Sperm Storage in the Female Reproductive Tract in Birds

The ability to store sperm in the female genital tract is frequently observed in vertebrates as well as in invertebrates. Because of the presence of a system that maintains the ejaculated sperm alive in the female reproductive tract in a variety of animals, this strategy appears to be advantageous for animal reproduction. Although the occurrence and physiological reasons for sperm storage have been reported extensively in many species, the mechanism of sperm storage in the female reproductive tract has been poorly understood until recently. In avian species, the specialized simple tubular invaginations referred to as sperm storage tubules (SSTs) are found in the oviduct as a sperm storage organ. In this review, we summarize the current understanding of the mechanism of sperm uptake into the SSTs, maintenance within it, and controlled release of the sperm from the SSTs. Since sperm storage in avian species occurs at high body temperatures (i.e., 41 C), elucidation of the mechanism for sperm storage may lead to the development of new strategies for sperm preservation at ambient temperatures, and these could be used in a myriad of applications in the field of reproduction.     

Mechanisms of sperm storage in the female reproductive tract: an interspecies comparison

Once semen has been collected for artificial insemination, it is diluted into extenders designed to prevent its deterioration over the period prior to insemination. If the semen is not frozen, the extenders provide protection for a period of a few hours to a few days, depending on species. Despite the efforts of biotechnologists to increase the duration of storage without compromising fertility, there has been relatively little progress for many years. However, comparative studies in diverse species have revealed that long-term sperm storage (up to months and years) within the female reproductive tract is relatively commonplace in reptiles, fishes, birds and amphibians. Even among mammals, some species of bat have evolved mechanisms for storing spermatozoa for several months in the uterus or oviduct so that they can mate in the autumn but postpone fertilization until the spring. We currently know little about the mechanisms that support such long-term sperm storage, mainly because evidence from such species is either absent or fragmentary. Nevertheless, parallels between mammalian and other systems, where spermatozoa are sequestered in sperm storage tubules, suggest that the enclosure of spermatozoa within pockets of epithelial cells may be sufficient to achieve long-term sperm storage. In addition, recent evidence from sperm-storing bats has suggested an alternative, or additional, hypothesis that the modulation of apoptosis within epithelial cells is important in controlling sperm survival. Despite a lack of direct experimental evidence from a wide variety of species, I propose that there is now enough evidence to warrant investigation of these hypotheses.     

Major ascaroside pheromone component asc-C5 influences reproductive plasticity among isolates of the invasive species pinewood nematode

Pheromones are communication chemicals and regulatory signals used by animals and represent unique tools for organisms to mediate behaviors and make “decisions” to maximize their fitness. Phenotypic plasticity refers to the innate capacity of a species to tolerate a greater breadth of environmental conditions across which it adapts to improve its survival, reproduction, and fitness. The pinewood nematode, Bursaphelenchus xylophilus, an invasive nematode species, was accidentally introduced from North America into Japan, China, and Europe; however, few studies have investigated its pheromones and phenotypic plasticity as a natural model. Here, we demonstrated a novel phenomenon, in which nematodes under the condition of pheromone presence triggered increased reproduction in invasive strains (JP1, JP2, CN1, CN2, EU1, and EU2), while it simultaneously decreased reproduction in native strains (US1 and US2). The bidirectional effect on fecundity, mediated by presence/absence of pheromones, is henceforth termed pheromone-regulative reproductive plasticity (PRRP). We further found that synthetic ascaroside asc-C5 (ascr#9), the major pheromone component, plays a leading role in PRRP and identified 2 candidate receptor genes, Bxydaf-38 and Bxysrd-10, involved in perceiving asc-C5. These results suggest that plasticity of reproductive responses to pheromones in pinewood nematode may increase its fitness in novel environments following introduction. This opens up a new perspective for invasion biology and presents a novel strategy of invasion, suggesting that pheromones, in addition to their traditional roles in chemical signaling, can influence the reproductive phenotype among native and invasive isolates. In addition, this novel mechanism could broadly explain, through comparative studies of native and invasive populations of animals, a potential underlying factor behind of the success of other biological invasions.     

The Mitochondrial Genome in Embryo Technologies

The mammalian mitochondrial genome encodes for 37 genes which are involved in a broad range of cellular functions. The mitochondrial DNA (mtDNA) molecule is commonly assumed to be inherited through oocyte cytoplasm in a clonal manner, and apparently species‐specific mechanisms have evolved to eliminate the contribution of sperm mitochondria after natural fertilization. However, recent evidence for paternal mtDNA inheritance in embryos and offspring questions the general validity of this model, particularly in the context of assisted reproduction and embryo biotechnology. In addition to normal mt DNA haplotype variation, oocytes and spermatozoa show remarkable differences in mtDNA content and may be affected by inherited or acquired mtDNA aberrations. All these parameters have been correlated with gamete quality and reproductive success rates. Nuclear transfer (NT) technology provides experimental models for studying interactions between nuclear and mitochondrial genomes. Recent studies demonstrated (i) a significant effect of mtDNA haplotype or other maternal cytoplasmic factors on the efficiency of NT; (ii) phenotypic differences between transmitochondrial clones pointing to functionally relevant nuclear–cytoplasmic interactions; and (iii) neutral or non‐neutral selection of mtDNA haplotypes in heteroplasmic conditions. Mitochondria form a dynamic reticulum, enabling complementation of mitochondrial components and possibly mixing of different mtDNA populations in heteroplasmic individuals. Future directions of research on mtDNA in the context of reproductive biotechnology range from the elimination of adverse effects of artificial heteroplasmy, e.g. created by ooplasm transfer, to engineering of optimized constellations of nuclear and cytoplasmic genes for the production of superior livestock.     

流式细胞仪分离精子研究进展

本文概述了近年来用流式细胞仪分离动物X、Y精子的研究进展、存在的问题和应用前景。流式细胞仪分离精子的研究已经取得了很大进展 ,在某些动物 (如牛 )分离的精子已开始用于人工授精。尽管该技术还存在许多亟待解决的问题 ,但随着流式细胞仪的改进和与各项辅助生殖技术 (如手术授精、体外受精、胞质内精子注射、低剂量精子人工授精 )结合 ,性别分离精子必将在实践中得到广泛的应用 ,产生巨大的社会和经济效益     

生殖免疫技术在动物繁殖中的应用

根据近年来在生殖免疫方面取得的研究进展,介绍了激素免疫技术的应用,H-Y精子免疫法性别化精液技术、早期胚胎性别控制免疫技术等在提高动物繁殖力方面的重要作用。     

Changes in Equine Reproduction: Have They Been Good or Bad for the Horse Industry?

In the past four decades there have been tremendous changes in equine reproduction. Most breeds now allow the use of artificial insemination with fresh, cooled and frozen semen. Artificial insemination has many advantages for the breeder, in particular the control of bacteria through the use of semen extenders containing antibiotics. Deposition of sperm in small volumes onto the uterotubal junction has allowed the use of relatively low numbers of sperm. Intracytoplasmic injection of sperm into oocytes allows older, subfertile stallions to be used as breeding stallions. Advances in mare reproduction have included developing tools for hastening the onset of the breeding season. Other advances include embryo transfer, oocyte collection and transfer, and cloning. The acceptance of reproductive technology depends on the success of the technology, the attitude of the breeders/veterinarians, and the cost/benefit ratio to the industry and breed registry.     

Development of New Stem Cell-based Technologies for Carnivore Reproduction Research

New reproductive technologies based on stem cells offer several potential benefits to carnivore species. For example, development of lines of embryonic stem cells in cats and dogs would allow for the generation of transgenic animal models, which could be used to advance both veterinary and human health. Techniques such as spermatogonial stem cell transplantation (SSCT) and testis xenografting offer new approaches to propagate genetically valuable individual males, even if they should die before producing sperm. These techniques might therefore have application to the conservation of endangered species of carnivores, as well as to biomedical research. Recently, our laboratory has successfully performed SSCT in the dog, with a recipient dog producing sperm of donor genetic origin. Testis xenografting has been used to produce sperm from pre-pubertal testis tissue from both cats and ferrets. These early steps reinforce the need not only for research on stem cell technologies, but also for additional research into complementary technologies of assisted reproduction in carnivores, so that the widest array of research and clinical benefits can be realized.     

Crocodylian conservation and evolution insights from an anatomical and histological examination of phalli from male false gharial (Tomistoma schlegelii)

As wild population threats for the endangered false gharial (Tomistoma schlegelii) persist, conservation breeding programs, including developing semen collection techniques for subsequent artificial insemination, are becoming important species conservation measures. Developing reproductive biology understanding of a species is important to developing best practices and hopefully maximizing reproductive successes. However, information on crocodylians functional copulatory anatomy in general is lacking. To that end, zoological facilities and conservation centres have the exceptional opportunity to contribute new understandings that may not otherwise be attainable regarding crocodylian reproductive anatomy, particularly during routine physical examinations or post-mortem necropsies. Therefore, to better understand T. schlegelii reproductive biology, to contribute knowledge in support of zoo breeding conservation efforts and to contribute to what is known overall about crocodylian reproduction, we investigated phallic anatomy of adult male Tomistoma from two zoological populations, the St. Louis Zoo, USA and Sungai Dusun Wildlife Reserve, Peninsular Malaysia. Here, we present the gross anatomical features and histological analysis of underlying tissue-level details in pursuit of a better understanding of copulatory function and associated gamete transfer mechanisms. While much of the overall Tomistoma phallic morphology and inferred function corresponds to that of other crocodylian species and speaks to conserved aspects of functional anatomy across taxa, species-specific aspects of glans and glans tip morphology are also identified. These novelties are discussed in a general function and overall broader evolutionary contexts.     

Recent advances in bovine sperm cryopreservation techniques with a focus on sperm post‐thaw quality optimization

Sperm cryopreservation facilitates the storage and transport of germplasm for its use in artificial insemination (AI) and other advanced reproductive technologies. The cryopreservation process can damage sperm and compromise functionality. Several cryobiological studies have found that the physical and biological factors that affect sperm survival at low temperatures during the cryopreservation process often involve the integrity of sperm membrane. In this review, the behaviour of the sperm membrane against cooling, cold shock, ice crystal formation, oxidative stress, osmotic changes, reorganization of the lipid bilayer and addition of cryoprotective agents (CPA) is discussed. In addition, the phenomenon of reactive oxygen species (ROS) and its relationship with the cryopreservation process is also described. Semen cryopreservation techniques have progressed slowly in past years, and the current performance, measured as post‐thawed survival, is not very different compared to past decades. Recent advances in understanding the structure of the cell membrane, its function and metabolism have driven to new conservation systems, including lyophilization and vitrification. However, none of these technologies is commercially available, although its future appears very promising.     

2021年国内外家兔遗传育种与繁殖研究进展

兔业是节粮、环保、低耗草食畜牧业中的代表性产业,是中国畜牧业的重要组成部分。家兔遗传育种与繁殖的相关研究是推进兔业发展的重要基础与保障。遗传学、分子生物学、统计学及计算机科学等学科的交叉融合与不断进步,为家兔育种提供了更加先进全面的技术手段。作者从家兔传统育种与分子育种2个方面对国内外2021年家兔遗传育种与繁殖研究进展进行了综述。国外在传统育种与分子育种上均作了一定研究,主要集中在选择与环境效应的影响。国内开展的家兔遗传育种与繁殖研究数量相较国外更多,主要以分子育种为主,包括品种与遗传多样性、皮毛性状功能基因、脂肪和肉质性状相关基因及繁殖性能相关基因的研究;传统育种主要包括选择和环境效应对家兔生长与繁殖性能的影响及生产性能测定等。本综述旨在为家兔育种研究和生产提供参考。     

Effect of Foetal Bovine Serum on sperm motility,acrosome reaction and spermatic interaction to zona pellucida in alpacas (Vicugna pacos)

The use of foetal bovine serum (FBS) in cell culture media is quite common. However, little is known about the effect of FBS on sperm. The severe difficulties in alpaca reproduction demand the search of new methods for in vitro reproductive management. In the present study, we use for the first time FBS as a supplement in the culture medium for sperm in alpaca, and the effect of FBS on motility, acrosome reaction and sperm binding to the zona pellucida in this species was evaluated. A concentration of 10% v/v FBS was used. The sperm motility with FBS at the first hour was 32.8% (vs. control = 30.0%), whereas at the second hour sperm motility with FBS was 30.2% (vs. control = 28.8%). The acrosome reaction reached an average of 44.0% for treatment with FBS (vs. control = 30.1%). The sperm‐zona pellucida binding assay showed that the samples incubated with FBS had an average of 2.7 bound sperm (vs. control = 1.7). Only a significant difference was observed for sperm motility at the first hour and for the acrosome reaction. It is concluded that FBS favours the capacitation of sperm in alpaca.     

哺乳动物精子线粒体研究进展

哺乳动物精子线粒体是维持精子活力的关键细胞器，对精子超激活运动、获能、顶体反应及受精等过程起到重要的调节作用。哺乳动物精子线粒体特有的形态特征与特异性酶异构体使其具有独特动力学和调节特性。精子线粒体中发生的氧化磷酸化过程是维持精子运动的重要途径，该过程产生的活性氧对精子功能的维持具有重要作用，但过量可能导致精子损伤，加速精子凋亡。哺乳动物精子质膜磷脂酰丝氨酸外翻和相关半胱氨酸蛋白酶激活级联反应引起细胞凋亡。区别于体细胞线粒体，精子线粒体钙信号可能并未参与精子固有的凋亡途径，作为衡量线粒体功能的敏感指标，其对线粒体膜电位和耗氧量的检测研究至关重要。哺乳动物精子线粒体具有自身的遗传系统，线粒体基因拷贝数可能作为无创衡量精子质量和受精能力的标记。作者重点阐述了哺乳动物精子线粒体的结构、线粒体鞘的形成及其生物功能，包括发生在线粒体中的氧化磷酸化过程、活性氧对精子的利与弊、线粒体参与钙稳态与细胞凋亡过程；介绍了线粒体膜电位和耗氧量的检测，简述了线粒体基因组的研究进展，为进一步探讨线粒体所涉及的精子功能机制奠定基础。     

Characteristics of capercaillie (Tetrao urogallus) semen analysed with flow cytometry combined with fertility results

In order to increase the reproductive indices of capercaillie kept in closed breeding facilities, it is necessary to constantly expand the methods of better understanding the characteristics of sperm and their fertilizing potency. The aim of the study was to analyse selected features of capercaillie sperm using flow cytometry and their connection with fertility results. The study included five males, three of which were kept in a family group with eight females and two were kept alone. For sperm viability, acrosome integrity, mitochondrial potential and DNA defragmentation were assessed. Paternity analyses were performed in order to confirm the paternity of the individual and to link the evaluated semen traits with reproductive success. Analyses carried out in the flow cytometer showed any significant differences between males in sperm characteristics. In the semen of male No. 101, the father of all chicks from the analysed family group, 91.3% of live sperm, 91.5% with intact acrosome, 83.6% with active mitochondria and 2.0% with DNA defragmentation were observed. The average fertility rate was 71.0%, and chick hatchability was 100%. Using flow cytometry in the analysis of capercaillie semen and its connection with the results of natural mating, we were able to obtain deeper knowledge about new sperm characteristics that were not examined before and which in the future may be helpful in selecting males for the reproductive flocks and developing assisted reproduction techniques.     

Latitudinal and seasonal variation in reproductive effort of the eastern fence lizard (Sceloporus undulatus)

Geographic variation in life‐history traits among populations of wide‐ranging species is influenced by both spatial and temporal aspects of the environment. Rarely, however, are the effects of both aspects examined concurrently. We collected gravid female lizards (Sceloporus undulatus) from northern (Indiana), central (Mississippi) and southern (Florida) populations, spanning nearly the full latitudinal range of the species, to examine amongpopulation differences in strategies of reproductive energy allocation. Adult females from the southern population were smaller, and produced fewer and smaller eggs in their first clutches than did females from the more northern populations. Southern females were more likely to produce a second clutch, and second clutches were smaller than first clutches for females from the 2 northern populations. Together these trends eliminated population differences in overall reproductive output after accounting for body size. The trend for greater reproductive energy to be allocated to first clutches at higher latitudes, and to later clutches at lower latitudes is corroborated by published data from field studies on multiple populations. Distributing reproductive effort by producing more clutches of smaller eggs may be an adaptive response to the long season available for egg incubation and lizard activity in sub‐tropical southern environments. In contrast, allocating greater resources to early reproduction may enhance maternal fitness in the relatively short activity seasons that characterize more northern sites.     

微流控技术在生殖领域中的应用

微流控技术（microfluidics）是微全分析系统（micro total analysis system,μTAS）和芯片实验室（lab-on-a-chip）的重要支撑技术,其微量化和微尺度的优势得到人们越来越多的关注。辅助生殖技术（assisted reproductive technology,ART）是生殖医学的重要组成部分,已被广泛应用于生产实践中,但由于其低效性,人们在不断寻求新的技术手段。笔者综述了近年来微流控技术在生殖领域中的应用,包括精子筛选、体外受精和配子/胚胎培养等方面的内容,为辅助生殖技术提供了新的平台。     

Molecular mechanisms underlying pig oocyte maturation and fertilization

Since the pig is not only an important farm animal, but also a model animal for biomedical applications, the development of reproductive technologies in this species has been very important. In vitro oocyte maturation and fertilization (IVM-IVF) are basic techniques for a number of oocyte- or embryo-related technologies. The practical aspects for pig oocyte IVM-IVF have been reviewed, while the molecular mechanisms underlying oocyte meiotic maturation and fertilization have not been well summarized, although accumulating data have been obtained in recent one decade. This review will focus on what is known about the molecular mechanisms of porcine oocyte maturation and fertilization such as first meiosis resumption, meiotic spindle assembly, second meiosis metaphase (MII) arrest during oocyte maturation, sperm-egg recognition and fusion, sperm acrosome reaction, second meiosis resumption, sperm chromatin decondensation, and pronucleus formation during fertilization, as well as the establishment of polyspermy block.     

Reproductive biology of an old endemic murid rodent of Australia,the Spinifex hopping mouse,Notomys alexis: adaptations for life in the arid zone

The Spinifex hopping mouse (Notomys alexis Thomas, 1922) is an arid adapted Australo–Papuan old endemic rodent that undergoes boom and bust population cycles. In this communication, we review our findings on the timing of reproduction and the potential reproductive rate of this species. To investigate the first question, the reproductive condition of adult females, and occurrence of immatures, in a population on a cattle station in central Australia was determined and, for the second, data from a laboratory colony compared to those previously published on closely related species in other environments. The findings show that, at least in the population at the times that monitoring was performed, reproductive activity was only taking place in spring and early summer, whereas the laboratory study indicates that females have a similar gestation length and litter size to those of most close relatives occurring in other environments. Males have extremely small testes and store relatively few sperm. The findings suggest that Notomys alexis might show some seasonality of reproduction at least in this region of central Australia and that this species does not have a higher reproductive rate than that of related species in other, more predictable, environments.