The effect of the staining technique on morphological and morphometric parameters of boar sperm

Assessment of Boar Semen Morphology and Morphometry

The evaluation of sperm morphology is crucial in assessing reproductive health in both humans and animals. In humans, the World Health Organization recognizes the importance of morphology in semen analysis. Similarly, in animal breeding programs, assessing sperm morphology is essential for selecting superior breeding candidates. This review specifically focuses on the pig as a model, given its importance in meat production and as a research model for reproductive biology. Several studies have demonstrated the impact of sperm morphological abnormalities on fertility in pigs, although some studies have reported conflicting results. Understanding the importance of semen morphology evaluation in boar production and describing the changes in semen morphology and evaluation procedures are the main objectives of this review. Factors influencing semen morphological abnormalities, such as breed, age, and environmental conditions, are discussed. Various techniques for assessing sperm morphology, including traditional microscopic evaluation, staining techniques, computer-assisted sperm analysis (CASA), and advanced imaging techniques, are reviewed. The relationships between morphology and other sperm parameters are explored, and the significance of morphology in the production of seminal doses is emphasized. Finally, future directions and challenges in the assessment of boar sperm morphology are discussed, including advances in imaging and analysis techniques, integration of molecular and genetic approaches, standardization of guidelines, and research into fertility outcomes and long-term follow-up studies. By addressing these challenges, improvements in the diagnosis and reproductive outcomes of individuals with abnormal sperm morphology can be achieved.

Diosmin protects the testicles from doxorubicin-induced damage by increasing steroidogenesis and suppressing oxido-inflammation and apoptotic mediators

BACKGROUND

Cancer chemotherapy with doxorubicin (DOX) has been linked to serious testicular damage and spermatotoxicity due to the induction of oxidative stress, inflammation, and apoptosis. Thus, the current study was carried out to assess the potential ameliorative impact of diosmin, an antioxidant drug, against DOX-mediated spermatoxicity and testicular injury in rats.

MATERIAL AND METHODS

In the experimental protocol, rats were grouped into 4: Group 1 received vehicle and saline for 8 weeks while group 2 received diosmin and saline concomitantly for 8 weeks. Group 3 was given 3 mg/kg intraperitoneal DOX once every 7 days for 8 weeks. Group 4 was given 40 mg/kg of diosmin orally for 56 days followed by DOX diosmin administration after one hour. After 56 days of treatment, sperm quality, hormonal testing, biochemical parameters, and histological alterations in the testes were evaluated.

RESULTS

DOX-induced reduce spermatogenic function, testicular 3- and 17β-Hydroxysteroid dehydrogenases, and serum follicle stimulating hormone, luteinizing hormone, and testosterone. It also enhanced inflammation, testicular oxidative damage, and apoptosis. The histopathologic examinations corroborated the biochemical results obtained. Significantly, diosmin treatment reduced DOX-induced injury, as evidenced by restored testicular architecture, increased steroidogenesis, preservation of spermatogenesis, suppression of oxide-inflammatory response, and apoptosis.

CONCLUSION

It was found that through diosmin antioxidant, anti-apoptotic, and anti-oxido-inflammatory it presents a possible therapeutic alternative for protecting testicular tissue against DOX's harmful effects.

Morphology and morphometry of sperm in Kurdish stallions, a local breed from western Iran

The present work was designed for a thorough investigation into the sperm morphology and morphometry of Kurdish stallions. The semen samples were collected from 10 Kurdish stallions. Three preparations from each ejaculate were stained with eosin-nigrosin (EN), Diff-Quik (DQ) and Rose Bengal (RB). The area, perimeter, length and width of the sperm head as well as tail length and total sperm length were measured. The parameters ellipticity, elongation, roughness and regularity were calculated. The morphology of sperm was also investigated under scanning and transmission electron microscopes. DQ and RB provided more clarified images for examining sperm structures compared to the EN method. The head length, head width, area and perimeter in EN were significantly higher than those in DQ and RB (p ≤ .05). Furthermore, the difference in head width, head area and head perimeter between DQ and RB was not significant (p ≥ .05). The tail length and total sperm length in all methods were close together (p ≥ .05). The highest percentage of normal sperm was seen in DQ and RB methods (82.55 ± 2.88 and 88.31 ± 5.19) respectively. The highest values for ellipticity, elongation and regularity were found in RB, whereas the highest value for roughness was measured in EN. Tail defects including coiled tails, and folded midpieces were the most frequent. Scanning electron microscope revealed two types of head shapes: heads with round anterior border, and heads with flat anterior border. The results indicated that despite the routine use of EN for morphological assessment of stallion sperm, RB and DQ can be considered for more clarified details of sperm structure including acrosome and midpiece. Furthermore, the Kurdish stallion sperm has morphometric traits in the normal range established for stallions; yet, some traits were larger than those reported for other breeds. It seems that the sperm of the Kurdish stallion has a longer head and tail in comparison with other horse breeds.

Kinematic and Morphometric Assessment of Fresh Semen, before, during and after Mating Period in Brahman Bulls

The objective of the present study was to determine the effects that the reproductive season has on the motility, kinematics, morphology, and sperm morphometry of Brahman bulls evaluated with a commercial CASA system. The experiment was carried out at the Costa Rica Institute of Technology from March to August 2021. A total of eight Brahman bulls were used. A total of 28 ejaculates were collected in the pre-mating period (PMP), during it (DMP), and after it (AMP) using an electroejaculator. The sperm concentration was measured with the Accuread photometer. The motility was measured using a Spermtrack® counting chamber. The analyses were performed with the CASA-Mot ISAS®v1 system. The morphology was analyzed using a microscope with a negative phase contrast objective. Morphometry was evaluated with the CASA-Morph. The sperm concentration did not present differences between the PMP and AMP; however, it was significantly higher than DMP (p > 0.05). Regarding the progressiveness variables, linearity on forward progression (LIN), straightness (STR), and wobble (WOB) were higher (p < 0.05) DMP. A kinematic principal component analysis grouped all the variables into three factors and an effect on the reproductive period was found (p < 0.05) in the parameters of the head and middle part of the sperm, such as width and perimeter, which were greater in the PMP. The length of the sperm head in the PMP and DMP did not show differences; however, both were larger (p < 0.05) than AMP. The insertion distance of the middle piece of the sperm was significantly greater than DMP. Finally, the PMP contained cells with a larger insertion angle (p < 0.05) than AMP. These findings are important to understand the implications of reproductive status on sperm quality and to consider them in andrological evaluations.

Multi- and transcriptomic changes of chronic exposure to bisphenol A reveals reproductive toxicity in male zebrafish

Bisphenol A (BPA) is considered to be a threat to marine organisms owning to its widespread usage and potential aquatic toxicity. However, the reproductive toxicity of BPA to transgenerational inheritance in aquatic organisms is still unclarified. In this study, the morphological, histological, and transgenerational changes by BPA in zebrafish testis were investigated. Results showed that BPA caused abnormities in sperm number, activity, and fertility rate. Testicular transcriptional alterations detected by RNA-seq identified 1940 differentially expressed genes (DEGs) after BPA exposure, of which 392 were upregulated and 1548 were downregulated. Gene Ontology analysis showed that acrosin binding, binding of sperm to zona pellucida, and positive regulation of acrosome reaction were significantly enriched in BPA-induced DEGs. Pathway analysis indicated that cell adhesion molecules, steroid hormone biosynthesis and fatty acid biosynthesis, elongation, and metabolism were remarkably changed after BPA treatment. Thus, we deduce here that multi- and transcriptomic changes of chronic exposure to BPA reveals reproductive toxicity in male zebrafish.

Animal board invited review: An update on the methods for semen quality evaluation in swine - from farm to the lab

Pig breeding is mainly conducted through artificial insemination with liquid-stored semen. It is, therefore, crucial to ensure that sperm quality is over the standard thresholds, as reduced sperm motility, morphology or plasma membrane integrity are associated with reduced farrowing rates and litter sizes. This work aims to summarise the methods utilised in farms and research laboratories to evaluate sperm quality in pigs. The conventional spermiogram consists in the assessment of sperm concentration, motility and morphology, which are the most estimated variables in farms. Yet, while the determination of these sperm parameters is enough for farms to prepare seminal doses, other tests, usually carried out in specialised laboratories, may be required when boar studs exhibit a decreased reproductive performance. These methods include the evaluation of functional sperm parameters, such as plasma membrane integrity and fluidity, intracellular levels of calcium and reactive oxygen species, mitochondrial activity, and acrosome integrity, using fluorescent probes and flow cytometry. Furthermore, sperm chromatin condensation and DNA integrity, despite not being routinely assessed, may also help determine the causes of reduced fertilising capacity. Sperm DNA integrity can be evaluated through direct (Comet, transferase deoxynucleotide nick end labelling (TUNEL) and its in situ nick variant) or indirect tests (Sperm Chromatin Structure Assay, Sperm Chromatin Dispersion Test), whereas chromatin condensation can be determined with Chromomycin A3. Considering the high degree of chromatin packaging in pig sperm, which only have protamine 1, growing evidence suggests that complete decondensation of that chromatin is needed before DNA fragmentation through TUNEL or Comet can be examined.

Comparative assessment of reproductive capacity of boar-sires depending on the breed and season

The article highlights the results of the reproductive capacity of different breeds of boar sires in the farms of eastern, southern, and central regions of Ukraine in dynamics over three years are given. It represented the influence of the year's season on sperm quality by estimating the ejaculate volume, concentration, and motility of sperm of boars-sires of the different breeds and their hybrids. Data were also calculated on the culling of ejaculates of boar sires of various breeds for the years 2019–2021 in the dynamics. In a comparative aspect, the indicators were analyzed by the following genotypes: Large White, Ukrainian Meat, Landrace, Duroc, Yorkshire, and synthetic line Makster. The reproductive capacity of boars was within the limits of the indicators for the elite and first classes. However, specific differences were observed between boars of different breeds, which were constant and took place during the three studied years. The difference in the concentration of sperm in the ejaculates of the Ukrainian Meat breed gradually decreased starting from 2019 and was the smallest in 2021. The highest ejaculate volume was found in boars of the Ukrainian meat breed (310.9 ± 113.2 cm3), and the sperm concentration was the highest in boar sires of the Large White breed (215.7 ± 83.5 million/cm3). On the other side, hybrids of the Large White breed had low indicators compared to other groups of animals (Large White × Yorkshire – 184.2 ± 68.5 million/cm3, Large White × Makster – 189.0 ± 59.7 million/cm3). Sperm motility did not undergo significant breed differences: the average annual indicator of motility was 7.6 ± 0.09 points, and it was the highest in the winter period (8.6 ± 0.11 points), however, for the established variances; the dilution was used 1.65–3.58 times and a high percentage of unusable sperm (15.4–29.4 % of the total amount) was established in a large number of samples. According to the results of the annual analysis of the sperm production of boars, a high degree of culling of ejaculates was established for various reasons (high level of sperm agglutination (52.3–74.0 %), low concentration of germ cells (14.5–29.8 %), presence of foreign impurities (5,8–12.4 %). The highest percentage of culling was in summer (20.3 %). Thus, the obtained results showed the breed and seasonal characteristics of the reproductive capacity of breeding boars.

Effects of six kinds of sperm staining methods on human sperm size and evaluation of their staining effects

BACKGROUND

Large- and small-headed sperm are common morphological abnormalities. If different sperm staining methods affect sperm size, they will make a difference in the accuracy of sperm morphological analysis results. In this case, the normal reference values of sperm head parameters for different staining methods should be established.

METHODS

Six sperm staining methods, including Papanicolaou, Diff-Quik, Shorr, Hematoxylin-eosin (HE), Wright, and Wright-Giemsa staining, were used to stain the sperm smears of 25 semen samples, respectively. Sperm head parameter's length (L), width (W), area (A), perimeter, acrosomal area (Ac), and the derived values L/W and Ac/A of 2500 sperm (100 for each specimen) per staining method were measured by a computer-aided sperm morphological analysis system.

RESULTS

The highest sperm head length and width were observed with the Wright-Giemsa and Wright staining, followed by the Diff-Quik. The lowest sperm head length and width were observed with the Papanicolaou staining, and the sperm head length and width of HE and Shorr staining were between those of Papanicolaou and Diff-Quik staining. There was the same trend in changes in sperm head area and perimeter. Diff-Quik and Shorr staining could clearly distinguish acrosome and nucleus, followed by HE staining, whereas the boundary between acrosome and nucleus was not evident in Papanicolaou, Wright, and Wright-Giemsa staining.

CONCLUSION

Different staining methods influence sperm size, and the normal reference values of sperm head parameters of each staining method should be established. Diff-Quik and Shorr staining may be suitable methods for routine sperm morphological analysis.

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

Simple Summary

To 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.

Abstract

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.

Comparison of two staining techniques on the manual and automated canine sperm morphology analysis

Detailed and direct analysis of semen, including sperm morphology, enables a diagnosis of male fertility. This study aimed to describe an economical and verified protocol for canine spermiograms and compare the effectiveness of Sperm Stain^® and Sperm Blue^® (Microptic, Spain) in veterinary practice. Sperm assessment was conducted manually, using a standard optical microscope, and via computerized semen analysis using the SCA^® CASA (Sperm Class Analyzer^® CASA System‐MICROPTIC, Spain). This study showed that Sperm Blue^® is a better solution for computerized sperm quality analysis of healthy dogs. At the same time, Sperm Stain^® turned out to be more helpful in identifying specific morphological defects of sperm. Automated canine sperm morphology analysis worked better with Sperm Blue stain, but Sperm Stain simplified manual evaluation of various organelles’ defects. Standard, manual examination is more error‐prone for an inexperienced andrology technician, but it seems to be still a gold standard technique for canine sperm assessment.

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).

Machine learning for sperm selection

Infertility rates and the number of couples seeking fertility care have increased worldwide over the past few decades. Over 2.5 million cycles of assisted reproductive technologies are being performed globally every year, but the success rate has remained at ~33%. Machine learning, an automated method of data analysis based on patterns and inference, is increasingly being deployed within the health-care sector to improve diagnostics and therapeutics. This technique is already aiding embryo selection in some fertility clinics, and has also been applied in research laboratories to improve sperm analysis and selection. Tremendous opportunities exist for machine learning to advance male fertility treatments. The fundamental challenge of sperm selection - selecting the most promising candidate from 10⁸ gametes - presents a challenge that is uniquely well-suited to the high-throughput capabilities of machine learning algorithms paired with modern data processing capabilities.

Assessment of the Morphometry of Heads of Normal Sperm and Sperm with the Dag Defect in the Semen of Duroc Boars

Introduction

The Dag defect is one of the primary morphological defects in sperm correlating with reduced fertility. This defect is found in the spermatozoa of many livestock species. The aim of the study was to assess the morphometry of the heads of normal sperm and sperm with the Dag defect in the semen of Duroc breeding boars.

Material and Methods

Sperm morphology was examined in ten ejaculates each from 12 Duroc boars. In total, 3,600 morphologically normal sperm and 838 sperm with the Dag defect were evaluated. The area, perimeter, length and width of the sperm head were measured and these basic morphometric parameters were used to calculate four additional shape indices characterising the sperm head, i.e. ellipticity, elongation, roughness and regularity.

Results

Sperm with this defect had markedly smaller heads, 0.32 μm shorter and 0.19 μm narrower than the heads of sperm with normal morphological structure. The heads of sperm with the Dag defect also had a 1.1μm smaller perimeter and a 2.5 μm² smaller surface area than the heads of morphologically normal sperm.

Conclusions

The Dag defect is found in boar sperm irrespective of the age of the individual. It affects the morphology of the sperm head.

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

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.

Effect of sperm concentration on boar spermatozoa mitochondrial membrane potential and motility in semen stored at 17 °C

The aim of the study was to assess the effect of sperm concentration in the ejaculate on the mitochondrial membrane potential and motility of Landrace boar spermatozoa during storage of diluted semen at 17 °C. The study was conducted on ejaculates collected from 10 boars aged 1.5–2 years. Based on sperm concentration measurements, two groups of boars were identified: Group 1 – boars providing ejaculates with a sperm concentration of at least 500 × 103/mm3 and Group 2 – boars providing ejaculates with a sperm concentration of less than 500 × 103/mm3. Four ejaculates were collected manually from each boar. Each ejaculate was diluted with Biosolvens Plus diluent, and insemination doses were prepared and stored at 17 °C. Mitochondrial membrane potential and motility of spermatozoa were evaluated at each insemination dose. The tests were carried out after 1, 24, 48, 96 and 168 h of storage. Based on the results, it was found that ejaculates with a sperm concentration ≥ 500 × 103/mm3 have a lower share of spermatozoa with high mitochondrial membrane potential than ejaculates with a sperm concentration below 500 × 103/mm3. A high correlation between the share of spermatozoa with a high mitochondrial membrane potential and motility of spermatozoa was demonstrated in the first 24 h and after 96 h of semen storage, which was confirmed by the calculated phenotypic correlation coefficients. Sperm cells in ejaculates with a higher sperm concentration are more sensitive to storage time than spermatozoa in ejaculates with a lower concentration.

Evaluation of sperm morphometry of rabbits (Oryctolagus cuniculus f. domesticus)

Sperm morphology and morphometry are considered parameters in fertility diagnosis. They are especially important in the case of species for which there is no standard with respect to morphometric sperm parameters. It is then crucial to apply the staining technique that has the least influence on the sperm structure and provides the most detailed image, so as to enable measurements. The aim of the research was to assess the morphometric parameters of rabbit sperm using silver nitrate staining. The staining process revealed a detailed image of the spermatozoon head and tail, thus enabling precise measurements. From these basic morphometric parameters, four additional shape indices characterizing the sperm head were calculated: ellipticity, elongation, roughness and regularity. These parameters more precisely characterize the shape of the sperm head. Silver nitrate staining can be used as an independent technique in assessment of sperm structure or to supplement routine diagnostics.

Morphometric Characteristics of the Spermatozoa of Blue Fox (Alopex lagopus) and Silver Fox (Vulpes vulpes)

Simple Summary

The present study describes a detailed morphometric analysis of the sperm of the blue fox (Alopex lagopus) and silver fox (Vulpes vulpes), together with determination of the shape indices of the sperm head. Staining with silver nitrate enables precise identification of the acrosome and reveals structural details of the sperm tail, so that they can be accurately measured. Statistically significant differences were found for most of the morphometric parameters of the two fox species. The blue fox sperm were generally larger, but the acrosome area and coverage were greater in the silver fox. There are no clear recommendations regarding sperm staining techniques for foxes, and no reference values for morphometric parameters of the sperm of foxes or for canines in general. Staining with silver nitrate for evaluation of the morphometry of fox sperm can be used as an independent technique or an auxiliary technique in routine analysis of canine semen.

Abstract

The results presented in this study are the first such extensive characterization of the sperm morphometry of the blue fox (Alopex lagopus) and silver fox (Vulpes vulpes), as representatives of the family Canidae. Canine spermatozoa, especially the sperm of farmed foxes, are not often described in studies on reproduction. The aim of the study was a detailed comparison of the morphometric dimensions and shape of the sperm of two fox species: silver fox and blue fox. Semen collected from 10 silver foxes and 10 blue foxes was used for the study. The specimens were stained with silver nitrate. Measurements were performed of the length, width, perimeter, and area of the head; the area of the acrosome and its coverage; the length of the midpiece and its coverage; the length of the tail; and the length of the end piece of the tail. In addition, four head shape indices were calculated: ellipticity, elongation, roughness and regularity. The following values for the morphometric parameters and shape indices were obtained for blue fox and silver fox, respectively: head length—6.72 µm and 6.33 µm; head width—4.54.µm and 4.21 µm; head perimeter—18.11 µm and 17.37 µm; head area—21.94 µm² and 21.11 µm²; acrosome area—11.50 µm² and 10.92 µm²; midpiece length—12.85 µm and 12.79 µm; tail end piece length—3.44 µm and 3.28 µm; tail length—65.23 µm and 65.09 µm; acrosome coverage—52.43% and 52.83%; midpiece coverage—19.71% and 19.65%; sperm length—71.95 µm and 71.42 µm; ellipticity—1.49 and 1.52; elongation—0.19 and 0.20; roughness—0.84 and 1.88; regularity—1.09 and 0.99. The significance of differences between species was verified by Tukey’s test at p ≤ 0.05. Statistically significant differences between species were found for the following parameters: head length, width, perimeter and area; acrosome area; tail, end piece, and total sperm length; roughness and regularity. The differences in the size and shape of sperm can be used to establish reference patterns for fox sperm enabling more accurate species identification.

Cryopreservation effects on canine sperm morphometric variables and ultrastructure: Comparison between vitrification and conventional freezing

Semen cryopreservation is an increasingly demanded technique in canids, particularly in order to preserve and spread high genetic value material. Sperm vitrification may represent an interesting alternative to costly and time consuming conventional freezing. The objective of this study was to evaluate the effect of sperm vitrification on sperm morphometry and ultrastructure compared to conventional freezing. Pools of nine beagle dogs were both frozen and vitrified. Computerized morphological parameters (length, wide, area and perimeter) and sperm ultrastructure, using scanning and transmission microscopy, were analysed in both fresh and in thawed/warmed samples. There were no differences (p > 0.05) between post-thaw and fresh morphometric variables of the sperm heads. However, cluster analysis revealed that sperm-heads turned out to be smaller after thawing (p < 0.05) in two of the four subpopulations. Vitrification-warming process led to an overall increase in sperm-head size. Furthermore, the sperm head size increased after warming in two subpopulations (p < 0.05). In conclusion, the variations in the sperm head area depended on the cryopreservation procedure (conventional freezing or vitrification). Conventional freezing tended to decrease the head dimensions, at least in some subpopulations, and vitrification led to an overall increase in the sperm head size. Decondensation of chromatin and plasma membrane blebbing in the head region was observed by transmission electron microscopy in several vitrified sperm, which might explain the increase of head dimensions detected by CASA-Morph system.

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.