Changes to shark family tree

Four new species of tropical walking sharks are causing a stir in waters off northern Australia and New Guinea.

Yes, you read that right, walking sharks.

This isn’t that episode of The Simpsons where the dolphins come out of the water, walking on their tails. Instead, these creatures use their fins to walk in very shallow water during low tide.

The researchers suggest this ability may have evolved after they became genetically isolated.

“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,” Dr Christine Dudgeon says. 

“We estimated the connection between the species based on comparisons between their mitochondrial DNA which is passed down through the maternal lineage. This DNA codes for the mitochondria which are the parts of cells that transform oxygen and nutrients from food into energy for cells.”

“Data suggests the new species evolved after the sharks moved away from their original population, became genetically isolated in new areas and developed into new species,” Dudgeon says.

“They may have moved by swimming or walking on their fins, but it’s also possible they ‘hitched’ a ride on reefs moving westward across the top of New Guinea, about two million years ago.”

A remarkable edge over their prey

While the idea of walking sharks might strike fear into the hearts of some people, the researchers say the only creatures that need to worry are small fish and invertebrates.

During low tides these walking sharks become the top predator on the reefs.

“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,” Dudgeon says.

Dudgeon says future research would help researchers to better understand why the region was home to some of the greatest marine biodiversity on the planet.

“We believe there are more walking shark species still waiting to be discovered.”

The walking sharks were discovered during a 12-year study with Conservation International, the CSIRO, Florida Museum of Natural History, the Indonesian Institute of Sciences and Indonesian Ministry of Marine Affairs and Fisheries.

The study was published in the CSIRO’s Marine and Freshwater Research journal.

This article was first published on Australia’s Science Channel, the original news platform of The Royal Institution of Australia.

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