No evidence for asymmetric sperm deposition in a species with asymmetric male genitalia (original) (raw)
Related papers
Morphopathology of Sperm: It's Impact on Fertilization
Journal of Reproductive and Stem Cell Biotechnology, 2012
Terato-, astheno- and necrozoospermia negatively influence fertility prognosis in spontaneous conditions or with the use of various assisted reproductive techniques including conventional in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). The correct identification of sperm pathologies will indicate different fertility potentials and outcomes in assisted reproduction technology. Anomalies of only the spermatozoa flagella bear a promising prognosis, but those affecting the sperm chromatin and the neck region entail an increasing chance of failure, which highlights the differential roles played by specific sperm components in fertilization, implantation and early embryonic development. Sperm pathology therefore allows an understanding of abnormal function that goes beyond that provided by classical sperm morphology classifications that are mainly based on descriptions of abnormal sperm shapes with no insight into the mechanisms or the pathological details.
Afterword to Sperm morphometrics today and tomorrow special issue in Asian Journal of Andrology
Asian Journal of Andrology, 2016
The fact that only one spermatozoon is enough to achieve a pregnancy has delayed spermatology research in human. On the other hand, the high variability of human infertility cases may make it seem an unattractive investment whereas the opposite is the case: the papers presented here show that investment in the equipment, and the researchers, to correlate clinical data with the morphometric results, would generate a range of observations on sperm subpopulations in fertile and infertile men that could explain currently unexplained causes of infertility. THE SIGNIFICANCE OF THE MORPHOMETRIC ANALYSIS OF SPERM CELLS The application of principal component (PC) and discriminant analysis to reveal subpopulations of spermatozoa is a powerful tool to evaluate raw semen and processed sperm cell suspensions, but not many clinicians are aware of the technique. As described in several papers here, PC analysis is a multivariate statistical method that reduces the number of variables used in subsequent calculations used to describe the data. By integrating the original variables according to their coherence in a database into a new complex mathematical variable, clearly defined homogeneous subpopulations of spermatozoa can be defined. In support of the theory above, the papers presented here showed that most of the variance from up to 13 morphometric variables could be explained by only two or three PCs: two in bulls, 16 adolescent humans, 8 adult human sperm head DNA, 9 domestic cats, 10 puma, 11 roosters, and guinea fowls 12 and three PCs in adult human split ejaculate samples. 7 From these PCs, discriminant analysis was used to generate clearly separable homogeneous subpopulations of morphological forms. Here, the number of subpopulations ranged from two to five: two (for the X-/ Y-bearing bovine sperm heads, 15 for large+elongated/small+elongated sperm heads in human adolescents 8), three (for large+round/elongated/ small spermatozoa in human sperm heads in split ejaculate fractions, 7 for elongated+intermediate/large+high acrosome/short+small sperm heads in the puma, 11 for small, wide and slightly elliptical/average size, long, narrow and very elliptical/very large, wide and elliptical sperm heads in the rooster 12), four (for large/high medium/low medium/ small in human sperm head DNA, 9 for small/short/large/narrow sperm heads in the bull, 14 for shape-related sperm heads in both normo-and terato-zoospermic cats 10) to five (for very small, wide, very short and slightly elliptical/small, very short, very wide and slightly elliptical/ very large, very wide, short and slightly elliptical/average size, very long, very narrow and very elliptical/average size, long, narrow and elliptical sperm heads in the guinea fowl 12). These awkward, convoluted, and very subjective descriptions of the nature of the sperm clusters generated by this technique highlight very well the difficulty in getting agreement (be it intra-or inter-laboratory, national or international) between observers on the definitions of normal sperm morphology, let alone abnormal forms. In contrast, the ability not only to detect, but also unambiguously define, subpopulations of spermatozoa by objective measurements derived from CASA-Morph is an important advance in morphological analysis. From this first step, advantage has to be taken of this knowledge for diagnosis of infertility, or promotion of reproductive performance in conservation biology, animal husbandry, or in the clinic. In other
An unexpected twist: Sperm cells coil to the right in land snails and to the left in song birds
Contributions to Zoology
In animals, cell polarity may initiate symmetry breaking very early in development, ultimately leading to whole-body asymmetry. Helical sperm cells, which occur in a variety of animal clades, are one class of cells that show clearly visible bilateral asymmetry. We used scanning-electron microscopy to study coiling direction in helical sperm cells in two groups of animals that have figured prominently in the sperm morphology literature, namely land snails, Stylommatophora (514 spermatozoa, from 27 individuals, belonging to 8 species and 4 families) and songbirds, Passeriformes (486 spermatozoa, from 26 individuals, belonging to 18 species and 8 families). We found that the snail sperm cells were consistently dextral (clockwise), whereas the bird sperm cells were consistently sinistral (counterclockwise). We discuss reasons why this apparent evolutionary conservatism of sperm cell chirality may or may not be related to whole-body asymmetry.
Sperm morphology and aneuploidies: defects of supposed genetic origin
Andrologia, 2006
As individuals with genetic sperm defects are intracytoplasmic sperm injection candidates, the study of the chromosomal constitution of their spermatozoa is of great interest. This study is a review of the current literature concerning fluorescence in situ hybridisation studies in spermatozoa with genetic sperm defect as 'round head', 'dysplasia of fibrous sheath' (DFS), 'primary ciliary dyskinesia' (PCD), the 'detached tail' and the 'absence of fibrous sheath'. Regarding sperm head defects, elevated XY disomy and diplodies were detected. Genetic defects affecting the sperm tail seemed to have a different correlation with chromosome meiotic segregation. Only chromosome 18, among the autosomes, was studied and the percentage of frequency of disomy was generally within the normal range. In the more frequently studied defect, DFS, the alterations in gonosome disomy and diploidy were recorded by different groups. Regarding PCD defects, elevated frequencies of disomy of sex chromosomes and diploidy were observed, whereas the absence of the fibrous sheath and the detached tail did not show any meiotic disturbance. The problem of genetic sperm defects should be seriously considered when these sperm are used for assisted reproduction, owing to the high risk of transmission of chromosomal imbalance and of mutations that could cause genetic sperm defects in offspring.
Human Reproduction, 1999
Round spermatids can be collected from testicular biopsy material or occasionally from semen samples. We evaluated the influence of the passage of round spermatids through the male reproductive tract on their reproductive potential. A model of abnormal release of round spermatids from the seminiferous epithelium was created in mature male rats (group A). Additional sham-treated rats of the same age served as a control group (group B). Round spermatids were collected from the testicles of rats of both groups, the epididymides of rats of group A, and the vaginae of mature female rats mated with rats of group A. Isolated round spermatids were processed for ooplasmic injections. Injected oocytes were cultured. At 96 h post-injection, the blastocyst development rate was significantly higher in the groups of oocytes injected with testicular spermatids than the groups of oocytes injected with spermatids recovered from the vaginae, or the head, body, or tail of the epididymides. It appears that round spermatids recovered from testicular biopsy material have larger reproductive capacity than ejaculated round spermatids, due to mechanical or chemical detrimental influences of storage/passage through the male reproductive tract (outside the testicle) on the capacity of round spermatids to induce optimal early embryonic development.
Importance of sperm morphology during sperm transport and fertilization in mammals
Asian Journal of Andrology, 2016
interactions and early embryo development. 9 Surprisingly, the "sex of the sperm cell" appears to modify the oviductal transcriptome in a sex-specific manner. 10 Once in the oviduct, the epithelial cells appear to exert rigorous selection, being able to bind spermatozoa with particular characteristics such as normal chromatin, 8 lack of capacitation, or morphological "normality" 11,12 among others. The failure of abnormal spermatozoa to reach the site of fertilization has also been demonstrated in various species. 13,14 One hypothesis is that females can select which spermatozoa reach and fertilize the oocyte; 15,16 this introduces the concept of the "sperm passport. " Just as each individual person has some characteristics that make him different from others, i.e., biometric identifiers which are physiological characteristics related commonly to the shape of the body, each spermatozoon could have its own biometric identifier, making it able (or not) to progress along the female tract and fertilize. Conversely, females could use such molecular mechanisms to recognize and obtain the information from an individual spermatozoon. 15 Moreover, it is known that an ejaculate is composed of different subpopulations of spermatozoa. 5 The subpopulations are characterized by differences in motility, DNA fragmentation status, morphology or shape and size, sensitivity to signaling molecules, and many other properties. Motility is very important; when females are inseminated with spermatozoa exhibiting different levels of motility, those spermatozoa with poor motility are found in the backflow after only INTRODUCTION A huge number of spermatozoa are deposited in the female genital tract at ejaculation, but little is known about the special characteristics which enable a particular spermatozoon to reach the oocyte and fertilize it in preference to the other millions around it. Within the female genital tract, spermatozoa have to negotiate different physical barriers and undergo complex interactions. In some species (i.e., humans, sheep), the cervix presents an important obstacle and is the first "filter" for abnormal spermatozoa. 1 Once in the uterus, spermatozoa are in contact with uterine fluid, which, in species such as the mouse, induces deleterious effects on spermatozoa unless they are provided with protein SVS2 present in seminal plasma. 2 Moreover, within the uterus, spermatozoa make contact with different cell types (cell-cell interaction), among them polymorphonuclear leukocytes (PMNs), that are present in the lumen of the uterus after insemination. It is not clear yet whether the PMNs are able to distinguish between abnormal and normal spermatozoa, although damaged, capacitated, and moribund spermatozoa seem to be eliminated by phagocytosis. 3-5 Once in the oviduct, the environment is more suitable for promoting sperm viability. In this respect, leukocytes in this anatomical region are sparse or even absent 6 and the interaction with oviductal epithelial cells and oviductal fluid modulates sperm function. 7,8 Moreover, the arrival of spermatozoa in the oviduct modulates local gene expression, thus preparing the oviduct for an adequate environment for gamete
Importance of sperm morphology during their transport and fertilization in mammals
Asian Journal of Andrology, 2016
interactions and early embryo development. 9 Surprisingly, the "sex of the sperm cell" appears to modify the oviductal transcriptome in a sex-specific manner. 10 Once in the oviduct, the epithelial cells appear to exert rigorous selection, being able to bind spermatozoa with particular characteristics such as normal chromatin, 8 lack of capacitation, or morphological "normality" 11,12 among others. The failure of abnormal spermatozoa to reach the site of fertilization has also been demonstrated in various species. 13,14 One hypothesis is that females can select which spermatozoa reach and fertilize the oocyte; 15,16 this introduces the concept of the "sperm passport. " Just as each individual person has some characteristics that make him different from others, i.e., biometric identifiers which are physiological characteristics related commonly to the shape of the body, each spermatozoon could have its own biometric identifier, making it able (or not) to progress along the female tract and fertilize. Conversely, females could use such molecular mechanisms to recognize and obtain the information from an individual spermatozoon. 15 Moreover, it is known that an ejaculate is composed of different subpopulations of spermatozoa. 5 The subpopulations are characterized by differences in motility, DNA fragmentation status, morphology or shape and size, sensitivity to signaling molecules, and many other properties. Motility is very important; when females are inseminated with spermatozoa exhibiting different levels of motility, those spermatozoa with poor motility are found in the backflow after only INTRODUCTION A huge number of spermatozoa are deposited in the female genital tract at ejaculation, but little is known about the special characteristics which enable a particular spermatozoon to reach the oocyte and fertilize it in preference to the other millions around it. Within the female genital tract, spermatozoa have to negotiate different physical barriers and undergo complex interactions. In some species (i.e., humans, sheep), the cervix presents an important obstacle and is the first "filter" for abnormal spermatozoa. 1 Once in the uterus, spermatozoa are in contact with uterine fluid, which, in species such as the mouse, induces deleterious effects on spermatozoa unless they are provided with protein SVS2 present in seminal plasma. 2 Moreover, within the uterus, spermatozoa make contact with different cell types (cell-cell interaction), among them polymorphonuclear leukocytes (PMNs), that are present in the lumen of the uterus after insemination. It is not clear yet whether the PMNs are able to distinguish between abnormal and normal spermatozoa, although damaged, capacitated, and moribund spermatozoa seem to be eliminated by phagocytosis. 3-5 Once in the oviduct, the environment is more suitable for promoting sperm viability. In this respect, leukocytes in this anatomical region are sparse or even absent 6 and the interaction with oviductal epithelial cells and oviductal fluid modulates sperm function. 7,8 Moreover, the arrival of spermatozoa in the oviduct modulates local gene expression, thus preparing the oviduct for an adequate environment for gamete
Behavioral Ecology and Sociobiology, 2019
Behavioural diversity is a basic component of biodiversity, with implications in ecological interactions at the intra-and interspecific levels. The reproductive behaviour of Odonata (dragonflies and damselflies) is unique among insects and conditioned by the anatomical separation between the male's reproductive organs and the intromittent organ. Prior to mating, males must translocate sperm from the genital pore in the ninth abdominal segment to the seminal vesicle located ventrally in the second abdominal segment. This behaviour, exclusive to odonates, is known as intra-male sperm translocation (ST). Here, we review the literature on ST and use phylogenetic comparative analyses to investigate the evolution of ST within the Odonata. Information on ST was compiled for 176 species, with the commonest variant being ST once per mating, after tandem formation (66%). Other variants found were ST involving precopulatory genital touching (10%), ST by the male alone before tandem (16%) or after copulation (5%), and repetition of ST during the same copulation (3%). The precopulatory genital touching might have evolved to detect female receptivity. ST before tandem formation might be favoured when mating opportunities are scarce and copulations are brief. ST after mating might be favoured if males need to be ready to copulate fast. Finally, repeated ST could have evolved through postcopulatory sexual selection in males with limited sperm removal ability, as a means to improve their sperm competition. The most plausible scenario for the evolution of ST is that the ancestors of the Odonata produced a spermatophore and attached it to the body, leading towards the evolution of the secondary genitalia in males. Our study emphasises the role of behavioural diversity to understand behavioural evolution. Significance statement Unique behaviours are exclusive of a few individuals, populations and/or species. The intra-male sperm translocation (ST) of dragonflies and damselflies is a unique behaviour in animals: before mating, males need to transfer sperm from the primary to the secondary genitalia, which are anatomically separated. Thus, the viability and quality of sperm (i.e. fertility) will depend on the timing of ST relative to copulation. Our literature review found a variety of ST variants, being ST in tandem and before copulation the ancestral strategy. We discuss putative evolutionary routes for all the variants found and emphasise the importance of retrieving detailed observations of such unique behaviours in the field, which could help to better understand behavioural evolution in this insect group. Behavioural diversity is rarely addressed by conservation strategies, despite unique behaviours being at a higher risk of extinction.