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Member Blog Post

The Great White Shark

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"There are angel sharks, goblin sharks, crocodile sharks, bramble sharks, monk sharks, carpet sharks, swell sharks, nurse sharks, silky sharks, cow sharks, bull sharks, basking sharks, frilled sharks, cat sharks, leopard sharks, dogfish, hammerheads, porbeagles, and wobbegongs, but the species that comes to mind when we think of attacks on us is the great white shark, Carcharodon carcharias."

 

JUST THE FACTS, PLEASE . . .

Let's face it, any animal that grows to be nearly 20 feet long and weighing 5000 lbs. with teeth as sharp as my mom's best steak knife would be pretty frightening almost any way you look at it. However, as regular viewers of the Discovery Channel can well attest to, the shark of fact is not really the shark of fiction . . . but it's pretty darn close!

While what follows is certainly not a complete picture of the great white shark (hereafter known as the GW to save typing!), it represents a collection of answers to questions commonly asked about the shark.

TALES OF THE PASTA SHARK

Let's start from the top. In the beginning, Carolus Linnaeus (1707 - 1778), the author of the taxonomic system for naming all living things, grouped all sharks together in the genus Squalus giving the GW its original designation as  Squalus carcharias. It was Sir Andrew Smith who suggested the genus Carcharodon in 1838 but it took 40 years of customary scientific bickering to settle on the now familar Carcharodon carcharias. This comes from the  Greek words carcharos, meaning "ragged," and odon for "tooth." For the record, among the "losing" species names were lamia, atwoodi & rondeletti. Thankfully, the latter didn't stick or my favorite animal would probably be known as the 'pasta shark' today! Just imagine what 'Jaws' would have been like: "This was no boating accident . . . it was a pasta shark!"

Scientific names are useful as the GW is known by many different names the world over. Here's a quick breakdown of some of them and the country of origin.

Germany

Weisshai

France grand requin blanc Italy grande squalo bianco Spain tiburon blanco Australia white pointer, white death Russia seldevaja akula Japan hohojirozame

However, the scientific name is always the same.

IT WAS HOW BIG??

The size of the GW is of great interest to not only the general public but also to marine biologists. It is not known how large the GW gets but a top size of approximately 7 meters (approx. 21 feet) is the most often quoted figure. How long is this? Picture a couple of Hondas parked in a row and then picture a shark as long as the two cars with a mouth about 3-4 feet wide and you've got a pretty good idea. The average GW is not nearly as large being only about 10-15 feet in length. However, this is still longer than my Outback . . . which is big enough for me!

A SKELETON MADE OF NOSES AND EARLOBES

Like all sharks, the GW's skeleton is composed of cartilage. This stiff flexible material is found in the ridge of your nose and also in your earlobes. While not are hard as bone, cartilage is still quite rigid. Because cartilage does not leave fossil remains like bone, we do not have any fossils of ancient sharks - just their teeth!

WHO ORDERED THE SEAL?

The GW is an apex predator meaning that it is at the top of the food chain with no natural predators. The Great White is the only Apex predator today that has not been kept or tamed by man and it should remain that way! This means that they have their pick of the buffet table when it comes to selecting their prey. It seems that they are not picky, choosing fish, squids, other sharks, dolphins,  & whales. Their favorite prey, however, are pinnipeds, a fancy name for seals & sea lions. They feed on carcasses as well, especially large whales.

OLD JAWS LIVED A LONG HEALTHY LIFE

No one knows accurately how long the lifespan of the GW is and the sharks themselves aren't making it any easier for us to find out. The GW population is quite isolated from one fish to the next. In addition, the sharks are highly migratory, moving from one spot to the next over a vast area. This makes it impossible for scientists to pick one fish and follow it for a long period of time to gather the data necessary to answer this question. 

Scientists have been observing GW's off the coast of the Farallon Islands near San Francisco for several years, identifying individual animals by scars and coloration markings. One such animal, nicknamed 'Stumpy' because the top portion of her caudal (tail) fin has been bitten off, has or had been observed returning to the islands each fall to feed on seals for several  years. In addition, examining growth patterns of sharks caught off the California coast revealed that they were approx. 14-15 years old. This indicates a lifespan of 20 or so years is not unrealistic.

 

WHAT BIG AMPULLAE OF LORENZINI YOU HAVE, GRANDMA . . .

The better to sense your electrical field, my dear little Red Riding Hood! The GW is equipped with two of the most powerful sensing mechanisms in Nature, a highly developed sense of "smell" and the ability to sense the electrical fields radiating from living creatures.

As anyone familiar with the 'Jaws' movie posters can tell you, GW's have a pair of nostrils near the tip of their snout. Since "breathing" takes place in the gills, the nostrils of a shark are used solely for olfactory purposes - to sniff out their prey. Each nostril is divided by a small skin flap that separates the water the shark is swimming through into two flows, one incoming and one outgoing. This flow passes through an area that contains a large number of small sensory organs known as lamellae. These lamellae are shaped like tiny flower petals and are in turn covered with millions of olfactory cells. These cells are in turn directly connected to the center of the brain responsible for detecting odors, turning the shark into a swimming nose.

 

The second system is the more specialized of the two and warrants a closer look due to its unusual nature. Notice in this picture the large number of tiny black dots marking the snout of the GW. These pore-like markings are the ampullae of Lorenzini, the secret weapon in the GW's arsenal of predation.  Each is a minute capsule filled with a gel-like substance excreted by the shark, sensitive to electrical discharges as small as .005 microvolts. Dr. John McCosker and Richard Ellis point out in their book 'The Great White Shark' that these ampullae collectively give the GW the ability to sense the electrical field distributed by a copper wire 1000 miles long hooked up to a D-sized battery! This amazing sensitivity is due to both the large number of ampullae present and also the fact that like the lamellae, each ampulla utilizes a large number of sensory cells to "pick up" the signal. These sensory cells lie inside alveoli, small sacs within each ampulla which are in turn connected directly to the brain of the shark - no muss, no fuss . . . just a straight signal to Eating Central that prey lies dead ahead, if you'll excuse the pun.

So what good does a built-in electrical field detection system do the GW? Plenty, it turns out. Every creature in the briny blue generates a small electrical field from where their skin meets the water.  The mucous membranes that coat the mouth and gills of fish also create steady current fields which are affected by their breathing patterns. Furthermore, a wounded animal bleeds, producing yet another set of electrical information. By honing in on this information, the GW can detect and distinguish between prey items who are swimming along peacefully, who are moving quickly about in a panic, and better yet, who might be bleeding and incapacitated - making them a hassle-free lunch.

In summary, these two sensory packages, the nasal lamellae and the ampullae of Lorenzini, have evolved over millions of years into detection systems for the very things that make prey more attractive to our friend the GW - blood, indicating animals that are injured and thus easier to catch and movement, telling the GW both where their prey is and what state it might be in when the shark catches it.

"Perhaps more than any other creature, the white shark seems more than the sum of its parts. A package of cartilage, guts, hide, and teeth has somehow become one of the more feared animals on earth."

 

CHECK OUT THE BOD ON THAT ONE . . .

The form of the GW is evolution at its best. Nearly every aspect of its physical makeup from the conical snout to the large, nearly symmetrical tail fin contributes to its efficiency as a hunter. As one of the Earth's oldest species, sharks represent millions of years of Mother Nature's poking and prodding - and judging from the GW, Mother Nature certainly seems to have a mean streak!

"OH THE SHARK HAS PRETTY TEETH, DEAR . . ."

Much has been made of the infamous jaws of the GW and rightly so. Each upper tooth is a marvel of compact engineering with hundreds of tiny serrations. This coupled with their enormous jaw strength enables the GW to cut through just about anything they feel needs cutting. The bottom teeth are not as large but serve the purpose of skewering the shark's prey, holding it in place for the upper teeth to do their work - which is to remove as much flesh from the shark's prey as possible!

Open wide! 

THE FINCTION OF THE FUNS 

Although the jaws and teeth of the GW are the first things most people think of when picturing the shark, the fins come in a close second. Who can forget the image of a sharp fin slicing the surface of the water? A quick rundown of the major fins and their proper names:

1. Dorsal fin 

2. Pectoral fins 3. Caudal fin

It has been said that sharks don't swim through the water as much as they "fly" through it. The fins serve important roles in this action. As the shark moves the caudal fin to propel it forward, careful adjustment of the pectoral and dorsal fins keeps the shark level and on course, much as the wings and tail of an airplane do.

In addition to the major fins pictured above, the GW has a smaller dorsal fin located closer to the caudal fin, a small pair of pelvic fins (visible in the photo at the top of this page), and a tiny anal fin just in front of the caudal fin. These minor fins help improve the way water flows over the shark as it swims.

 

 

 

 

 

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