野生小型兽繁殖的调查方法

在研究野生小型兽的繁殖中,详细比较雌雄两性在外形上的差别、性成熟时间、年产窝数、每窝仔数、繁殖期(交配、妊娠、哺乳)是很重要的。剖检雌兽卵巢、输卵管、子宫发育状况,以及雄兽睾丸体积和是否下降到阴囊,副睾大小及其是否有成熟精子,记录体重、体长、尾长、后足长和耳长等项,保留头骨作年龄鉴定,有了这些原始资料,经统计分析,才能对其繁殖强度作正确推断。作者依据多年的野外工作经验,初步总结如下。一、雌兽繁殖的研究方法(一)检查乳头和乳腺乳头小,隐藏毛中,难发现,挤压乳头基部时,没有乳汁外流,表示无哺乳;乳头大而显见,周围无毛或…     

高龄大熊猫繁殖的饲养研究

通过营造冬暖、夏凉、通风良好的洞穴兽舍,改造饲料营养,采用先粗后精、少量勤添的饲喂方法,增加活动量,接受阳光照射,让雌、雄大熊猫有较多直接或间接接触的机会和增强其信息交流等技术管理措施,使高龄大熊猫“新星”雌兽20岁受配产仔,同时一胎产2仔,高龄大熊猫雄兽“新8号”25岁龄自然交配,并在25～27岁龄连年自然配种,使受配雌兽怀孕产仔,创下了圈养大熊猫雌、雄兽高龄繁殖的新记录。     

小翅稻蝗的精子竞争及交配行为的适应意义

许多昆虫有多次交配行为 ,因多次交配而引起不同雄虫的精子竞争 ,提供雌虫一种有效的性选择方式。小翅稻蝗 (Oxyayezoensis Shiraki)具多次交配行为 ,雌雄交配时间长 ,且交配后常伴有长时间的抱对行为。利用近缘种的种间交配 ,对小翅稻蝗的精子竞争、交配后抱对行为的适应意义进行了探讨。结果表明 ,小翅稻蝗的 P2 值 (最后交配雄虫子代的比例 )达 94 .3%±5 .3% ,说明最后交配雄虫的精子优先用于卵子的受精 ,交配时存在着精子置换。长时间的交配后抱对行为是为了阻止雌虫与不同雄虫个体的再交配 ,保护精子免被置换。     

笼养雌性果子狸同性数量对发情状态的影响及繁殖季节尿液雌激素浓度的变化

本研究试图揭示 (1)社会环境影响雌性果子狸 (Pagumalarvata)的交配日期 ,(2 )哺乳期母兽有雌二醇浓度升高的现象。通过检查是否排出交配栓并结合交配行为的发生与否确定开始交配的日期 ,使用放射免疫方法测定尿中雌二醇浓度。结果表明 (1)一雄两雌组中优势雌兽开始交配的日期显著早于劣势雌兽和单雌组雌兽 ,劣势雌兽和单雌组雌兽之间无差异 ;交配期优势雌兽尿液中雌二醇浓度明显高于劣势雌兽 ,而与单雌组中的雌兽无差异 ,但单雌组中雌兽尿液中雌二醇的浓度明显高于劣势雌兽雌二醇的浓度 ;(2 ) 5头母兽产后第二天雌二醇浓度开始上升 ,在第 5天时达到高峰 ,其中 4头母兽的雌二醇浓度共出现了两个峰值 ,其间隔为 16 75± 4 4 6 (4)天。上述结果说明 :(1)社会影响仅对优势雌性个体的繁殖有促进作用 ;(2 )哺乳期雌二醇水平的升高是季节性多次发情的基础。     

雄性大熊猫配种期的性行为观察

本文通过对西安动物园大熊猫雄兽弯弯于１９８６－１９９１年与３只雌兽相继本交,爬跨３３次,交配２１次,产５胎,获６仔,育成６仔的性行为观察。获得雄兽在发情季节的爬跨与酱姿式,交配的时间与叫声,配种期的食量下降与活动量变化等资料。     

三突伊氏蛛雌蛛不同交配史对雄蛛交配行为的影响

近年来越来越多研究表明,雄性产生精子(精液)也需付出代价。在多次交配的动物中,雄性为获得最大生殖潜力,必须依据配偶的质量策略性地调整每次交配的生殖投入。雄性策略性的生殖投入主要体现在两个方面,一是精子竞争(sperm competition),二是柯立芝效应(Coolidge effect)。目前精子竞争研究主要集中于昆虫类群,而柯立芝效应研究集中于高等脊椎动物,同时验证结果也时常与假说不一致。以多次交配的三突伊氏蛛为材料,以雄蛛交配行为为指标,在蜘蛛类群中探讨和验证雄性精子竞争强度假说和柯立芝效应。设定3个交配组合:2只雄蛛依次与1只雌蛛各交配1次(A组)、2只雄蛛依次与2只雌蛛各交配1次(B组)和1只雄蛛与1只雌蛛交配2次(C组),分析比较3个交配组合的三突伊氏蛛第1次交配和第2次交配在交配潜伏期、交配持续时间和交配回合数方面的差异,比较三突伊氏蛛雌蛛不同交配史对雄蛛交配行为的影响,以此验证雄性精子竞争强度假说和柯立芝效应。研究结果表明A和B组的三突伊氏蛛第2次交配的交配潜伏期和交配持续时间显著长于第1次交配。同时,C组的三突伊氏蛛第1次交配的交配潜伏期和交配持续时间与第2次交配都没有显著差异。同时,A、B和C组的三突伊氏蛛第1次交配的交配回合数与第2次交配都没有显著差异。研究结果支持精子竞争强度假说,而不支持柯立芝效应。     

繁殖盛期雄性普通东方小蛙的个体大小不影响交配成功率

通过比较抱对和非抱对普通东方小蛙(Crinia signifera) 的吻尾干骨长(体长) 和检测个体较大或状态较好的雄体是否为成功繁殖个体, 检测雌蛙体长与交配成功的雄蛙的体长和相对状态(体重/体长) 之间是否存在线形关系, 评估交配与个体大小之间的关系。在实验室内, 令未交配雌体选择随机选出的雄体, 观测雌体是否与最大的雄体交配; 将抱对的蛙暴露于其它雄蛙, 观测其它较大或较小的雄蛙是否取代已抱对的雄蛙。结果表明: 抱对雄蛙和雌蛙的个体大小无显著的关系, 成功交配的雄蛙并不比未交配的雄蛙大, 其它雄蛙不能取代已抱对的雄蛙。在这一C. signifera种群中, 繁殖盛期雄性个体的大小似乎不影响交配成功率, 在此期间即便存在配偶选择, 亦决定于与雄性个体大小无关的其它因素。在更长的繁殖期内, 雄性个体大小则与交配成功率有关, 这是该种的典型特征。     

铃虫交配过程中精子的转移

统计了棉铃虫交配前后贮精囊、复射精管和精包内真核精子(束)的数量,以此来验证棉铃虫交配过程中是否存在精子回流现象。结果表明,棉铃虫在交配时将复射精管内的精子全部转移至雌蛾体内,不存在精子回流现象。     

蜂王体内的精子贮存

蜜蜂最重要的生殖特征是一雌多雄交配,蜂王交配后将精子贮存于受精囊中长达数年之久,并仍能保持活力。这些特征使蜜蜂成为研究精子长期贮存的模式动物。文章介绍蜂王的交配和精子贮存过程,精子贮存器官,贮存过程中的精子竞争和隐秘雌性选择,以及蜂王精子的长期贮存机制,并对将来的研究方向进行了展望。     

飞蝗抱对行为的进化意义及两型间相异的交配策略

飞蝗Locusta migratoriaL.不仅交配时间长,而且进行频繁的、长时间的交配前抱对。一般认为,交配前抱对行为是雄虫为了等待时机获取适时的交配。最近的研究表明,飞蝗的交配时间与P2值(最后交配雄虫子代的比例)、交配前抱对时间与交配时间存在显著的正相关关系,即飞蝗长时间的交配前抱对行为能延长其后续的交配时间,从而提高P2值。飞蝗具变型现象,散居型和群居型在形态特征、生理机能、行为及体色等方面存在明显差异。最近的研究结果显示,散居型较群居型具更高的P2值,较短的交配前抱对和较长的交配时间。冲绳和筑波种群散居型成虫的交配前抱对时间与交配时间存在显著的正相关关系,而群居型无此相关性。这些结果证实飞蝗散居型和群居型之间存在着繁殖策略的差异。     

Postmating sexual selection: the effects of male body size and recovery period on paternity and egg production rate in a water strider

The role of male body size in postmating sexual selection wasexplored in a semiaquatic insect, the water strider Gerris lateralis.To separate effects of male size per se from those due to numericsperm competition, male recovery period (shown here to be proportionalto ejaculate size) was manipulated independently of body sizein a factorial experiment where virgin females were mated firstwith sterile males and then with focal males. Both relativemale fertilization success and female reproductive rate were measured.The number of sperm transferred increased with male recoveryperiod, an effect that was mediated by longer copulation duration,but there were no effects of body size on ejaculate size. Neithermale size nor recovery period had any significant direct effectson male fertilization success. However, copulation durationinfluenced relative fertilization success, suggesting that malesable to transfer more sperm also achieved higher fertilizationsuccess. Females exercised cryptic female choice by modulatingtheir reproductive rate in a manner favoring large males andmales that were successful in terms of achieving high relativefertilization success. Thus, successful males gained a twofoldadvantage in postmating sexual selection. This study has important implicationsfor previous estimates of sexual selection in this group of insectsbecause pre- and postmating sexual selection will be antagonisticdue to limitations in male sperm production: males mating frequently(high mating success) will on average transfer fewer sperm ineach mating and will hence tend to fertilize fewer eggs permating (low fertilization success).     

Female Remating Behavior in a Lekking Moth

In polyandrous species, male reproductive success will at least partly be determined by males' success in sperm competition. To understand the potential for post‐mating sexual selection, it is therefore important to assess the extent of female remating. In the lekking moth Achroia grisella, male mating success is strongly determined by female choice based on the attractiveness of male ultrasonic songs. Although observations have indicated that some females will remate, only little is known about the level of sperm competition. In many species, females are more likely to remate if their first mating involved an already mated male than if the first male was virgin. Potentially, this is because mated males are less well able to provide an adequate sperm supply, nutrients, or substances inhibiting female remating. This phenomenon will effectively reduce the strength of pre‐copulatory sexual selection because attractive males with high mating success will be more susceptible to sperm competition. We therefore performed an experiment designed both to provide a more precise estimate of female remating probability and simultaneously to test the hypothesis that female remating is influenced by male mating history. Overall, approximately one of five females remated with a second male. Yet, although females mated to non‐virgin males were somewhat more prone to remate, the effect of male mating history was not significant. The results revealed, however, that heavier females were more likely to remate. Furthermore, we found that females' second copulations were longer, suggesting that, in accordance with theory, males may invest more sperm in situations with an elevated risk of sperm competition.     

Female mating status does not affect male mating behavior in the West Indian sweetpotato weevil, Euscepes postfasciatus

Because multiple mating by females encourages sperm competition, the assessment of female mating status before insemination is important for males in order to avoid the risk of sperm competition or to intensify sperm competition. When interacting with females before sperm transfer, males can alter their mating tactics according to the risk or intensity of sperm competition. Information on how mating systems are associated with sperm competition is essential for sterile insect technique eradication programs, which depend on successful mating of released sterile males with wild females. We tested whether males of the West Indian sweetpotato weevil, Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae), adjusted their mating behavior in response to female mating experience and/or age. As virgin/young female weevils accepted males more easily than non-virgin/old females, assessing females before insemination can be adaptive for male weevils. We found that E. postfasciatus males were unable to adjust their mating tactics in response to female mating status. Although this mating strategy would be costly for individual male weevils, the ability in males to discriminate female mating status can prevent the chance of mating with already-mated females containing the sperm of wild male(s). Therefore, the mating tactics of male E. postfasciatus are advantageous for sterile insect technique eradication programs.     

The role of male age, sperm age and mating history on fecundity and fertilization success in the hide beetle

Models of age-related mate choice predict female preference for older males as they have proven survival ability. However, these models rarely address differences in sperm age and male mating history when evaluating the potential benefits to females from older partners. We used a novel experimental design to assess simultaneously the relative importance of these three parameters in the hide beetle, Dermestes maculatus. In a two-part experiment we first explored age-related male mating success and subsequently examined the consequences of male age, sperm age and male mating history on female fecundity and fertilization success. In a competitive mating environment, intermediate-age males gained significantly higher mating success than younger or older males. To test the consequences for females of aged-related male mating success, a second set of females were mated to males varying in age (young, intermediate-age and old), in numbers of matings and in timing of the most recent mating. We found that male age had a significant impact on female fecundity and fertilization success. Females mated to intermediate-age males laid more eggs and attained consistently higher levels of fertilization success than females with young and old mates. A male's previous mating history determined his current reproductive effort; virgin males spent longer in copula than males with prior mating opportunities. However, differences in copulation duration did not translate into increased fecundity or fertilization success. There was also little evidence to suggest that fertilization success was dependent on the age of a male's sperm. The experiment highlights the potential direct benefits accrued by females through mating with particular aged males. Such benefits are largely ignored by traditional viability models of age-related male mating success.     

Mating success of male guppy <Emphasis Type="Italic">Poecilia reticulata</Emphasis> in the wild

To understand how the diversity among male sexual traits is maintained despite directional female choice for attractive traits, it is important to study male reproductive success in each reproductive episode. Male reproductive success is indeed the comprehensive result of several processes such as mate choice, mating, and fertilization. In this study, male mating success was estimated in a wild guppy Poecilia reticulata population of Hiji River, Okinawa Island, in southern Japan. The mating success of males was estimated as the percentage of sperm transferred in relation to the total sperm reserve. In a preliminary experiment, it was confirmed that the sperm reserves of males were partly replenished after 12 h and fully replenished after 72 h, when all sperm were released. In addition, the results of investigation in the wild population revealed that approximately 20% of males had no sperm reserves at all, although their sperm reserves should have been replenished by sexual isolation. Male sexual traits such as body size or color pattern did not affect the percentage of sperm transferred. Results from this study provide important insights into male sperm transfer ability and sperm production in this population. However, the high frequency of male sperm-transfer success estimated in this study should to be taken with caution, and whether it is due to differences between wild and laboratory conditions, sex ratio or the rates of multiple matings by females in the wild population remain to be fully explored.     

The Effect of Female Quality on Male Ejaculatory Expenditure and Reproductive Success in a Praying Mantid

Strategic ejaculation is a behavioural strategy shown by many animals as a response to sperm competition and/or as a potential mechanism of cryptic male choice. Males invest more mating resources when the risk of sperm competition increases or they invest more in high quality females to maximize their reproductive output. We tested this hypothesis in the false garden mantid Pseudomantis albofimbriata, where females are capable of multiply mating and body condition is an indicator of potential reproductive fitness. We predicted male mantids would ejaculate strategically by allocating more sperm to high quality females. To determine if and how males alter their ejaculate in response to mate quality, we manipulated female food quantity so that females were either in good condition with many eggs (i.e. high quality) or poor condition with few eggs (i.e. low quality). Half of the females from each treatment were used in mating trials in which transferred sperm was counted before fertilisation occurred and the other half of females were used in mating trials where fertilisation occurred and ootheca mass and total eggs in the ootheca were recorded. Opposed to our predictions, the total number of sperm and the proportion of viable sperm transferred did not vary significantly between female treatments. Male reproductive success was entirely dependent on female quality/fecundity, rather than on the number of sperm transferred. These results suggest that female quality is not a major factor influencing postcopulatory male mating strategies in P. albofimbriata, and that sperm number has little effect on male reproductive success in a single mating scenario.     

Interactions Between Multiple Forms of Nuptial Feeding in the Wood Cricket Nemobius sylvestris (Bosc): Dual Spermatophores and Male Forewings

Nuptial feeding is widespread in insects, with many species showing one form of feeding. In the wood cricket Nemobius sylvestris, the male may provide multiple forms of feeding during an encounter: two kinds of edible spermatophores (microspermatophore and macrospermatophore) and forewing secretions. We examined the roles and interactions of the spermatophores and forewing exposure in the mating sequence of this species. The small microspermatophore was not found to contain sperm, whereas the larger macrospermatophore contained sperm. In mating trials, the microspermatophore may be transferred to the female early in the trial. Transfer of the microspermatophore was not a necessary prerequisite to the subsequent transfer of one or more sperm‐filled macrospermatophores. Forewing exposure increased male mating success, as males with exposed forewings were more successful in transferring the macrospermatophore than males with experimentally covered forewings, both in terms of occurrence of successful transfer and the number of macrospermatophores transferred. Male mating success was very low when the male’s forewings were covered and when the male did not transfer a microspermatophore. The sperm‐filled macrospermatophore may have nutritional value, as females eventually consumed all transferred macrospermatophores, and males consumed all rejected macrospermatophores. Somewhat unexpectedly, this study casts doubt on the role of the forewings in nuptial feeding. Although males with exposed forewings were more successful in macrospermatophore transfer, females actually palpated these males’ forewings less. We posit the alternative hypothesis that the forewing secretions play a role in chemical communication to the female (e.g., signaling male quality), possibly instead of female nourishment.     

Determinants of Sperm Transfer by Males of the Noctuid Moth Heliothis virescens

Ejaculate composition can be an important determinant of male reproductive success in the face of sperm competition, which varies with the mating history of the female. Here we examine the effect of various male and female mating histories and morphological traits on ejaculate sperm numbers in the polyandrous moth Heliothis virescens. We show that when mating with nonvirgin females, males passed larger sperm packages (spermatophores) but did not alter either the sperm count or the ratio of nucleated-to-nonnucleated sperm. Males also passed fewer sperm in their second ejaculates. Finally, older males passed more sperm than did younger males. Earlier research found that females store more sperm from older males and that older males are more likely to gain sperm precedence over younger rivals. These earlier results, taken together with the present results, indicate that the advantage enjoyed by older males is due to an increased sperm count.     

Drosophila melanogaster females change mating behaviour and offspring production based on social context

In Drosophila melanogaster, biological rhythms, aggression and mating are modulated by group size and composition. However, the fitness significance of this group effect is unknown. By varying the composition of groups of males and females, we show that social context affects reproductive behaviour and offspring genetic diversity. Firstly, females mating with males from the same strain in the presence of males from a different strain are infecund, analogous to the Bruce effect in rodents, suggesting a social context-dependent inbreeding avoidance mechanism. Secondly, females mate more frequently in groups composed of males from more than one strain; this mitigates last male sperm precedence and increases offspring genetic diversity. However, smell-impaired Orco mutant females do not increase mating frequency according to group composition; this indicates that social context-dependent changes in reproductive behaviour depend on female olfaction, rather than direct male-male interactions. Further, variation in mating frequency in wild-type strains depends on females and not males. The data show that group composition can affect variance in the reproductive success of its members, and that females play a central role in this process. Social environment can thus influence the evolutionary process.     

Influence of male mating history on female reproductive success among monandrous Naryciinae (Lepidoptera: Psychidae)

1. Multiple male copulations can have detrimental effects on female fitness due to sperm limitation. 2. Monandrous Naryciinae females are immobile while the males are short‐lived and do not feed. Multiple male mating is therefore expected to lead to sperm limitation in females. Sperm limitation and male limitation are hypothesised as causes of the repeated evolution of parthenogenetic reproduction in the Psychidae. 3. In this study, the effects of multiple male mating on female reproduction are investigated in several species of Naryciinae by allowing males multiple copulations. The results for two species, Siederia listerella and Dahlica lichenella, are compared. The sex ratios of 53 natural populations are examined for indications of male limitation. 4. Previous copulations by the male increased the female's risk of remaining unfertilised. However, contrary to expectations, those unfertilised females were capable of successful re‐mating. 5. In S. listerella, the number of previous copulations of males negatively influenced female fitness. Females produced 30% fewer offspring if they mated with a previously mated male. In D. lichenella, the older the male and the lower its number of total lifetime copulations, the higher the female's reproductive success. 6. Only a fraction of the investigated populations had a female‐skewed sex ratio, but differences in development time between males and females could lead to reproductive asynchrony. 7. In conclusion, male mating history did not lead to strong sperm limitation in Naryciinae as had been suggested by their life history.