 © The Fins United Initiative property Arguably the most (in)famous of all shark species... the great white shark. Scientifically known as Carcharodon carcharias, it is well loved by Shark Week specials. The great white shark was thrust into the spotlight by the movie Jaws, which starred a "killer" great white out for blood. The movie ended with an explosion of said animal (disproven by Mythbusters of actually happening, along with other things from Jaws), and since then people have been either wary or fascinated of this massive animal. In this bio, we'll uncover the animal behind the myth. So buckle up, we're diving in!  © Andy Murch The genus name Carcharodon is from the Greek "karcharos" meaning, "to sharpen" and "odous" translates into "teeth." The species name carcharias, also Greek, means "point" or "type of shark." This actually lends to one of its nicknames, "white pointer" (in Australia). They are also known as "white death," due to their reputation of 'attacking' surfers. These mackerel sharks (family Lamnidae) can reach total lengths of up to 6.1 m (~20 ft) and weigh up to 1.9 tons (3,800 lbs). These animals are characterized by a K-selected life history (slow growing, late maturing, and long-lived species with low fecundity) and cosmopolitan range. These animals have main populations in South Africa (SA; Melissa's undergraduate thesis focus), Australia/New Zealand (ANZ) and the northeastern Pacific (NEP). There have been great white sharks spotted in the Mediterranean, prompting some scientists to say there’s another population "central" there. #Finfact: There have been great white shark pups caught in the Mediterranean area! See the video here. *ADVANCED SCIENCE SECTION ALERT* Mitochondrial DNA (mtDNA) shows that SA and ANZ sharks are genetically different populations! The relationship between these two populations is still largely unknown and not well researched. However, a white shark performed a previously unknown fast transoceanic return migration spanning the entire Indian Ocean, swimming coast-to-coast from South Africa to Australia and back. And what about the NEP population? Turns out the NEP population is a descendant of the ANZ group. In the NEP population, data from satellite pop-up achival transmitting (PAT) tags have shown that white sharks tagged in California and in Guadalupe Island, Mexico share their regions with each other. And if you're a shark enthusiast, we're sure you've heard about the great whites off Cape Cod, Massachusetts. In our search to find out how this small population is related to others, we were unable to find anything. However, learn a little bit about the great white shark research currently ongoing (Dr. Gregory Skomal of the Division of Marine Fisheries, working with the Atlantic White Shark Conservancy tagged the second great white shark of the 2016 season recently). Massachusetts made worldwide news when its beach-goers helped saved a young beached great white shark.  © Brandon Cole / Biosphoto Although great white sharks have garnered the interest of both the science and public realms, large gaps still exist in our understanding of these sharks. For example, we don't know much about their reproduction, only that they are viviparous and that embryos are nourished through oophagy; scientists are unsure of how frequently they reproduce, their gestation periods or where they mate/give birth (though some areas are suspected, such as the Gulf of California). #Finfact: While in the uterus, the embryonic white sharks swallow their own sets of shed teeth; this may be to re-utilize calcium and other minerals. So what do they eat? Well, it depends. These sharks can eat different prey based on their age, size, and location. Great white sharks >3m in length have a diet comprised of predominantly fish. After this youth stage, they exhibit a dietary shift to larger prey (i.e. marine mammals). However, many retain their multi-prey tastes as they age. How do we know this? As great white sharks age, their vertebrae accumulate new rings yearly. Thus, each ring holds chemical information from that year in the shark’s life (Kim et al. 2012). By comparing the isotope ratios in different vertebral bands, this research showed dietary shifts of individual sharks over the course of their lives. In order for these sharks to catch the faster prey, like seals, they have something called rete-mirable, like the mako shark. Refresher: the rete-mirable is closely packed veins/arteries on either side of the shark that helps in conserving heat (especially in the stomach), making the shark warmer than the surrounding environment. This allows them internally regulate their body temperature. See one of these spectacular breach events below. Carcharodon carcharias is categorized as Vulnerable (VU) by the IUCN. Abrupt declines in C. carcharias observations have been described in the north Atlantic (Baum et al. 2003) and the Mediterranean (Compagno 1984 ; Cavanagh and Gibson, 2007). However, both in the western and eastern coast of the United States of America, there has been a comeback of these animals.
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Author
TFUI Founder Melissa C. Marquez is author of all animal bios and "Behind the Fins" segments.
A proud #LatinainSTEM, Marquez is a marine biologist who focuses on shark habitat use and movements; she is also a science communicator (follow her on Twitter) who focuses on diverse Chondrichthyan education and who focuses on the media coverage of sharks. You can learn more about her on her website.
SEE MELISSA'S TEDx TALK HERE:
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