Exposure: A menstruating male was discovered

In a recent study conducted at Ben-Gurion University, it became clear that male marine shrimp of the species Litopenaeus vannamei have a monthly cycle. This is the first report in animals of males having reproductive cycles similar to females. This finding sheds new light on the common assumption that males are always ready to mate

In a recent study conducted at Ben-Gurion University, it became clear that male marine shrimp of the species Litopenaeus vannamei have a monthly cycle. This is the first report in animals of males having reproductive cycles similar to females. This finding sheds new light on the common assumption that males are always ready to mate.

Males of this marine shrimp produce two sperm sacs which are attached to the female during mating and then produce two new ones. Also, it was known until now that if the male does not use the sperm bags, they may harden over time until the male's inability to expel them. This means that the sperm cells have an expiration date after which the male may become impotent.

To the surprise of the team of researchers, headed by Prof. Amir Sagi of the Center for Marine Biology and Biotechnology at Ben-Gurion University, it turned out that males have a mechanism that allows them, at least in their youth, to avoid hardening of the scrotum and impotence. The researchers of Prof. Sagi's laboratory, Shmuel Farnes, Shaul Raviv and Assaf Shechter, raised about 50 males, followed their behavior for eight months and recorded their mating cycles. At the end of each shedding cycle, which is about two weeks long, the sea shrimp sheds its old armor and puts on a new armor. In unmated males, it was found that the old sperm sacs disappear in the last hours of the molting cycle and new ones appear immediately after shedding the old armor. In other words, the male shrimp renewed their sperm bags cyclically, once every two weeks, in exact coordination with the molting cycle which itself is under hormonal control.

"In this respect" explains Shmuel Farnes "the phenomenon is similar to the female reproductive cycle in women and female apes." In this way, even if the male shrimp does not have success with females during a particular mating cycle, he will not lose his chances of producing offspring in subsequent cycles. This finding sheds new light on the common assumption that males are always ready to mate."

The surprising research findings were published, among others, in the newspapers "Experimental Biology", "New Scientist" and - BBC widlife.