A Sydney aquarium has successfully bred a critically endangered grey nurse shark. A male shark pup was born at Oceanworld Manly on 6 February to 20-year-old mother Pallas. To get as far as he has, the pup has already beaten the odds. Developing grey nurse embryos feed on other fertilised eggs until there is only one left in each of the sharkâs two wombs. Grey nurse sharks are often born in pairs – one from each of two uteruses – they can hunt and survive without parental care. The grey nurse species, known as the sandtiger shark in the UK and US, and the ragged tooth shark in South Africa, is vulnerable to extinction worldwide. But it is critically endangered off Australiaâs east coast where there are only 500 left in the wild.