‘Walking sharks’ are familiar to scuba divers – hooded epaulette sharks (Hemiscyllium strahani) feature in the current issue of DIVER magazine. But now researchers in Australia have almost doubled the number of recognised species overnight.
The discovery of four new species brings to 9 the total number, say the scientists.
The leader of their 12-year study, Dr Christine Dudgeon of the University of Queensland, says that the small sharks live in their own separate region off northern Australia and Papua New Guinea, and are the top reef predator during low tides, using their fins to walk in very shallow water.
“At less than a metre long on average, walking sharks present no threat to people but their ability to withstand low-oxygen environments and walk on their fins gives them a remarkable edge over their prey of small crustaceans and molluscs,” she said.
“These unique features are not shared with their closest relatives the bamboo sharks or more distant relatives in the carpet-shark order, including wobbegongs and whale sharks.”
DNA testing was used to work out the connections between the species, which evolved after the sharks “moved away from their original population, became genetically isolated in new areas and developed into new species”, said Dr Dudgeon.
“They may have moved by swimming or walking on their fins, but it’s also possible that they ‘hitched’ a ride on reefs moving westward across the top of New Guinea, about two million years ago,” she said. “We believe there are more walking shark species still waiting to be discovered.”
The study was carried out with Australia’s Commonwealth Scientific & Industrial Research Organisation (CSIRO), Conservation International, Florida Museum of Natural History, the Indonesian Institute of Sciences and the Indonesian Ministry of Marine Affairs & Fisheries, and is published in CSIRO’s Marine & Freshwater Research.