Interestingly, a specific octopus species has developed a strategy to impregnate the female while avoiding harm: using its venom.
Dimorphism. Many animal species exhibit pronounced sexual dimorphism, meaning there are significant size differences between the sexes. Males tend to be larger in many mammals since they often compete for territory and mating opportunities. In contrast, females are typically larger in birds of prey, arthropods, amphibians, and reptiles.
In the case of octopuses, some females can be up to 10 times larger than their male counterparts. An example is the blue-lined octopus (Hapalochlaena fasciata). This small but highly venomous creature is capable of delivering a potent neurotoxin, which both males and females possess. Despite their small size–barely larger than a golf ball–they’re extremely dangerous.
A strategy to survive. The female blue-lined octopus is twice the size of the male, leading to a rather unfortunate mating dynamic for the male, who often loses its life during the process. However, researchers from the University of Queensland in Australia recently published a study in Science Direct which found that males have adapted a toxic method to survive mating.
Due to the significant size difference, males can’t use tactics found in other octopuses. Some species have developed a longer reproductive arm to inseminate from a safe distance, while others have a detachable reproductive arm that allows them to escape. As such, the only option left for male blue-lined octopuses is to bite the female and inject her with neurotoxin directly.
Here is a full video of how blue-lined octopuses mate:
Venom in the heart. Researchers suggest that this evolution “likely co-evolves between demand for protection/predation and mating.” Males “bite” the female before attempting to copulate. They target an area near the aorta to inject a precise amount of tetrodotoxin that paralyzes their mate during the process.
To test this, the team placed six pairs of octopuses in separate aquaria and observed the behavior in each case. “[All female octopuses] quickly succumbed to the males,” researchers pointed out. Then, they lost all reflexes to light stimuli, became pale, and experienced pupil constriction due to a loss of nervous system control.
What just happened? Males experienced an increase in heart rate from 20 to 25 contractions per minute at rest to 35 to 45 during copulation. Meanwhile, females experienced a sharp drop in heart rate and stopped breathing altogether after about eight minutes from the bite.
Importantly, none of the females died, indicating that either the amount of neurotoxin injected is very precise or, evolutionarily, females have developed countermeasures. The bite to the back of the head was evident. “Once the females are immobilized, the males successfully copulated, and mating ended when the females regained control of their arms and pushed the males off,” the team explained.
In this video, you can see how the male approaches while the female remains motionless:
Sexual arms race. Although they didn’t directly measure the levels of neurotoxin, researchers suggested that this behavior indicates a “co-evolutionary arms race between the sexes.” In it, “a cannibalizing large female is counteracted in males through the use of venom.” As a result, the posterior salivary glands of males, where symbiotic bacteria produce the toxin, are three times larger than those of females.
Researchers also note that octopuses aren’t the only animals that accumulate this toxin. Several fish, mollusks, and amphibians also produce it. The team plans to continue its studies to determine whether other animals use this toxin during reproduction to survive mating. Interestingly, in one instance, a male bit a bit too far from its mate’s aorta, causing the female to regain consciousness in less time (35 minutes).
Image | Stephanie Harlacher
The post Sex Can Be Deadly for Many Male Species. Octopuses Have a Unique Strategy to Survive: Injecting Venom Into Their Partner appeared first on Xataka On.
