Jessica Morgan and her team from the University of Queensland in Brisbane have been following the development of two shark species off the Australian east coast for two years. On behalf of the fisheries authorities, they are investigating the occurrence of the Australian blacktip shark and the lesser blacktip shark along the 2000 km long coastline between southern New South Wales and northern Queensland.
"When we examine these shark species, we do it anatomically on the one hand, so we measure the body length, weigh the animals, count the vertebrae and so on, and then we also take tissue samples for genetic analysis. We had the case for the first time around a year ago that we could not assign this data to exactly one species, because there was a contradiction between anatomy and genetics. "
While this shark looked like a representative of the Australian blacktip shark based on its body size, number of vertebrae and other anatomical details, from a genetic point of view it belonged to the small blacktip sharks. But it was not an isolated case. Within a year, the marine biologists working with Jessica Morgan discovered a total of 57 hybrid sharks. In contrast to hybrid descendants of other animals, such as mules or mules, these sharks are fertile and have offspring. It is very unusual. Actually, the textbook opinion says that in this case there cannot be two species, but that they just have to be representatives of the same species that belong to different subspecies, i.e. races. Jessica Morgan disagrees.
"We can identify genetic differences between the two representatives, the number of vertebrae varies and they are of different sizes. One species is only found in Australian waters, the other lives in all oceans. So there is plenty of evidence that it is two species It is possible that the species split took place relatively recently, so that the two are genetically similar enough to be able to have fertile offspring together. But whether this is perhaps sterile in the second generation, we simply do not know . "
Representatives of the lesser black tip sharks live only in tropical waters. Your hybrid offspring, on the other hand, can also be found in cooler areas. This indicates that the new shark shape is well adapted to the environmental conditions, possibly even better than the parent or grandparent generation. If this is the case, these animals should prevail in the long term.
“We have no idea why this intermingling occurred in the first place, and how long it has existed. We cannot answer that with today's genetic methods, but we hope that we will be able to do so soon. Then maybe we can also see in which direction the animals develop, i.e. whether there will continue to be two species or whether all animals join together to form one species. "
It is only clear that the 57 known mixed sharks will no longer participate in the further development, because they have already been eaten. Jessica Morgan and her colleagues examined the fish as bycatch by the Australian Fisheries Authorities. After the investigation, the sharks were cut up: the fins went straight to Asia, the meat was sold on the Australian market as a delicacy.
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