Sperm Swimming Velocity Research Articles

Variation in sperm swimming behaviour and its effect on fertilization success in the serpulid polychaete Galeolaria caespitosa

Summary Established models of fertilization kinetics in free-spawning marine invertebrates predict that fertilization success is dependent upon sperm swimming velocity. Despite the prevalence of these models, there are very few published tests of this assumption. To test this, the effects of sperm swimming characteristics on fertilization success were studied in Galeolaria caespitosa (Polychaeta, Serpulidae). Both sperm activity (% motility) and sperm swimming velocities were highly variable within this species. Sperm were motile for up to 6–7 h after activation; however, mean motility, swimming velocity and fertilization success decreased after 4 h. Eggs of G. caespitosa were fertilizable up to 10 h after spawning; however, the number of embryos resulting from fertilization by fresh sperm also decreased after 4 h. Sperm motility and velocity were not affected by water-soluble egg extracts. When gamete concentration, contact time, and age were held constant, fertilization success in G. caespitosa remained highly variable. Some of this variability was attributable to observed variability in sperm motility and velocity. Fertilization success was positively related to sperm velocity (P = 0.014), but there was no correlation between percent sperm motility and fertilization success (P = 0.85). Cross-fertilization experiments indicated that individual egg fertilizability and male-female compatibility also play an important role in determining the fertilization success and thus may obscure any effects of sperm motility.

Helical nature of sperm swimming affects the fit of fertilization-kinetics models to empirical data.

Models of fertilization kinetics rely upon estimates of the swimming velocity of sperm to predict collision rates between egg and sperm. Most investigators measure sperm swimming velocity without accounting for the helical motion of sperm, thereby obtaining an inflated estimate of the velocity with which sperm approach eggs. In turn, models of fertilization predict inflated rates of sperm/egg collision. I observed sea urchin sperm colliding with eggs, quantified the rate of sperm/egg collision, and measured sperm velocity as a component of the helix through which they swim. I also adjusted the "target size" of eggs to reflect the diameter of the helix. My estimate of sperm swimming velocity is an order of magnitude lower than other estimates for the same species. By using helical parameters in fertilization kinetics models and accounting for dead sperm in laboratory trials, I was able to accurately predict lower rates of sperm/egg collision. Moreover, making these adjustments in the model increased the estimated proportion of sperm that initiate fertilization by 6- to 7-fold, suggesting that a better understanding of sperm swimming might lead to a more complete understanding of fertilization biology and natural selection on gamete traits.

Determination of semen quality of the rainbow trout, Oncorhynchus mykiss, by sperm motility, seminal plasma parameters, and spermatozoal metabolism

This study investigated the relationships between semen fertilization capacity and sperm motility, seminal plasma composition and sperm metabolism in the rainbow trout, Oncorhynchus mykiss, to find out biomarkers for semen quality. Variations in semen fertilization rate could be best described by three multiple regression models: Firstly, a model including the seminal plasma pH ( x 1), β- d-glucuronidase activity ( x 2), total lipid levels ( x 3) ( y=894.77 x 1−53.13 x 1 2−6.58 x 2−0.0006 x 1 x 2−0.62 x 3+0.008 x 3 2−3666.19, F-value=10.35, R 2=0.805, P<0.001), secondly, a model including the sperm metabolism parameters malate dehydrogenase activity ( x 1), respiration activity ( x 2) aspartate aminotransferase activity ( x 3), total lipid levels ( x 4) ( y=−2.06 x 1−1.63 x 2+0.073 x 1 x 2−0.049 x 3+0.029 x 4+0.0031 x 4 2+97.96, F-value=12.41, R 2=0.754, P<0.001) and thirdly, a model including sperm motility rate ( x 1) and total swimming velocity ( x 2) ( y=0.44 x 1−0.38 x 2+0.011 x 2 2−0.00006 x 2 3+32.87, F-value=51.31, R 2=650, P<0.001). For practical application, the utilization of simple regression models is of value, too, as the technical effort for parameter determination is lower. Fertilization rate can be best described by sperm motility rate ( y=0.72 x+25.99, R 2=0.594, P<0.001), seminal plasma pH ( y=1460.2 x−89.41 x 2−5881.2, R 2=0.525, P<0.001) and spermatozoal respiration activity ( y=−1.85 x+84.59, R 2=0.554, P<0.001) as these parameters explain a high percentage of variance in fertilization rate and especially seminal fluid pH and motility rate are easy to determine. Subsequently high quality semen (fertilization rate >80%) is characterised by high sperm motility rate ≥75%, medium sperm swimming velocities of 100–120 μm/s, optimal seminal fluid protonic composition (pH of 8.0–8.2), balanced energy metabolism (spermatozoal respiratory activity≤5 μmol/min/100 mg protein, spermatozoal malate dehydrogenase activity≤2.5 μmol/min/100 mg protein, medium seminal fluid total lipid levels of 20–60 mg/100 ml and spermatozoal total lipid levels of 100–400 μmol/100 mg protein), and low seminal fluid lytic activity ( β- d-glucuronidase≤0.4 μmol/min/l [≤0.5 μmol/min/100 mg protein]).

Temperature-dependent hyperactivated movement of hamster spermatozoa.

Immotile hamster spermatozoa from the caudal epididymis were activated in physiological medium at a temperature range between 22 and 40 degrees C. With rising temperature, the sperm swimming velocity and flagellar beat frequency increased, but the flagellar bend angles and waveforms did not change dramatically. All spermatozoa exhibited a symmetric and progressive movement at this temperature range. Hyperactivation was induced by incubating activated spermatozoa in vitro at 37 degrees C for 3.5 h under 5% CO2 in air. When examined at 37 degrees C, spermatozoa expressed a hyperactivated motility characterized by asymmetric and circular flagellar beating with large principal and reverse bends. When the temperature was lowered to 33 degrees C, the sperm motility pattern characteristic of hyperactivation became less prominent. In particular, the reverse bend originating in the flagellar middle piece did not propagate to the principal piece. However, normal hyperactivated movement was restored as the temperature was raised to 37 degrees C, indicating that in vitro expression of hyperactivated motility of hamster spermatozoa is a temperature-dependent phenomenon. To further investigate temperature effects on the flagellar motor apparatus, spermatozoa were demembranated and then reactivated with ATP. In contrast to membrane-intact hyperactivated spermatozoa, demembranated spermatozoa exhibited a hyperactivation-like motility independent of the temperature range tested (22-40 degrees C). This strongly suggests that temperature regulates initiation and maintenance of hyperactivated motility and that its effect is mediated by the plasma membrane.

Sperm motility and seminal fluid composition in the burbot, Lota lota

Sperm motility and composition of the seminal fluid in Lota lota were investigated. Fives after motility initiation, 88.2 ± 12.4% of the spermatozoa were motile, their mean average path swimming velocity was 61.6 ± 16.3 μm s−1 and their principal swimming type the linear motion (77.4 ± 20.9%). In distilled water the rate of motile spermatozoa decreased to 0% in 40s. In 25–50 mosmol kg−1 electrolyte (NaCl) or non-electrolyte (glucose, sucrose) solutions, motility was prolonged for 10s and these solutions can therefore increase the efficiency of artificial fertilization when used for sperm motility activation. When semen was diluted in electrolyte or non-electrolyte solutions with osmolalities higher than 50 mosmol kg−1, sperm motility rates and swimming velocities decreased, and at osmolalities of 400 mosmol kg−1 motility was completely suppressed. In the seminal fluid with an osmolality of 290.08 ± 45.22 mosmol kg−1, sodium levels of 139.86 ± 23.79 mmol × 1−1, potassium levels of 11.59 ± 2.45 mmol × 1−1 and calcium levels of 0.20 ± 0.08 mmol × 1−1, sperm motility was inhibited. Under in vitro conditions, artificial saline solutions resembling the seminal plasma composition and 400 mosmol kg−1 NaCl or glucose solutions were useful as motility inhibiting solutions for predilution of semen. Sperm motility was not affected by pH 7.5–9.0, but at pH 6 the motility rate and the swimming velocity were reduced; seminal fluid pH was 8.47 ± 0.02. Therefore buffering of the artificial saline solutions can provide more stabile conditions for semen during storage and activation. Temperature optimum of semen was between 2 and 5°C. At higher temperatures semen became spontaneously motile. Therefore, controlled temperature conditions are an important factor for handling of semen. The qualitative, organical composition of seminal fluid was similar as in other fresh water teleosts.

Male display rate reveals ejaculate characteristics in the Trinidadian guppy,Poecilia reticulata.

Previous work (Reynolds and Gross 1992) has demonstrated that mate choice enables female guppies, Poecilia reticulata , to obtain heritable benefits (‘good genes’) for their offspring. It is not yet known whether males also signal their functional fertility, that is, their viability as fathers, to female guppies. Our study tested the hypothesis that a male9s behaviour reveals characteristics of his ejaculate. We uncovered a strong correlation between display rate and sperm number in male guppies derived from two wild Trinidadian populations. This result indicates that information on the functional fertility of potential mates is available to females. However, our investigation also found a significant relationship between the frequency of sneaky mating and sperm number. Female guppies in wild populations, particularly those experiencing a high predation regime, are constantly subjected to sneaky mating attempts. As the males responsible for these sneaky matings have highest reserves of sperm they may have the capacity to undermine female choice. The implications of these findings for sperm competition are discussed.

Male phenotype and ejaculate quality in the zebra finch Taeniopygia guttata.

We tested the idea that female preference for relatively attractive extra-pair males arises because the morphological and behavioural features that females find attractive covary with ejaculate features: Sheldon's (Proc. R. Soc. Lond. B 257 25-30 (1994) phenotype-linked fertility insurance hypothesis. Two phenotypic traits that female zebra finches find attractive in males are song rate and symmetry of chest band plumage, but we found neither of these to be significantly related to any of the following ejaculate features: number of sperm, percentage of live sperm, absolute number of sperm, sperm length or sperm swimming velocity. Furthermore, and surprisingly, we did not find the predicted negative relationship between male song rate and fluctuating asymmetry of chest band plumage. Because most ejaculate features (except sperm numbers in rested males) show low levels of repeatability, it is unlikely that female zebra finches could reliably obtain a better quality ejaculate by choosing to copulate with a more attractive male. There was thus no evidence for the phenotype-linked fertility insurance hypothesis. Nor did we obtain evidence for the more general fertility insurance hypothesis: we found that female zebra finches paired to a vasectomized male, and hence receiving no sperm, were no more likely to seek an extra-pair copulation than females paired to an intact male.

Ejaculate quality and the success of extra-pair copulations in the zebra finch

IN many passerine birds, sperm competition1,2 is intense and extra-pair paternity frequent3. The outcome of sperm competition is often determined by relative sperm numbers4,5, and theory predicts that males should maximize the number of sperm they ejaculate during extra-pair copulations6,7. Differences in sperm quality between males also affect the outcome of sperm competition4. Here we report that the swimming velocity of sperm of the zebra finch, Taeniopygia guttata, varies predictably within males, and is determined, together with sperm numbers, by the time since last ejaculation. By performing extra-pair copulations outside their own-pair copulation period, males maximize both the quality and number of sperm in ejaculates. These effects are a consequence of the way sperm are stored and mature in the male reproductive tract. The disportionate success of extra-pair copulations8, also seen in other birds9, may therefore be explained in terms of the independent effects of sperm numbers and velocity.

Kinetics of Fertilization in the Sea Urchin Strongylocentrotus franciscanus: Interaction of Gamete Dilution, Age, and Contact Time.

Determining fertilization success of free spawning organisms in the field requires knowledge of how eggs and sperm interact under varying encounter frequencies and durations. In the laboratory, we investigated the relative influence of sperm concentration, egg concentration, sperm-egg contact time, and sperm age on fertilization in the sea urchin Strongylocentrotus franciscanus. Our results indicated that sperm concentration, sperm-egg contact time, sperm age, and individual variability were sequentially the most important factors influencing fertilization success. Egg concentration was not significant over the range tested. A theoretical model of fertilization (Vogel-Czihak-Chang-Wolf model) was used to estimate the two rate constants of fertilization kinetics: the rate constant of sperm-egg encounter and rate constant of fertilization. This model explained 91% of the variation in fertilization success, provided estimates of the rate constants involved in fertilization, and indicated the proportion (3%) of sperm-egg contacts that result in fertilization. Estimates of sperm swimming velocity and egg diameter were used to independently calculate the rate of sperm-egg encounter and confirm the predictions of the model. This model also predicts the non-significant effect of egg concentration on fertilization success found empirically.

Sperm swimming velocity as evaluated by frame lapse videography and computer analysis.

A videographic method is described to measure the swimming velocity of fresh human, frozen-thawed bull and white mussel (Donax serra) sperm. The method can be accurately controlled. The pattern of sperm movement can be analyzed on a frame-by-frame basis or over 0.0206-sec intervals. Sperm velocities can be standardized per time unit. Sperm swimming velocity of different species ranging from very slow to very fast erratically moving sperm can be measured. Parameters such as swimming speed, progressive swimming speed, progressiveness ratio, and percentage motility can be evaluated.