Carolina Hammerhead Shark: 'Cryptic Species' Discovered Off South Carolina Coast
Scientists from the University of South Carolina have announced the discovery of a new hammerhead shark species swimming in the Carolina waters. The appropriately-named Carolina hammerhead has gone unnoticed until now because it is a "cryptic species"--an animal that looks like a more common species, but is genetically distinct. It also seems to be a rare species, further delaying its discovery until now.
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"Outside of South Carolina, we've only seen five tissue samples of the cryptic species," said ichthyologist Joe Quattro, who led the discovery team. "And that's out of three or four hundred specimens."
Quattro and his team discovered the new hammerhead shark when they noticed an anomaly in the scalloped hammerhead sharks they collecting. It appeared that the mitochondrial and nuclear genomes of the hammerheads they were looking at had two different genetic signatures entirely. So Quattro's team scoured the scientific literature on hammerhead sharks, and they came upon a description of an unusual hammerhead shark written by Carter Gilbert, a veteran curator of the Florida Museum of Natural History.
In 1967, Gilbert had written of a hammerhead shark caught near Charleston, S.C., which had 10 fewer vertebrae than the "normal" scalloped hammerhead shark. This hammerhead shark was still in a museum, so Quattro's team was able to study it, and that's when they realized they were looking at a new species.
In 2006, Quattro and his colleagues published a preliminary study identifying the new hammerhead shark, which they dubbed Sphyrna gilberti, in honor of Gilbert. Now they've published a more comprehensive study, which marks the official debut of the new species, in the pages of Zootaxa. In the intervening years, Quattro's team has examined and measured 24 scalloped hammerhead sharks and 54 specimens of the new hammerhead shark. They found that the defining difference between the two hammerheads was indeed the different number of vertebrae.
As to the number of Carolina hammerheads out there, that's anyone's guess.
"The biomass of scalloped hammerheads off the coast of the eastern U.S. is less than 10 percent of what it was historically," Quattro said. Because the Carolina hammerhead is even more rare, "God only knows what its population levels have dropped to," he added.
Scalloped hammerhead sharks are globally endangered. In North Carolina alone, their numbers dropped 98 percent between 1972 and 2003, according to the ICUN Red List.
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