background: the aim of the study was to assess the effect of four repeated ejaculations on the same day at two-hour intervals on conventional and functional semen parameters. methods: three healthy men (32±3.6 years) donated the first semen samples after 3-4 days of sexual abstinence followed by three subsequent samples on the same day at two-hour interval each. semen samples were processed and...

background: ubiquitin, an 8.5 kda peptide that marks other proteins for proteasomal degradation, tags defective sperm dur­ing epididymal passage. thus, sperm ubiquitination is a universal marker for sperm defects and can be used as a sperm func­tion test. the objective of the present study was to examine the relationships between sperm ubiquiti­nation and clinical se­men parameters, using simpl...

background:  wi-fi allows electronic devices such as laptops to exchange data or connect to a network resource. the main goal of this study was to assess the bioeffects of short term exposure to 2.4 ghz microwave radiation emitted from a common wi-fi router on sperm quality. materials and methods: male wistar rats were divided into 7 groups; i, sham exposed 4 h/day for 7days at 30 cm from the r...

sperm selection techniques have became an important tool to improve sub fertile ejaculates. the main aim of this study was to assess the dynamics of motile sperm subpopulations of ejaculates from subfertile stallions subjected to density gradient centrifugation (dgc) involving a double layer colloid [dgc2], before and after storage for 24 and 48 hours. ejaculates from eight stallions with ferti...

Sperm competition, whereby sperm from multiple males compete to fertilize an egg, selects for adaptations that increase fertilization success. Because fertilization success is related to sperm number, size, and quality, both interspecific and intraspecific variation in these traits are predicted to correlate with the level of sperm competition. Specifically, species and individuals that experie...

Female sperm storage is an essential component of reproduction in many animals. In insects, female sperm storage affects fecundity, sperm competition/preference and receptivity to re-mating. Female sperm storage consists of several stages, including sperm entry into the sperm storage organs (SSOs), maintenance within the SSOs and exit from the SSOs. The Drosophila melanogaster male seminal prot...

Damselflies (Odonata: Zygoptera) have a more complex sperm transfer system than other internally ejaculating insects. Males translocate sperm from the internal reproductive organs to the specific sperm vesicles, a small cavity on the body surface, and then transfer them into the female. To examine how the additional steps of sperm transfer contribute to decreases in sperm quality, we assessed s...

Sperm competition, when sperm from different males compete to fertilize a female's ova, is a widespread and fundamental force in the evolution of animal reproduction. The earliest prediction of sperm competition theory was that sperm competition selected for the evolution of numerous, tiny sperm, and that this force maintained anisogamy. Here, we empirically test this prediction directly by usi...

Post-copulatory sexual selection, in the form sperm competition, has influenced the evolution of several male reproductive traits. However, theory predicts that sperm competition would lead to trade-offs between numbers and size of spermatozoa because increased costs per cell would result in a reduction of sperm number if both traits share the same energetic budget. Theoretical models have prop...