Calcium-induced quiescence of sperm motility in the bluegill (Lepomis macrochirus)

Before dilution in hypoosmotic media sperm of freshwater fish are maintained quiescent by a range of factors including osmolality, K+ and pH, and the onset of motility is generally associated with an increase in cytoplasmic Ca2+. In contrast, Ca2+ in conjunction with osmolality was found to inhibit motility of intact bluegill sperm. Consistent with seminal plasma composition, 0.16 mmol/L Ca2+ and greater, in conjunction with an osmotic concentration of 290 mOsm/kg, inhibited the onset of bluegill sperm motility; sperm diluted in saline at 290 mOsm/kg without Ca2+ became motile. Cations Mn2+ and Sr2+, in conjunction with osmolality, had an inhibitory effect on initiation of sperm motility similar to that of Ca2+. Sperm motility was inhibited by Ca2+ channel blockers nimodipine and nifedipine, the mitochondrial Ca2+ uniporter inhibitor ruthenium red and the calmodulin inhibitors W-7 and trifluoperazine dihydrochloride. These results provide evidence that elevated cytoplasmic Ca2+ inhibits sperm motility and yet low levels permit or promote motility. This study demonstrates a unique inhibitory action of Ca2+ on the motility of intact fish sperm at physiologically relevant levels.     

Activation of sperm motility in striped bass via a cAMP-independent pathway

The objective of the present study was to identify the effect of osmolality, ions (K+, H+, Ca2+, Mg2+) and cAMP on the initiation of sperm motility in striped bass (Morone saxatilis). Striped bass spermatozoa remained motile in solutions isotonic to seminal plasma (350 mOsm/kg) until osmolality reached 600 mOsm/kg. K+ (0-100 mM) had no effect ( p>0.05 ) on sperm motility, and sperm displayed a high percentage of motility over a wide range of pH (6.0-8.5). Sperm motility could be initiated in Ca2+-free solutions. In contrast, sperm motility was inhibited (P<0.01) by solutions containing > or =10 mM Ca2+, and sperm could not be reactivated by a Ca2+-free solution. This Ca2+ inhibition was not affected by verapamil, a Ca2+ channel blocker. However, if sperm motility was first initiated in a Ca2+-free solution, the addition of Ca2+ solutions, up to 80 mM, failed to inhibit sperm motility, suggesting that Ca2+ inhibited the initiation of motility, but had no control of motile spermatozoa. Mg2+ solutions had similar inhibitory effects on sperm motility as Ca2+ solutions. Therefore, initiation of motility in striped bass sperm may be related to voltage-gated channels across the cell's plasma membrane. Membrane permeable cAMP did not initiate motility of quiescent, intact striped bass spermatozoa, and motility of demembranated sperm could be activated in the absence of cAMP.     

Sperm motility in fishes. I. Effects of temperature and pH: a review

Sperm motility is a key factor in allowing us to determine semen quality and fertilizing capacity. Motility in semen is mainly controlled by K+ in salmonids, and probably also in sturgeons, and by osmotic pressure in other freshwater and seawater fish species, but other factors, such as concentration of surrounding metabolites and ions (Ca2+, Mg2+, etc.), pH and temperature also influence motility characteristics. In the present study, we have mainly reviewed and summarized the effects of temperature and pH on the motility of spermatozoa in three fish species: salmonids, cyprinids and sturgeons. Data in the literature show that motility, fertilizing ability and velocity of spermatozoa, as well as the duration of the motility period, depend on the temperature of the assay medium and also of that of the brood fish holding tank. In contrast, the pH of the swimming medium, and thus the intracellular pH of spermatozoa, has less influence on sperm motility parameters in cyprinids, salmonids and sturgeons.     

Initiation of sperm motility depending on a change in external osmotic pressure in the noncopulatory marine cottid fish Gymnocanthus herzensteini

 The initiation of sperm motility in a noncopulatory marine cottid fish, Gymnocanthus herzensteini, was examined. The spermatozoa, which were immotile in seminal plasma, initiated motility at osmolalities of more than 500 mOsm kg⁻¹ in NaCl solution and 400 mOsm kg⁻¹ in KCl and mannitol solutions, indicating that the initiation of sperm motility depends on changes in external osmolality, in contrast with that of the sperm of other marine cottid fish, which are motile in seminal plasma. This study revealed that there are plural manner of initiation of sperm motility in marine cottid fish, which are oviparous but include both copulatory and noncopulatory modes. Received: May 24, 2001 / Revised: December 19, 2001 / Accepted: January 8, 2002     

The influence of water salinity and stage in life history on ion concentration of fish blood serum

(1) The Na, K, Ca, Mg concentration of blood serum have been studied in nearly 60 fish species from various waterbodies (the Neva, Lake Dal'nee, the Volga, Lake Baikal, the White Sea, the Black Sea, the Barents Sea etc.). In fishes (Cyprinidae, Percidae, Siluridae etc.) from fresh water (Lake Dal'nee, the Baikal, the Neva) with low 0.18–0.24 mEq/1 Na concentration Na content in blood serum was lower than in closely related species from fresh water (the Volga, Lyutoga River) with larger Na concentration–nearly 0.5–1 mEq 1. Blood serum of marine teleosts Na concentration (156–210 mEq/1) was higher than in migrating and freshwater species (90–174) mEq/1) and it did not depend on seawater salinity: Barents Sea–465, White Sea–255, Black Sea–227 mEq/1.
(2) Rather a considerable specific variation of ion concentration was found in blood serum of fishes from different families living in the same water body (Lake Baikal: Cyprinidae 90–95 mEq/1, Percidae 114 mEq/1, Salmonidae 126–129 mEq/1 etc.; the Volga: Siluridae 139 mEq/1, Percidae 142–150 mEq/1, Clupeidae 174 mEq/1).
(3) No relation has been detected between K, Ca and Mg concentrations in blood serum of fishes and the concentrations of these ions in the environment.
(4) Na concentration in the blood serum of sockeye salmon juveniles (101 mEq/1) migrating seaward was less than in adult fishes (132 mEq/1) returning to the lake to spawn. Na concentration in the blood of non-migrating salmonids ( Oncorhynchus nerka adult residual 104 mEq/1, Salvelinus alpinus juvenile 140 mEq/1, adult residual 141 mEq/1) changed insig- nificantly during life history. Notable hypopotassemia was observed in spawning time in Salmonidae.
(5) The comparison of blood serum ion concentration in males and females of fishes from different taxonomic groups (Acipenseridae, Salmonidae, Cyprinidae) showed no significant variation.     

Roles of osmolality, calcium - Potassium antagonist and calcium in activation and flagellar beating pattern of sturgeon sperm

The present study shows the roles of osmolality, calcium (Ca(2+))-potassium (K(+)) antagonist and Ca(2+) in sperm activation and flagellar beating of a sturgeon species, sterlet (Acipenser ruthenus). Sperm motility was activated at hypoosmolality relative to seminal plasma and suppressed at 175 mOsmol kg(-1). Sperm activation was totally suppressed by 0.35mM K(+), but Ca(2+) could fully reverse K(+) inhibitory effect at Ca(2+): K(+) ratio of 0.25. Neither EGTA (a chelator of Ca(2+) ions) nor nifedipine (a Ca(2+) channel blocker) prevented sperm activation. But, sperm motility and velocity were significantly decreased by EGTA, nifedipine and an inhibitor for Ca(2+)/calmodulin activated phosphodiesterase (w-7) that suggest role of Ca(2+) signaling after triggering sperm activation through hypoosmolality. Symmetric flagellar beating was also turned to asymmetric after activation in w-7, which is an evidence for modulation of Ca(2+)-binding proteins activity. Sturgeon sperm, similar to salmonids, is immotile in seminal plasma due to high K(+) concentrations, but the mechanism of sperm activation seems to be closer to other fish species where osmolality prohibits sperm activation in seminal plasma. In these species, hypoosmolality is the primary signal for sperm Ca(2+)-dependent signaling of axonemal beating.     

鱼类精子活力研究进展

鱼类精子在精巢和精浆中一般不活动,只有当精子被排到体外并被外界环境的溶液稀释后才能活动．鱼类精子活力受渗透压、离子、ｐＨ 值、温度及ＣＯ２ 等因子的调节和影响, 不同的鱼类其精子活力有不同的调节方式;外界因子对鱼类精子活力的影响, 是通过影响ｃＡＭＰ－ＡＴＰ－Ｍｇ２＋ 系统来影响鞭毛的活动而实现的． 精子活力的评价指标主要有：精子激活后的运动时间、精子激活比例、精子运动速度及精子鞭毛摆动频率等． 大多数鱼类的精子,其活动能力是在生殖管道中获得的．     

Chemical composition of seminal and ovarian fluids of chinook salmon (Oncorhynchus tshawytscha) and their effects on sperm motility traits

The relationships between the compositions of ovarian, seminal fluids and sperm function are not well known in teleostean fish species. The objective of the present study was to determine the concentration of the major inorganic ions (Na(+), K(+), Ca(2+), Mg, Cl(-)), osmolality, and pH of ovarian and seminal fluid of sexually mature chinook salmon (Oncorhynchus tshawytscha), and to determine if the composition of these fluids influences sperm motility traits (swimming speed, duration of forward mobility, swimming path trajectory, and percent motility). Cation concentrations and osmolality were significantly different in the two fluids. The ionic composition of ovarian fluid differed among individual females, and also among samples collected at different times through the spawning season. Carbonate and bicarbonate were the principal buffer ions in ovarian fluid, and its viscosity was considerably greater than that of water and was shear-dependent. The duration of forward motility (longevity) of spermatozoa, swimming speed, percent motility, and path trajectory were measured using milt from 10 males activated in the ovarian fluid from 7 females whose ion concentrations were known. No significant correlations were observed between the composition of the seminal fluid and sperm traits. However, in ovarian fluid, sperm longevity was negatively correlated with variation in [Ca(2+)] and [Mg(2+)], while percent motility increased with increasing [Mg(2+)]. These observations provide a possible chemical basis for cryptic female mate choice whereby female ovarian fluid differentially influences the behaviour of sperm from different males, and thus their fertilization success.     

In vitro maturation of the potential for movement of carp spermatozoa

Carp semen obtained from isolated fish after hormonal stimulation was highly variable in terms of volume of semen, osmotic pressure of the seminal plasma, and sperm capacity to move. Moreover, this last parameter was unstable when the spermatozoa were kept within the seminal plasma, and the present work was designed to investigate and possibly correct this phenomenon. Sperm potential movement was the major parameter studied and was measured by the percentage of motile cells in a final 3.000-fold dilution in a medium of low osmotic pressure in which sperm movement is known to occur (Morisawa and Suzuki, Science 210:1145-1147, 1980). This was completed with occasional measurements of flagellar beat frequencies and demembranation-reactivation of axonemal movement. The results showed that sperm potential movement was preserved upon dilution of the semen into cold 200 mM KCl medium and that semen of initially "poor" quality or spermatozoa that had lost their capacity to move during storage in the semen recovered gradually their potential movement during incubation at 2 degrees C in the same medium. The K+ dependence for both the conservation and the regeneration of sperm capacity to move showed a minimal requirement of 50 mM KCl in media of high osmotic pressure. Na+ ions had similar properties but not divalent cations. The K+ activation was not pH dependent between pH 9.03 and 6.04. Whatever the functional state of live spermatozoa, demembranation-reactivation occurred in ATP-Mg2+. It is concluded that, with dilution of the semen in appropriate conditions, carp spermatozoa retain or acquire potential movement and therefore are a lower vertebrate spermatozoa model available year-round. In addition, obtaining potentially nonmotile sperm and reversion in vitro might be useful to study the control of in vitro maturation.     

The effects of age on the composition of uterine fluid of broiler breeder hens and on maintenance of quality of fowl spermatozoa when stored in uterine fluid or in a synthetic medium

We studied effects of aging of hens on some physio-chemical parameters of uterine fluid taken at 2 stages of the ovulatory cycle (12 and 18 h after the oviposition) and of uterine fluid properties as a semen diluent in vitro at 41 degrees C. The volume, pH, osmotic pressure, Na+, K+, Ca2+, glucose and total protein concentrations of uterine fluid were measured. The percentage of motile spermatozoa and the fertilizing ability of fowl semen diluted 1:9 in uterine fluid were tested throughout the laying cycle in meat-type hens and compared to those of semen diluted in synthetic medium M199. The results showed that the volume and the K+ and Ca2+ concentrations in uterine fluid decrease with the hens' aging, while osmotic pressure is significantly higher in older hens. But in spite of the composition differences, uterine fluids from hens of different ages have little influence as semen diluents either on sperm motility or on fertilizing ability. These observations suggest that the variations of the composition of uterine fluid with hens' aging does not contribute to the late seasonal decline in fertility observed during the later stages of the reproductive season in this species. In any case, uterine fluid is harmful to sperm quality in vitro, while M199 is an appropriate semen diluent at 41 degrees C. The high glucose concentration in M199, however, slightly decreases motility and the duration of the fertile period of spermatozoa.     

The effect of inorganic and organic pollutants on sperm motility of some freshwater teleosts

Using four different sperm types from brown trout Salmo trutta fario (Salmonidae), chub Leuciscus cephalus (Cyprinidae), burbot Lota lota (Gadidae) and African catfish Clarias gariepinus (Clariidae) the effect of inorganic (cadmium, copper, mercury, lead, zinc and nitrite) and organic (cyclohexane and 2,4‐dichlorophenol) environmental pollutants on sperm motility was investigated. Spermatozoa were activated in double distilled water containing the different test substances and the motility was compared to controls of similar pH. From the investigated motility variables the sperm motility rate and swimming velocity reacted most to the environmental pollutants whereby the changes depended on the species and on the test substance. African catfish spermatozoa were the most resistant, chub and burbot spermatozoa showed medium resistance and brown trout spermatozoa were the most sensitive to the pollutants. With exception of 2,4‐dichlorophenol and zinc the effective concentrations of the tested pollutants exceeded the recommendation for surface waters 100–10·000‐fold and were in a range lethal for the fish themselves. Therefore, it was concluded that fish sperm motility is not a suitable marker for risk assessment of environmental pollutants.     

Semen of Perca fluviatilis L.: sperm volume and density, seminal plasma indices and effects of dilution ratio, ions and osmolality on sperm motility

The objectives of the present study were to characterize sperm volume and density, seminal plasma indices (ionic contents and osmolality) and to study the effects of dilution ratio, ions and osmolality on sperm motility parameters (percentage of motile sperm and sperm velocity) in farmed European perch (Perca fluviatilis L.). The means of sperm volume (ml), sperm density (x10(9)spermml(-1)) and total number of sperm (volumexdensity) per fish were 2.75+/-0.51, 29.19+/-3.15 and 82.19+/-15.26. The seminal plasma osmolality (mOsmkg(-1)), sodium, chloride, potassium and calcium ions concentrations (mM) were measured to be 298.07+/-5.09, 130.97+/-2.19, 106.75+/-2.37, 10.70+/-0.61 and 2.41+/-0.09, respectively. At 15s post-activation of stripped sperm, the percentage of motile sperm (%) and sperm velocity (mums(-1)) were 91.90+/-1.27 and 115.54+/-1.25, respectively, and decreased significantly following sperm activation (P<0.05). The optimal sperm motility was observed when the sperm was prediluted in immobilizing solution (IS) at a ratio 1:50. Prediluted sperm showed the maximum velocity when activated in 2.5mM Ca(2+), 50mM K(+) and sucrose with osmolality 100mOsmkg(-1). Neither Ca(2+) nor K(+) showed a significant effect on the percentage of motile sperm at 15s post-activation. Osmolality higher than 200mOsmkg(-1) significantly decreased the percentage of motile sperm, while osmolality of 300mOsmkg(-1) or above totally suppressed sperm motility.     

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.     

Motility of fish spermatozoa: from external signaling to flagella response

For successful fertilization, spermatozoa must access, bind, and penetrate an egg, processes for which activation of spermatozoa motility is a prerequisite. Fish spermatozoa are stored in seminal plasma where they are immotile during transit through the genital tract of most externally fertilizing teleosts and chondrosteans. Under natural conditions, motility is induced immediately following release of spermatozoa from the male genital tract into the aqueous environment. The nature of an external trigger for the initiation of motility is highly dependent on the aquatic environment (fresh or salt water) and the species’ reproductive behavior. Triggering signals include osmotic pressure, ionic and gaseous components of external media and, in some cases, egg-derived substances. Extensive study of environmental factors influencing fish spermatozoa motility has led to the proposal of several mechanisms of activation in freshwater and marine fish. However, the signal transduction pathways initiated by these mechanisms remain clear. This review presents the current knowledge with respect to (1) membrane reception of the activation signal and its transduction through the spermatozoa plasma membrane via the external membrane components, ion channels, and aquaporins; (2) cytoplasmic trafficking of the activation signal; (3) final steps of the signaling, including signal transduction to the axonemal machinery, and activation of axonemal dyneins and regulation of their activity; and (4) pathways supplying energy for flagellar motility.     

Significance of regional difference in ion concentrations in lizard, Hemidactylus flaviviridis (Rüppell): assessment of ionic influence on sperm motility in vitro

A gradual increase in the concentration of Ca2+ from anterior to the posterior region was observed when mono- and divalent cations were estimated in different segments of the epididymis in wall lizard. Na+ and K+ levels increased from anterior to middle segment but declined significantly in the posterior segment. However, no significant difference in the levels of Mg2+ was observed in various segments. To study the influence of mono- and divalent cations on sperm motility in vitro, the spermatozoa from posterior region of the epididymis were incubated in medium with varying concentrations of Na+, K+, Ca2+ and Mg2+. Spermatozoa were non-motile when suspended in Na+-free medium. Addition of NaCl induced the acquisition of sperm motility in a concentration-dependent manner. Further, amiloride, a Na+-influx blocker, markedly reduced the Na+-induced forward progressive motility. Unlike Na+, the presence of K+ or Ca2+ in the incubation medium reduced the motility of spermatozoa even at very low concentrations. The inhibitory effect of Ca2+ decreased when nifedipine, a Ca2+-influx blocker, was added to the medium. Mg2+ at high concentrations only was able to reduce the forward progressive motility.     

Fertilization environment of the non-copulating marine sculpin, Hemilepidotus gilberti

To clarify the extracellular environment for external fertilization in the non-copulating marine sculpin Hemilepidotus gilberti, sperm motility was measured in NaCl, KCl, mannitol solutions, seawater, and ovarian fluid. Spermatozoa of H. gilberti actively moved in seminal plasma the moment they were removed from the genital papilla. Spermatozoa showed higher motility in NaCl solution at osmolalities between 300–400 mOsmol kg^-1. In KCl and in mannitol solutions, spermatozoa actively moved at osmolalities between 500 and 800 mOsmol kg^-1, and at osmolality 300 mOsmol kg ^-1, respectively. The ovarian fluid was a transparent and viscous gelatinous material, rich in sodium with an osmolality of 340 mOsmol kg^-1. Sperm motility in the ovarian fluid lasted more than 90 min, which was six times longer than in seawater. This sperm motility under conditions isotonic to body fluid is similar to that of copulating marine sculpins rather than to other non-copulating marine fishes. In addition, eggs of H. gilberti could be fertilized in the ovarian fluid. This suggests that external fertilization takes place under physiological conditions similar to the internal conditions of the ovary provided by the ovarian fluid, which isolates the eggs from sea water for several hours after spawning. This manner of fertilization is thought to be one of the evolutionary pre-adaptations allowing copulation among marine sculpins.     

Effects of osmolality on sperm morphology, motility and flagellar wave parameters in Northern pike (Esox lucius L.)

Northern pike (Esox lucius L.) spermatozoa are uniflagellated cells differentiated into a head without acrosome, a midpiece and a flagellar tail region flanked by a fin structure. Total, flagellar, head and midpiece lengths of spermatozoa were measured and show mean values of 34.5, 32.0, 1.32, 1.17 μm, respectively, with anterior and posterior widths of the midpiece measuring 0.8 and 0.6 μm, respectively. The osmolality of seminal plasma ranged from 228 to 350 mOsmol kg⁻¹ (average: 283.88 ± 33.05). After triggering of sperm motility in very low osmolality medium (distilled water), blebs appeared along the flagellum. At later periods in the motility phase, the tip of the flagellum became curled into a loop shape which resulted in a shortening of the flagellum and a restriction of wave development to the proximal part (close to head). Spermatozoa velocity and percentage of motile spermatozoa decreased rapidly as a function of time postactivation and depended on the osmolality of activation media (P < 0.05). In general, the greatest percentage of motile spermatozoa and highest spermatozoa velocity were observed between 125 and 235 mOsmol kg⁻¹. Osmolality above 375 mOsmol kg⁻¹ inhibited the motility of spermatozoa. After triggering of sperm motility in activation media, beating waves propagated along the full length of flagella, while waves appeared dampened during later periods in the motility phase, and were absent at the end of the motility phase. By increasing osmolality, the velocity of spermatozoa reached the highest value while wave length, amplitude, number of waves and curvatures also were at their highest values. This study showed that sperm morphology can be used for fish classification. Sperm morphology, in particular, the flagellar part showed several changes during activation in distilled water. Sperm motility of pike is inhibited due to high osmolality in the seminal plasma. Osmolality of activation medium affects the percentage of motile sperm and spermatozoa velocity due to changes in flagellar wave parameters.     

Sperm metabolism of the telost fishes Chalcalburnus chalcoides and Oncorhynchus mykiss and its relation to motility and viability.

In the teleost fish Chalcalburnus chalcoides (Cyprinidae) the influence of metabolic inhibitors, substrates, coenzymes, and oxygen concentrations on spermatozoal parameters during motility and during immotile incubation was studied, the respiration rate was characterized, representative metabolite levels were measured, and the results were compared with Oncorhynchus mykiss (Salmonidae). In Chalcalburnus chalcoides the sperm motility rate, the average path swimming velocity, the motility duration, and the viability of immotile semen were significantly reduced in the presence of inhibitors of respiration (potassium cyanide, 2.4-dinitrophenol, atractyloside). Anaerobic conditions (<1 mg O(2)/liter) and inhibition of the tricarboxylic acid cycle by malonate and >7.5 mmol/liter succinate had similar effects on the sperm motility parameters and on the viability of immotile spermatozoa. Pyruvate and coenzyme A (an acyl-group carrier during oxidative carboxylation of pyruvate) prolonged the duration of sperm motility and the viability of immotile incubated spermatozoa, and also increased the spermatozoal respiration rate. Glucose levels significantly decreased during motility and during immotile storage and, under anaerobic conditions, the levels of lactate increased indicating that pyruvate derived from glycolysis. The respiration rate and the glycolytic rate significantly increased during motility. Therefore oxidative phosphorylation, tricarboxylic acid cycle, and aerobic glycolysis are central energy-supplying pathways for spermatozoa of Chalcalburnus chalcoides. The stimulatory effect of pyruvate and coenzyme A indicated that glycolysis is a rate-controlling pathway. Similar results were obtained for Oncorhynchus mykiss with the only exception that the stimulatory effect of coenzyme A was more significant than the stimulatory effect of pyruvate. When the sperm motility-activating saline solutions were optimized in aspects of energy supply, ionic composition, and osmolality, about 50% of the motile spermatozoa swam progressively (>20 mm/sec) for about 3 min in Chalcalburnus chalcoides and in Oncorhynchus mykiss. About 20% swam progressively for >2 hr in Chalcalburnus chalcoides and for >30 min in Oncorhynchus mykiss. J. Exp. Zool. 284:454-465, 1999.     

Relationship between semen characteristics and body size in Barbus barbus L. (Teleostei: Cyprinidae) and effects of ions and osmolality on sperm motility

The objectives of the present study were to determine the relationships among length and weight of males, sperm volume, spermatozoa concentration, total number of spermatozoa, ionic contents and osmolality of seminal plasma in Barbus barbus. The effect of osmolality on sperm motility parameters after activation in NaCl, KCl, or sucrose solutions was also examined. There were significant correlations between spermatozoa concentration – length (R = + 0.7) and – weight (R = + 0.8) of males. No significant correlations were observed between the total number of spermatozoa, sperm volume, and length and weight of males. Seminal plasma osmolality was higher when the total number of spermatozoa (R = + 0.6) and sperm volume (R = + 0.6) were higher. Sperm motility and velocity was positively correlated with osmolality (R = + 0.5). The correlation between sperm motility and K⁺ was negative (R = 0.5), but positively correlated with Ca²⁺ (R = 0.8), Na⁺ (R = 0.8), and Cl⁻ (R = 0.8). There was a rapid decrease (P < 0.05) in sperm motility parameters after sperm activation. Just after sperm activation, beating waves propagated along the full length of flagella. At latter stages post sperm activation, the waves appeared only in proximal part of the flagellum. The highest spermatozoa velocity and percentage of motility were observed at 215–235 mOsmol kg^− 1 in NaCl, KCl or sucrose. The tip of the flagellum became curled into a loop shape which shortened the flagellum after activation of sperm in distilled water. B. barbus sperm is very similar to that of other cyprinids in terms of ionic contents and osmolality of the seminal plasma, mechanism of sperm activation and behavior and motility of sperm during swimming period.     

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.