Flatworm uses ‘hypodermic penis’ to inject sperm into own head

Jul 7, 2015

by Philip Oldfield

The pursuit of reproductive success in the animal kingdom sometimes calls for extreme measures. But few creatures can match the hermaphrodite flatworm, which scientists have discovered can reproduce by injecting sperm into its own head.

The tiny aquatic worm, Macrostomum hystix, is able to self-fertilise because it produces both eggs and sperm. Although it prefers to reproduce with other flatworms, when no mating opportunities are present it resorts to using its needle-like penis to inject sperm into its own head.

The sperm then swim down the creature’s transparent body to fertilise eggs in the tail region, leading to viable offspring.

Dr Steven Ramm, an evolutionary biologist who led the work at Bielefeld University in Germany, said: “To us it sounds very gruesome, but to them it may be their best option. The alternative is not reproducing at all, so it’s making the best of a bad situation.”


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