Xenoturbella, marine worm related to humans

A light micrograph of Xenoturbella, a 3-cm long marine worm that eats molluscs and is thought to be related to humans, having shared a common ancestor with them in the distant past. Xenoturbella lives in mud at the bottom of a Swedish fjord. DNA analysis shows it is a deuterostome, related to the chordates. Worm illuminated from below.