Researchers from the Queensland Brain Institute have found that males blue-ringed octopus Hapalochlaena fasciata inject females with venom before mating to avoid being eaten.
This type of octopus is armed with a powerful neurotoxin called tetrodotoxin. Adult females are twice as large as males, about the size of a golf ball. This one difference in size can be dangerous for males, because voracious partners can easily eat them.
Because of this, males before mating bite their mate in the aorta area and inject a certain amount of tetrodoxin to paralyze them and protect themselves. According to the authors of the study, a large number of octopus species have a significant size difference between the male and female, which sometimes eat their smaller partners.
In males of some species octopuses have a well-developed long hectocotylus — a special tentacle with which they transfer spermatophores
— a capsule filled with sperm and serving to transport them and protect them from drying out, keeping them at a distance from females during mating. Males of some species simply tear off this hectocotylus in order to escape from aggressive females in time.
However, males The blue-ringed octopus Hapalochlaena fasciata does not have such defense mechanisms. Both males and females have a neurotoxin called tetrodotoxin in their saliva, which they use to protect themselves from predators and immobilize prey during hunting.
Despite the fact that males grow up to be half the size of females, their salivary glands in the back are three times heavier than those of females. According to the researchers, the larger salivary glands in males are associated not only with the requirements of hunting, but also mating with dangerous females.
As part of the study, the researchers placed six pairs of octopuses Hapalochlaena fasciata into tanks and observed their mating behavior. The scientists note that all females quickly submitted to the males. After that, the pairs did not move for about an hour.
Researchers point out that during mating, the respiratory rate of males varied from 20-25 times per minute to 35-45. Females showed a sharp decrease in respiratory rate at the beginning of mating. Then, after about eight minutes, they stopped breathing completely. In this state, they became pale, their pupils constricted, and they did not respond to bright flashes of light. The researchers attribute this to the action of tetrodoxin.
After immobilizing the females, the males successfully performed sexual intercourse and the mating was over. After females regained control over their bodies, they pushed males away.
In addition, the researchers noted that since none of the females died after the males injected the venom, this indicates a certain level of adaptability to tetrodotoxin.
Source: ScienceAlert
