Australian Waters Harbor Hybrid Sharks

Marine scientists from the University of Queensland have discovered hybridized sharks off Australia´s east coast, leading them to believe that some of these predatory beasts display a tendency to interbreed, challenging long-standing scientific theories regarding shark behavior.

This is the first time scientists have confirmed a substantial number of hybrid sharks off Australia´s coast, speculating that it may be an adaptation or reaction to climate change; and scientists now believe it may indicate that other shark and ray species may interbreed in reaction to climate change.

“Hybridization could enable the sharks to adapt to environmental change as the smaller Australian black tip currently favors tropical waters in the north while the larger common black tip is more abundant in sub-tropical and temperate waters along the south-eastern Australian coastline,” said researcher Jennifer Ovenden of the University of Queensland in a press release.

Ovenden and her colleagues said they had discovered 57 sharks that are a cross between the Australian blacktip shark and the common blacktip shark. Both are genetically distinct species, but are closely related, making it easier for the hybridization to occur.

“Wild hybrids are usually hard to find, so detecting hybrids and their offspring is extraordinary,” Ovenden said. “To find 57 hybrids along 2000km [1240 miles] of coastline is unprecedented.”

The hybridization was confirmed using DNA measurements. The Fisheries Research and Development Corporation co-funded the research, which identified a mismatch between species identification using mitochondrial DNA sequencing and species identification using morphological characters — mature length, birth length, and number of vertebrae.

A nuclear DNA marker was sequenced to confirm the hybridization. Dr. Colin Simpfendorfer of James Cook University´s Fishing and Fisheries Research Center said blacktip sharks were one of the most studied species in tropical Australia. “The results of this research show that we still have a lot to learn about these important ocean predators,” he said.

Scientists from The University of Queensland, James Cook University´s Fishing and Fisheries Research Center, the Queensland Department of Employment, Economic Development and Innovation and the New South Wales Department of Primary Industries are further investigating the full extent of the hybrid zone and are attempting to measure hybrid fitness.

Jess Morgan, another University of Queensland researcher, said that hybrid species are common in fish because their eggs are fertilized in the water. “Sharks physically mate, which is usually a good way to make sure you don’t hybridize with the wrong species,” he told The Australian newspaper.

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