Urine cloud makes crayfish mad, and lustful

The mating habits of crayfish are something of a pissing contest.

Fiona Berry and Thomas Breithaupt from the University of Hull, UK, investigated the effects of urine-based chemical signaling on sexually active crayfish.

“Walking through urine drives crayfish into an aggressive sexual frenzy,” according to the researchers, writing in the open access journal BMC Biology.


Crayfish fight in a cloud of visualized urine.

Photo courtesy of Fiona Berry; BMC Biology

“Our results confirm that females initiate courtship behavior; males will only attempt to mate if they receive urinary signals from the female.

“Females, however, send a mixed message by releasing an aphrodisiac while also acting very aggressively towards the males,” Breithaupt said in a new statement about the research.


Crayfish fight in a cloud of visualized urine.

Photo courtesy of BMC Biology

Females could profit in different ways from displaying such conflicting signals, the scientists explained.

By stimulating aggressive behavior in males, females can gauge male size and strength and thereby ensure that only the fittest males get to fertilize their eggs, they add.

“Timing seems to be key to this interaction as urine induces aggression in both sexes. Males will discontinue urine release early in the sexual encounter, which may mitigate the female’s antagonism and enhance mating success.”


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