"If males have their sperm consumed, rather than used for egg fertilization, they will lose that reproductive opportunity. Therefore, it is in the male's best interests to try to ensure at least some of his sperm reaches the female's eggs," lead author Benjamin Wegener, a researcher at Monash University's School of Biological Sciences, told Discovery News.
Wegener said that ejaculate consumption is well documented among numerous species. Humans are included in that group, but the behavior is not a standard part of our reproductive process.
According to Columbia Health, human male ejaculate contains fructose sugar, water, ascorbic acid (aka Vitamin C), citric acid, enzymes, protein, zinc and more. It reads like the ingredients list of a protein-infused sports drink.
Sperm consumption-as opposed to just ejaculate swallowing-in the animal kingdom "is far less common," according to Wegener.
Species that exhibit this include carrion flies, picture wing flies, a strange marine invertebrate known as Spadella cephaloptera, a type of leech, a marine nudibranch and the southern bottletail squid Sepiadarium austrinum.
Humans again may swallow sperm, but it's not standard behavior during reproduction.
It appears to happen a lot among squid, the focus of the new study. Wegener and his team discovered the behavior and tracked how the nutrients were utilized after consumption. It is the first time that the phenomenon has been observed in a female with external fertilization.
"This is an important distinction as even if the female consumes some of the ejaculate in those internal fertilizers, at least some of the sperm remains inside in the reproductive tract," he said.
The study is published in the journal Biology Letters.