These spiders catapult each other to escape sexual cannibalism

For a type of spider native to East Asia, the mating process culminates in a spectacular finale. The male indeed catapults himself from the female’s body at breakneck speed so as not to be devoured. This daring maneuver was recently the subject of a study published in Current Biology.

In the animal world, many mechanisms described allow extremely rapid actions or reactions thanks to the slow storage of energy (most often in elastic structures) which is then released almost instantaneously. Many of these catapult-like mechanisms are used for capturing prey or avoiding predators. This is particularly the case for certain species of shrimp or ants. However, such lightning-fast actions had never before been described as a means of dodging sexual cannibalism. It is now done.

As part of a study, a team led by Shichang Zhang, from Hubei University in Wuhan, has indeed observed this phenomenon in a species of spiders found in Japan, Taiwan, South Korea and China. .

Catapult yourself so as not to be devoured

Among the spiders Philoponella prominensmales only measure three millimeters longwhile females are about double. These arthropods live in colonies that can hold more than two hundred spiders in a vast network of webs.

Observing one of these colonies in Wuhan three years ago, researchers noticed that after mating, some males extricated themselves from their partner’s body at breakneck speed. The phenomenon is also so fast that it is almost invisible to the naked eye or to the eyes of ordinary cameras. So the team decided to take a closer look at it using specialized instrumentation.

In one study, researchers collected about 600 specimens and conducted 155 successful mating trials. To capture these lightning-fast ejection maneuvers, they used a special camera capable of shooting over 1,500 frames per second. They then used software to measure the energy and speed of these expulsions.

During these experiences, 97% of males catapulted successfully after the first mating. All of them survived. Conversely, the few males who failed to catapult were captured, killed and eaten by females“, report the authors. The same was also true for about thirty males whose expulsion mechanism had been deliberately inhibited by the researchers.

The mechanism filmed in slow motion. Credits: Shichang Zhang

A jump at 88 cm/s

To fly away, these spiders fold their legs against the female before releasing them. The hydraulic pressure then causes rapid expansion. When the spiders were able to successfully take flight, the energy stored in their legs could propel their tiny bodies up to 88 centimeters per second. For comparison, imagine an adult human jumping in the air and landing a second later at a distance of more than 500 meters.

For now, these little orb-weavers are the only animals known to use this technique as protection against sexual cannibalism.

Prior to mating, male spiders attached themselves to the female’s web with a silk “safety line”, so that after being catapulted, they could ascend to mate again. Some could thus mate with the same female up to five times. For the authors, this post-sexual expulsion maneuver therefore probably evolved as a survival mechanism.

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