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Sperm Traits (sperm + trait)
Selected AbstractsSPERM MORPHOLOGY AND VELOCITY ARE GENETICALLY CODETERMINED IN THE ZEBRA FINCHEVOLUTION, Issue 10 2009Jim Mossman Sperm morphology (size and shape) and sperm velocity are both positively associated with fertilization success, and are expected to be under strong selection. Until recently, evidence for a link between sperm morphology and velocity was lacking, but recent comparative studies have shown that species with high levels of sperm competition have evolved long and fast sperm. It is therefore surprising that evidence for a phenotypic or genetic relationship between length and velocity within species is equivocal, even though sperm competition is played out in the intraspecific arena. Here, we first show that sperm velocity is positively phenotypically correlated with measures of sperm length in the zebra finch Taeniopygia guttata. Second, by using the quantitative genetic "animal model" on a dataset from a multigenerational-pedigreed population, we show that sperm velocity is heritable, and positively genetically correlated to a number of heritable components of sperm length. Therefore, selection for faster sperm will simultaneously lead to the evolution of longer sperm (and vice versa). Our results provide, for the first time, a clear phenotypic and genetic link between sperm length and velocity, which has broad implications for understanding how recently described macroevolutionary patterns in sperm traits have evolved. [source] Geographic variation in sperm traits reflects predation risk and natural rates of multiple paternity in the guppyJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2010K. E. ELGEE Abstract Guppies (Poecilia reticulata) are models for understanding the interplay between natural and sexual selection. In particular, predation has been implicated as a major force affecting female sexual preferences, male mating tactics and the level of sperm competition. When predation is high, females typically reduce their preferences for showy males and engage more in antipredator behaviours, whereas males exploit these changes by switching from sexual displays to forced matings. These patterns are thought to account for the relatively high levels of multiple paternity in high-predation populations compared to low-predation populations. Here, we assess the possible evolutionary consequences of these patterns by asking whether variation in sperm traits reflect differences in predation intensity among four pairs of Trinidadian populations: four that experience relatively low levels of predation from a gape-limited predator and four that experience relatively high levels of predation from a variety of piscivores. We found that males in high-predation populations had faster swimming sperm with longer midpieces compared to males in low-predation populations. However, we found no differences among males in high- and low-predation populations with respect to sperm number, sperm head length, flagellum length and total sperm length. [source] Effect of male age on sperm traits and sperm competition success in the guppy (Poecilia reticulata)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2010C. GASPARINI Abstract Deleterious mutations can accumulate in the germline with age, decreasing the genetic quality of sperm and imposing a cost on female fitness. If these mutations also affect sperm competition ability or sperm production, then females will benefit from polyandry as it incites sperm competition and, consequently, minimizes the mutational load in the offspring. We tested this hypothesis in the guppy (Poecilia reticulata), a species characterized by polyandry and intense sperm competition, by investigating whether age affects post-copulatory male traits and sperm competition success. Females did not discriminate between old and young males in a mate choice experiment. While old males produced longer and slower sperm with larger reserves of strippable sperm, compared to young males, artificial insemination did not reveal any effect of age on sperm competition success. Altogether, these results do not support the hypothesis that polyandry evolved in response to costs associated with mating with old males in the guppy. [source] Sexual colouration and sperm traits in guppiesJOURNAL OF FISH BIOLOGY, Issue 1 2007T. E. Pitcher The relationships among the area, hue, saturation and brightness of orange colouration and sperm traits in the guppy Poecilia reticulata were investigated. Males with greater areas of orange colouration had significantly larger sperm loads, more motile sperm and longer sperm relative to males with relatively little orange colouration. Males with greater areas of orange colouration did not possess more viable sperm than males with relatively little orange colouration. There was no evidence that any of the sperm traits were related to the hue, saturation or brightness of the orange colouration. These results are discussed in the context of the roles that direct and indirect selection might play in maintaining female preference for male guppies with large areas of orange colouration. [source] Relationship between sperm density, spermatocrit, sperm motility and spawning date in wild and cultured haddockJOURNAL OF FISH BIOLOGY, Issue 2 2004R. M. Rideout Semen was collected repeatedly from captive haddock Melanogrammus aeglefinus and the effect of seasonality on various sperm parameters was investigated. No differences in sperm traits were observed for wild and cultured haddock. A highly significant positive relationship existed between spermatocrit and spermatozoa density. A significant increase in mean spermatocrit occurred throughout the spawning season but the amount of variability explained by collection date was low (35·1%) due to variability between males. Each of 10 males sampled repeatedly throughout the spawning season demonstrated an increase in spermatocrit. No relationship existed between spermatocrit and proportion of motile spermatozoa when spermatocrit was ,70%. Motility was reduced in semen samples with spermatocrits >70%. The proportion of spermatozoa that were motile decreased with time since activation. Some motility was still observed after 60 min in sea water (0·1,15·2%) for sperm collected at all times within the spawning season. Of those spermatozoa that were motile, the proportion that exhibited forward swimming motion decreased and the proportion that had only vibratory movement increased with time post-activation. The speed of forward swimming spermatozoa showed no significant relationship with spermatocrit at any time between 0 and 60 min after activation. Swimming speed was negatively related to time since activation, decreasing from 174,240 ,m s,1 at 0 min to 80,128 ,m s,1 at 60 min after activation. [source] | ||||||||||