Thus, large animals like elephants produce small sperms but in very large numbers which enhance the chances of sperm fusing with an egg, While in the case of smaller animals like mouse, it is better to produce large sperms in low quantity as the females have smaller duct. However, elephants have almost 200 billion sperms in a single ejaculate compared to 9.5 million sperms contained in single ejaculate of a mouse.
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The study appeared in the Proceedings of the Royal Society of London.
However, the study conducted by researchers from the Universities of Zurich and Stockholm now shows that the size of the animals also matters.
Sperms have been a continual source of fascination since its first discovery around 350 years back.
A male’s sperm has one job – to fertilize a female’s eggs. Longer sperm often seem to have a competitive advantage. It is being said that sperm competition has an important role to play in sperm evolution.
New meta-analytical methods allowed the researchers to discover species battling significant sperm competition, such as rodents, must invest more in their ejaculates than more monogamous larger animals. This mystery has been solved out by a team of researchers from the University of Zurich and University of Stockholm explaining the reasons behind mice having longer sperm than many other mammals. The bigger the size of the animal, the more important it becomes the count of sperm compared to the length of sperm. Within the bigger reproductive tracts of females, there are higher possibilities of losing or dilution of sperm during their journey to the egg.
Unlike previous studies, however, they did not just consider sperm length, but also the number of sperm per ejaculate, which is important as the resources available for sperm production need to be shared between sperm size and number.
Long sperm is more commonly found in small rodents like mice and rats in comparison to larger animals.
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John Fitzpatrick and his colleague Stefan Lüpold, from the University of Zürich, examined how competition between sperm from different males and the size of the female reproductive tract influence the evolution of sperm in 100 mammalian species. The elephant sacrifices the sperm’s length in order to produce so many sperm that at least one will get to the egg. In other words, the longer every individual sperm, the fewer of them a testicle of a certain size can produce. In contrast, in small species where sperm have an easier time finding the egg, males produce comparatively longer sperm.
