Respiratory behaviour of sea-urchin spermatozoa. I. Effect of pH and egg water on the respiratory rate.

Effects of pH and egg water on the respiration of sea-urchin spermatozoa were polarographically studied in three sea-urchins and one starfish species. Sea-urchin sperm respiration is extremely sensitive to change in the pH of the suspending medium over a wide range. In normal-sea water, the pH of the sperm suspension decreased from 8.02 to 7.62, after four to five minutes' incubation at 18 degrees C. The Respiratory Dilution Effect could be recognized in the same medium. However, when sea water was buffered with HEPES at pH 8.2, the Effect was no longer observed. The diffusate from egg water (jelly coat solution) brought about a striking increase in the respiration when added to moderately respiring spermatozoa in HEPES-sea water of pH values lower than 7.9. No inccrease in the respiration was observed when the diffusate was added to vigorously respiring spermatozoa in HEPES-sea water of pH values higher than 8.2. Sperm motility was also inhibited by acid pH, and this inhibition was reversed by the addition of the diffusate. It does not seem that there is any species-specificity among three sea-urchins and one starfish used. The role of the diffusate is discussed in relation to the penetration of spermatozoa through the jelly coat to the egg surface.     

Initiation,prolongation, and reactivation of the motility of salmonid spermatozoa

The motility of salmonid spermatozoa initiated by dilution of the milt with ovarian fluid or isotonic saline is brief duration; it was believed that it can be activated only once in the life of the spermatozoon. Dilution of the milt with an equal volume of isotonic saline (0.12 M-NaCl) containing 5 mM-3-isobutyl-1-methylxanthine (MIX) prolonged and intensified sperm motiliy. When motility had stopped after initial mobilization with saline or ovarian fluid, it could be reactivated by addition of MIX; reactivated spermatozoa fertilized eggs. Dilution with saline containing K⁺ (24 mEq/liter) did not initiate sperm motility even in the presence of MIX. The spermatozoa were mobilized by subsequent with 0.12 M-NaCl. The concentration of adenosine triphosphate (ATP) in sperm suspensions dropped on dilution with saline and rose as motility ceased, but declined without subsequent recovery following dilution with MIX-saline. The concentration of cyclic adenosine monophosphate (cAMP) rose and fell sharply on initiation of motility and rose again after motility had declined. While salmonid spermatozoa can be mobilized by dilition with saline alone, the effectiveness of MIX in reactivating “spent” spermatozoa supports the assumption that cAMP plays a role in the initiation of sperm motility.     

Motility activation and metabolism characteristics of spermatozoa of the black-lip-pearl oyster Pinctada margaritifera var: cumingii (Jameson, 1901)

Motility of Pinctada margaritifera (Linnaeus, 1758); var: cumingii (Jameson, 1901) (P. margaritifera) spermatozoa collected from gonads are not immediately activated at spawning in seawater (SW) but motility occurs when spermatozoa are transferred into alkaline seawater (pH ranging from 9.0 to 11.4). This motility-activating effect of alkaline pH is reversed when pH is shifted back to more acidic values. In both cases, activity of sperm (% motile cells) increases gradually after alkaline pH activation then lasts for several minutes. The characteristics of these fully motile spermatozoa are described in details at the level of flagella: the wave amplitude and wave-length range 5 to 6 μm and 15 μm respectively, while the flagellar beat frequency is approximately 49 Hz. The velocity of sperm displacement is from 220 to 230 μm/sec. The general swimming pattern is almost circular: the head trajectories describe portions of circles intercalated with small linear segments. Spermatozoa saved in natural seawater at 4°C retain potent motility for several days and can be subsequently activated by alkaline seawater. Respiration and ATP concentration were measured in 3 conditions: regular seawater (pH 7.8), artificial diluent (pH 8.2), and alkaline Tris-buffered seawater (pH 10.5). Results show that sperm respiration rates are higher whereas ATP levels are lower in the latter two media.     

Sperm motility in turbot,Scophthalmus marimus: initiation of movement and changes with time of swimming characteristics

Synopsis Turbot sperm motility is observed using dark field microscopy and stroboscopic illumination combined with video recording. Sperm motility is triggered by dilution of spermatozoa in sea water or in non ionic media (glucose or saccharose), presenting osmotic pressure ranging from 300 to 2100 mOsmol. The percentage of motile spermatozoa reaches 100% under conditions of osmotic pressure of 300 to 1100 mOsmol and pH close to 8.0. In full sea water, glucose or saccharose solutions an agglutination of spermatozoa is observed; this is prevented by addition of bovine serum albumin (5 mg ml^–1). Immediately after transfer in activation solutions, 100% spermatozoa are motile in most samples freshly stripped. This percentage drops suddenly between 15 and 30% after 70 to 100 sec. The beat frequency remains at a constant value of 50 Hz during 40 s post activation and then drops suddenly between 15 and 30 Hz. The spermatozoa velocity is about 200 micrometers s^–1 during 30 to 40 s and then declines to a stable value of 100 micrometers s^–1 at 50 s post activation. After 1.20 mn, more and more spermatozoa become motionless. The minimum calculated and averaged distance covered during 1.20 min, is about 12 mm. The high performances of turbot spermatozoa motility are interpreted as a compensatory mechanism for the low sperm production.     

Respiration of Sea Urchin Spermatozoa in the Presence of a Synthetic Jelly Coat Peptide and Ionophores

Sperm respiration and motility of the sea urchin Hemicentrotus pulcherrimus were studied at pH 6.8 in the presence of a synthetic jelly peptide (Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly) and monovalent cationic ionophores. The synthetic peptide stimulated sperm respiration and motility to the level of that found in normal sea water (pH 8.2) with half-maximal stimulation at approximately 100 pM. Monensin and valinomycin also stimulated sperm respiration with half-maximal effects at 7 μM and 0.7 μM, respectively. The stimulation of sperm respiration by the peptide and monensin was dependent on external Na⁺, but was not dependent on the osmolarity of the suspending medium. Approximately 50 mM Na⁺ was required for half-maximal respiratory responses to the peptide and monensin.     

Characterization of zebra mussel (Dreissena polymorpha) sperm motility: duration of movement, effects of cations, pH and gossypol

We have examined effects of time after activation, pH, sodium and potassium, and gossypol concentrations on sperm motility of zebra mussel (Dreissena polymorpha). Zebra mussel spermatozoa appeared to have remarkable viability in the fresh water in comparison with freshwater fish sperm. Duration of sperm motility in fresh water is possibly one of the longest among freshwater animals, since it was not significantly changed 3 h after incubation at room temperature (20 °C) or 24 h of incubation at ±0 °C. High osmotic pressure suppresses sperm motility and effects of sodium and potassium are similar. Spermatozoa were inactive at acid pH and became gradually motile when exposed to pH 6.0–9.0. Gossypol appeared to be a very potent spermicidal agent and inhibited motility. This compound also inhibited fertilization. We observed some differences in gossypol effects on spermatozoa between North American and European zebra mussels. These data on zebra mussel sperm biology may be useful for better handling of gametes under laboratory conditions.     

Combined effects of physicochemical variables (pH and salinity) on sperm motility: characterization of sperm motility in European sea bass Dicentrarchus labrax

Gamete activation in fish is an important step in terms of artificial fertilization of oocytes, cryopreservation studies and other experimental manipulations. Salinity and pH differences in activation media affect to sperm motility and fertilizing ability. These experiments were therefore designed to investigate the combined effects of pH (range 5.0–9.0) and salinity (20, 30, 37, and 45‰) of activation media on sperm motility of European sea bass Dicentrarchus labrax. The best results were obtained at salinity 37‰ and a pH of 9.0. Our results also demonstrated that non-progressive motility at salinity 45‰ was observed in the range of 5.0–9.0 pH. In conclusion, spermatozoa can be motile at a wide range of pH and salinity values although the percent of motile spermatozoa and motility duration are negatively affected by low pH values.     

Effects of Sperm-Activating Peptide I on Hemicentrotus pulcherrimus Spermatozoa in High Potassium Sea Water

The effects of sperm-activating peptide I (SAP-I: Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly) on Hemicentrotus pulcherrimus spermatozoa in high [K⁺] sea water were examined. In high [K⁺] sea water, the respiration rates and motility of H. pulcherrimus spermatozoa were lower than those in normal sea water. SAP-I did not stimulate the lowered respiration rate or motility, although the peptide bound to the spermatozoa as it does in normal sea water. SAP-I elevated the sperm cGMP level in 100 mM K⁺ sea water (from 0.37 to 4.81 pmol/mg wet weight spermatozoa) more than those in normal sea water (from 0.21 to 0.93 pmol/mg wet weight). A phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX) and SAP-I synergistically elevated the cGMP level from 0.35 to 33.08 pmol/mg wet weight in 100 mM K⁺ sea water. However, in high [K⁺] sea water, SAP-I did not increase the cAMP level even in the presence of IBMX. SAP-I caused rapid, transient elevation of the intracellular pH and Ca²⁺ concentration of spermatozoa in normal sea water but not in 100mM K⁺ sea water. SAP-I did not decrease the apparent molecular weight of sperm guanylate cyclase from 131,000 to 128,000 in high [K⁺] sea water. These results suggest that the SAP-I-induced elevation of the cGMP level in sea urchin spermatozoa occurs before or independently of membrane hyperpolarization induced by the opening of K⁺ channels.     

The Role of External Potassium Ion in Activation of Sea Urchin Spermatozoa

When sperm of the sea urchin, Hemicentrotus pulcherrimus, are diluted into K⁺-free seawater, the pH of the suspension gradually decreases, whereas a rapid decline in pH is observed following dilution into regular seawater. Sperm motility and respiration are also activated after dilution into K⁺-free seawater, but levels of activity are less than those observed following dilution into regular seawater. Upon addition of 10 mM K⁺ to K⁺-free seawater, rapid acid release occurs and motility and respiratory rate in sperm are reactivated. The effect of K⁺ on respiration was competitive with respect to the external Na⁺ concentrations. Harmaline, a potent inhibitor of Na⁺/K⁺-ATPase, causes a decrease in movement and respiration of the sperm. Harmaline does not inhibit the rapid decline in pH, although it depresses the release of acid from mitochondria. These results suggest that external K⁺ plays an important role in intracellular alkalinization of sea urchin sperm.     

Roles of pH and cyclic adenosine monophosphate in the acquisition of potential for sperm motility during migration from the sea to the river in chum salmon

In the natural process of the migration of chum salmon from the sea to the river, spermatozoa moved from the testis to the sperm duct, and the pH value of seminal plasma, concentration of cyclic adenosine monophosphate (AMP) in the sperm cells, and potential for sperm motility increased. Cyclic AMP levels and the potential for motility gradually increased when testis spermatozoa with no capacity for movement were incubated in the artificial seminal plasma of which the pH was much the same as, or higher than, the pH of natural seminal plasma from the sperm duct. Such correlation in motility, pH, and cyclic AMP suggests that the increases in seminal pH and intracellular cyclic AMP level during passage of spermatozoa from the testis to the sperm duct cause the acquisition of potential for motility. Motility of testicular spermatozoa demembranated with Triton X-100 was very low in fish caught in the sea, while motility of spermatozoa from the posterior portion of the sperm duct was much higher in fish caught in the river. Furthermore, nondemembranated, intact spermatozoa showed a lag in the timing of the acquisition of potential for motility vs. demembranated spermatozoa: The demembranated sperm exhibited the potential earlier than the nondemembranated sperm. These data suggest that increase in activity of the motile apparatus, the axoneme, is a prerequisite, in part, for the acquisition of sperm motility, whereas the development of some function of the plasma membrane also contributes to this phenomenon. © 1993 Wiley-Liss, Inc.     

Characterization of sperm motility in sea bass: the effect of heavy metals and physicochemical variables on sperm motility

Computer assisted sperm analysis (CASA) was used to characterize the motility of sea bass Dicentrarchus labrax spermatozoa and to study the effect of several physicochemical variables and heavy metals on sperm swimming performance. Duration of sperm motility in sea bass was very short (<50 s). During the first 20 s all the motility variables measured remained approximately constant, the velocity and linearity of the movement being maximum during this period, while both variables decreased sharply later. While slight variations in pH did not significantly modify sperm swimming performance, changes in osmolality affected all the measured motility variables. Two of the heavy metals tested, Cu²⁺ and Pb²⁺, did not affect sperm motility when the activating media contained up to 100 ppm of the metal salts. In contrast, Hg²⁺ modified the morphology of post-swimming spermatozoa at 0·4–1 ppm (sperm dilution rate 1:39) and completely arrested sperm motility at concentrations as low as 0·1 ppm (sperm dilution rate 1:2500). Assuming a covalent binding to sperm cells, this revealed a finite number of c. 10 million Hg²⁺ binding sites per spermatozoon. Complementary results using demembranated spermatozoa suggested that the main target of HgCl₂ would be located in the plasma membrane and that HgCl₂ would inhibit water channels, hence preventing sperm motility.     

Relationships between reproductive characteristics in male Vimba vimba L. and the effects of osmolality on sperm motility

In Vimba vimba, GSI, sperm volume, and spermatozoa concentration range from 3.4-7.4 %, 0.1-1.1 ml, and 13.3-34.8 × 10⁹ spz ml⁻¹, respectively. Gonad mass (r = 0.90) and sperm volume (r = 0.35) significantly correlated with weight of males. Significant correlation was also found between gonad mass and length of males (r = 0.85). Sperm motility (r = 0.99) and velocity (r = 098) significantly decreased after activation in Tris-HCl 20 mM, pH 8.5. Osmolality of the seminal plasma was 273.2 mOsmol kg⁻¹. Sperm motility and velocity were significantly affected by the osmolality of the activation medium (P < 0.01). Hyper-osmolality compared to seminal plasma osmolality totally suppressed the sperm activation. At 15 s post-activation, the sperm motility significantly decreased at 240 mOsmol kg⁻¹ in KCl or NaCl media. The highest sperm motility and velocity (at 60 s post-activation) were observed at 200 mOsmol kg⁻¹ in NaCl, KCl, or sucrose media. In all treatments, the tip of the flagellum of spermatozoa became curled into a loop shape after activation of sperm in distilled water containing 20 mM Tris-HCl, pH 8.5 that shortened the flagellum.     

The effect of the acrosome reaction on the respiratory activity and fertilizing capacity of echinoid sperm.

We have examined the relationship between the acrosome reaction, sperm respiration, and fertilization using gametes of the sea urchin Strongylocentrotus purpuratus. The results indicate that when sperm are exposed to jelly coat isolated from homologous eggs, the following sequence of events occurs: (1) Sperm undergo the acrosome reaction within 30 sec with little or no loss in their capacity to fertilize eggs; (2) by 60 sec there is a dramatic decrease in fertilizing capacity which stabilizes after 4 or 5 min at a greatly reduced level; (3) by 1.5 to 2 min a progressive decrease in the rate of mitochondrial respiration becomes detectable and continues for 8 to 10 min, finally stabilizing at a greatly reduced rate. This decrease in respiration rate is paralleled by a decline in sperm motility. The effects of jelly coat on the acrosome reaction, sperm respiration, and motility are species specific. From these results we conclude that sperm which have undergone the acrosome reaction retain full fertilizing capacity for a very short time. The rapid decline in fertilizing capacity is followed by a decrease in respiration rate and motility.     

Changes in Intracellular Concentrations of Cyclic Nucleotides during the Initiation Process of Starfish Sperm Motility

Changes in the intracellular concentrations of cyclic nucleotides during the initiation of starfish sperm motility were examined. The intracellular concentration of cGMP decreased just after dilution of sperm with sea water, whereas that of cAMP increased concomitant with initiation of sperm motility. In acidic sea water, the intracellular concentration of cGMP decreased but no increase in that of cAMP was observed and sperm remained immotile. The presence of a phosphodiesterase inhibitor enhanced the rate of increase in the intracellular concentration of cAMP and the sperm motility.
These results indicate that cAMP is involved in the initiation of sperm motility in starfish.     

Respiration and Motility in Starfish Spermatozoa at Various Times in the Breeding Season

In the spermatozoa of Asterias amurensis , patterns of changes in the respiratory rate and motility following dilution of dry sperm in sea water varied among batches and were classified into three types. The type I spermatozoa were immotile and exhibited quite low respiratory rate. Ethylenediamine tetraacetic acid made the type I spermatozoa motile and elevated their respiratory rate. The type II spermatozoa were also immotile and the respiratory rate remained quite low for about 5 min after the dilution. Thereafter, they spontaneously became motile and the respiratory rate increased. The type III spermatozoa became motile upon their dilution and exhibited high respiratory rate. Differences in the motility and respiratory rate of spermatozoa among batches probably result from degree of their maturation. In moving spermatozoa, the ADP and AMP levels increased at the expense of ATP. 2,4-Dinitrophenol elevated the respiratory rate only in immotile spermatozoa, which showed a high ATP level and quite low ADP level, but did not made them motile. Oligomycin inhibited the respiration of both motile and immotile spermatozoa. Probably, the respiratory rate is made low by a shortage of ADP in immotile spermatozoa and is enhanced by ADP production due to the initiation of their movement.     

Change in the Respiratory Rate of Sea Urchin Spermatozoa following Sperm-egg Interaction in the Absence of Mg2+

Spermatozoa of the sea urchin, Hemicentrotus pulcherrimus (10⁸ cells/ml), preincubated with unfertilized eggs deprived of jelly coats (more than l0⁵ cells/ml) at 20°C for 20min in Mg²⁺ free artificial sea water containing 1 mM Ca²⁺ (MFASW), exhibited very low respiration, which was enhanced by 2, 4 dinitrophenol (DNP). The fertilization rate in MFASW was usually less than 5% and was about 25% at most. Preincubation with fertilized eggs (with and without a fertilization membrane) in MFASW did not reduced the respiratory rate of spermatozoa. The rate of sperm respiration was lower in MFASW than in artificial sea water (ASW), but was higher than the respiratory rate of spermatozoa preincubated in MFASW with unfertilized eggs. Sperm respiration in MFASW or in ASW was not stimulated by 2, 4 dinitrophenol. Almost complete inhibition of sperm respiration was obtained with unfertilized eggs fixed with glutaraldehyde at concentrations of above 10⁵ cells/ml in MFASW and of about l0⁴ cells/ml in ASW. The respiratory rate of spermatozoa treated with fixed eggs was enhanced by DNP. It is concluded that the respiratory rate of the spermatozoa is reduced by their interaction with unfertilized eggs before their penetration into the eggs.     

Inhibitory effect of osmotic concentration, potassium and pH on motility of the sperm of the North American burbot Lota lota maculosa

Seminal plasma factors maintaining North American (NA) burbot Lota lota maculosa sperm quiescent were examined. Sperm were diluted into buffered saline solutions of various compositions and motility assessed. After 1 h in these solutions at 10° C, aliquots of the suspension were diluted with tap water and motility again assessed. Dilution of sperm in an incubation solution containing Ca²⁺ in the absence of K⁺ initiated sperm motility resulting in low motility when sperm were subsequently diluted in tap water. Incubation solutions with osmolalities >200 mOsm kg⁻¹ and containing 12·5 mM K⁺ prevented the onset of sperm motility and were associated with maximal sperm motility upon dilution in tap water. Sperm maintained at lower osmolalities exhibited limited motility upon dilution in tap water indicating interdependence between K⁺ and osmolality in maintaining sperm quiescent in the presence of Ca²⁺. Sperm kept in incubation solution at pH values < c. 7·5 for 1 h demonstrated reduced motility when subsequently diluted in tap water. That motility of sperm was pH sensitive was further indicated by CO₂ inhibition of motility. Therefore, NA burbot sperm are probably maintained in an immotile state, yet with potential for motility, by combination of high K⁺, osmolality and possibly pH. The results from this study differ from published information on sperm quiescence in the temporally and geographically distinct Eurasian burbot Lota lota lota .     

A peptide associated with eggs causes a mobility shift in a major plasma membrane protein of spermatozoa

A peptide (resact) associated with the eggs of the sea urchin, Arbacia punctulata, which stimulates sperm respiration rates by 5-10-fold, was purified and its amino acid sequence was determined. The sequence was found to be Cys-Val-Thr-Gly-Ala-Pro-Gly-Cys-Val-Gly-Gly-Gly-Arg-Leu-NH2. The peptide was subsequently synthesized by solid phase methods, amidated at the carboxyl-terminal Leu, and shown to be identical to the isolated, native material. The peptide half-maximally stimulated A. punctulata spermatozoan respiration at 0.5 nM and half-maximally elevated cyclic GMP concentrations at 25 nM at an extracellular pH of 6.6. The increase in oxygen consumption was coupled with a stimulation of motility. However, at elevated extracellular pH (pH 8.0), resact failed to appreciably stimulate respiration while the elevations of cyclic GMP continued to occur. Resact did not cross-react with sperm cells obtained from Lytechinus pictus or Strongylocentrotus purpuratus; a peptide (speract) obtained from S. purpuratus eggs (Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly) which activates S. purpuratus sperm respiration did not stimulate A. punctulata spermatozoa. Resact caused a shift in the apparent molecular weight (160,000-150,000) of a major sperm plasma membrane protein; as with cyclic GMP elevations, this response was evident at extracellular pH values of both 6.6 and 8.0. The protein exists in the cell as a phosphoprotein and 32P is released coincident with the molecular weight change. Approximately 115 nM resact caused one-half-maximal conversion of the 160,000-dalton protein after 1 min of incubation. Resact caused the apparent molecular weight conversion of the protein within 5 s and appeared to do so in an irreversible manner. The molecular weight change of the protein was also observed after the addition of monensin A (25 microM) and NH4Cl (40 mM), two agents known to elevate intracellular pH and to increase sperm respiration rates. The membrane protein appears to be the enzyme guanylate cyclase, but since concentrations of resact causing one-half-maximal conversion of the Mr = 160,000 form of the enzyme are about 250 times higher than those causing one-half-maximal stimulation of respiration, the relationship of the apparent molecular weight conversion to a subsequent physiological event remains unclear.     

Modulation of mammalian sperm motility by quercetin

The flavonoid quercetin inhibits collective motility of ejaculated ram spermatozoa in the first 2 hr of incubation; during the next 3-4 hr motility is stimulated. To explain this interesting effect, we followed the influence of quercetin on sperm glycolysis, extracellular pH, ATP content, mitochondrial respiration, and lipid peroxidation. The collective motility of untreated cells is decreased to about 40% of the original motility during two hours of incubation. During this time, the rate of glycolysis is constant, respiration rate is increasing, there is no change in ATP content, the rate of lipid peroxidation is very slow, and the extracellular pH became very acidic (pH 5.5). It is concluded that motility is decreased due to this acidification. This acidification is prevented to some extent by quercetin, which indirectly inhibits glycolysis. Quercetin inhibits motility due to the inhibition of the plasma membrane calcium pump, as we showed previously (Breitbart et al., J Biol Chem 260:11548-11553, 1985). The motility of untreated cells is arrested after 3.5 hr of incubation, whereas quercetin-treated cells show high motility, which continues for additional 2-3 hr. After 3.5 hr, the control cells show no glycolytic activity, ATP content and respiration rates are decreased, and rate of lipid peroxidation is highly increased. At this time, quercetin-treated cells show no glycolytic activity, only a small decrease in ATP content and respiratory rate, and a very low rate of lipid peroxidation. Based on these data it is concluded that sperm motility after 3.5 hr of incubation is dependent mainly on mitochondrial respiration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Studying sperm motility in marine fish: an overview on the state of the art

This contribution reviews existing literature and some new own findings on teleost sperm motility and factors controlling it, emphasizing selected marine species. In marine teleosts with external fertilization (halibut, turbot, sea bass, hake, cod and tuna serving as examples), mainly the osmolality controls sperm motility: movement is activated by transfer from the seminal fluid into sea water, representing a large upward step in osmolality. The exception are flatfishes (such as halibut or turbot) where CO₂ is responsible for flagellar immotility in seminal fluid. In all cases, the duration of motility is short and limited to minutes ranges due to partial exhaustion of the ATP energy and to increase of internal ionic concentration as suggested by studies with de‐membranated/ATP reactivated flagellae. In this overview, we compare motility characteristics (percentage of active spermatozoa, velocity, linearity), flagellar waves parameters (wave length and amplitude, number of waves) and energy content (respiration and ATP concentration) within species where these data have been established. All parameters show a rapid decrease after activation; therefore progressive forward movement needed by the sperm to effectively reach the egg surface, is limited to a short initial period following activation. In two species (turbot and sea bass) the rapid decrease of sperm motility is reflected by a corresponding decrease of the fertilizing ability. Exposure to external environments (sea water) at activation also leads to local defects of the sperm flagella posing additional limitations on motility duration. However, minor flagellar damages as well as energetic exhaustion are reversible: after a resting period in a non‐swimming solution at the end of the motility period, spermatozoa can be re‐activated for a second motility period. From these results and from additional data obtained from de‐membranated/ATP re‐activated spermatozoa, a paradigm has been developed which establishes a link between external osmolality (sea water), internal ionic concentration and control of axonemal activity.