Evolution at work! Why hybridization of the sharks made such big news? Are the previous scientific theories regarding the “survival of the fittest” true? Let’s find out!
Before we move on to the recent findings it is important that we completely understand the term, “Hybridization”. Hybridization involves crossing of two different species of animals or plants. It can take place naturally or can be induced artificially.
The existence of the earliest shark species is believed to be more than 420 million years ago. Since that time 470 diverse species of sharks have been identified. These species range in size from 6.7 inch to 39 feet (whale shark).
So what’s all the hype about shark hybridization? The lead researcher Jess Morgan from the University of Queensland states, “It’s very surprising because no one’s ever seen shark hybrids before, this is not a common occurrence by any stretch of the imagination,” she adds “This is evolution in action.”
So where were these hybrid sharks found? On the eastern coast of Australia stretching over 1,240 miles from NSW to Queensland, a team of 10 researchers found the multiple generations of these sharks. They are known to be the world’s first hybrid sharks.
This is what the researchers have to say, “To find a wild hybrid animal is unusual,” they wrote further in the journal of Conservation Genetics. “To find57 hybrids along 2,000 km [1,240 miles] of coastline is unprecedented.”
This discovery leads to the fact that for the survival and adaptation to the changing conditions of the ocean, the sharks interbreed with other shark species. In this case the two species of shark were Australian blacktip shark (scientifically known as Carcharhinus tilstoni) and common blacktip shark (known as Carcharhinus limbatus). The Australian blacktip shark is relatively smaller in size and lives in warmer water as compared to common blacktip shark. Australian blacktip sharks reach to a length of 5.2 feet whereas common blacktips reach a size of 6.6 feet. Both of these species are virtually identical.
The researchers are not still sure about the exact reason for this hybridization but it has been assumed that the factors causing it could be due to climatic changes and fishing pressure.
Usually the common balcktips are found in temperate and sub-tropical waters, near the south-eartern coastline of Australia whereas the Australian blacktips restrict themselves to the area around Brisbane which consists of tropical waters. The hybrid sharks can swim more than thousand miles towards south of Sydney, in cooler water areas. According to Dr. Colin Simpfendorfer, director at the Centre for Sustainable Tropical Fisheries and Aquaculture, states that the hybrid species have an evolutionary edge over climatic changes. He explains, “We are now seeing individuals carrying the more tropical species genes in more southerly areas. In a changing climate, this hybridization may therefore allow these species to better adapt to different conditions”.
The members of the research team belonged to New South Wales Department of Primary Industries, James Cook University’s Fishing and Fisheries Research Centre, The University of Queensland and the Queensland Department of Employment, Economic Development and Innovation. The research was co-funded by the Fisheries Research and Development Corporation.
To distinguish among the variety of shark species, scientists use vertebrae counting technique. In the case of hybrid sharks size differences and genetic testing was undertook.
The researchers working on this project notified something different about these sharks. Their genetic code matched with the common blacktip sharks but their vertebrae count did not correspond with them.
The researchers working on this project notified something different about these sharks. Their genetic code matched with the common blacktip sharks but their vertebrae count did not correspond with them.
There was a mismatch found according to the mitochondrial DNA sequencing analysis of all the species. Morphological characters such as length at the time of birth and sexual maturity and vertebrae count was also taken under consideration. All of the results supported the existence of hybridization. Researches also agree that the reason of this crossbreeding could also be the close relationship between the two shark species.
The question is whether the hybrid sharks are stronger than their parent species? Are they a threat for the other sharks?
Dr. Simpfendorfer states that here the phrase “survival of the fittest” is applicable as the hybrid sharks have more chances of outlasting than their predecessors.
He explains “We don’t know whether that’s the case here, but certainly we know that they are viable, they reproduce and that there are multiple generations of hybrids now that we can see from the genetic roadmap that we’ve generated from these animals. Certainly it appears that they are fairly fit individuals.”
These sharks are extraordinarily abundant in some areas and accounts for 20% of the black tip population.
Dr Jennifer Ovenden, a renowned expert in fisheries genetics tells us about the success of their finding. She states that the discovery of shark hybridization lays ground for the fact that other species of sharks and ray fish might also be hybridizing all over the world.
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