Although it seems hard to believe but yes, mice have larger sperm size when compared elephants, largest living animal on the ground. But the story doesn’t end here and what’s even more mind-boggling is that the tiny fruit fly has the longest sperm which is nearly 20 times the length of its own body and about 1000 times the size of human sperm.
While studying the sperm science, researchers from the University of Zurich examined the sperm count and size of sperm and tried to find its link with the size of any species. They found that larger animal produces small size sperm in very large quantities. However, smaller produces larger sized sperms but in low numbers.
While giving examples, study authors said that a mouse ejaculates nearly 9.5 million sperms each of 124 micrometers long in one go while an elephant releases more than 200 billion sperms each of size 56 micrometers at a time. Thus, a mouse has nearly twice the sperm size when compared to gigantic elephants. In addition, a fruit fly Drosophila bifurca produces highly-coiled sperms that are nearly 5.8 centimetres (2.3 inches) long.
While explaining the reason behind such distinction, John Fitzpatrick and his colleague Stefan Lupold, from the University of Zurich said that sperm size and its quantity depends on the size of the female. Female elephants have longer duct thus, there is high risk for longer sperm in low numbers to get diluted or lost in the midway of the journey before fusing with an egg. 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.
“This demonstrates that the location where sperm compete – inside the female’s reproductive tract in mammals – determines when it pays a male to produce longer or more sperm,” Fitzpatrick said.
The study appeared in the Proceedings of the Royal Society of London.