蜡皮蜥的两性异形和繁殖输出

为研究蜡皮蜥(Leiolepis reevesii)两性异形和繁殖输出,于2002、2003年4月下旬从海南乐东一种群捕获423头蜡皮蜥。经检测得到繁殖雌体的最小体长为89．0mm,据此判定≥89．0mm的个体为性成熟。研究结果表明：①蜡皮蜥具有两性异形,雄性大于雌性且具有较大的头部。成体雄性头长和头宽随体长的增长速率大于雌性,幼体头长和头宽随体长的增长速率无显著的两性差异。以性别和年龄(成、幼体)为因子的双因子ANOVA比较两性头长和头宽与体长的回归剩余值发现,雄性头部大于雌性,幼体头部相对大于成体。②饲养于实验室的母体中有42头于2002、2003年5月22日～7月16日产出正常卵,这些繁殖雌体具有年产多窝卵的潜力。窝卵数和卵重的变异系数分别为0．18和0．13,前者变异度大于后者。窝卵数、窝卵重和卵重均与母体体长无关。卵重与相对生育力之间无显著的负相关性,表明蜡皮蜥缺乏卵数量与卵大小之间的权衡。相对窝卵重与母体体长呈显著的负相关,表明较小的母体具有相对较大的繁殖输出。因雌体繁殖会滞缓其生长,小母体具有相对较大的繁殖输出,至少部分地解释了雌性蜡皮蜥的成体为什么个体较小。     

Investigation on Sexual Reproductive Cycle in Torreya grandis

Before May the first, the ovular primordium of Torreya grandis has differentiated. From this early moment the primordium look like the parabolic form and it is surrounded by many pairs of scales, of which a pair of the inner scales are lying at the same level as the primordium of ovule. About May the first of the second year, the differentiation of the various tissues in the ovule has essentially completed. And the fertilization takes place from the end of August to the beginning of September. After overwintering, the proembryo developes into a young embryo in April of the third year, and at the last stage both the seed and the embryo become mature from September to November. In the Taxaceae, the embryogenesis is similar in Amentotaxus,Austrotaxus, Taxus, and Pseudotaxus; their proembryos form cell wall all at the stage of 16-free nuclei and simple polyembryony is common among them. In Torreya, however, the cell wall of proembryo appear at the stage of 4 or 8-free nuclei, and cleavage polyembryony is its feature. On the basis of our observation, the sexual reproductive cycle of Torreya grandis seems to have two important features, one of which is rather long (31 moths from ovular primordium to seed maturity; about 4 months from pollination to fertilization and 7-8 months for development of proembryo). The state of the long sexual cycle in Amentotaxus and Austrotaxus is different from each other; in the former development of young embryo lasts 10-11 months, and in the latter the interval between pollination and fertilization is 13.5 months. The second feature of the sexual cycle in Torreya grandis is over two winters: development of the sporogenous cells in the first, and the proembryo development in the second. From the point of view of phylogenesis, some primitive characters are present in the sexual cycle of Torreya grandis although a specialized feature of the embryogenesis occurs in some degree.     

饰纹姬蛙的两性异形及雌性繁殖能力

用采自云南省西双版纳傣族自治州勐腊县的53只(28♂♂,25♀♀)成体饰纹姬蛙(Microhyla fissipes),测量全部个体的体长、头长、头宽、体重等16项形态特征和雌体怀卵量数据,通过独立样本t检验和协方差检验该物种所有形态特征的两性差异,进而采用线性回归方法分析雌雄成体局部形态特征与体长的相关性,以及雌性成体怀卵量与局部形态特征的相关性。结果表明,饰纹姬蛙平均体长雌性为(25.08±0.40)mm,雄性为(24.78±0.31)mm,体长和体重在雌雄两性间差异不显著(P> 0.05),两性个体大小基本同形。该蛙的所有局部形态特征与体长均存在极显著正相关性(P <0.01);雌雄两性间只在头宽和前臂及手长这两个形态特征上存在显著差异(P <0.05),且随体长的增大其生长速率也存在显著差异。雌性成体的怀卵量与体长、体重、眼间距、前臂宽、胫宽和跗足长均存在显著正相关性(P <0.05),且与体重存在极显著正相关性(P <0.01)。分析认为,饰纹姬蛙成体两性异形主要表现在头宽和前臂及手长,与生存竞争中对食物的获取能力及雄性争夺交配权的成功率有关;而...     

Theoretical Reproductive Outcomes of the Sexual Conflict in Humans

Doklady Biological Sciences - This paper presents an updated mathematical model of the evolutionary dynamics of the sexual conflict (“battle of the sexes”) and its simulated...     

黄颡鱼的两性异形和雌性繁殖特征

测定了黄颡鱼成体的体长、头长、头宽、头高、吻长、眼径、眼间距、眼后头长、体高、尾柄高、背鳍基前距、背鳍基长、尾柄长、腹鳍基前距、背鳍脂鳍间距、腹鳍臀鳍间距、尾鳍长、体重、去内脏体重等形态指标以及雌体的怀卵数量。雌性成体的体长显著小于雄性成体。其它局部特征皆与体长呈正相关,回归剩余值的t—检验表明,雌性成体的眼径、头高、体高、腹鳍基前距、体重显著大于雄性成体,其它局部形态特征不存在显著的两性差异。黄颡鱼雌体通过个体大小的增加和腹部形态的改变增加腹腔容量,增加繁殖输出。     

黑斑侧褶蛙的两性异形和雌性繁殖特征

测定了黑斑侧褶蛙成体的体长、体重、头长、头宽、眼径、鼓膜径、前肢长、后肢长等形态指标以及雌体的怀卵数量。黑斑侧褶蛙雌体的体长和体重显著大于雄体。其它局部形态特征指标与体长呈正相关,协方差分析表明,雄体的鼓膜径大于雌体,其余形态指标不存在明显的两性差异。黑斑侧褶蛙雌体怀卵数量与体长和体重皆成正相关关系,表明黑斑侧褶蛙通过增加个体大小增加繁殖输出。     

Sexual Maturation, Annual Reproductive Cycle, and Spawning Periodicity of the Shore Scorpionfish, Scorpaenodes littoralis

The ovarian structure, sexual maturation, annual reproductive cycle, and spawning periodicity of the shore scorpionfish, Scorpaenodes littoralis, in Uchiura Bay, central Japan, were examined using specimens collected between May 1995 and March 1998 and fishes reared in laboratory. The ovarian stroma and blood vessels run longitudinally through the center of each ovarian lobe. The ovarian peduncles radiate from the central stroma. During the spawning season, gelatinous material is secreted from the epithelia of both the ovarian peduncle and ovarian wall, and the epithelia show morphological changes accompanying the ovarian maturation cycle. The minimum standard length at maturity was 55.2mm for males and 40.2mm for females. Males with mature testes were collected from March to November. Females in the mature or post spawning stages were collected between May and October, when the mean gonadosomatic indices were also high. This indicates that the spawning season of this species occurs between May and October. Four successive types of oocytes were grouped in the mature ovary, comprised of mature, late and early vitellogenic and previtellogenic oocytes respectively, suggesting that this species is a multiple spawner. Four captive females spawned repeatedly at intervals of 2–8 days over a prolonged period (4–8 months); a 2-day spawning interval was the most common for all females. This suggests that female S. littoralis have a 48-h spawning cycle in captivity.     

海陆蛙的两性异形和雌性繁殖特征

用采自海南东寨港红树林保护区的58只(35 ♀♀,23 ♂♂)成体海陆蛙(Fejervarya cancrivora),通过测量头体长、体重、头长、头宽、吻长等11个形态特征指标和雌体卵巢质量(窝卵重),研究该种形态特征的两性异形和雌性繁殖特征,并检验雌性成体大小(头体长和体重)与其繁殖的相关性.雌雄两性个体的最小头体长分别为44.9 mm和45.2 mm.除吻长和眼间距外,其余局部形态特征与头体长皆呈正相关性.头体长在雌雄两性之间差异显著,雌性显著大于雄性;而体重、头长、头宽等局部形态均无两性差异.海陆蛙雌体的窝卵重与头体长和体重之间皆成正相关关系,表明雌性可能是通过增大体型从而增加繁殖输出,而向较大体型发展.     

鄂尔多斯丽斑麻蜥两性异形及繁殖输出

两性异形和雌性繁殖输出是丽斑麻蜥(Eremias argus)种群生活史研究的重要内容。本文研究了丽斑麻蜥成体两性异形及雌性繁殖输出,研究用的95条怀卵雌体和38条(18♂、20♀)成体于2013年6月及8月捕自内蒙古鄂尔多斯。被测形态特征有体重、头体长、头长、头高、头宽、上臂长、前臂长、腕指长、大腿长、小腿长、踝趾长、腋跨距和尾长;怀卵雌性个体在实验室条件下饲养至产卵,称量产后母体体重、卵重,记录窝卵数。丽斑麻蜥成体存在两性异形,表现为雄性个体的头部、四肢长及尾长都显著大于雌性,腋跨距显著小于雌性。本实验中最小的产卵雌体头体长为44.0 mm,产卵期在6月4日至7月15日,窝卵数2~5枚,平均2.9枚,窝卵数(P=0.043)、窝卵重(P=0.026)与头体长显著正相关,相对窝卵重(P=0.001)与头体长负相关;窝卵数(P=0.000)、卵均重(P=0.000)与窝卵重显著正相关,窝卵数与卵均重不显著负相关(P=0.200)。     

Female Reproductive Effort and Sexual Selection on Males of Waterfowl

To test the hypothesis that female reproductive effort influences sexual selection on males, the degree of sexual dichromatism in waterfowl (Aves: Anseriformes) was correlated with female reproductive effort, measured as average clutch mass expressed as a percentage of adult female body mass. Sexual dichromatism was found to be significantly positively associated with female reproductive effort in 21 phylogenetically independent matched-pair comparisons in the subfamily Anatinae, and this result could not be explained by body mass differences alone. The results are consistent with the hypothesis that increased female reproductive effort increases competition among males for access to females and thus the strength of sexual selection.     

Intense Sperm-Mediated Sexual Conflict Promotes Reproductive Isolation in Caenorhabditis Nematodes

Conflict between the sexes over reproductive interests can drive rapid evolution of reproductive traits and promote speciation. Here we show that inter-species mating between Caenorhabditis nematodes sterilizes maternal individuals. The principal effectors of male-induced harm are sperm cells, which induce sterility and shorten lifespan by displacing conspecific sperm, invading the ovary, and sometimes breaching the gonad to infiltrate other tissues. This sperm-mediated harm is pervasive across species, but idiosyncrasies in its magnitude implicate both independent histories of sexually antagonistic coevolution within species and differences in reproductive mode (self-fertilizing hermaphrodites versus females) in determining its severity. Consistent with this conclusion, in androdioecious species the hermaphrodites are more vulnerable, the males more benign, or both. Patterns of assortative mating and a low incidence of invasive sperm occurring with conspecific mating are indicative of ongoing intra-specific sexual conflict that results in inter-species reproductive incompatibility.     

Ethical Issues in Adolescents' Sexual and Reproductive Health Research in Nigeria

There is increasing interest in the need to address the ethical dilemmas related to the engagement of adolescents in sexual and reproductive health (SRH) research. Research projects, including those that address issues related to STIs and HIV, adverse pregnancy outcomes, violence, and mental health, must be designed and implemented to address the needs of adolescents. Decisions on when an individual has adequate capacity to give consent for research most commonly use age as a surrogate rather than directly assessing capacity to understand the issues and make an informed decision on whether to participate in research or not. There is a perception that adolescents participating in research are more likely to be coerced and may therefore not fully comprehend the risk they may be taking when engaging in research. This paper examines the various ethical issues that may impact stakeholders' decision making when considering engaging adolescents in SRH research in Nigeria. It makes a case for lowering the age of consent for adolescents. While some experts believe it is possible to extrapolate relevant information from adult research, studies on ethical aspects of adolescents' participation in research are still needed, especially in the field of sexual and reproductive health where there are often differences in knowledge, attitudes and practices compared to adults. The particular challenges of applying the fundamental principles of research ethics to adolescent research, especially research about sex and sexuality, will only become clear if more studies are conducted.     

宁波滑蜥两性异形和雌性繁殖

蜥蜴的雌性繁殖特征对理解两性异形的进化原因起着重要作用。于2011年4月在安徽滁州采集宁波滑蜥(Scincella modesta),定量研究该种形态特征的两性异形和雌性繁殖特征,检验成体形态特征两性异形与雌性繁殖的相关性。研究共采集43条(17♀♀,26♂♂)宁波滑蜥,雄性和雌性个体的最大体长分别为47.4 mm和46.6 mm。雌雄两性在体长和头宽上没有差异,而在腹长和头长上差异显著,雄性有较大的头长,雌性有较大的腹长。宁波滑蜥年产单窝卵。窝卵数和窝卵重与雌体体长及腹长呈正相关,卵重与雌体体长无相关性。窝卵数及卵重的变异系数分别为0.20和0.12。卵长径与窝卵数呈负相关,而卵短径与窝卵数无关。雌体主要通过增加窝卵数来增加繁殖输出。这些结果表明,宁波滑蜥是雌雄个体大小同形的两性异形模式,性选择使得雄性有着较大的头长,以具有较高的交配成功率,生育力选择使得雌性有着较大的腹长,以具有较大的生育力和繁殖输出。     

Female Reproductive Cycle and Sexual Conflict over Precopulatory Mate-guarding in Thermosphaeroma (Crustacea, Isopoda)

In species with time-limited opportunities for insemination, precopulatory mate-guarding is expected to coevolve with the duration of female reproductive cycles. Despite this adaptation to female characteristics, it may also be advantageous for males to adjust the duration of guarding with respect to sex ratio because the benefits of guarding are dependent on the availability of females. If female fitness is reduced because of guarding, male guarding behavior leads to intersexual conflict. We studied these aspects of male mate-guarding behavior in two closely related, thermal-spring isopods (Thermosphaeroma). First, guarding duration showed species specificity which was related to the duration of reproductive cycle; cycle length for females and duration of guarding by males in T. milleri were twice as long as in T. thermophilum. Second, males in both species adjusted their guarding duration with sex ratio, guarding longer when a competing male was present. Third, in T. thermophilum, ovarian development began immediately after the birth of the previous brood and continued through guarding, sexual molt and post-molt periods until oviposition, whereas in T. milleri, ovarian development was largely postponed until the post-molt period. Because guarding during ovary provisioning periods may be costly for females, we tested the existence of intersexual conflict over guarding duration in T. thermophilum. We compared the duration of guarding of control pairs with those of pairs in which either male guarding ability or female ability to resist guarding was reduced experimentally. Guarding durations for manipulated and control males were equal, but manipulated females were guarded longer, suggesting that conflict exists and that females can effectively shorten guarding duration by their behavior. Moreover, we suggest that selection in the context of intersexual conflict may play an important role in the evolution of delayed oviposition and sperm-storage organs in mate-guarding crustaceans.     

Reproductive biology of Echinodorus longipetalus (Alismataceae): Sexual morphs,breeding system and pollinators

The floral biology, pollinators and breeding system of Echinodorus longipetalus Micheli were studied in a marshy area of the district of Taquaritinga (State of São Paulo), southeastern Brazil. E. longipetalus is gynodioecious and as far as is known, this is the first record of unisexual flowers, besides perfect flowers, in Echinodorus. Proportion of female individuals in the studied population is 50% and produces 31% more flowers than hermaphrodites. Perfect and pistillate flowers of E. longipetalus are similar in appearance and are pollinated by several species of Hymenoptera (mainly by Xylocopa (Neoxylocopa) suspecta Moure & Camargo). Perfect flowers offer pollen as a reward. Pistillate flowers attract floral visitors by deceit with their staminodes that resemble the stamens of the perfect flowers. Visits to pistillate flowers are quick (1–2 s), while visits to perfect flowers last up to 120 s. The perfect flowers are self-compatible and produce fruits through spontaneous self-pollination (control flowers), whereas the pistillate ones only set fruits through cross-pollinations. Perfect and pistillate flowers set more fruits under natural conditions than in manual treatments, respectively. Although the pistillate and perfect flowers bear a strong similarity, the selective pollinator behavior seems to be responsible for the increase of fruit set in perfect flowers.