Mating can be risky, especially if you’re just a small male spider.
In many species, the female—often larger and more intimidating than any potential suitor—completes the act of copulation by enjoying her mate as a tasty post-coitus meal.
So a man often has to choose between biological imperatives: survive or reproduce. Reproduction usually wins, leading to… well, welcome to snack town, mate.
Many spiders have developed defensive strategies to avoid this unpleasant fate, such as: start with speed away from the female once mating is complete or wrap them in silk to prevent them from attacking. But funnel-web spiders of the species Aterigena aculeataa native of China, go a different way.
The species’ females signal their safety and receptivity as mates by curling up and playing dead, new research explains, allowing males to approach, mate and scurry away again without damaging their fangs.
“Sexual catalepsy by females in the funnel-web spiders can send a sexually receptive signal to the courting males, thereby benefiting both the signal-senders and signal-receivers.” writes a research team led by Jihe Liu from Jinggangshan University in China.
“Therefore sexual catalepsy in A. aculeata may not reflect conflict, but rather a confluence of interests between the sexes.”
Playing dead aka tonic immobility or thanatosis, is a well-known strategy for escaping predators in the animal kingdom, and many animals engage in it.
Since most predators seek only living prey, tipping over and presenting a seemingly already deceased target can be an effective way of escaping an extremely threatening situation.
In this state, animals can remain aware of their surroundings but may slow their heart rate and breathing rate to better imitate death.
Several species of funnel spiders have also been found to enter a thanatosis-like state to mate over the years, but what drives them has been difficult to pinpoint.
“Experimental evidence suggests that sexual catalepsy is a male-induced mechanism to reduce the risk of sexual cannibalism,” the researchers said explain.
“Females can remain motionless and unresponsive for anywhere from a few minutes to several hours, during which time the courting male can position the female to allow him to insert his pedipalps without risk of attack.”
However, it is not clear that this represents a strategy by the man. So, Liu and his team collected some spiders and observed their reproductive activity in several situations in the lab.
The spiders were collected a month before their normal mating season, and the researchers kept them in individual containers, feeding and grooming them.
The female spider was placed in an observation chamber; After constructing a web, the male was brought into the chamber with her for the pair to mate as usual in the wild.
In nine of the 12 matings observed, the female would go into sexual catalepsy, lying still and curling her legs as if dead. These instances resulted in a successful mating. In the three remaining cases, the male made advance attempts, but the female remained awake and normal, so mating did not occur.
Next, the researchers induced catalepsy-like conditions in six fresh females by introducing males. They induced thanatosis by gently shaking the six other females in a test tube to startle them until they became immobile.
The remaining group of females were stunned to mimic what might happen if a male spider’s chemical signal had triggered catalepsy.
The researchers then froze the three groups of six spiders with liquid nitrogen, ground them up and examined the powdered spiders. They wanted to study the chemistry of what was going on inside the spiders when they were unlatched. A control group of normal, awake female spiders was also included.
The results showed that the state of sexual catalepsy was chemically most similar to thanatosis, suggesting that female spiders choose to play dead to mate. This agrees with the researchers’ observations: the female spiders usually resume activity fairly quickly once mating is complete, while the male leaves.
None of the observed mating attempts – even the unsuccessful ones – resulted in arachnid cannibalism. However, the behavior can be a means by which the female spiders can choose who they want to sire their spiders.
“While female sexual catalepsy initially appears to reflect a case of male-controlled sexual conflict, our experiments suggest that it is under female control and benefits both women and men.” write the researchers.
“Perhaps sexual catalepsy allows females to exercise some mate selection: Initially, females remain potentially aggressive toward males, remain so toward non-preferred males, and inherit sexual catalepsy from males capable of touching the female.” .”
Who said romance is dead?
The research was accepted Current zoology.
