Sperm and male sex organ extremes are revealed in a new study of more than 100 mammal species. The study also answers a question that has baffled scientists for years: Which is favored more during evolution, sperm size or sperm count? Quantity is key for mammals such as this roaring male lion, which can mate up to 60 times per day. The findings are published in the Proceedings of the Royal Society B.
Lead author Stefan Lüpold explained that he and colleague John Fitzpatrick of Stockholm University were "able to tease apart the relative importance of sperm size and number at different body sizes and show that in small species, both traits seem to respond to selection, because probably both of them can significantly influence competitive fertilization success."
"By contrast, in larger species, where ejaculates have a much higher risk of being diluted or sperm being lost within the much larger female reproductive tract, sperm number becomes so much more important than sperm size that the focus of selection seems to shift almost entirely toward sperm number," Lüpold, now at the University of Zurich, told Discovery News. He and Fitzpatrick conducted the research when they were both at the University of Manchester.
Read on to see which mammals bring the most impressive sexual goods to the table.
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