Scientists may have thought they've seen it all when it comes to mating habits of species — until they found a worm that "self-injects" itself with its own sperm.
The tiny aquatic flatworm, Macrostomum hystix, is capable of self-fertilization because it is a hermaphrodite with both male and female reproductive organs and produces both eggs and sperm, researchers explain.
Although its normal mating preference involves a partner worm, if one isn't available, the tiny flatworm can use a hypodermic-like penis to inject sperm into its own head, which then travel down its body to fertilize its eggs.
The result? Viable offspring, all on a "do-it-yourself" basis.
"To us it sounds very gruesome, but to them it may be their best option," says Steven Ramm from Bielefeld University in Germany.
"The alternative is not reproducing at all, so it's making the best of a bad situation," says Ramm, an evolutionary biologist and lead author of a study published in the Proceedings of the Royal Society B.
Scientists have coined a word for the ability of an individual to self-fertilize or self-pollinate: "selfing."
Selfing "occurs in a broad range of hermaphroditic plants and animals and is often thought to evolve as a reproductive assurance strategy under ecological conditions that disfavor or prevent outcrossing (breeding with an unrelated species)," Ramm says.
Scientists previously believed selfing could not occur in hermaphroditic species because the male and female reproductive organs were isolated and strictly separated from each other.
The tiny M. hystic doesn't seem to have any such limitation, apparently.
Reproduction by selfing isn't ideal, the researchers point out, because it results in offspring with no genetic variation. Genetically diverse populations are more capable of surviving many environmental pressures and threats, they note.
Still, they suggest, it at least makes reproduction possible even in situations where there are no mates readily handy.
Also, the worm has obviously evolved the equipment that makes it possible.
"Lots of animals are able to self-fertilize, but this is the first example of one that uses a hypodermic appendage to do so," says Ramm.
