A random sting has helped Japanese researchers prove that some male wasps have a rather unusual predator defense weapon: penile spikes.
While wasps are known for their stinging attacks, only females have a real sting in their tail. Their male counterparts generally avoid predators by mimicking the fairer sex.
Scientists had theorized that some male wasps may have other defense mechanisms, including perhaps deploying their genital spikes.
“However, the evidence was lacking,” explained Shinji Sugiura, an ecologist at Japan’s Kobe University.
Sugiura studies animal defense against predators, but it was only by chance that he investigated the unusual wasp mechanism, after his graduate student and co-author reported being stung by a brick wasp.
– I tried to get stabbed after hearing her experience, Sugiura told AFP.
“Because I had thought of male wasps as harmless, I was very surprised to experience the pain.”
Female wasps sting via an ovipositor, a tube-like projection that lays eggs, but which can also produce a poisonous sting.
Male wasps lack the organ, but are equipped with two large spikes that sit on either side of the penis.
To test the effectiveness of this defense, Sugiura’s team offered male brick wasps to two different types of frogs to see how the spikes were deployed.
“Male wasps were often observed piercing the mouth or other parts of frogs with their genitalia while being attacked,” Sugiura reported in research published Tuesday in Current Biology journal.
The attacks are documented in a video that shows an unlucky frog repeatedly trying to pounce on a wasp, before using its front legs to pull the stinging insect out of its mouth.
Frogs happily ate all the males as well as stinging females, but over a third of the tree frogs rejected the male wasps after being stung.
When the experiment was repeated with the genital spikes removed from the wasps, the tree frogs no longer held back and ate them without hesitation.
“The difference was statistically significant. Even a small difference in survival can cause the evolution of anti-predator devices in insects,” Sugiura said.
There has been little research on the insect’s genitalia outside of its role in reproduction, according to Sugiura, although the wasp defense mechanism is not entirely without precedent.
For example, previous research has found that some species of hawks use their genitalia to emit ultrasounds that block bat sonar.
Sugiura is no stranger to uncovering some of the weirdest ways animals avoid their predators.
He has documented how some beetles can escape after being swallowed, by following the alimentary canal to its logical conclusion and escaping from the anus.
And he has shown that other insects can make any unfortunate toad that has eaten them regurgitate them.
He now hopes to expand his current research to find out whether other wasp families have the same sexual spike defense mechanism.
Shinji Sugiura, Wasp male genitalia as a defense against predators, Current Biology (2022). DOI: 10.1016/j.cub.2022.11.030
© 2022 AFP
Citation: A guard! Wasps use penis spikes to fend off predators (2022, December 25) Retrieved December 25, 2022, from https://phys.org/news/2022-12-en-garde-wasps-penis-spikes.html
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