The BBC reports on an invasive species of shrimp found in the Grafham Water reservoir in Cambridgeshire. Originally from the region between the Black and Caspian seas, it's thought to have spread to Western Europe via the Danube. Apparently it's a vicious little beastie that kills all sorts of other water fauna and could threaten them: native shrimps, water boatmen, even fish.
Should we worry? As with so many similar stories, it does raise the difficult question of whether we should or shouldn't interfere in the natural comings and goings of species. It's no doubt gone on down the millennia before we were on the scene, with vast numbers of species dying out and new ones coming to prominence before maybe fading away themselves. We seem to be keen to stop time and freeze the natural world as it is – but that sounds fairly unnatural in itself.