Carolina hammerhead

7/31/2017

Credit: Joe Quattro et al / ZooTaxa

If you didn’t know it, TFUI founder Melissa’s husband is from Southern USA. Back when they were dating, he was living in South Carolina. So it was no wonder that Josh passed along the news about the newly-discovered Carolina Hammerhead to Melissa ASAP.

The story behind the Carolina Hammerhead is rather interesting, as it was just thought to be a scalloped hammerhead (S. lewini). Back in 2000 (17 years ago—oh jeez, we feel old), Dr. William Driggers, was sampling for sharks in, you guessed in, good ole’ South Carolina. Dr. Driggers was collecting tissues from various shark species for Dr. Joseph Quattro’s genetic work. Dr. Quattro is a professor at the Marine Science Program and Department of Biological Sciences at the University of South Carolina (fun fact: Melissa applied to this same department before choosing to go to New Zealand), and had been in the middle of characterizing the population genetics of fish in South Carolina.

The project revealed something rather surprising. The specimens that were labeled as scalloped hammerhead (S. lewini) were different from know S. lewini sequences. “Wait, whaaaaat?” Confused, huh? Don’t worry, genetics does that.

(TL;DR-- tangent for those who are curious about DNA sequences: DNA stores biological information in a code made up of four chemical building blocks, called ‘bases’: adenine (A), guanine (G), cytosine (C), and thymine (T). These make up the DNA molecule. A more in-depth look about the Carolina shark and the preliminary genetic evidence of cryptic speciation within hammerheads can be seen in the above links.)
Once this was noted, they began to bring back whole specimens, in order to look are morphological differences, if any. The first whole specimen—this new species—was brought back from Bulls Bay in 2001.
In 2006, Dr. Quattro and his team published “Genetic evidence of cryptic speciation within hammerhead sharks,” discussing the possibility of a new shark species that had been previously written off as scalloped hammerheads.

The genetic samples of scalloped hammerheads, great hammerheads and bonnethead sharks were phylogenetically mapped, showing that there were two genetic lineages within, what was previously thought of as just one species (the scalloped hammerheads). Well, you can imagine the surprise—and excitement! A new species! Hooray!

This type of species was to be known, for the time being, as a the “cryptic hammerhead,” the term defined by Bickford et al. 2007 as “two or more distinct species classified as a single species.” It isn’t a new concept, and has been recognized for nearly 300 years.

It wasn’t until 2013 that this cryptic shark would be given a different name… the Carolina hammerhead, Sphryna gilberti. The fun thing about discovering new species is getting to name them! The species name, “gilberti” is actually dedicated to the Florida Museum of Natural History curator Carter Gilbert. Why? He actually was the first to talk about an unusual scalloped hammerhead specimen— in 1967! It’s now believed that Gilbert was referring to the Carolina hammerhead.

So how can you tell these two sharks (scalloped vs Carolina) apart? You really can’t… unless you have an x-ray machine. Vertebral column numbers are the only way thus far. And as we continue to learn more about this animal, we’ll get to know more about its lifestyle! To Melissa’s knowledge, the IUCN has not determined a conservation status of this species.

did you hear about the carolina hammerhead?

glossary

Bay: Water connected to an ocean or lake partially surrounded by land (may also be called a “gulf,” “cove,” “sea,” “sound” or “bight”).
Genetic analysis: The process of studying in the fields of science that involve genetics and molecular biology. There are a number of applications and ways to go about this research.
IUCN: International Union for Conservation of Nature.
Phylogenetics: The study of the evolutionary history and relationships among individuals or groups of organisms (e.g. species, or populations).
Population genetics: The study of genetic variation within populations.
Specimen: An individual animal, plant, piece of a mineral, etc. used as an example of its species or type for scientific study or display.