It may be astonishing for many to know, but it is true that elephants have smaller sperm than mice. Since their discovery of almost 350 years ago, sperms have been found to be the most diverse cells when it comes to their size and shape.

It was quite strange to know the differences in size of sperms in animals when they have to perform the same thing, which is to fertilize a female's egg. It is being said that sperm competition has an important role to play in sperm evolution.

The competition takes place when many males have to mate with the same female and their sperm competes to fertilize the limited eggs of female. As per study researchers, longer sperm has been considered to have an edge.

Long sperm is more commonly found in small rodents like mice and rats in comparison to larger animals. The researchers said that the rodents' sperm is twice as long as big-sized animals, ungulates, primates and even whales.

Stefan Lüpold from the Department of Evolutionary Biology and Environmental Studies, University of Zurich along with this colleague, John Fitzpatrick, University of Stockholm, carried out an analysis to know the influence of sperm competition in the evolution of sperm in 100 mammalian species.

In the evaluation, the researchers included factors like sperm length and even number of sperm per ejaculate. It was found that longer is the sperm, the fewer of them a testicle of a specific size can produce. The researchers also found that the size of the animal adds to the selection pressure on ejaculations. The researchers said that most complex sperm are in smaller species.