Different staining techniques change the morphometric dimensions of the human sperm head, probably due to the fact that either the fixatives or stains are not iso-osmotic in relation to human semen. Since these changes in sperm head dimensions are not uniform, care should be taken when selecting a staining technique. Ideally, stained spermatozoa should have dimensions as close to spermatozoa in fresh semen as possible, as was found with the SB staining method, resulting in accurate evaluations of sperm head morphometry.

Our study was aimed at exploring a simple procedure to stain differentially the acrosome, head, midpiece, and flagellum of human and animal sperm. A further prerequisite was that sperm morphology of the stained samples could be analyzed using automated sperm morphology analysis (ASMA). We developed a new staining process using SpermBlue fixative and SpermBlue stain, which are iso-osmotic in relation to semen. The entire fixation and staining processes requires only 25 min. Three main steps are required. First, a routine sperm smear is made by either using semen or sperm in a diluting medium. The smear is allowed to air dry at room temperature. Second, the smear is fixed for 10 min by either placing the slide with the dried smear in a staining tray containing SpermBlue fixative or by adding 1 ml SpermBlue fixative to the slide. Third, the fixed smear is stained for 15 min by either immersing the slide in a staining tray containing SpermBlue stain or adding four drops of SpermBlue stain to the fixed smear. The stained slide is dipped gently in distilled water followed by air drying and mounting in DPX or an equivalent medium. The method is simple and suitable for field conditions. Sperm of human, three monkey species, horse, boar, bull, ram, mouse, rat, domestic chicken, fish, and invertebrate species were stained successfully using the SpermBlue staining process. SpermBlue stains human and animal sperm different hues or intensities of blue. It is possible to distinguish clearly the acrosome, sperm head, midpiece, principal piece of the tail, and even the short end piece. The Sperm Class Analyzer ASMA system was used successfully to quantify sperm head and midpiece measurements automatically at either 600 x or 1000 x magnification for most of the species studied.

BackgroundWe have studied sperm structure and motility in a eusocial rodent where reproduction is typically restricted to a single male and behaviourally dominant queen. Males rarely compete for access to the queen during her estrus cycle, suggesting little or no role for sperm competition.ResultsOur results revealed an atypical mammalian sperm structure with spermatozoa from breeding, subordinate and disperser males being degenerate and almost completely lacking a "mammalian phylogenetic stamp". Sperm structure is characterized by extreme polymorphism with most spermatozoa classified as abnormal. Sperm head shapes include round, oval, elongated, lobed, asymmetrical and amorphous. At the ultrastructural level, the sperm head contains condensed to granular chromatin with large open spaces between the chromatin. Nuclear chromatin seems disorganized since chromatin condensation is irregular and extremely inconsistent. The acrosome forms a cap (ca 35%) over the anterior part of the head. A well defined nuclear fossa and neck with five minor sets of banded protein structures are present. The midpiece is poorly organized and contains only 5 to 7 round to oval mitochondria. The flagellar pattern is 9+9+2. A distinct degenerative feature of the tail principal piece is the absence of the fibrous sheath. Only 7% motile spermatozoa were observed which had exceptionally slow swimming speeds.ConclusionIn this species, sperm form has simplified and degenerated in many aspects and represents a specialised form of degenerative orthogenesis at the cellular level.

SUMMARYSperm competition is a post-copulatory, sexual selection force that, together with phylogeny and fertilization mode, has been regarded as one of the main factors explaining the diversity in sperm size across species. This universal sperm selection mechanism favors traits that enhance a male's fertilizing ability and paternity success. Surprisingly, however, sperm characteristics and semen quality in monogamous species, with low risk of sperm competition, have barely received any attention. In this review, we consider sperm competition and monogamy as two ends of the selective spectrum, and discuss its effect on sperm structure and function. We address the issue of a lack of sperm competition by comparing sperm traits of essentially monogamous speciesÀ Àtheir largely degenerative sperm features and high degree of polymorphisms could be norms for monogamous species. Further, the level of sperm competition in humans is discussed by comparing its mating strategy, relative testis size, and sperm traits to other primate species. In terms of sperm concentration, sperm swimming speed, and sperm morphology, humans seem to be closer aligned to the low-risk sperm competition situation in gorillas than to promiscuous chimpanzees.

Motility is an essential characteristic of all flagellated spermatozoa and assessment of this parameter is one criterion for most semen or sperm evaluations. Computer-aided sperm analysis (CASA) can be used to measure sperm motility more objectively and accurately than manual methods, provided that analysis techniques are standardized. Previous studies have shown that evaluation of sperm subpopulations is more important than analyzing the total motile sperm population alone. We developed a quantitative method to determine cut-off values for swimming speed to identify three sperm subpopulations. We used the Sperm Class Analyzer ® (SCA) CASA system to assess the total percentage of motile spermatozoa in a sperm preparation as well as the percentages of rapid, medium and slow swimming spermatozoa for six mammalian species. Curvilinear velocity (VCL) cut-off values were adjusted manually for each species to include 80% rapid, 15% medium and 5% slow swimming spermatozoa. Our results indicate that the same VCL intervals cannot be used for all species to classify spermatozoa according to swimming speed. After VCL intervals were adjusted for each species, three unique sperm subpopulations could be identified. The effects of medical treatments on sperm motility become apparent in changes in the distribution of spermatozoa among the three swimming speed classes.Motility is an important characteristic of spermatozoa, especially flagellated spermatozoa. Because the ultimate goal of a spermatozoon is to fertilize an ovum, it must be motile and travel relatively long distances in internal fertilizers (Holt and van Look 2004). This type of motility is characteristic of freshly ejaculated mammalian spermatozoa, where the flagellum generates a symmetrical and low amplitude waveform that propels the spermatozoon in a relatively straight line (Turner 2003).The importance of sperm motility is highlighted further by the fact that measurement of this parameter is an essential criterion of most semen or sperm evaluations (Mocé and Graham 2008). One frequently encountered problem in subfertile or infertile males is a low population of motile spermatozoa (asthenozoospermia) (Mortimer 1994). Earlier studies have demonstrated a relationship between decreased sperm motility and decreased fertilization rates, which often requires resorting to assisted reproductive techniques to achieve fertilization (Turner 2003). Greater sperm motility also has been