Social control of sex reversal in a coral-reef fish

Males of Labroides dimidiatus control the process of sex reversal within social groups. Each group consists of a male with a harem of females, among which larger individuals dominate smaller ones. The male in each harem suppresses the tendency of the females to change sex by actively dominating them. Death of the male releases this suppression and the dominant female of the harem changes sex immediately. Possible genetic advantages of the system are considered.     

Sex chromosome-linked species recognition and evolution of reproductive isolation in flycatchers

Interbreeding between species (hybridization) typically produces unfit offspring. Reduced hybridization should therefore be favored by natural selection. However, this is difficult to accomplish because hybridization also sets the stage for genetic recombination to dissociate species-specific traits from the preferences for them. Here we show that this association is maintained by physical linkage (on the same chromosome) in two hybridizing Ficedula flycatchers. By analyzing the mating patterns of female hybrids and cross-fostered offspring, we demonstrate that species recognition is inherited on the Z chromosome, which is also the known location of species-specific male plumage traits and genes causing low hybrid fitness. Limited recombination on the Z chromosome maintains associations of Z-linked genes despite hybridization, suggesting that the sex chromosomes may be a hotspot for adaptive speciation.     

鹅伴性羽色性状的遗传分析

【目的】 豁眼鹅是我国著名的白鹅品种,其1日龄雏鹅往往呈现黄色或淡黄色。然而,笔者在进行豁眼鹅纯系继代选育过程中,发现自由交配群体的后代中有20%雏鹅个体绒羽呈现浅褐色,且公母比例差别明显（公母比例接近1﹕3）,推测豁眼鹅群体白羽性状存在伴性遗传可能。以雏鹅期浅褐色公鹅和黄色母鹅为亲本,利用杂交试验,检验雏鹅绒羽表型的情况是否符合孟德尔遗传规律,从而揭示鹅羽色性状的遗传方式。为此开展鹅的羽色性状遗传规律及机制研究,以期对鹅新品种或品系的培育以及鹅羽色自别雌雄配套系生产提供指导。【方法】 选用40只豁眼鹅公鹅和200只豁眼鹅母鹅为亲本,组建随机交配群产生豁眼鹅纯系G₁代,观察G₁代中1日龄雏鹅中黄色绒羽和浅褐色绒羽表型的表现和分离比例;4只浅褐色豁眼鹅公鹅和20只黄色豁眼鹅母鹅为亲本,杂交产生F₁代,观察其1日龄雏鹅中黄色绒羽和浅褐色绒羽表型的表现和分离比例。【结果】 ①在豁眼鹅随机交配G₁代中,浅褐色绒羽表型个体的比例为19.5%。其中,公母雏之间浅褐色个体占比差别比较大,公雏中浅褐色的比例在10%左右,而母雏有30%左右的个体呈现浅褐色。根据Hardy-Weinberg定律,绒羽颜色性状等位基因频率计算如下,母雏中浅褐色个体的比例就是豁眼鹅群体中绒羽浅褐色等位基因的频率,本试验中29.8%的母雏个体是呈现浅褐色,所以该等位基因的频率约为0.3。同时,公雏中浅褐色个体比例的开方也能计算出豁眼鹅群体中浅褐色等位基因的频率,本例中,10%的公雏是浅褐色,所以该等位基因的频率约为0.3左右,同母雏计算所得基因频率比较接近。相应的,绒羽黄色等位基因频率则为0.7左右。②杂交F₁中,黄羽81只,占50%;浅褐色79只,占50%。且黄羽全为公雏,浅褐色羽全是母雏。结果表明,浅褐色性状呈伴性遗传;已研究证实,银色羽（S*S）和不完全白化（S*AL）是位于Z染色体上的一对等位基因控制,不完全白化基因AL对银色羽基因S为隐性。因此,根据杂交试验结果,可以初步判断浅褐色和黄色是由一个基因座的复等位基因所决定的结果,且浅褐色对于黄色性状呈隐性遗传。【结论】 本试验通过羽色性状选配杂交和随机交配试验,分析了豁眼鹅1日龄雏鹅绒羽颜色表型的分离情况,结果表明：（1）浅褐色绒羽性状相对黄色绒羽性状为隐性遗传;（2）豁眼鹅雏鹅绒羽浅褐色/黄色性状呈伴性遗传;（3）豁眼鹅雏鹅绒羽颜色性状主要为Z染色体银色羽基因座控制,控制该基因座的等位基因存在变异位点与相应表型关联。     

Male fertility and sex ratio at birth in red deer

Efforts to test sex ratio theory have focused mostly on females. However, when males possess traits that could enhance the reproductive success of sons, males would also benefit from the manipulation of the offspring sex ratio. We tested the prediction that more-fertile red deer males produce more sons. Our findings reveal that male fertility is positively related to the proportion of male offspring. We also show that there is a positive correlation between the percentage of morphologically normal spermatozoa (a main determinant of male fertility) and the proportion of male offspring. Thus, males may contribute significantly to biases in sex ratio at birth among mammals, creating the potential for conflicts of interest between males and females.     

中国梨木虱冬型成虫性信息素成分的提取和GC-MS鉴定

通过鉴定中国梨木虱性信息素的成分,为进一步开发其性引诱剂提供基础资料.本试验利用正己烷分别提取梨木虱冬型雌、雄成虫体表浸提物,用Y型嗅觉仪测试了浸提物对中国梨木虱冬型雌和雄成虫行为反应的影响,并运用气相色谱-质谱联用仪对浸提物进行了分析和鉴定.雌虫浸提物对雄性梨木虱有较强的引诱作用,雄虫浸提物对雄木虱,雌、雄浸提物对雌木虱均无引诱作用,说明雌虫浸提物中含有雌木虱释放的性信息素.气相色谱-质谱联用仪(GC-MS)分析结果表明,雌虫浸提物中13-甲基二十七烷和2-甲基二十七烷的含量多于雄虫浸提物中的含量.在保留时间为23.136 min时,雌虫浸提物出现色谱峰,而雄虫浸提物没有出峰.这3种化合物可能是中国梨木虱冬型雌成虫的性信息素成分.     

普通大蓟马子代性比对同种成虫气味的响应

为了探究同种成虫的气味对普通大蓟马(Megalurothrips usitatus)交配期间性比调节的影响,设置对照（无气味）、已交配雌虫、未交配雌虫和已交配雄虫等4种气味源,分别处理单对刚羽化成虫24 h,然后用幼嫩豇豆(Vigna unguiculata)豆荚单头饲养被测雌虫,观测每日所产子代的性别和数量,计算子代性比。结果表明:已交配雌虫气味处理的子代雌虫数（22.80头）最少,跟其他处理差异显著。同对照的子代性比（0.31）相比,已交配雌虫和未交配雌虫的气味分别导致子代性比显著提高和降低,子代性比分别为0.48和0.22,而已交配雄虫气味对子代性比无显著影响。4个处理中,仅已交配雌虫气味处理的雌虫在产卵最后1天的日性比达到1.00,即雌虫体内的精子已消耗殆尽。成虫气味源对雌虫产卵天数没有明显影响。实验结果说明,普通大蓟马在交配期间能依靠嗅觉判别周边雌虫的交配状况,然后通过调控雌虫的获精数量,实现对子代性比的自调节。     

Sex Discrimination in Gerris remigis: Role of a Surface Wave Signal

Even when blinded with masks, adult male water striders (Gerris remigis) accurately ascertain the sex of other adult water striders in the laboratory. Freely moving females that were artificially made to play back computer-generated male surface wave and body-contact signals of about 90 waves per second were treated as males by the masked males and as females when no such playbacks were made. Thus, the males can use presence or absence of the male signal as the sole means for sex discrimination.     

Sexual selection in males and females

Research on sexual selection shows that the evolution of secondary sexual characters in males and the distribution of sex differences are more complex than was initially suggested but does not undermine our understanding of the evolutionary mechanisms involved. However, the operation of sexual selection in females has still received relatively little attention. Recent studies show that both intrasexual competition between females and male choice of mating partners are common, leading to strong sexual selection in females and, in extreme cases, to reversals in the usual pattern of sex differences in behavior and morphology.     

四川白鹅活体拔毛产毛绒量测定

从四川白鹅种群中抽取试验鹅106只，分别进行“成年公鹅常年拔毛”、“种鹅体产期拔毛”、“种鹅育成期投毛”及“肉鸽一次性拔毛”四个试验．除“成年公鹅常年拔毛”试验不设对用外，其余备试验均设对照。试验结果表明成年公鹅一年可拔毛8次，平均每只一年获得毛绒736．7克．种鹅休产期拔毛二次，平均每只获毛纺157．2克，休产期拔毛对其体重和产蛋性能并无不良影响。种鹅育成期拔毛二次，平均每只获得毛绒111．3克，对有成期生长发育未见不良影响。肉鹅一次性拔毛虽然每只可获得毛绒50．9克，但拔毛后要饲养25天以上方好出售，结果毛绒收入不延长饲养期支出，因此没有推广价值。     

棉大卷叶野螟雌虫性信息素对雄虫的诱集作用

为生物防治棉大卷叶野螟提供科学依据,研究棉大卷叶螟雌虫性信息素对雄虫的诱集作用,在野外和室内用棉大卷叶野螟雌虫及其性信息素提取物对雄虫进行诱集试验.研究发现:1～7日龄雌成虫及相应日龄雌成虫性信息素提取物随着日龄的增高,对雄蛾的引诱力逐渐降低;随着距离的加大,其诱集作用亦逐渐下降;1～7日龄雌成虫性信息素提取物对雄成虫...     

Sex attractant of sugar beet wireworm: identification and biological activity

The sex attractant produced by adult females of the sugar beet wire-worm, Limonius californicus (Mannerheim) has been isolated and identified as valeric acid. In the laboratory, male wireworm beetles are repelled by the pure attractant but are drawn with intense sexual excitement to its dilute solutions; in the field, male beetles are lured from a distance of 12 meters. The pheromone occurs in unusually large amounts in the female's body.     

Androgens prevent normally occurring cell death in a sexually dimorphic spinal nucleus

The spinal nucleus of the bulbocavernosus (SNB) contains many more motoneurons in adult male rats than in females. Androgens establish this sex difference during a critical perinatal period, which coincides with normally occurring cell death in the SNB region. Sex differences in SNB motoneuron number arise primarily because motoneuron loss is greater in females than in males during the early postnatal period. Perinatal androgen treatment in females attenuates cell death in the SNB region, reducing motoneuron loss to levels typical of males. The results suggest that steroid hormones determine sex differences in neuron number by regulating normally occurring cell death and that the timing of this cell death may therefore define critical periods for steroid effects on neuron number.     

Sexual role reversal in mate-finding strategies of the cabbage looper moth

The mate-finding behavior of the cabbage looper moth Trichoplusia ni (Lepidoptera: Noctuidae) includes both female- and male-produced sex pheromones used in distinct mate-finding strategies. Both sexes release multicomponent pheromones attractive to the opposite sex. Male pheromone is comprised of d-linalool, m-cresol, and p-cresol released from abdominal hair pencils. Males exposed to host plant odor or to the female sex pheromone (Z)-7-dodecen-1-ol acetate are more attractive to females, suggesting stimulation of male pheromone release.     

Maternally Inherited Sex Ratio in the Parasitoid Wasp Nasonia vitripennis

Facultative control of the sex ratio has been reported in the wasp Nasonia vitripennis. In a newly wild-eaught strain, females produced few or no male offspring and did not show the usual alterations of sex ratio in response to external conditions. The aberrant trait is inherited through females.     

天府肉鹅新品系绒羽特性的研究

本试验采用天府肉鹅父系、母系为材料，测定了9-17周龄绒羽的生长发育及理化特性。结果表明，父系的产线性能优于母系．17周龄时，父系的绒重、毛绒重分别比母系高71．4％和35．8％，含水率、含脂率明显低于母系。第一次活体羽的适宜时间为13或14周龄。本文还就羽绒生长性状间的相关性进行了分析。     

Dynamic paternity allocation as a function of male plumage color in barn swallows

Paternity in male animals can be influenced by their phenotypic signals of quality. Accordingly, the behavior underlying patterns of paternity should be flexible as signals of quality change. To evaluate the dynamics of paternity allocation, we analyzed paternity before and after manipulating plumage coloration, a known signal of quality, in male barn swallows Hirundo rustica. We found that, in successive breeding bouts, only males whose plumage color was experimentally enhanced received greater paternity from their social mates, demonstrating evidence for flexible and dynamic paternity allocation and the importance for males of maintaining signals of quality well after pair bond formation.     

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。     

Physiological sex predicts hybrid sterility regardless of genotype

Reproductive isolation between biological species is characterized by Haldane's rule, which states that the heterogametic sex (XY or ZW) suffers the most dysfunctional effects of hybridization. It has been hypothesized that, in addition to X-linked recessive genes, Haldane's rule also reflects the faster evolution of genes related to male reproduction (faster-male evolution). We used sex-reversed hybrid Xenopus to test faster-male evolution by examining the fertility of sex-reversed individuals with the genotype of the inverse phenotypic sex. Hybrid males are sterile and hybrid females are fertile irrespective of their genotypic sex. Gene expression profiles match these adult phenotypes, and our results demonstrate that faster-male evolution is the most likely mechanism producing hybrid male sterility.     

Progress in studies of sex determination mechanisms and sex control techniques in Cynoglossus semilaevis (half-smooth tongue sole)

The Cynoglossus semilaevis (half-smooth tongue sole) is a marine flatfish of great commercial value for fisheries and aquaculture in China. It has a female heterogametic sex determination system (ZW/ZZ) and environmental factors can induce sex-reversal of females to phenotypic males, suggesting that it is a promising model for the study of sex determination mechanisms. Additionally, females grow much faster than males and it is feasible to improve the aquaculture production through sex control techniques. This paper reviews the progress in research on sex determination mechanisms research in our laboratory. We have completed whole-genome sequencing and revealed the genome organization and sex chromosome evolution of C. semilaevis. A putative male determining gene dmrt1 was identified and DNA methylation was verified as having a crucial role in the sex reversal process. Genetic maps and sex-specific biomarkers have been used in a marker-assisted selection breeding program and for differentiation of the fish sex. Development and improvement of sex control technologies, including artificial gynogenesis and production of breeding fry with high proportion of females, is also reviewed. These research advances have provided insight into the regulation of sex determination and enabled efficient sex management in artificial culturing of C. semilaevis.     

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.