对蜜蜂性比研究提出了一些建议。     

Monitoring the AIDS epidemic in the United States: a network approach

Respondents in the 1988 General Social Survey (GSS) were asked to scan their acquaintance networks to identify all those who had been a victim of a homicide or had acquired immunodeficiency syndrome (AIDS). Estimates of the sex, race, age, and regional breakdowns for homicides in the last year and for people with AIDS were compared with official statistics. The GSS estimates for the distribution of homicide victims replicate the official statistics quite well. The GSS estimates for AIDS cases suggest that the data provided to the Centers for Disease Control may underestimate by a substantial margin the prevalence of AIDS in the white population of higher socioeconomic status, overstate the relative prevalence of the disease in the minority populations, underestimate the prevalence of the disease in the Midwest, and overstate it for the East.     

暗黑鳃金龟成虫产卵量的影响因素

[目的]明确暗黑鳃金龟成虫产卵量的影响因素,为人工饲养暗黑鳃金龟提供参考。[方法]采用不同食物、不同性比、不同饲养密度、不同土壤类型以及不同根际土等条件处理暗黑鳃金龟成虫,研究其对暗黑鳃金龟成虫产卵量的影响。[结果]喂食榆树叶成虫的产卵量最高,喂食槐树叶成虫的产卵量最低;不同性比条件下,雌虫的比例大产卵量高,雌雄比例为3∶1时产卵量最高,雌雄比例为1∶1时最早达到产卵高峰期;不同密度下,暗黑鳃金龟成虫单位面积产卵量随成虫数量增加而增大,但单雌产卵量随密度增大而降低;单箱饲养密度在200头左右最佳;黏土为最适宜成虫产卵的土壤环境;成虫在种植小麦的根际土中的产卵量最高。[结论]在暗黑鳃金龟的室内人工饲养中,暗黑鳃金龟成虫的产卵量受食物、性比、饲养密度、土壤等多种因素的影响。     

Average potassium concentration of the human body as a function of age

Potassium-40 measurements on 1590 males and females ranging in age from less than 1 year to 79 years show sex differences and age trends in the ratio of muscle mass to the mass of other body constituents. A difference first at approximately 12 years of age. While females show a continuous decrease in potassium concentration, males show a rapid increase between the ages of 14 and 16. During adult life both sexes show a persistent and parallel decrease, which may be related to physiologic aging.     

Environmental sex determination: interaction of temperature and genotype in a fish

Sex determination in an atherinid fish, the Atlantic silverside (Menidia menidia), is under the control of both genotype and temperature during a specific period of larval development. The sex ratios of the progeny of different females are variable and differ in their responsiveness to temperature. This demonstrates that sex ratio in fishes that normally have separate sexes can be influenced by the environment.     

江西省乐平市农村人口性别比例与受教育程度相关与回归分析

以江西省乐平市农民为调查对象,运用实证分析法对乐平市农村地区男女性别比例进行了调查研究,得出乐平市农村地区男女性别比例高于全国平均水平,且男女比例值与受教育程度有一定的关联,基于此,提出了大力发展农村教育等措施,以解决乐平市农村男女性别比例失衡的问题。     

控制甜瓜雄花分化基因的遗传分析及初步定位

利用甜瓜全雌系WI998(无雄花)与雌雄异花同株品系3-2-2(有雄花)杂交,F1代全部表现为雌雄异花同株(有雄花)。F2代群体分离比率有雄花:无雄花为3:1。F1代作父本与全雌系WI998(无雄花)回交,群体分离比率有雄花:无雄花为1:1;F1代作父本与雌雄异花同株品系3-2-2(有雄花)回交,群体全部表现为有雄花。结果表明,控制甜瓜雄花分化的基因为一对显性基因,命名为An。同时以F2代分离群体为试材,采用SSR分子标记初步构建了甜瓜的遗传图谱,定位了控制甜瓜雄花分化基因(An)。图谱由5个连锁群组成,包括18个SSR标记,1个形态学标记,覆盖基因组总长度442.7 cM,标记间平均距离为24.6 cM。初步将控制甜瓜雄花分化基因(An)定位在第2连锁群上,其两侧标记分别是MU4182-2和MU5028-1,与An的间距分别为42.8和26.0 cM。控制甜瓜雄花分化基因的发现进一步完善了甜瓜性别分化基因的表达机理。     

沙柳木蠹蛾性行为的生物学特性

沙柳木蠹蛾(Holcocerus arenicola staudinger)是为害沙柳(Salix psammophila)根部的一种钻蛀性害虫。通过对沙柳木蠹蛾羽化行为、性比和寿命的调查,对各日龄雌蛾求偶和交尾发生时间的统计分析,明确了沙柳木蠹蛾性行为的动态节律。结果表明:沙柳木蠹蛾在19:00～21:00羽化最为集中;雌雄性比平均为0.66∶1;成虫平均寿命4.8±2.2d,其中雌蛾的寿命稍高于雄蛾。雌蛾在进入暗期1～2h内求偶行为明显,最大求偶百分率出现在羽化后的第二晚。1日龄成虫的交配高峰在暗周期的前2h,而2～4日龄成虫的交配高峰是在暗期的1h内;交配持续的平均时间为38.41±11.42min。随着蛾龄的增大,雌虫的求偶和交配行为发生的时间提前。沙柳木蠹蛾的性活动高峰出现在羽化后连续3个暗周期的前半段,可作为利用性信息素防治沙柳木蠹蛾最佳时段的参考依据。