Researchers at Ben-Gurion University in Negev, Israel, have identified whiteleg shrimp as the only known species where the male has a reproductive cycle or "period." The male whitelegs--actually a type of prawn--generate two sperm packets per month which they attach to their female mates during reproduction. If, however, these packets are not used, they can solidify and prevent the male from getting rid of them. Thus, these prawns have developed a period or cycle of every two weeks, whereby they lose their sperm packets and develop new ones.
Scientists were first tipped off when they noticed that in predictable intervals, male whiteleg shrimp would take significantly more time choosing an outfit to wear when they were going out. They then noticed the shrimp staring into the mirror and crying uncontrollably. When asked what was wrong, the prawns could become suddenly enraged sometimes even attacking the researchers or launching into vicious verbal tirades about their male shrimp friends, pointing out all of their flaws and claiming them all to be back stabbers. Usually following these outbursts, the whitelegs would start laughing and joking around like nothing had happened.
"Even if the young whiteleg male does not have success producing progeny during one cycle," said Shmuel Parnas, one of the researchers, "he still has another chance with the next cycle without becoming impotent. This finding puts a new light on the common belief that males always want to mate."
Whiteleg shrimp can be found off the coast of Mexico all the way down to Northern Peru.