All Cartilage. No Bone

SHARK ANATOMY

All creatures that live under the sea have similar functions, such as the need to breathe, reproduce, eat, and even make social contact with other members of their species, but of course they all have their own unique anatomical builds as well. Sharks for instance, may have similar structures to those of other sea worthy fish and even humans, but are equipped with special eyes, senses, gills, fins, teeth, and a skeletal structure made of all cartilage.

SKELETON:                                                                                           

Most other fish species have skeletons made of calcium, just like humans, but shark have a skeleton made up of cartilage that specifically helps the shark to stay afloat in the ocean since cartilage weighs a lot less than bone. Another advantage to having a cartilage skeleton is the ability for the shark to make sharper turns in smaller areas of water and can even be useful in a stronger bite since a shark keeps growing new cartilage during its whole lifetime and contributes to mineral deposits in the shark’s jaws.

EYES:

Sharks eyes consist of the same parts and functions as other fish and humans do, such as pupils, rods, cones, lenses, and retinas, but with a few differences. A shark’s eyesight has been well adapted to see within many light and dark ranges in the marine environment, this adaption has been possible due to sharks having a specialized mirror-like tissue behind the retina called the tapetum lucidum. Light hits this tissue and reflects back so that the shark can successfully navigate and hunt through dark waters. A common question amongst a lot of humans is that sharks do have eyelids, but do they ever blink? No, they don’t, because the water cleans their eyes for them. Though most sharks possess these key features, they have all diverged to different ocean environments over time, hence some sharks have protective membranes over their eyes, while others simply roll back their eyes during attacks to keep from hurting their eyes. The eye behaviors of sharks are all very unique and are more important to the function of a shark’s lifestyle than most people would think.

GILLS:

One of the most important part s of a shark! While most other fish species have only one gill slit, sharks can have up to 5 or 7 gill slits   on both sides of their bodies. As the shark swims, the oxygen in the water passes over the gills and the oxygen is then absorbed into the blood stream, this is one of the main reasons why most shark species have to keep swimming in order to breathe. However, some other sharks have a gill pump, which allows them to pump water in through their mouth and out through their gills while remaining in a still position, this process can also be termed as buccal pumping, which is named for the cheek muscle that is used to undergo this type of shark breathing.

SHAPE & COLOR:

All sharks have a torpedo-shaped body that allows them to swim even faster underwater even though they have a lighter cartilage skeleton, which is also an advantage to swimming farther distances without wearing out. If you compare the shape of a shark to the shape of a DC-9 airplane, you’ll see that they are amazingly similar and built for the same purpose, and that is faster travel.

All sharks have a typical color design of a darker top side (dorsal side), and a lighter underside (ventral side), which allows sharks to participate in a type of camouflage called countershading.  This camouflage trait is very useful in either hiding from a predator, or slowly stalking their prey while remaining visually unseen.

FINS & Tail:

All sharks have anal and dorsal fins which help them to swim and balance themselves within their living environments and the tail of a shark also helps to contribute to fast speed in the water. What’s interesting about these fins though is that they can pick up vibrations nearby, whether it is a distressed fish or the motor of a passing boat.

TEETH: The Most powerful jaws on the planet

Believe it or not, sharks have three to five rows of teeth, each row having a different shaped tooth. The front row consists of teeth that take a shape similar to that of a steak knife, serrated edges that rip through the flesh of the sharks prey, and the back rows have teeth shaped like needles, which pose to help keep the prey within the shark’s mouth while attacking. These are a common shape found in most shark teeth, but on the occasion due to environmental differences and diet, the teeth of a shark may have only one single shape.  Unlike most other animal jaws, both the upper and lower jaws of a shark move, leading to the advantage of grasping its prey first with the lower jaw, and then with the second only to then toss its head back and forth to rip away a bite of the prey and swallow it whole. Sharks never run out of teeth and can have up to 20,000 teeth in their lifetime.

 

Reeling in the Truth

Reeling in The Truth About Shark Myths

It really is amazing how sharks can stir up so much emotional fear as well as strong beliefs that they are man-eating monsters, and these thoughts have been brought about over the past by many aspects of our world’s culture, such as literature, films, and simple ignorance. I’m here to tell you that there are plenty of shark myths and legends out there and though a lot of people lead themselves to believe that they are true, more than half of them are completely and utterly false.

Myth #1: Sharks have poor vision. This Myth is False. Most people tend to think that because sharks have a highly developed sense of smell that can detect prey as far as 1 mile away or even further that they’ve evolved to have no use for their eyes since they seem to rely solely on scent. Actually, the eyes of a shark are composed of the same anatomical parts as ours, but of course with a few slight differences. The eye is made up of the usual rods, cones, and retinas that allow the shark to navigate and see in the ocean as it travels and yes, sharks do see in color. The only thing that distinguishes their eyes from ours is that they have a tapetum lucidum, which is a layer of mirrored crystals behind their retina that provides extra light for them and helps them to see in dark or murky water about 10 times better than a human can see in clear water.

Myth #2: Sharks are not found in freshwater. LIES! Though most shark species do live in the salty waters of the ocean, there are a few species that can live in freshwater, one of these sharks being the bull shark. How can the bull shark do this? Well, it has a specialized osmoregulatory system that allows it to adapt to environments composed of different salinity levels, that is levels of salt within the water.

Myth #3: Sharks must keep swimming or they will die. Also False! The Nurse shark is one of only a handful of shark species that does not need to keep swimming in order to breathe. Constant swimming sharks need the movements to run oxygen in the water across their gills so they can breathe, but the nurse shark is able to breathe by opening its mouth and then closing it allowing them to pump water into their mouths and out their gills. Here’s another fun fact about nurse sharks, they don’t migrate! So instead they have evolved to live on the oceans bottom and adjust to the temperature of the water in which they live.

Myth #4: If being attacked by a Shark, punching it in the nose, eyes, or gills will get it to go away. Plausible, because it’s not very common to have had an encounter with a shark where actions like this is necessary. However, located within most of the sharks head are specialized sensory receptors that detect electrical fields within large ranges of the ocean, the most popular sense being the splashing of a distressed fish. If a shark were to be hit within this area, it may go away for a small amount of time, but will definitely be back. Just put it this way, would you continue attacking your prey if it punched you in the nose or eye? Not really. You’d turn away, relive yourself of any pain you’ve just received, and then if you’re still hungry, you go back for more. Attached bellow is a video that directly tests this particular myth, the team that does this is of course, The Mythbusters!

One of the most important and straight forward myths of all. Myth #5: Sharks eat humans. This myth may have been strengthened when the classic film JAWS came out, but believe it or not, sharks are picky eaters and would rather not make human meat part of their regular diet. In most shark attack cases, the shark was engaging in a “test bite” which means that it was curious about what it was seeing and wanted to investigate and if not out of curiosity, the unfortunate human on the surfboard may have been mistaken for a seal or sea lion, which is an organism that sharks regularly eat. Luckily, less than a hundred people get attacked annually by sharks and more than half of them are not fatal. It is also true that you are more likely to be killed by a dog or struck by lightning than to be attacked by a shark, unless you’re a beach-bound surfer, yet even then, chances of an attack are still rare.

Small little Jaws, no bigger than a chocolate bar.

Not all sharks are big enough to eat seven 50 pound tuna fish. In fact, the smallest shark that exists today is the Dwarf LanternShark, Etmopterus perryi, measuring at only 17 cm in length when full grown and can perfectly fit in the palm of your hand. This small little shark was first discovered in 1985 along the coast of the Caribbean living in a water level of 290 feet which is within the bathypelagic ocean zone ranging from 1000 to 4000 meters below sea level. This particular shark species has remained a local to the deep Caribbean waters and though it has been officially discovered, it is actually a rare experience to ever encounter one of them.

Due to their small size, which is a weight of only ½ an ounce, not much is known about this shark species, but enough research has been done to be able to share basic knowledge about the lifestyle of this rare species. Since they live within the deepwater range and lives in a darker environment than other marine species, it has recently been discovered that this tiny shark possesses bio-luminescent qualities, meaning that they can produce a glowing green light on their underside.

At sexual maturity, males reach to be about 17.5 cm long while females only tend to reach 15.5 cm in length, and the small born pups are even smaller coming to about only 6 or 7 cm long that come in liters of 2 or 3. These dwarf sharks are equipped especially with five sets of rigid fins that all function help carry them along through the water and also to help stabilize their movements.

Since they are a deepwater species, their fins and torpedo-shaped body help them to swim fast and catch their prey which consists of zooplankton, small shrimp and other fish that also make a living within the bathypelagic environment. Every species of shark has its own evolutionary advantages, this shark has evolved to its environment and its teeth specifically have evolved as well to help them to catch these small delicious fish and crustaceans. Like many other deepwater-living species, these small sharks are exposed to the dangers of deep sea fisheries which have been known to accidently scoop up this shark as bycatch, which was probably how it had been discovered in the first place.

 

Next to the Dwarf LanternShark, there are yet a few more small sharks including the Spined Pygmy Shark which also reaches a full length of 28 cm, and the Dwarf Gulper Shark being a little bigger and growing to a full length of 2 feet long as at adulthood. These sharks may not be much bigger than the LanternShark, but have completely different geographic habitats which is in the Indian and pacific oceans along the coasts of Japan and Taiwan for the Gulper Shark, and along the coasts of the United States, Bermuda, and Brazil for the Pygmy Shark.

Though these sharks live in a different geographical area than the other, their anatomy, feeding habits, and overall lifestyles very closely math each other. It’s pretty amazing how similar sharks of similar size can all live the same lifestyles yet while also being distributed in different areas all around the world. But one of the main things that both these small species share is the common and constant threat of human activity. All three of these sharks are a rare deepwater species and though they may be very small, they too deserve to have their rightful place within today’s oceans.