The image shows the differences in size of the sperm of a Chinese hamster and a bull. The rodent is five times larger than the other. / E. Roland and M. Tourmente
The males of the same species compete through their seminal characteristics in order to ensure the paternity of a higher proportion of young. It is what is known as sperm competition, a form of post-coital sexual selection influences the evolution of semen characteristics of animals. Sometimes the size of the sperm can be an advantage because a longer scourge swimming speed increases; other, the important thing is to generate a greater number of competitors arriving to fertilize the egg.
Based on the idea that each male has a fixed energy budget committed to sperm production, theoretical models predict an increase in the amount of sperm implies that it will not be possible to increase its size.
According to Eduardo Roldan, researcher at the National Museum of Natural Sciences (MNCN-CSIC), “this is not necessarily so.” “We wanted to see if the number or size of cells or if compensation between both traits occurs, given that there can be a fixed budget for energy generation is prioritized sperm in sperm competition,” said Roland.
The number and size are characteristics of sperm that can increase at a time, ie, that “there is no trade-off between”
The study, published in Journal of Evolutionary Biology , shows that the number and size are characteristics of sperm that can increase at a time, ie, that ” there is no compensation between them, “explains Maximilian Tourmente, also a researcher at MNCN.
Prioritizing size or number depending on each stage
In the testes, cellular processes that determine the number of sperm are different from those that influence the cell size. Furthermore, in mammals, the traits studied come into play at different times of the transport process of spermatozoa takes place on the way to fertilization.
In the first stage, when sperm are deposited in the tract female, the number has an important role. In the later stages, when the sperm have to actively swim to reach the egg and participate in fertilization rate, which is strongly influenced by the size, is essential.
“The increase in both the number of sperm and its size is affected by different energy requirements and metabolic constraints at each stage of sperm formation, “Tourmente says.
” The results of this study represent an important advance in understanding the male determinants fertility and how evolution can influence maximizing reproductive success of males, “says Roland.
Original article here
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