Discovered in the deep: the rainbow fish that’s born female and becomes male

Scientists in the Maldives were only able to reach the rose-veiled fairy wrasse by using specialised diving gear

Around the Maldives, between 40 and 70 metres (130-230ft) beneath the Indian Ocean, there are flickering shoals of brightly coloured, finger-length fish that never venture up to the coral reefs at the surface.

The rose-veiled fairy wrasse (Cirrhilabrus finifenmaa) is one of many species that deep-diving scientists have found in the mesophotic (or twilight) zone, which lies between the sunlit shallows and the dark, deep ocean. It extends about 150 metres down and contains its own distinct mix of species.

The mesophotic zone is one of the least explored regions in coral reefs," says Yi-Kai Tea, postdoctoral fellow at the Australian Museum Research Institute in Sydney, by email from a research ship in the Indian Ocean. This area is generally situated at an awkward depth - not deep enough to survey with submarines, too complex to trawl and dredge, and too deep to dive with traditional scuba techniques."