Biologists have been studying the mating behavior of a species of flatworm called Macrostomum hystrix. If the animal cannot find a mate it will subject itself to some extreme practices in order to reproduce.
Flatworms generally prefer to mate with another worm. However, being hermaphrodites (which means possessing both male and female sex organs) the worms will fall back to “self-mating” practices if the situation becomes desperate. Flatworms are simple unsegmented, soft-bodied invertebrates. They are flat in shape to allow oxygen to diffuse through their bodies. They also only have one cavity for taking in food and for pumping out waste material.
The self-fertilization is achieved by a method, dubbed by the researchers a little inelegantly as “selfing” (and clearly nothing to do with taking “selfies”). Here the worm manages to inject sperm from its head for the fertilization process. Through this process the worm can self-inject sperm from its head into the anterior of its body. The sperm then gravitates towards the eggs. This method is needed because there is no direct connection between the male and female regions in the worm. This solution, while working, leads to a risk of inbreeding and the associated genetic problems that come with it.
So far Macrostomum hystrix is the only species of flatworm known to be capable of this “selfing” behavior.
To find out more about what is happening, researchers studied transparent variants of the worm and took microscopic images. They found that worms in groups tended to have sperm in their tail region, in readiness for mating; whereas worms in isolation tended to have sperm in their head area, ready for self-fertilization.
The research was inducted at the University of Basel and the University of Bielefeld. The findings have been published in the journal Proceedings of the Royal Society B, in a paper titled “Hypodermic Self-Insemination as a Reproductive Assurance Strategy.”
