World-first discovery of hybrid sharks off Australia's east coast

Dec 22, 2011
Hybrid black tip shark containing both Common and Australian black tip DNA.

(PhysOrg.com) -- Hybrid black tip shark containing both Common and Australian black tip DNA.

A group of leading marine scientists has discovered that sharks on Australia's east coast display a mysterious tendency to interbreed, challenging several accepted scientific theories regarding shark behaviour.

In a joint-UQ research project, scientists have discovered widespread hybridisation in the wild between two commonly caught in Australia's east coast shark fisheries.

The Australian black tip shark (Carcharhinus tilstoni) and the common black tip shark (C. limbatus) have overlapping distributions along the northern and eastern Australian coastline.

Using both genetic testing and , 57 hybrid animals were identified from five locations, spanning 2000km from northern NSW to far northern Queensland. Although closely related, the two grow to different maximum sizes and are genetically distinct.

Dr Jennifer Ovenden, an expert in genetics of fisheries species and a member of the scientific team said this was the first discovery of sharks hybridising and it flagged a warning that other closely related shark and ray species around the world may be doing the same thing.

"Wild hybrids are usually hard to find, so detecting hybrids and their offspring is extraordinary," Dr Ovenden said.

"To find 57 hybrids along 2000km of coastline is unprecedented.

"Hybridisation could enable the sharks to adapt to environmental change as the smaller Australian black tip currently favours 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."

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

The research, co-funded by the Fisheries Research and Development Corporation, identified a mismatch between species identification using mitochondrial DNA sequence and species identification using morphological characters (length at sexual maturity, length at birth and number of vertebrae).

A nuclear DNA marker (inherited from both parents) was sequenced to confirm the hybrid status.

Dr Colin Simpfendorfer from James Cook University's Fishing and Fisheries Research Centre said black tip 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.

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Nanobanano
1 / 5 (1) Dec 22, 2011
it flagged a warning that other closely related shark and ray species around the world may be doing the same thing


Why would you be alarmed by it?

They are probably just mis-classified or something.

Maybe this is just normal variation within the "real" species, sort of like calico cats and tabby cats or something.

Marine biologists find stuff they never imagined before all the time.

New worms.

New crabs
New shark

What's the difference?

Isn't really "New" just means they weren't noticed previously.
drel
5 / 5 (1) Dec 22, 2011
Misleading Headline. I expected a mechanical shark that could run on gas or electric.
BigTone
5 / 5 (2) Dec 22, 2011
lol @drel - you just made me smile
that_guy
1 / 5 (1) Dec 22, 2011
I wonder how genetically distinct each species is compared to the difference in human races.

I think speciation is even more ambiguous than biologists would like to admit - and that if we applied the same standards to other animals that we do to humans, we would end up with a lot fewer species...
mabarker
1.8 / 5 (5) Dec 23, 2011
3 cheers for 'that guy' - speciation is VERY ambiguous, "Speciation remains 1 of the most controversial & least understood topics in evolution" -Miglietta, Symposium, Integrative & Comparative Biology v 51 #3, p. 449. I'm a non-darwinian zoologist and maintain that sharks have always been sharks (if the fossil record means anything). Atheist J.A. Long said in his 2011 book, "The mystery remains as to how sharks first evolved" p. 92. What about all that elasmobranch dentition? "The past few years have witnessed a remarkable flurry of research on the origin or origins of vertebrate teeth. While this work is progressing, the details of when, where, why and how teeth 1st appeared still elude consensus" -Ungar, P. 2010, p. 73. OK, OK - so where did fins come from? "The origin of paired appendages such as the fins of modern fishes is an unsolved problem" - Colbert, 5th ed. p. 51. *Sigh!* Fish have always been fish, people have always been people, clams have always been clams . . .
Ethelred
3.7 / 5 (3) Jan 17, 2012
3 cheers for 'that guy' - speciation is VERY ambiguous,
Only if you use an ambiguous definition. Speciation is quite biologically. Interbreeding is either possible or it isn't. Sometimes its difficult in which case it is pretty clear that there are two gene pools that have nearly separated.

I'm a non-darwinian zoologist
No. Your a Creationist and there is not sign in any of your posts that you know one thing about zoology, biology or Darwin that you didn't get from another Creationist.

aintain that sharks have always been sharks (if the fossil record means anything).
The fossil records means a lot and there sharks have only always been sharks if you define it that way and ignore the evidence that they had non-shark ancestors.

Atheist J.A. Long said in his 2011 book, "The mystery remains as to how sharks first evolved" p. 92.
Only because the fossil record is not complete.>>
Ethelred
3 / 5 (2) Jan 17, 2012
This is another attempt to jam the Jehovah of Genesis into a tiny gap. Admittedly Jehovah's morals would fit in the tiniest of gaps but that Flood simply never happened so that particular version of Jehovah cannot have existed.

*Sigh!* Fish have always been fish, people have always been people, clams have always been clams
And ignorance has always been a specialty of yours. No reasonable person expects us to know everything. Jehovah didn't know everything in Genesis(He WALKED down to Sodom to check out rumors) so why do you expect us to?

We may never know all the answers but sharks do evolve. We have adequate evidence that they have done so. And we more than adequate evidence that humans evolved and changed from non Homo(Australopithecus) to Homo (Erectus then Sapiens)over time.

Just how tiny is that god of yours that you have to cram into such gaps.

I am curious to when you think the Great Flood occurred. Are you ever going to tell us? Or is running all you can do.

Ethelred