Sperm Behavior Research Articles

Media viscosity affects post-thaw ram sperm rheotactic behaviour.

The aim of this experiment was to assess the effect of media viscosity on ram sperm motility, kinematics and rheotaxis in vitro by using methylcellulose as a media thickener. Frozen-thawed semen of three rams was thawed and diluted in Tyrode's albumin lactate pyruvate (TALP) media supplemented with 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6% and 0.7% w/v of methylcellulose. Sperm motility and kinematic characteristics were analysed using computer-assisted sperm analysis (CASA). The rheotactic behaviour was assessed in a microfluidic channel, and the number of spermatozoa that passed the 10 mm point of a microfluidic channel over a 2min period against a flow rate of 30 μm/sec was assessed. The use of media with higher viscosity (higher levels of methylcellulose) resulted in significantly lower (p < .05) sperm motility and kinematic parameters. Moreover, higher levels of methylcellulose reduced (p < .05) the number of spermatozoa that exhibited positive rheotaxis. In conclusion, viscosity affected the kinematic properties and rheotactic behaviour of ram sperm.

Exploring sperm cell rheotaxis in microfluidic channel: the role of flow and viscosity

Rheotaxis is a fundamental mechanism of sperm cells that guides them in navigating towards the oocyte. The present study investigates the phenomenon of sperm rheotaxis in Newtonian and non-Newtonian fluid media, which for the first time explores a viscosity range equivalent to that of the oviductal fluid of the female reproductive tract in rectilinear microfluidic channels. Three parameters, the progressive velocity while performing rheotaxis, the radius of rotation during rheotaxis, and the percentage of rheotactic sperm cells in the bulk and near-wall regions of the microfluidic channel were measured. Numerical simulations of the flow were conducted to estimate the shear rate, flow velocity, and the drag force acting on the sperm head at specific locations where the sperms undergo rheotaxis. Increasing the flow velocity resulted in a change in the position of rheotactic sperm from the bulk center to the near wall region, an increase and subsequent decrease in the sperm's upstream progressive velocity, and a decrease in the radius of rotation. We observed that with an increase in viscosity, rheotactic sperms migrate to the near wall regions at lower flow rates, the upstream progressive velocity of the sperm decreases for Newtonian and increases for non-Newtonian media, and the radius of rotation increases for Newtonian and decreases for non-Newtonian media. These results quantify the effects of fluid properties such as viscosity and flow rate on sperm rheotaxis and navigation, thereby paving the way for manipulating sperm behavior in microfluidic devices, potentially leading to advancements in assisted reproduction techniques.

The effect of mixed honeybee drone semen on sperm quality characteristics: A preliminary study

Following copulation, sperm of multiple honeybee (Apis mellifera (A.m.) Linnaeus (Apidae)) drones are mixed inside the spermatheca of a queen, and sperm behaviour in this environment is of importance for sperm survival and successful fertilization. The polyandrous mating system of honeybees further may allow for cryptic female choice and sperm competition to select for specific sperm traits to enable successful reproduction. This preliminary study therefore examined multiple sperm quality parameters in mixed drone semen. Thirty-one drone ejaculates were collected and split to be mixed with one and two other drones’ semen. A computerised sperm analysis system was used for analysing sperm functionality parameters, at baseline and 60 minutes. Morphology measurements included head, tail, and total sperm length. Sperm concentration was significantly higher in three-drone samples compared to other groups (p &lt; 0.001), while comparisons of sperm functional and morphometric parameters did not reveal differences. However, after 60 minutes, mixed semen samples displayed changes in terms of sperm functionality. The motility percentage significantly decreased in two-drone samples (p = 0.004). In contrast, three-drone samples had consistently lower motility and kinematic parameters at baseline, but following an hour it was the only group to show improvement in sperm progressive motility, swimming speed and kinematics. Sperm concentration correlated with the majority of functionality parameters, while, morphological measurements did not. Sperm functionality changes observed in this study, can be attributed to a combination of factors, including, mixing of drone semen, sperm concentration, and time allowing for potential sperm interaction.

Rheotaxis of sperm: Hydrodynamics behavior of human sperm in a passive microfluidic system

Rheotaxis of sperm: Hydrodynamics behavior of human sperm in a passive microfluidic system

Sperm Behavior in Microfluidic Channels with Groove (Effect of Groove on Motile Sperm)

Sperm Behavior in Microfluidic Channels with Groove (Effect of Groove on Motile Sperm)

Microfluidic sperm trap array for single-cell flagellar analysis with unrestricted 2D flagellar movement.

Sperm capture techniques that immobilize sperm to halt their motility are essential for the long-term analysis of individual sperm. These techniques are beneficial in assisted reproductive technologies such as intracytoplasmic sperm injection (ICSI) by allowing selective screening of sperm. However, there is a notable lack of high-throughput and non-destructive sperm capture methods that allow the flagellum to beat freely, which is crucial for accurately reflecting the behavior of unfettered, freely swimming sperm. To bridge this gap, we introduce a novel microfluidic device specifically engineered to capture sperm without restricting flagellar motion. The design utilizes sperm's innate boundary-following behavior in both 3D and 2D environments to direct them into a capture zone. Once captured, the sperm head is restrained while the flagellum remains free to exhibit natural beating patterns. Utilizing this device, we explore the effects of hyperactivating agents, temperature, and their combined influence on the dynamics of bovine sperm flagella. The unrestricted flagellar motion offered by our device yields two prominent advantages: it mirrors the flagellar behavior of free-swimming sperm, ensuring research findings are consistent with natural sperm activity, and it prevents imaging overlap between the flagellum and the capture structures, simplifying the automation of flagellar tracking and analysis. This technological advancement facilitates the collection of waveform parameters along the entire flagellum, addressing inconsistencies that have arisen in previous research due to differing measurement sites, and enabling precise extraction of sperm behavioral properties.

Impact of inclusion of post-spermatic ejaculate fraction in boar seminal doses on sperm metabolism, quality, and interaction with uterine fluid

Boar ejaculate is composed of sperm cells and seminal plasma (SP) and is emitted in different fractions (pre-sperm fraction; spermatic-rich fraction; intermediate fraction; post-spermatic fraction), with different composition of SP and volume, which could influence the sperm quality during seminal doses preparation, conservation, and interaction with the female reproductive tract. In artificial insemination (AI) centers, seminal doses are usually prepared with the spermatic-rich and intermediate fractions, but the inclusion of other ejaculate fractions, although controversial, is beginning to be applied. The objective was to evaluate the synergic effect of accumulative ejaculated fractions on sperm functionality during seminal doses preparation, throughout storage and after incubation with uterine fluid (UF). For this purpose, a total of 57 ejaculates were collected, and the following experimental groups were prepared (n = 19 per group): (F1) spermatic-rich fraction; (F2) F1 plus intermediate fraction; (F3) F2 plus post-spermatic fraction. Each group was stored for 5 days at ∼16 °C, and the following parameters were evaluated: sperm metabolism of pure and diluted semen (day 1), sperm quality parameters (days 1, 3, 5), thermal-resistance test (TRT) and incubation with uterine fluid (UF) (day 5). Sperm metabolic rates between accumulative ejaculate fractions from pure and diluted semen did not show differences. Also, sperm quality parameters were not affected by the ejaculate fraction during storage. However, sperm subjected to TRT showed similar results except for progressive motility, which was better in F2 and F3 than F1. When sperm were incubated with UF, the quality decreased in each group, but sperm from F2 and F3 were less affected than those from F1. In conclusion, the post-spermatic fraction can be included in seminal doses for their use in AI-centers, with functionality of sperm of different SP origins not being impaired throughout the storage, and responding better to thermal and UF stress. However, further research in AI-centers is necessary to test the sperm behaviour under presented conditions.

Design of a gradient-rheotaxis microfluidic chip for sorting of high-quality Sperm with progressive motility

Assisted reproductive technology (ART) is an important invention for the treatment of human infertility, and the isolation of high-quality sperm with progressive motility is one of the most critical steps that eventually affect the fertilization rate. Conventional sperm separation approaches include the swim-up method and density gradient centrifugation. However, the quality of isolated sperm obtained from both approaches can still be improved by improving sorted sperm motility, minimizing the DNA fragmentation rate, and removing abnormal phenotypes. Here, we report a Progressive Sperm Sorting Chip (PSSC) for high-quality sperm isolation. Based on the rheotaxis behavior of sperm, a gradient flow field is created in the chip for progressive sperm sorting. Clinical experiment results for 10 volunteers showed that greater than 90% of isolated sperm exhibit high motility (> 25μm/s), high linearity (0.8), and a very low DNA fragmentation rate (< 5%). In addition, the whole process is label and chemical free. These features aid in gentle sperm sorting to obtain healthy sperm. This device uniquely enables the selection of high-quality sperm with progressive motility and might be clinically applied for infertility treatment in the near future.

In vivo characterization of sAC null sperm.

Targeted disruption of the soluble adenylyl cyclase (ADCY10; sAC) gene results in male-specific sterility without affecting spermatogenesis, mating behavior, or spermatozoa morphology and count; however, it dramatically impairs sperm motility and prevents capacitation. These phenotypes were identified in sperm from sAC null mice surgically extracted from the epididymis and studied in vitro. Epididymal sperm are dormant, and never exposed to physiological activators in semen or the female reproductive tract. To study sAC null sperm under conditions which more closely resemble natural fertilization, we explored phenotypes of ejaculated sAC null sperm in vivo post-coitally as well as ex vivo, collected from the female reproductive tract. Ex vivo ejaculated sAC null sperm behaved similarly to epididymal sAC null sperm, except with respect to the physiologically induced acrosome reaction. These studies suggest there is a sAC-independent regulation of acrosome responsiveness induced upon ejaculation or exposure to factors in the female reproductive tract. We also studied the behavior of sAC null sperm in vivo post-coitally by taking advantage of transgenes with fluorescently labelled sperm. Transgenes expressing GFP in the acrosome and DsRed2 in the mitochondria located in the midpiece of sperm (DsRed2/Acr3-EGFP) allow visualization of sperm migration through the female reproductive tract after copulation. As previously reported, sperm from wild type (WT) double transgenic mice migrated from the uterus through the uterotubular junction (UTJ) into the oviduct within an hour post-copulation. In contrast, sperm from sAC null double transgenic mice were only found in the uterus. There were no sAC null sperm in the oviduct, even 8h after copulation. These results demonstrate that sAC KO males are infertile because their sperm do not migrate to the fertilization site.

Frequency-dependent viscosity of salmon ovarian fluid has biophysical implications for sperm-egg interactions.

Gamete-level sexual selection of externally fertilising species is usually achieved by modifying sperm behaviour with mechanisms that alter the chemical environment in which gametes perform. In fish, this can be accomplished through the ovarian fluid, a substance released with the eggs at spawning. While the biochemical effects of ovarian fluid in relation to sperm energetics have been investigated, the influence of the physical environment in which sperm compete remains poorly explored. Our objective was therefore to gain insights on the physical structure of this fluid and potential impacts on reproduction. Using soft-matter physics approaches of steady-state and oscillatory viscosity measurements, we subjected wild Atlantic salmon ovarian fluids to variable shear stresses and frequencies resembling those exerted by sperm swimming through the fluid near eggs. We show that this fluid, which in its relaxed state is a gel-like substance, displays a non-Newtonian viscoelastic and shear-thinning profile, where the viscosity decreases with increasing shear rates. We concurrently find that this fluid obeys the Cox-Merz rule below 7.6 Hz and infringes it above this level, thus indicating a shear-thickening phase where viscosity increases provided it is probed gently enough. This suggests the presence of a unique frequency-dependent structural network with relevant implications for sperm energetics and fertilisation dynamics. This article has an associated ECR Spotlight interview with Marco Graziano.

Synthesis and Functional Characterization of Novel RU1968-Derived CatSper Inhibitors with Reduced Stereochemical Complexity.

The sperm-specific Ca2+ channel CatSper (cation channel of sperm) controls the intracellular Ca2+ concentration and, thereby, the swimming behavior of sperm from many species. The steroidal ethylenediamine RU1968 (1) represents a well-characterized, potent, and fairly selective cross-species inhibitor of CatSper. Due to its two additional centers of chirality in the amine-bearing side chain, RU1968 is a mixture of diastereomeric pairs of enantiomers and, thus, difficult to synthesize. This has hampered the use of this commercially not available inhibitor as a powerful tool for research. Here, simplifying both structure and synthesis, we introduced novel stereochemically less complex and enantiomerically pure aminomethyl RU1968 analogues lacking the C-21 CH3 moiety. Starting from (+)-estrone, a five-step synthesis was developed comprising a Wittig reaction as the key step, leading to a diastereomerically pure 17β-configured aldehyde. Subsequent reductive amination yielded diastereomerically and enantiomerically pure amines. Compared to RU1968, the novel ethylenediamine 2d and homologous trimethylenediamine derivative 2e inhibited CatSper with similar and even twofold enhanced potency, respectively. Considering that these aminomethyl analogues are enantiomerically pure and much easier to synthesize than RU1968, we envisage their common use in future studies investigating the physiology of CatSper in sperm.

Sperm tendency to agglutinate in motile bundles in relation to sperm competition and fertility duration in chickens

A unique sperm behavior was observed in Egyptian chickens. Sperm showed a tendency to agglutinate forming motile thread-like bundles. Sperm agglutination behavior, kinematics, and some morphometric measures were studied in relation to sperm competition and fertility duration in Sharkasi and Dandarawi chickens. Sperm tendency to agglutinate was assessed by examining sperm morphology using scanning electron microscopy, Acridine orange-stained semen smears using fluorescence microscopy, and recording videos of sperm under phase contrast microscope. Sperm velocity and morphometric measures were evaluated using image-J software. To assess sperm competition, Sharkasi and Dandarawi hens were artificially inseminated by semen pools possessing equal number of Sharaksi and Dandarawi sperm. Artificial insemination was repeated ten times. The eggs obtained were incubated, and the hatchlings were discriminated as descending from Sharkasi or Dandarawi fathers according to their phenotype. To assess the fertility duration, Sharkasi and Dandarawi hens were inseminated by semen collected from roosters of the same strain. Eggs were collected for a period of 28 days post-insemination and incubated. Sharkasi spermatozoa showed higher tendency to agglutinate forming longer and thicker motile bundles. No significant differences were observed in sperm curvilinear and straight line velocity and in sperm morphometric measures between Sharkasi and Dandarawi chickens. Sharkasi roosters fathered 81.6% and 67.7% of the hatchlings produced by Sharkasi and Dandarawi mothers, respectively. The fertility period in Sharkasi and Dandarawi was 22 and 14 days, respectively. We suggest that the differences seen in sperm competitiveness and fertility duration can be attributed to sperm agglutination behavior.

Bundle formation of sperm: Influence of environmental factors

Cooperative behaviour of sperm is one of the mechanisms that plays a role in sperm competition. It has been observed in several species that spermatozoa interact with each other to form agglomerates or bundles. In this study, we investigate the effect of physical and biochemical factors that will most likely promote bundle formation in bull sperm. These factors include fluid viscosity, swim-up process, post-thaw incubation time and media additives which promote capacitation. While viscosity does not seem to influence the degree of sperm bundling, swim-up, post-thaw migration time and suppressed capacitation increase the occurrence of sperm bundles. This leads to the conclusion that sperm bundling is a result of hydrodynamic and adhesive interactions between the cells which occurs frequently during prolonged incubation times.

P-094 Fundamental understanding of sperm motion in viscoelastic media

Abstract Study question How does viscosity influence the flagellar beating behaviour of free-swimming bull, mouse, and human sperm? Summary answer Sperm flagellar beating behaviour exhibits a transition from an irregular three-dimensional (3D) beating at 5 mPa·s to an organized two-dimensional (2D) waveform at 20 mPa·s. What is known already Sperm migrate in a complex viscoelastic environment through the female reproductive tract. The viscoelastic properties of the oviductal fluid significantly influence the progressive motility of sperm, acting as one of the key guidance mechanisms in vivo. However, the biomechanics of sperm flagellar activity in response to varying viscosity of the oviductal fluid is poorly understood. Understanding sperm flagellar behaviour in physiologically relevant environments is crucial to understanding reproduction and may help to describe unknown causes of infertility. Lack of high-speed high-resolution imaging techniques and automated image-analysis capabilities have been the main barriers to fully describe the flagellar beating behaviour. Study design, size, duration We used a custom-built high-speed high-resolution dark-field microscopy platform to resolve the flagellar dynamics of human, bull, and mouse sperm near surfaces in viscoelastic media ranging in viscosity from 1 to 250 mPa·s. The imaging system includes an automated image analysis algorithm to quantify sperm flagellar waveform and motility characteristics by extracting the flagellar centreline, reconstructing the waveform and calculating tangent-angle profiles. 20 sperm from 3 different bull, mice and humans were analyzed. Participants/materials, setting, methods Bull, mouse, and human sperm were used in this study. In each experiment, a diluted sperm sample in a buffer supplemented with methylcellulose was used and free-swimming sperm were imaged using dark-field microscopy at 200 frames per second. An automated image analysis algorithm was used to extract sperm flagellar centreline and Proper Orthogonal Decomposition (POD) was then used to study sperm flagellar waveform. Statistical analysis was performed using one-way ANOVA. Main results and the role of chance The reconstructed flagellar beating pattern was different for sperm swimming in low and high-viscosity media. Bull sperm exhibited a lower flagellar beating amplitude along the end piece when swimming in a high-viscosity media, a potential energy-efficient strategy to navigate a high viscosity fluid. The first two dominant POD modes (shape modes) describe more than 90% of the beating pattern for all species. Bull sperm exhibited a transition mode with irregular loops in 5 mPa·s buffer, but the flagellar shape cycle created an organised repetitive circular cycle in 1 mPa.s (3D beating) buffer and at viscosities higher than 5 mPa·s (2D beating). Human sperm also indicated a similar behaviour but with the transition happening at higher viscosities. Mouse sperm in high-viscosity media had a lower flagellar beating amplitude across the principal piece and higher beating amplitude across the end piece. The flagellar shape cycle in mouse sperm showed a periodic flagellar beating behaviour at high-viscosities (&amp;gt;20 mPa·s), but a shape cycle with distorted loops at lower viscosities. Our results showed in quantitative detail that increasing viscosity alters sperm flagellar beating pattern, and how sperm migration behaviour in low viscosity media can be distinct from their swimming behaviour in vivo. Limitations, reasons for caution A more comprehensive study of sperm motility parameters such as curvilinear velocity, average path velocity and straight line velocity with a larger sample size is required to fully characterise sperm swimming behaviour as a function of viscosity. Wider implications of the findings The increasing viscosity of the oviductal fluid regulates the sperm flagellar beating behaviour to switch from a 3D swimming behaviour with irregular shape cycles at lower viscosities to a 2D slithering mode with repetitive circular shape cycles at higher viscosities to achieve a more energy-efficient beating pattern for navigation. Trial registration number Not applicable

Sperm-oviduct interactions: Key factors for sperm survival and maintenance of sperm fertilizing capacity.

BackgroundAlthough millions or even billions of sperm are deposited in the female genital tract, only very few sperm reach the oocyte, and only one single spermatozoon will successfully fertilize. During the journey of the sperm within the female genital tract, the interactions between spermatozoa and fallopian tube are critical for sperm selection, sperm survival, and maintenance of sperm fertilizing capacity.ResultsThis review will provide a comprehensive overview of the latest findings regarding sperm transport and behavior of sperm within the oviduct, sperm selection in the oviduct, the formation of the sperm reservoir, and the release of sperm in the presence of the oocyte. It will primarily focus on recent novel insights on sperm‐oviduct interactions, which have been obtained by cutting‐edge technologies under in vivo or near in vivo conditions.ConclusionsThe comprehensive analysis of the findings to date will elucidate the complex molecular changes in the tubal epithelium, which are induced by the presence of the sperm and will highlight how the epithelial cells of this organ affect transport, behavior, and function of sperm. This knowledge is essential for scientists and clinicians involved in assisted reproductive technologies.

Lower reactive oxygen species production and faster swimming speed of human sperm cells on nanodiamond spin-coated glass substrates.

The sperm selection stage is what assisted reproductive technologies have in common and is crucial as it affects the success of the treatment cycle. The employment of microfluidic platforms for sperm selection has emerged showing promising results. In microfluidic platforms, sperm cells encounter micro-confined environments meanwhile having contact with channel walls and surfaces. Modification of contact surfaces using nanoparticles leads to the alteration of surface characteristics which in turn affects sperm behavior especially motility which is an indicator for sperm health. In this article, we present the results of investigating the motility parameters of sperm cells in contact with surface-modified glass substrates using nanodiamond particles. The results show that the sperm swimming velocities are significantly improved within the range of 12%-52% compared to the control surface (untreated). Reactive oxygen species production is also decreased by 14% justifying the increase in swimming speed. Taken together, bonding these modified surfaces to sperm selection microfluidic devices could enhance their efficiency and further improve their outcomes offering new solutions to patients facing infertility.

Selection of healthy sperm based on positive rheotaxis using a microfluidic device.

For conception, sperm cells travel towards the oocyte. This journey is accomplished by only a few sperm cells, following various guidance mechanisms. Of these mechanisms, rheotaxis plays a significant role in guiding the sperm over a long distance. By taking advantage of this natural rheotaxis behavior of sperm, we have developed a microfluidic chip that isolates healthy sperm cells. The developed chip consists of different chambers separated by microchannels that facilitate separation of motile sperm cells from unprocessed semen samples with the help of fluid flow. The sperm cells are subjected to different velocities in different parts of the chip that direct functional sperm towards the collection chamber utilizing positive rheotaxis. The results from the developed microfluidic chip (with 0.5 μL min-1 flow rate) have shown almost 100% motility, a significantly higher percentage of morphologically normal sperm cells with lesser sperm DNA fragmentation than the control (no-flow) and raw semen sample. This chip satisfies the need of a clinical setting as it is low-cost, easy to operate and uses a small semen volume for sperm sorting.

Sperm Behavior and Response to Melatonin under Capacitating Conditions in Three Sheep Breeds Subject to the Equatorial Photoperiod

In this study, we demonstrated that, in seasonal Mediterranean ovine breeds, supplementing the TALP medium with cAMP-elevating agents (the cocktail medium) is effective for achieving ram sperm capacitation, and that melatonin is able to regulate this phenomenon. We investigated the behavior under capacitating conditions using the TALP and cocktail mediums, and the response to melatonin, of spermatozoa from three sheep breeds (Colombian Creole, Romney Marsh, and Hampshire) subject to the equatorial photoperiod, during the dry and the rainy seasons. The cocktail medium was able to induce sperm capacitation, assayed by chlortetracycline staining and phosphotyrosine levels, to a greater extent than TALP, without a higher loss of viability (membrane integrity and viable spermatozoa without phosphatidylserine (PS) translocation). The addition of melatonin at 100 pM or 1 µM in the cocktail medium partially prevented the decrease in viability without PS translocation and the increase in capacitated spermatozoa from all breeds, with no significant effect on phosphotyrosine levels. Differences between breeds and seasons were evidenced. This study shows that melatonin is able to exert direct effects on spermatozoa in ovine breeds under equatorial photoperiod conditions, as it does in seasonal breeds located in temperate regions.

A New Automated Method for Microscopy Image Analysis: Curvelet Paradigm as a Framework for Sperm Detection

Analyzing sperm behavior in semen microscopy images is a modern approach for infertility treatment. distinguishing low contrast sperms from other parts of semen specimen is the major bottleneck of this technique. Machine vision approaches are fitting solutions for detection of sperms but they are challenging. In this article a new method is introduced which utilizes nonlinear mapping in curvelet framework to detect sperms in microscopy images. The proposed method may detect sperms despite of their poor contrasts and vague distribution, thanks to its better sparse representation and more directionality feature than existing approaches. Furthermore, adapting the parameters of the nonlinear mapping due to curvelet components is effective for reinforcement weak ridges as well as better compatibility with different microscopy images. The obtained results show the proposed method achieves the detection rate minimally 4 and maximally 17 percent better than its alternatives, in presence of zero false detection. Furthermore, it is shown that better detection of sperms by proposed method not only does not lead to extract more false objects but also may improve false positive rate by extent of [3-33] percent compared to other examined algorithms.

Curvature in the reproductive tract alters sperm\u2013surface interactions

The fallopian tube is lined with a highly complex folded epithelium surrounding a lumen that progressively narrows. To study the influence of this labyrinthine complexity on sperm behavior, we use droplet microfluidics to create soft curved interfaces over a range of curvatures corresponding to the in vivo environment. We reveal a dynamic response mechanism in sperm, switching from a progressive surface-aligned motility mode at low curvatures (larger droplets), to an aggressive surface-attacking mode at high curvatures (smaller droplets of <50 µm-radius). We show that sperm in the attacking mode swim ~33% slower, spend 1.66-fold longer at the interface and have a 66% lower beating amplitude than in the progressive mode. These findings demonstrate that surface curvature within the fallopian tube alters sperm motion from a faster surface aligned locomotion in distal regions to a prolonged physical contact with the epithelium near the site of fertilization, the latter being known to promote capacitation and fertilization competence.