For some worms, ho... Accessibility statement Skip to main content. ... An instance of cross-species breeding gone awry: fluorescence microscopy reveals sperm, in red, invading a female worm's body.

Worm sperm is feisty at the best of times as it often has to compete with the sperm of multiple worms -- depending on how many males a female has mated with -- in order to gain access to the eggs.

Scientists have discovered a new kind of 'killer sperm' which stops a female from being able to mate with another species. Luckily, it's only female nematode worms that are affected. The study by ...