A surprise finding off the coast of Australia came when marine scientists found several generations of naturally occurring hybrid sharks. Hybrids happening in nature are well documented, but never before in sharks. The cause is hypothesized as global warming.
“This is evolution in action,” said University of Queensland lead researcher Jess Morgan. The two breeds that hybridized are the Australian Blacktip shark (Carcharhinus tilstoni) and the common Blacktip (Carcharhinus limbatus); they are related but genetically distinct.
The hybrids were observed at five different locations throughout 2,000 kilometers (1,242 miles) of eastern Australia coastline.
The Australian blacktip favors tropical waters in the north white the common blacktip is found in the sub-tropical waters of south-eastern Australia. “Hybridization could enable the sharks to adapt to environmental change,” said University of Queensland researcher Jennifer Ovenden.
Identification of the hybrids was determined through DNA studies. Scientists report the 57 individual hybrid sharks discovered are healthy and robust and span several generations. This is a significant finding because it shows the first generation hybrids went on to reproduce.
Hybrids occur more commonly in fish because their eggs are fertilized in the water. But sharks mate through internal fertilization, like mammals.
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