Literatura académica sobre el tema "Sperm velocity"

Sperm velocity is one of the main determinants of the outcome of sperm competition. Since sperm vary considerably in their morphology between and within species, it seems likely that sperm morphology is associated with sperm velocity. Theory predicts that sperm velocity may be increased by enlarged midpiece (energetic component) or flagellum length (kinetic component), or by particular ratios between sperm components, such as between flagellum length and head size. However, such associations have rarely been found in empirical studies. In a comparative framework in passerine birds, we tested these theoretical predictions both across a wide range of species and within a single family, the New World blackbirds (Icteridae). In both study groups, sperm velocity was influenced by sperm morphology in the predicted direction. Consistent with theoretical models, these results show that selection on sperm morphology and velocity are likely to be concomitant evolutionary forces.

Spermatozoa vary enormously in their form and dimensions, both between and within species, yet how this variation translates into fertilizing efficiency is not known. Sperm swimming velocity is a key determinant of male fertilization success, but previous efforts to identity which sperm phenotypic traits are associated with swimming velocity have been unsuccessful. Here, we examine the relationship between the size of several sperm components and sperm swimming velocity in natural populations of red deer ( Cervus elaphus hispanicus ) where selective pressures to enhance male reproductive success are expected to be strong. Our results show that there is little within-male and considerable between-male variation in sperm dimensions. Spermatozoa with longer midpieces swim more slowly, a finding which does not support the hypothesis that the size of the midpiece determines the amount of energy which is translated into swimming speed. In contrast, spermatozoa with elongated heads, and those in which the relative length of the rest of the flagellum is longer, swim faster. Thus, the hydrodynamic shape of the head and the forces generated by the relative size of the rest of the flagellum seem to be the key determinants of sperm swimming velocity.

Evolutionary biologists have argued that there should be a positive relationship between sperm size and sperm velocity, and that these traits influence a male's sperm competitiveness. However, comparative analyses investigating the evolutionary associations between sperm competition risk and sperm morphology have reported inconsistent patterns of association, and in vitro sperm competition experiments have further confused the issue; in some species, males with longer sperm achieve more competitive fertilization, while in other species males with shorter sperm have greater sperm competitiveness. Few investigations have attempted to address this problem. Here, we investigated the relationship between sperm morphology and sperm velocity in house mice ( Mus domesticus ). We conducted in vitro sperm velocity assays on males from established selection lines, and found that sperm midpiece size was the only phenotypic predictor of sperm swimming velocity.

Abstract The aim of the study was to find out whether the single nucleotide polymorphism (SNP) within arylsulfatase D (ARSD) gene is associated with kinematic parameters of sperm motility in Holstein- Friesian bulls. 367 Holstein-Friesian bulls kept in one AI center were included in the study. Point mutation C/T at position 139037255 on chromosome X (rs42207167) was identified by PCR-RFLP method (Pflm I). Significant associations were found between ARSD genotypes and CASA-derived sperm motility parameters: average TM (Total Motility), average VSL (Straight Velocity), average VCL (Curvilinear Velocity) and for fraction of sperms showing progressive motility (a) of sperms (VSLa, VCLa and BCFa -Beat Cross Frequency). Most significant differences were observed between alternative homozygotes (CC vs TT). Our results suggest new role of arylsulfatase D gene as being involved in sperm motility.

As sperm production is costly, males are expected to strategically allocate resources to sperm production according to mating opportunities. While sperm number adjustments have been reported in several taxa, only a few studies investigated whether sperm quality shows adaptive plasticity as well. We tested this prediction in the guppy, Poecilia reticulata . A total of 46 males were initially stripped of all retrievable sperm before being randomly allocated to one of two treatments simulating different levels of mating opportunities (visual contact with females or female deprived). After 3 days, males were stripped and sperm velocity was assayed using Computer Assisted Sperm Analysis. Males in the presence of females produced significantly faster sperm than their counterparts. Implications for the evolution of this ejaculate plasticity in the light of results of sperm competition studies are discussed.

We investigated the possible effects of sperm interactions and homogenized eggs on sperm velocity in blue mussels ( Mytilus edulis L., 1758) using computer-assisted sperm analysis. To test whether sperm competition results in an increase in sperm velocity, using seven pairs of males, we compared the mean curvilinear and average path velocities of sperm from two males measured separately with the corresponding values from a mixture of sperm from the same two males. To test whether the presence of eggs results in an increase in sperm velocity, we compared curvilinear and average path velocities from 11 individual males with the corresponding measures from the same 11 sperm samples mixed with aliquots of homogenized eggs. Neither experimental treatment resulted in an increase in sperm velocity. We interpret these results as consistent with the hypothesis that mussel sperm have been selected to immediately begin swimming at an optimal initial velocity that is adaptive for the particular environment in which they are located. Critical factors affecting the evolution of sperm velocity for broadcast spawning, external fertilizers such as M. edulis likely include population density and intraspecific spawning synchronicity. As has been suggested by others, the importance of sperm limitation (i.e., having much less than 100% of eggs being fertilized in the wild) may be as important an evolutionary driving force in broadcast spawning invertebrates as sperm competition is in internally or directly fertilized species.

Selection imposed through sperm competition is commonly thought to promote the evolution of longer sperm, since sperm length is assumed to be positively associated with sperm swimming velocity. Yet, the basis for this assumption remains controversial, and there is surprisingly little intraspecific evidence demonstrating such a link between sperm form and function. Here, we show that sperm length and velocity are highly correlated in the sea urchin Heliocidaris erythrogramma , but importantly we report that failure to account for within-male variation in these sperm traits can obscure this relationship. These findings, in conjunction with the mounting evidence for extremely high levels of intra-specific variance in sperm traits, suggest that a functional link between sperm morphology and velocity may be more prevalent than what current evidence suggests. Our findings also suggest that selection for faster swimming sperm may promote the evolution of longer sperm, thereby supporting recent findings from macroevolutionary studies.

The relationship between sperm energetics and sperm function is poorly known, but is central to our understanding of the evolution of sperm traits. The aim of this study was to examine how sperm morphology and ATP content affect sperm swimming velocity in the zebra finch Taeniopygia guttata . We exploited the high inter-male variation in this species and created extra experimental power by increasing the number of individuals with very long or short sperm through artificial selection. We found a pronounced quadratic relationship between total sperm length and swimming velocity, with velocity increasing with length up to a point, but declining in the very longest sperm. We also found an unexpected negative association between midpiece length and ATP content: sperm with a short midpiece generally contained the highest concentration of ATP. Low intracellular ATP is therefore unlikely to explain reduced swimming velocity among the very longest sperm (which tend to have a shorter midpiece).

In species with internal fertilization, the female genital tract appears challenging to sperm, possibly resulting from selection on for example ovarian fluid to control sperm behaviour and, ultimately, fertilization. Few studies, however, have examined the effects of swimming media viscosities on sperm performance. We quantified effects of media viscosities on sperm velocity in promiscuous willow warblers Phylloscopus trochilus . We used both a reaction norm and a character-state approach to model phenotypic plasticity of sperm behaviour across three experimental media of different viscosities. Compared with a standard medium (Dulbecco's Modified Eagle Medium, DMEM), media enriched with 1% or 2% w/v methyl cellulose decreased sperm velocity by up to about 50%. Spermatozoa from experimental ejaculates of different males responded similarly to different viscosities, and a lack of covariance between elevations and slopes of individual velocity-by-viscosity reaction norms indicated that spermatozoa from high- and low-velocity ejaculates were slowed down by a similar degree when confronted with high-viscosity environments. Positive cross-environment (1% versus 2% cellulose) covariances of sperm velocity under the character-state approach suggested that sperm performance represents a transitive trait, with rank order of individual ejaculates maintained when expressed against different environmental backgrounds. Importantly, however, a lack of significant covariances in sperm velocity involving a cellulose concentration of 0% indicated that pure DMEM represented a qualitatively different environment, questioning the validity of this widely used standard medium for assaying sperm performance. Enriching sperm environments along ecologically relevant gradients prior to assessing sperm performance will strengthen explanatory power of in vitro studies of sperm behaviour.

Made available in DSpace on 2017-07-10T18:13:17Z (GMT). No. of bitstreams: 1 Mauricio Spagnolo Adames.pdf: 2594661 bytes, checksum: 4bbc4710428addfb51d141108a994f72 (MD5) Previous issue date: 2014-03-31
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The aim of this study was to evaluate the effects of fructose as a modulator of sperm movement on the optimization of the sperm: oocyte in artificial reproduction procedures with the use of cryopreserved semen in Rhamdia quelen. Through the Computer Assisted Sperm Analysis (CASA) were evaluated in four replicas the motility rates, speed and time of sperm activation of the cryopreserved semen after thawing (10 seconds after activation) into six activating solutions containing fructose, concentrated at 0.0; 0.9; 1.8; 2.7; 3.6 and 4.5%. For the testing of fertilization an factorial experimental design (5 x 6) composed of five sperm:oocyte ratio (1x104, 3x104, 5x104, 7x104 e 9x104), six activating solutions containing fructose (0.0; 0.9; 1.8; 2.7; 3.6 and 4.5%) and three replicas or experimental blocks ("pools" of oocytes from three female groups). The effects were evaluated over variable rates of fertilization, hatching and larval normality. In the evaluation of sperm variables a regression analysis showed effect (p<0,05) of the solutions in motility, speed and duration of sperm activation. It was also verified effect (p<0,05) in the index obtained from clustering of such variables called index of sperm movement, with results of theoretical peak performance when 2.85% of fructose in solutions was employed. In the fertilization assay the analysis of response surface showed interactive effect (p<0.05) between sperm:oocyte ratio and fructose concentrations in activating solutions, on the fertilization and hatching rates and of the clustering index of two variables called index of reproductive success. According to the statistical model, sperm:oocyte ratio can be reduced keeping up the rates of fertilization and hatching. The inclusion of fructose in activating solutions has promoted similar theoretical maximum levels for fertilization and hatching when compared to fertilization only in distilled water, however with a saving of 17.77% of mobile spermatozoa: oocyte. The larval normality showed effect (p<0.05) just for the block. It is concluded that the sperm:oocyte ratio can be reduced through the employment of fructose-based activating solutions, without affecting the fertilization, hatching rates and larval normality.
O objetivo deste estudo foi avaliar os efeitos da frutose como modulador do movimento espermático sobre a otimização da relação espermatozoide:ovócito em procedimentos de reprodução artificial com o uso do sêmen do Rhamdia quelen criopreservado. Através do Computer Assisted Sperm Analysis (CASA) foram avaliadas em quatro réplicas a motilidade, a velocidade e o tempo de duração da ativação espermática do sêmen criopreservado após o descongelamento (10 segundos após a ativação) em seis soluções ativadoras contendo frutose na concentração de 0,0; 0,9; 1,8; 2,7; 3,6 e 4,5%. Para o ensaio de fertilização foi aplicado um delineamento experimental em esquema fatorial (5 x 6) composto de cinco relações espermatozoides:ovocito (1x104, 3x104, 5x104, 7x104 e 9x104), seis soluções ativadoras contendo frutose (0; 0,9; 1,8; 2,7; 3,6 e 4,5%) e três replicas ou blocos experimentais ( pools de ovócitos provenientes de três grupos fêmeas). Os efeitos foram avaliados sobre as taxas de fertilização, eclosão e normalidade larval. Na avaliação das variáveis espermáticas, a análise de regressão mostrou efeito (p<0,05) das soluções na motilidade, velocidade e tempo de duração da ativação espermática. Também foi verificado efeito (p<0,05) no índice obtido pelo agrupamento destas variáveis, denominado de índice de movimento espermático, com resultados de máximo desempenho teórico quando empregado 2,85% de frutose na solução ativadora. No ensaio de fertilização a analise de superfície de resposta mostrou efeito interativo (p<0,05) entre a relação espermatozoides:ovócito e as concentrações de frutose das soluções ativadoras, sobre as taxas de fertilização e de eclosão e do índice de agrupamento das duas variáveis denominado índice de sucesso reprodutivo. De acordo com o modelo estatístico a relação espermatozoides:ovócito foi reduzida mantendo-se as taxas de fertilização e eclosão. A inclusão de frutose nas soluções ativadoras promoveu níveis máximos teóricos semelhantes para fertilização e eclosão quando comparada à fertilização apenas em água destilada, porém com uma economia de 17,77% de espermatozoides móveis. A normalidade larval apresentou efeito (p<0,05) apenas do bloco. Conclui-se que a relação espermatozóides:ovócito pode ser reduzida através do emprego de soluções ativadoras a base de frutose, sem causar prejuízos ás taxas de fertilização e eclosão e normalidade larval.

The aim of this diploma thesis is to compare quality of northern pike sperm collected by different methods. First method is collection of stripped sperm by abdominal massage of the belly. Second method is collection of stripped sperm with special catheter to eliminate sperm contamination by urine. The last method is collection of testicular sperm. Differently collected sperm was evaluated and compared its quality. The main observed parameters were sperm volume, spermatozoa concentration, spermatozoa motility and velocity and osmolality of seminal fluid. Sperm samples were used for eggs fertilization. In fertilized eggs, the fertility of eggs and larvae hatching rate were observed.