Sperm Dimensions Research Articles

Egg Yolk-Supplemented Tris-Citric Acid Extender Improves the Prefreezing and Post-Thaw Sperm Quality Indices of Guinea Pig (Cavia porcellus) Epididymal Spermatozoa.

This study aimed to assess the suitability of egg yolk (EY) supplementation to a tris-citric acid-based extender on cryosurvival of guinea pig (Cavia porcellus) epididymal spermatozoa. Two synthetic-based extenders, tris-citric acid-glucose plus 20% EY (TCG-EY) and tris-citric acid-fructose (TCF) both with 5% glycerol, were compared. Thirty-two epididymides were recovered from 16 adult guinea pig males by gonadectomy, and then the sperm samples were retrieved by retrograde flushing using TCG-EY and TCF extenders for left or right epididymis, respectively. TCG-EY and TCF sperm samples were frozen in static liquid nitrogen vapors through a two-step cooling procedure. Before freezing, the percentage of progressive sperm motility and sperm with intact plasma and acrosome membranes from TCG-EY sperm samples were higher (p < 0.05) than those diluted with TCF. Post-thaw sperm kinematic variables and membrane integrity were drastically reduced (p < 0.001) compared with prefreezing samples, regardless of extender type. The post-thaw plasmatic and acrosome membrane integrity from TCG-EY sperm samples was higher (p < 0.05) than those from TCF samples. Except for the length, the morphometric head dimensions of sperm diluted with TCG-EY or TCF did not vary (p > 0.05) after the freezing-thawing process compared with the prefreezing samples. In conclusion, despite greater cell cryoinjury with both extenders, the EY supplementation exerted greater cell membrane protection before and after the freezing-thawing process. This research shows an in-depth analysis of guinea pig sperm cryopreservation; however, more studies are recommended.

Identification of Honey Bee Sperm Structures Following the use of Various Staining Techniques.

Bees are currently artificially inseminated on a large scale for breeding and research purposes. The sperm of bees has a complex and varied structure, and determination of specific morphological defects in it is very difficult. Its comprehensive analysis by inspecting morphology and morphometry is an important tool for improving honey bee lines. The staining technique should interfere with the cells as little as possible while clearly showing the boundaries of the head and other elements. In this study, a comparative analysis of the morphometry of sperm was performed with various techniques for staining drone semen. Semen was collected from 150 sexually mature Buckfast bee drones by artificially everting the copulatory organ. The morphology and morphometry of the sperm were assessed on slides prepared by three staining methods according to the protocols described online, using the Sperm Class Analyzer system. The lengths of the acrosome, nucleus, head in total, midpiece, tail without midpiece, tail with midpiece, and entire sperm were measured. The most details of the drone sperm structure could be seen when stained with the eosin-nigrosin complex. This method made it possible to identify all structures and revealed the uneven distribution of sperm proteins in different parts of the tail. With the Sperm Stain method fewer details of the sperm structure were recognisable, and the fewest were with SpermBlue. The staining method, and thus the chemical reagents used, affect the dimensions of drone sperm. Given the great research potential of modified spermatozoa of insects, a standard for slide preparation for the evaluation of morphological and morphometric semen parameters should be established, as this would facilitate result comparison between laboratories and increase the value of morphological analysis of sperm for predicting and assessing fertility.

Morphometry of Boar Spermatozoa in Semen Stored at 17 °C—The Influence of the Staining Technique

Simple SummaryTo obtain satisfactory results in artificial insemination, it is necessary to use high-quality ejaculates for the production of insemination doses and then maintain the biological value of the sperm during storage. Boar spermatozoa, owing to the specific structure of the cell membrane, are particularly sensitive to temperature changes. For this reason, cryopreservation cannot be used in artificial insemination practice, and there may be limitations to successful storage of semen in a liquid state. The practice of using boar semen for artificial insemination does not include analyses of the effect of storage time of boar semen on sperm dimensions. Therefore, the aim of the study was to analyse the morphometry of sperm during storage of liquid boar semen. An attempt was also made to evaluate the suitability of three staining methods for assessment of boar sperm morphometry. The morphometric dimensions of boar sperm were shown to change during storage of liquid semen. These changes affected the sperm head more than the tail and were due to the staining method used. The analyses are very important as they provide more information about the morphometric dimensions of the sperm during preservation of boar semen. The applied sperm staining techniques allows for a more accurate assessment of male reproductive cells.The aim of the study was to assess the morphometry of sperm during storage of liquid boar semen at 17 °C. An attempt was also made to evaluate the suitability of three staining methods for assessment of boar sperm morphometry. The study was carried out on 20 Landrace boars. Semen was collected from the boars every 5 days by the manual method. Four ejaculates from each boar were analysed (80 ejaculates in total). Analyses were performed five times: at 1 h, 24 h, 48 h, 96 h, and 168 h after semen collection. Blisters with insemination doses were opened immediately before the analyses. From each insemination dose, smears were prepared for morphometric evaluation of sperm, which were stained by three methods (eosin-nigrosin—EN, eosin-gentian—EG, and SpermBlue—SB). Morphometric measurements of 15 randomly selected sperm with normal morphology were performed on each slide. The morphometric measurements included the following parameters: sperm head length, width, area, and perimeter; tail length; and total sperm length. The results of the morphometric measurements were used to calculate the head shape index. The morphometric dimensions of the sperm were shown to change during storage of semen at 17 °C. The extent of these changes, however, depended on the staining method used, as the three methods result in different morphometric dimensions of sperm, in the case of both the head and the tail. In the slides stained by the eosin-nigrosin method, the dimensions of the head and tail were smaller at every time of storage than in the slides stained by the SpermBlue and eosin-gentian methods.

Influence of Prolactin Secretion Changes on Sperm Head Size and Freezability in Ibex and Mouflon.

Aim: This work examined the influence of induced changes in prolactin (PRL) secretion on sperm cryoresistance of ibex and the mouflon. Materials and Methods: PRL secretion was modified in a first experiment by the use of bromocriptine (BCR, dopamine agonist) during the non-breeding season, and in a second experiment by the use of sulpiride (SLP, dopamine D2-receptor antagonist) during the rutting season. Slow and ultra-rapid freezing protocols were used to cryopreserve sperm samples. Results: BCR decreased blood plasma PRL concentrations, whereas SLP increased them. Cryoresistance ratios (CRs) for curvilinear velocity (VCL), straight-line velocity (VSL), and average path velocity (VAP) in BCR-treated mouflons were lower than in controls using slow-freezing (p < 0.05), while CRs of motility and morphologically normal sperm of BCR-treated mouflons were greater than controls with ultra-rapid freezing (p < 0.05). BCR increased the head sperm dimensions in ibexes (p < 0.001); conversely, BCR decreased the head dimensions in mouflons (p < 0.001). CR-motility, CR-amplitude of lateral head displacement (ALH), CR-viability, and CR-acrosome integrity in SLP-treated mouflons were lower than in controls with slow-freezing (p < 0.01); CR-viability and CR-acrosome were lower than controls with ultra-rapid freezing (p < 0.05). In ibexes, CR-ALH was lower for SLP-treated (p < 0.05). SLP treatment increased head dimensions in ibexes (p < 0.001) but did not affect the sperm head of mouflons. Conclusion: Our findings show that high levels of blood plasma PRL negatively affect the cryoresistance of ibex and mouflon sperm.

Weapons Evolve Faster Than Sperm in Bovids and Cervids.

In polyandrous species, males face reproductive competition both before and after mating. Sexual selection thus shapes the evolution of both pre- and postcopulatory traits, creating competing demands on resource allocation to different reproductive episodes. Traits subject to strong selection exhibit accelerated rates of phenotypic divergence, and examining evolutionary rates may inform us about the relative importance and potential fitness consequences of investing in traits under either pre- or postcopulatory sexual selection. Here, we used a comparative approach to assess evolutionary rates of key competitive traits in two artiodactyl families, bovids (family Bovidae) and cervids (family Cervidae), where male–male competition can occur before and after mating. We quantified and compared evolutionary rates of male weaponry (horns and antlers), body size/mass, testes mass, and sperm morphometrics. We found that weapons evolve faster than sperm dimensions. In contrast, testes and body mass evolve at similar rates. These results suggest strong, but differential, selection on both pre- and postcopulatory traits in bovids and cervids. Furthermore, we documented distinct evolutionary rates among different sperm components, with sperm head and midpiece evolving faster than the flagellum. Finally, we demonstrate that, despite considerable differences in weapon development between bovids and cervids, the overall evolutionary patterns between these families were broadly consistent.

Evaluation of the Morphometry of Sperm from the Epididymides of Dogs Using Different Staining Methods.

Simple SummarySperm morphometry is an important indicator of the quality of the spermatozoon and its effectiveness in fertilizing the egg. The morphological analysis of sperm collected from dog epididymis may be helpful in the diagnosis of reproductive disorders, valuable for breeding. There are no studies evaluating the morphometry of sperm in individual parts of the epididymal duct in dogs. For this reason, a study was carried out to evaluate the morphometry of sperm from the epididymides of dogs (caput, corpus, cauda) subjected to routine castration. This assessment was performed with the use of four staining methods (DiffQuick (DQ), SpermBlue (SB), eosin-nigrosin (EN) and eosin-gentian (EG)), popular in the assessment of sperm morphology and morphometry. The morphometric dimensions of sperm vary according to the segment of the epididymal duct, from which the cells are collected. Sperm taken from cauda of the epididymides had the smallest dimensions. These were sperm cells with smaller head dimensions (length, area, perimeter) and shorter length of the tail and the sperm total length than the sperm collected from corpus and caput. The study is especially important because it provides a more complete picture of the morphometry of sperm collected from the epididymides of dogs. Knowledge of the sperm morphometric dimensions can be helpful in developing semen preservation methods and assisted reproduction techniques. The combined use of multiple sperm staining techniques enables a more precise evaluation of male reproductive cells. These methods are appropriate for the evaluation of sperm structure, and the possibility of using all four methods enables a full characterization of sperm collected from the caput, corpus and cauda of the epididymides of dogs.Evaluation of sperm morphometry is an important criterion in the diagnosis of a male animal’s suitability for breeding. The aim of the study was to evaluate the morphometry of sperm from the epididymides of dogs subjected to routine castration using various staining methods. The study was carried out on semen collected from ten healthy dogs. Gonads were obtained from each dog during routine castration at a veterinary surgery. Then, the epididymides (caput, corpus, cauda) were isolated from the gonads, semen was collected from them and microscope slides were prepared. The slides for evaluation of sperm morphometry were prepared by four methods: DiffQuik, SpermBlue, eosin-nigrosin and eosin-gentian. A total of 2400 sperm were analyzed (240 sperm from the dog). The sperm collected from the caput and corpus of the epididymis were found to have larger heads and tails than those collected from the cauda of the epididymis. The staining method was shown to affect the morphometry of sperm taken from the epididymides of dogs. The staining methods differentiate the dimensions of the head of sperm in different parts of the epididymis but do not affect the length of the sperm tail. The occurrence of differences in the head dimensions of sperm may be linked to the use of different fixatives and chemical reagents in the staining procedure. Sperm stained by the EN method had the smallest head and tail dimensions. The greatest head area was noted in the sperm stained by the EG method. In the slides stained by the SB method, the sperm heads were relatively long but narrow. The methods used are suitable for the evaluation of sperm structure, and the possibility of using all four methods enables a full characterization of sperm collected from the caput, corpus and cauda of the epididymides of dogs.

Spermatozoon head size - the main differentiating feature between spermatozoa of blue and white Arctic fox (Vulpes lagopus).

Morphology and sperm morphometry, this is an important determinant of male reproductive capacity. Morphometric data may provide relevant information in studies focused on evolutionary biology, sperm quality assessment, including prediction of the potential fertility, semen cryopreservation, or the effect of reprotoxicants. The paper presents the morphometric analysis of spermatozoa from two colour morphs of Arctic fox (Vulpes lagopus), and attempts to determine the relationship between selected quality indicators and dimensions and shape of spermatozoa. The research material consisted of ejaculates collected once by manual stimulation from 20 one-year-old Arctic foxes (10 individuals of the blue morph and 10 of the white morph). Ejaculates were analysed for standard parameters (volume, sperm concentration, total number of spermatozoa in the ejaculate) and used for the preparation of microscopic specimens. It was found that, the dimensions of spermatozoa from Arctic foxes depend on the male colour morphs. Spermatozoa from white Arctic foxes were significantly longer (by 1.82 µm) and had larger heads (0.32 µm longer and 0.15 µm wider) compared to spermatozoa from blue Arctic foxes (P<0.05). The interactions between particular sperm dimensions indicated the occurrence of gametes differing in shape. The all correlation coefficients between the morphometric traits of spermatozoa were statistically significant. Our research proved that in the blue Arctic foxes, sperm dimensions (tail length and total sperm length) can be related to the percentage of spermatozoa with primary changes (respectively: r = -0.68 and r = -0.75; at P <0.05). However, in the case of white Arctic foxes, these characteristics depend on the ejaculate volume (respectively: r = 0.65 and r = 0.68; at P <0.05).

Effects of breed and ejaculate volume on sperm morphology and semen parameters of boars.

The aim of the study was to determine the relation between the semen quality, frequency of sperm defects, sperm dimensions and shape, and the ejaculate volume of Large White and Landrace boars. A total of 648 ejaculates collected from 31 Large White and 30 Landrace boars were divided into three groups according to the criterion of the ejaculate volume. In this study Landrace boars produced ejaculates with higher volume, sperm concentration, and total numbers of spermatozoa than Large White boars. Landrace boars also showed a lower frequency of sperm with morphological abnormalities (P < 0.05). Landrace boars sperm had larger heads, which were by 0.15 μm longer, and by a larger perimeter and area (P < 0.05). Landrace boar spermatozoa also had a longer flagellum and were generally larger and by 2.07 μm longer than Large White boar sperm (P < 0.05). Significant differences were also found in the shape of sperm of the two breeds (P < 0.05). Landrace boars sperm had more elongated heads, and the ratio of head size to flagellum length was lower than in Large White boars sperm (P < 0.05). Sperm from ejaculates with low volume had a shorter flagellum and a greater head length/flagellum length ratio than sperm from medium- and high-volume ejaculates (P < 0.05).

Impact of sperm concentration on sperm morphology of large white and landrace boars

The aim of the study was to determine the dependence of semen quality, frequency of sperm defects, and sperm dimensions and shape on sperm concentration in ejaculates of Large White and Landrace boars. A total of 648 ejaculates collected from 31 Large White and 30 Landrace boars were divided into three groups according to the criterion of sperm concentration. The physical characteristics of all ejaculates were determined, and morphological and morphometric examination of spermatozoa was performed. The characteristics of the ejaculates, frequency of sperm defects, and dimensions and shape of spermatozoa were shown to depend on the sperm concentration. Ejaculates with a high sperm concentration contain a large number of sperm, but have a smaller volume than ejaculates with a lower sperm concentration. Sperm from ejaculates with the lowest sperm concentration have larger dimensions than sperm from ejaculates with intermediate and high sperm concentrations. This is expressed in a larger head area and perimeter and in greater total sperm length. The dependence of the ejaculate characteristics and the size and shape of sperm on the sperm concentration is influenced by the breed. In the ejaculates of Landrace boars, these relationships are more pronounced than in Large White boars. An increased sperm concentration reduces the occurrence of the Dag defect but promotes the occurrence of sperm with a proximal droplet, a pseudodroplet, or a distal droplet.

Comparison of the structure of chinchilla sperm isolated from semen and from the tail of the epididymis.

Sperm cells isolated from the tail of the epididymis and from the semen of the same individuals were analysed. The use of silver nitrate to stain sperm cells isolated from the tail of the epididymis made it possible to identify structures that were not visible in the sperm from semen. Silver nitrate very clearly distinguished the acrosomal and distal parts of the sperm head. Following silver nitrate staining, the sperm isolated from the tail of the epididymis were characterized by dark 'collars' in the distal part of the head. These 'collars' are not visible in the sperm cells isolated from semen. The results of the study indicate differences in the dimensions of sperm isolated from the tail of the epididymis and sperm in semen. Sperm isolated from the tail of the epididymis had smaller heads, despite their longer length, and had longer midpieces and tails than ejaculate sperm. Silver nitrate staining is a simple and fast technique. Silver nitrate makes it possible to identify the acrosome and post-acrosomal region of the sperm head and to clearly identify the midpiece. Therefore, it can be successfully used to supplement routine techniques for evaluating sperm morphology or as an independent technique.

The Effect of Age in the Shape of the Spermatozoa Frozen Friesian Bulls

This study was aimed to determine whether there are any differences in the shape and dimensions of bulls sperm using different ages, as well as to know the maturity of the sperm, then choose the bull for insemination or to freeze the taken semen to be used in artificial insemination. Now a day become morphology shape for sperm important item in the valuation of the semen and chose the best normal sperm whence dimension and shape. Methods were used and bulls were classified by age into three groups, the first group includes 4 bulls aged 2-4 years, the second group includes 4 bulls 4-6 years old, the third group includes 4 bulls 6-8 years old. Semen of each group was taken randomly and the mature and intact semen were examined. The results were revealed that the highest value of head’s length (6-8 years category) was (8.20), while for 4-2 years category was the least (7.81). For the width, the third category was recorded the highest (4.51) along with the other. The Ellipticity inducts that 4-2 years group was the highest value (1.85), while for elongation character the 2-4 years group was the highest with (0.3) compared with the other.&#x0D; It can be concluded our study in the current to the next score whenever the bull offers in the form of life has become the best sperm beltala can choose sperm in the freezer.

Moderate heritability and low evolvability of sperm morphology in a species with high risk of sperm competition, the collared flycatcher Ficedula albicollis

Spermatozoa represent the morphologically most diverse type of animal cells and show remarkable variation in size across and also within species. To understand the evolution of this diversity, it is important to reveal to what degree this variation is genetic or environmental in origin and whether this depends on species' life histories. Here we applied quantitative genetic methods to a pedigreed multigenerational data set of the collared flycatcher Ficedula albicollis, a passerine bird with high levels of extra-pair paternity, to partition genetic and environmental sources of phenotypic variation in sperm dimensions for the first time in a natural population. Narrow-sense heritability (h2 ) of total sperm length amounted to 0.44±0.14 SE, whereas the corresponding figure for evolvability (estimated as coefficient of additive genetic variation, CVa ) was 0.02±0.003 SE. We also found an increase in total sperm length within individual males between the arrival and nestling period. This seasonal variation may reflect constraints in the production of fully elongated spermatozoa shortly after arrival at the breeding grounds. There was no evidence of an effect of male age on sperm dimensions. In many previous studies on laboratory populations of several insect, mammal and avian species, heritabilities of sperm morphology were higher, whereas evolvabilities were similar. Explanations for the differences in heritability may include variation in the environment (laboratory vs. wild), intensity of sexual selection via sperm competition (high vs. low) and genetic architecture that involves unusual linkage disequilibrium coupled with overdominance in one of the studied species.

The use of two staining methods for identification of spermatozoon structure in roosters

Many of the methods used to stain semen result in very pronounced coloring of the sperm, but unfortunately they do not distinguish their individual structures, which play a key role in the fertilization process. Hence the aim of this study was to identify sperm structures using two staining techniques in the semen of roosters from breeding flocks. The subject of the study was the sperm of roosters from a Ross 308 breeding flock. To capture the differences in the dimensions of sperm subjected to the effect of different chemical substances in dyes, microscope slides were stained by two techniques: with an AgNO3 solution and by a differential method (eosin-nigrosin test). Assessment was made of the degree of coloration and the number of details that could be identified in the morphological structure of the sperm. The use of AgNO3 allowed accurate identification of the acrosome, nucleus, and midpiece, which were visible in the slides stained with eosin-nigrosin, but only in dead spermatozoa. The AGNO3 staining technique used in this study reveals the cell nucleus within the head and can be an alternative method to analysis with a scanning electron microscope. This staining technique can be used to stain sperm structures that cannot be seen in other methods of slide preparation, which means that it can be considered for routine use in assessing the fertility of roosters in breeder flocks.

Sperm structure in Parasitidae mites (Parasitiformes: Mesostigmata: Gamasina)

This contribution reviews the ultrastructure of ribbon-type sperm in 14 genera of both subfamilies (7 in Pergamasinae and 7 in Parasitinae) of the Parasitidae family (Parasitiformes: Mesostigmata: Gamasina); in total 27 species were considered, of which sperm ultrastructure was studied for the first time in 17 species and 9 genera. We found a wide range of sperm dimensions and nucleus lengths, but basic external and internal structures were substantially constant across genera. Spermatozoa are rod- or club-shaped cells with an elongated nucleus. The chromatin granules are focused in the middle zone of the nucleus. The cytoplasm around the nucleus and in the adjoining postnuclear region is filled with inclusion bodies with striated content (striated inclusion bodies, sIBs), whereas in the distant postnuclear region they are replaced by larger granular inclusion bodies (gIBs) usually containing a striated core surrounded by granular material. Mitochondria are distributed mostly subplasmalemmally in the nuclear region and between gIBs in the postnuclear region of the sperm cell. The most variable feature of the spermatozoa is the number of compound longitudinal ribbons of plasmalemmal origin alternating with subplasmalemmal cisterns: 9 (Leptogamasus anoxygenellus) to 21 (Pergamasus barbarus) in Pergamasinae and 5 (Parasitus berlesei and Paracarpais loricatus) to 30 (Paracarpais lunulata) in Parasitinae. In general, ribbons are electron-dense in the nuclear region but more lucent in the postnuclear region. The variation in sperm structure was not reflected in the taxonomic arrangement of genera and subfamilies within Parasitidae, but it must be emphasized that the taxonomy of Parasitidae is still awaiting a comprehensive modern revision.

Dimensional characteristics of spermatozoa of Nili-Ravi buffalo bulls: seasonaland climatic influences

This study was conducted in 2 different climatic zones of Punjab Province of Pakistan, the Sahiwal and Bahawalpur divisions, simultaneously for the period of 1 year divided into seasons. Seven adult Nili-Ravi buffalo breeding bulls from each division were used. Dimensional characteristics of spermatozoa were determined. Season had a nonsignificant effect on the sperm head length in both divisions and a nonsignificant difference was also observed between bulls of the Sahiwal and Bahawalpur divisions. The buffalo bulls of both divisions exhibited significantly increased sperm head breadth in autumn, whereas a nonsignificant difference was observed between divisions. Sperm head shape values were significantly different among the seasons in both the divisions whereas they were nonsignificantly different between the two divisions. Midpiece length value was significantly higher in winter than spring in both divisions and also significantly different between the divisions. Sperm tail length was significantly increased in autumn in Sahiwal and in autumn and spring in Bahawalpur. It was significantly longer in Sahiwal than Bahawalpur. The pattern of seasonal and climatic influence on total sperm length was similar to that of sperm tail length. In conclusion, autumn and spring seasons and the climate of the Sahiwal division have additive effects on sperm dimensions, except midpiece length.

Importance of sperm morphology during sperm transport and fertilization in mammals.

After natural or artificial insemination, the spermatozoon starts a journey from the site of deposition to the place of fertilization. However, only a small subset of the spermatozoa deposited achieves their goal: to reach and fertilize the egg. Factors involved in controlling sperm transport and fertilization include the female reproductive tract environment, cell-cell interactions, gene expression, and phenotypic sperm traits. Some of the significant determinants of fertilization are known (i.e., motility or DNA status), but many sperm traits are still indecipherable. One example is the influence of sperm dimensions and shape upon transport within the female genital tract towards the oocyte. Biophysical associations between sperm size and motility may influence the progression of spermatozoa through the female reproductive tract, but uncertainties remain concerning how sperm morphology influences the fertilization process, and whether only the sperm dimensions per se are involved. Moreover, such explanations do not allow the possibility that the female tract is capable of distinguishing fertile spermatozoa on the basis of their morphology, as seems to be the case with biochemical, molecular, and genetic properties. This review focuses on the influence of sperm size and shape in evolution and their putative role in sperm transport and selection within the uterus and the ability to fertilize the oocyte.

The Importance of Ejaculate Volume for the Physical Parameters of Ejaculates and Sperm Morphology of Hypor Boars

The study aimed at analysing the effects of ejaculate volume on the physical parameters of ejaculates and the sperm morphology of Hypor boars. The analyses involved 114 ejaculates collected from 12 Hypor insemination boars. The ejaculates were classified according to the criterion of ejaculate volume. Three groups were specified: ejaculates with a volume of 251 ml or lower (Group I), ejaculates with a volume of 252-310 ml (Group II), and ejaculates with a volume of 311 ml or higher (Group III). The ejaculates were assessed to identify the basic physical traits and determine the incidence of morphological abnormalities in the spermatozoa, specifying major and minor abnormalities. Furthermore, the morphological structure indices for the spermatozoa were also calculated. Rising ejaculate volume accompanied with a rise in the total number and motility of spermatozoa, and a simultaneous slight fall in sperm concentration in the ejaculates. The ejaculates with the highest volumes turned out to contain more morphologically well-formed spermatozoa. We also determined that rising ejaculate volume is accompanied with increasing sperm dimensions, especially those of the head. The increased parameters were the length and the width of sperm heads, as well as their perimeters and areas. Ejaculate volume has an impact on the shape of Hypor boar spermatozoa. As the ejaculate volume increases, the shape of sperm heads becomes increasingly more oval. Additionally, spermatozoa in ejaculates with greater volumes have larger heads in relation to flagellum length.

No evidence for effects of formalin storage duration or solvent medium exposure on avian sperm morphology

Morphometric analysis of avian spermatozoa from sperm samples preserved in formalin is a frequently adopted procedure in basic science (e.g. evolutionary ecology) and applied disciplines (e.g. animal breeding). Many research questions such as individual-based longitudinal studies of sperm traits require comparisons of formalin-stored sperm samples collected across multiple sampling events, which may be separated by years. Such analyses presuppose that prolonged storage in formalin does not affect sperm morphology, an assumption often implicitly made in the analysis of avian sperm morphology. This assumption, however, has never been tested, although for many study designs a potential effect of sperm storage duration may well confound the focal analysis. Based on pairwise comparisons of 22 experimental ejaculates from three passerine bird species, we found no evidence that differential storage duration of more than 1 year had affected the total length of spermatozoa stored in a 5 % formaldehyde solution. This suggests that formalin-stored sperm samples from long-term studies or museum collections can be merged in combined analyses without confounding differential storage duration with natural between-year variation in sperm dimensions or age effects in longitudinal studies. Based on pairwise comparisons of 29 split ejaculates, we also found no evidence that spermatozoa differed in length when solved initially in either phosphate buffered saline or Dulbecco’s Modified Eagle Medium, a standard medium for videotaping live sperm, prior to preservation and storage in formalin. Sperm samples treated differently in this respect may thus be merged into combined analyses, too.

The spermatozoa structure peculiarities of the subgenus Sumeriomys (Rodentia, Arvicolinae, Microtus)

Owing to distinct differences in size and shape in different taxa, spermatozoa can be of a high diagnostic value. The functional and evolutionary nature of such diversity is poorly understood. The purpose of the study was to summarize the data on the differences in sperm design and linear parameters between the subgenera Sumeriomys and Microtus (the genus Microtus) and to carry out the same compar- ison between the socialis and groups of species within the subgenus Sumeriomys. We obtained the data on shape and size of spermatozoa in seven nominal forms of the subgenus Sumeriomys. The species of the subgenus Sumeriomys are quite similar in sperm design, which distinctly differs from that in the representatives of the subgenus Microtus. The spermatozoa of the Sumeriomys species also differ from those of the Microtus representatives in some linear measurements and quantitative indices. These data confirm the taxonomic distinctness of the social voles as an independent subgenus Sumeriomys. Within the subgenus Sumeriomys some essential differences were revealed in sperm dimensions. The largest spermatozoa are observed in the species of the group, especially in M. guentheri (a head length 7.60 µκ). In M. hartingi they are slightly smaller in size (in two subspecies correspondingly 6.96 and 7.25 mk). In three nominal forms of the socialis group the spermatozoa are smaller (a head length 7.01-7.21 µκ), than in the group. The ratio of head length to its width in M. guentheri and M. hartingi is respectively 1.5 and 1.46, while in the socialis group, 1.42-1.47. In voles of the subgenus Microtus it is 1.8-2.4. The length of the medium part of spermatozoon's tail is the most variable character. The ratio of the sperm tail medium part length to head length in Microtus is higher than 2.8 (2.8-3.2), but in Sumeriomys it is lower than 2.8 (2.4-2.7).

Sperm morphology in two house mouse subspecies: do wild-derived strains and wild mice tell the same story?

Being subject to intense post-copulatory selection, sperm size is a principal determining component of male fitness. Although previous studies have presented comparative sperm size data at higher taxonomic levels, information on the evolution of sperm size within species is generally lacking. Here, we studied two house mouse subspecies, Mus musculus musculus and Mus musculus domesticus, which undergo incipient speciation. We measured four sperm dimensions from cauda epididymis smears of 28 wild-caught mice of both subspecies. As inbred mouse strains are frequently used as proxies for exploring evolutionary processes, we further studied four wild-derived inbred strains from each subspecies. The subspecies differed significantly in terms of sperm head length and midpiece length, and these differences were consistent for wild mice and wild-derived strains pooled over genomes. When the inbred strains were analyzed individually, however, their strain-specific values were in some cases significantly shifted from subspecies-specific values derived from wild mice. We conclude that: (1) the size of sperm components differ in the two house mouse subspecies studied, and that (2) wild-derived strains reflect this natural polymorphism, serving as a potential tool to identify the genetic variation driving these evolutionary processes. Nevertheless, we suggest that more strains should be used in future experiments to account for natural variation and to avoid confounding results due to reduced variability and/or founder effect in the individual strains.