Interesting facts about teeth in the animal kingdom

Do you think teeth are boring or gross? From the Komodo dragon’s iron-laden teeth to the sea unicorn’s horn, the animal kingdom is full of surprising dental adaptations that will make you think again.

Sharks are covered in tooth-like scales called dentates

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Cartilaginous fish such as sharks, rays, skates, and chimeras grow three-dimensional scales on the surface of their skin. Each tooth-like scale contains a pulp cavity filled with blood vessels and nerves, and is covered with calcified enamel tissue called enameloid. These scales are very different from the flat, dish-like scales of teleosts, are called dentates, and have shapes and characteristics that vary widely between species as well as within individual fish. The teeth seen on a shark’s nose may be flat and rounded, similar to the patched surface of a soccer ball. However, elsewhere on the body, the odontoid may look like overlapping cupped hands with ridges and points.

These teeth can serve a variety of functions, including reducing drag while swimming or directly increasing thrust, explains Purdue University biomechanist Dylan Wainwright. “We think they also act as protection for the sharks in some way,” Wainwright continues. “It may protect them from both big things, like bites from other sharks, and little things like ectoparasites.” (Some fish rub against sharks’ rough skin to protect themselves. It has been observed chipping away at its own parasitic riders.

We still don’t know where teeth come from

Two competing theories about the evolutionary origins of teeth have been debated back and forth for decades, shaken by the latest supporting discoveries in developmental biology and the fossil record. The “outside-in” hypothesis suggests that tooth-like dermal scales with pulp-like centers covered with hardened minerals, similar to the teeth seen today, gradually migrate across the outer surface of the body through generations of fish. This suggests that it then migrated inward and settled in the jawbone of our ancestors. . The “inside-out” hypothesis suggests that teeth arose internally before moving forward in the oral cavity and becoming oral teeth.

Examination of the fossilized saw shark’s rostral dentition (the “tooth” of its serrated beak) reveals a complex internal structure that is incredibly similar to that found in shark teeth. This finding suggests that the developmental gap between dermal scales and teeth is smaller than originally thought, giving the outside-in hypothesis the upper hand once again over inside-out. But given the inherently spotty nature of the fossil record, there’s a good chance we’ll never know exactly where our oral teeth came from.

Some fish species have not one, two, but three types of teeth.

Most fish have two sets of teeth. Mouth teeth are located near the front of the mouth for grasping and munching, and pharyngeal teeth are located in the throat for slicing and dicing. However, some fish that make up the group known as dysosteomorphs have a third tooth, a bony plate formed by the palate and tongue (“osteo” means “bone” and “grossy” (meaning “tongue”) is also well-developed. Help crush or grind food. “Fish seem to grow teeth wherever they want,” says Cory Evans, a fish biologist at Rice University. “It’s really amazing that fish can keep producing teeth for their entire lives.” .

The most abundant vertebrate fossils on Earth are microfossil fish teeth.

When fish regularly replace their teeth, the shed teeth fall to the bottom of the water column and become buried in sediment. Unlike porous bone, these hardened teeth are less susceptible to erosion and deterioration. Considering that fish have been around for some 530 million years, it’s no wonder that sediments around the world are chock-full of fossilized fish teeth. But you’re lucky if you can find them in the wild. “Although smaller than a human hair, these tiny little fish teeth can tell great stories,” says Elizabeth Sibert, an oceanographer and paleontologist at Woods Hole Oceanographic Institution.

These tiny teeth, which resemble microscopic ice cream cones, vary in thickness, length, curvature, and presence or absence of barbs. The relative abundance of these teeth over time, as well as the geographic distribution of teeth of different shapes, allow Sibert and her collaborators to predict animal diversity, animal richness, and food sources from the oceans in the distant past. We can reason about webs. And just how many of these microfossil teeth are there? “Billions, for sure,” Sibert estimates. “And I think trillions may not be that far off.”

Parrotfish beaks are made from compressed teeth and contain the hardest biominerals ever discovered.

Most parrotfish species munch on coral for polyps and algae (which contribute to white sand beaches), but nibbling coral is no easy task. The parrotfish beak is composed of the hardest biomineral ever discovered, replacing the previous record holder, the teeth of the limpet (snail).

Parrotfish beaks are formed by compressing up to 1,000 teeth arranged in up to 15 rows into one hard conglomerate structure covered with a layer of enamel. Enamelloid crystals are woven like a fabric, but on a scale of 2 to 5 microns (smaller than a red blood cell). This woven structure allows one square inch of a parrotfish’s beak to withstand forces equivalent to the weight of 88 elephants.

Transparent teeth of deep-sea fish may serve as camouflage

Deep-sea fish will never win a beauty contest, but surviving hundreds, if not kilometers, of water is no easy feat. And these fish are full of incredibly strange adaptations that should definitely win some awards. The long, spindly, transparent teeth of angler fish and dragonfish are attractive in many ways. First, long fangs may look sharp, but these teeth are actually designed for capturing, not stabbing. Many deep-sea fish have “recessed” teeth that curve only inward, acting like one-way valves. Food can come in, but it cannot go out. Additionally, research shows that a dragonfish’s smile doesn’t light up a room. Ambient light (such as that produced by luminescent prey) passes through the tooth structure, rather than bouncing off a dense surface and reflecting outward, like our own pearly whites. Masu. This allows the deep-sea nightmare to approach its prey without exposing its teeth and approaching the prey.

Snake fangs have evolved many times, but they all still look the same

Although most reptiles have neither fangs nor venom, many different snake species have evolved mechanisms to deliver venom through their teeth. Snakes exhibit two main types of venom-carrying fangs. One is a grooved fang where the venom flows through channels on the backside, and the other is a tubular fang where the venom flows through a sealed delivery duct within the fang itself. Tubular fangs have evolved in three separate snake families: vipers, cobras, and burrowing asps. In a class of animals where tusks are less common, how did they evolve not just once, but multiple times across different snake families, converging on roughly the same structure each time?

The answer seems to have an underlying cause. Many reptile teeth have a zigzag pattern of depressions called pricidents around the base where they attach to the jaw. Scientists hypothesize that one of the zags may eventually develop into a long channel running the length of the tusk, and then become completely enclosed within the tusk as a canal. The presence of prisidentin formed an evolutionary shortcut to venom delivery and increased the likelihood of repeated evolution of that adaptation.

Long before humans invented saws, nature evolved metal teeth

For a few lucky creatures, “jaws of steel” is not far from the truth. Some animals have evolved champers that contain iron to strengthen their teeth and protect them from wear. Beavers are a prime example of mammals. The enamel of the incisors is rich in iron and can withstand repeated gnawing and munching on fibrous plant tissue. Researchers recently learned that Komodo dragon teeth also contain iron strategically placed along their serrated edges. This is especially surprising considering that Komodo dragons, like most reptiles, frequently replace their teeth. The metabolic cost of investing in and growing thousands of iron-rich teeth over a lifetime must be worth it.

Narwhal fangs are overgrown canine teeth.

Narwhals, also known as “unicorns of the sea,” are characterized by their long, spiral-shaped tusks that grow from their foreheads. But it’s not a horn, it’s a tooth. Narwhals have two large teeth embedded horizontally in their skulls, one of which (usually the left tooth, but sometimes the right tooth, or rarely both teeth) protrudes from the skull. , continues to grow until what we think of as horns. And even more bizarrely, even in the odd case of a narwhal having two horns, these tusks always spiral counterclockwise. This may be the mechanism by which narwhal tusks grow straight compared to the curved tusks of elephants and wild boars, or the impressively curved canines of walruses and hippos. Additionally, fangs are not covered with enamel like most teeth, but with cementum, a more flexible mineral coating. Given that most narwhal tusks are grown by males, it is no surprise that they have been shown to play a role in sexual selection.

Bacteria and fungi that cause plaque roam on the surface of your teeth.

It has long been known that bacteria that live on human teeth can damage the surface, leading to plaque buildup and cavities. But scientists recently made some surprising discoveries that may motivate you to brush and floss your teeth a little more regularly. Not only did they discover fungi in saliva samples from children with severe tooth decay, they also observed bacteria and fungi interacting under the microscope. These aggregates can spread, or “walk,” across the surface of the tooth, combining with other Frankenstein bacterial and fungal colonies to grow larger and larger.