Starfishes are weirdly shaped animals. Scientists have long puzzled over how a starfish body equates to the more typical animal arrangement of a head on one end and trunk or tail on the other. Humans wear trousers on the bottom of their trunks, so you could extrapolate out from that to suggest solutions to the 'trouser question' for dogs, horses, spiders and even slugs.

But what about a starfish? Now there's a new possible answer based on the expression of their genes….

Subscribe to Nature Briefing, an unmissable daily round-up of science news, opinion and analysis free in your inbox every weekday.