These flatworms stab themselves in their heads with their penises to reproduce

Researchers have discovered that Macrostomum hystix, the hermaphrodite flatworm, can reproduce by injecting sperm into its own head.

According to The Guardian the sperm swim down its body to fertilise eggs in its tail region - creating viable offspring.

“The alternative is not reproducing at all, so it’s making the best of a bad situation,” said Dr Steven Ramm, an evolutionary biologist who led the work at Bielefeld University in Germany.

According to Ramm's study, which was published in the Proceedings of the Royal Society B, 100 flatworms were spliced into two batches - the first as isolated individuals, the second in groups of three.

After four weeks, the ones living in groups had more sperm in their tails - meanwhile the singles had more in their head or middle reasons - revealing that they had swung their sharpened penises around to inject themselves in the head.