CHOMPions of the Sea Trivia Quiz

Answer: cartilage

Shark teeth are frequently discovered in the fossil record due to their durable nature, unlike the rest of the shark's skeleton, which is mostly composed of cartilage. Cartilage, unlike bone, does not fossilize easily, which is why complete shark skeletons are rare finds. Shark teeth are made of a dense mineralized tissue called dentin, which has a higher resistance to decay and can withstand the fossilization process.

This means that even though the rest of the shark's body may decompose, its teeth can endure and become fossilized over time.

Answer: cranial

Sharks possess five main types of fins, each serving distinct purposes in their aquatic lifestyle. The dorsal fin (1), positioned along the back, aids in stability and steering while swimming. A secondary dorsal fin (1) is often located on the back as well. The caudal fin (1), also known as the tail fin, is crucial for propulsion, propelling the shark forward through the water. Pectoral fins (2), located on either side of the body near the head, assist in steering and maneuvering, while pelvic fins (2), found on the ventral surface near the pelvic area, contribute to stability and control. Additionally, sharks have an anal fin (1), situated on the ventral surface near the tail, which helps maintain balance during movement.

Although most sharks possess these eight fins, there are exceptions. For instance, the Port Jackson shark, a species native to Australia, is notable for having only four fins.

Answer: liver

Shark livers play a crucial role in helping them maintain buoyancy in the water. One key component of this is the production of squalene, a lightweight compound found in high concentrations in the liver. Squalene's low density helps counteract the shark's overall density, enabling it to stay buoyant and effortlessly navigate the ocean depths.

Sharks also utilize a method known as dynamic lift, where they generate lift by swimming forward with their pectoral fins while simultaneously adjusting their body angle. This dynamic lift further aids in maintaining buoyancy and allows sharks to glide efficiently through the water with minimal effort. Combined, these mechanisms enable sharks to thrive in their aquatic environments.

Answer: True

Tonic immobility, a state of temporary paralysis, can be induced in some sharks by gently stroking their snouts or by placing them upside down. This phenomenon is believed to be linked to the shark's sensory biology and neurological responses. Marine scientists often take advantage of this state to help study, relocate, or medicate sharks.

While the exact reasons why sharks are prone to tonic immobility are not fully understood, it is thought to be related to their sensitivity to tactile and electrical stimuli in the water. Interestingly, orcas have been observed using tonic immobility as a hunting strategy against sharks. By flipping sharks upside down, orcas induce tonic immobility, making the sharks temporarily vulnerable and easier to prey upon.

Answer: plankton

While many people associate sharks with fierce predators hunting larger prey, some species actually feed primarily on plankton. These sharks, known as planktivorous sharks, have evolved unique feeding mechanisms to capture tiny organisms like plankton.

Instead of sharp teeth for tearing flesh, they possess specialized filter-feeding structures in their mouths, such as gill rakers or sieve-like structures, which allow them to filter plankton from the water as they swim. This adaptation has enabled them to exploit a niche in the ocean's ecosystem where plankton is abundant.

Answer: True

Sharks are attracted to various smells in their environment, with some scents playing a significant role in their hunting and feeding behaviors. One of the primary smells that attract sharks is the scent of blood. Sharks possess an exceptional sense of smell, enabling them to detect even tiny amounts of blood in the water. This scent acts as a signal for potential prey, as injured or weakened marine animals often release blood, indicating vulnerability.

Additionally, sharks are attracted to the smell of decomposing matter, such as dead fish or marine animals. While it may seem surprising, sharks are scavengers and play a crucial role in marine ecosystems by feeding on dead or dying organisms.

Answer: shark eggs

Sharks employ a variety of reproductive strategies, including viviparity, oviparity, and ovoviviparity. Viviparous sharks give birth to live pups, while oviparous sharks lay eggs externally, and ovoviviparous sharks retain eggs inside their bodies until they hatch. Shark eggs come in various shapes and sizes, depending on the species.

The eggs of many shark species (such as those shown in the image) are elongated or rounded. In contrast, the eggs of oviparous sharks, such as the Port Jackson shark, are sometimes spiral-shaped and adorned with distinctive tendrils. These spiral-shaped egg cases serve to anchor the eggs to the seafloor, providing protection from predators and strong currents.

Answer: bottom-dwelling sharks

Sharks rely on gills (and sometimes spiracles) to facilitate their breathing underwater. Gills are specialized respiratory organs located on the sides of a shark's head. As water passes over the gills, oxygen is extracted and absorbed into the bloodstream while carbon dioxide is expelled. This process enables sharks to extract oxygen from water efficiently. Some sharks also possess spiracles, which are small openings located behind the eyes. While gills primarily facilitate respiration, spiracles aid in ventilation by allowing water to flow directly to the shark's respiratory system, particularly when the shark is resting on the ocean floor.

Bottom-dwelling sharks, such as nurse sharks and angel sharks, are more likely to have well-developed spiracles. This adaptation is advantageous for bottom-dwellers because it allows them to draw in oxygen-rich water while lying still on the seabed, where water movement may be limited.

Answer: gastric eversion

Some species of sharks practice gastric eversion, also known as stomach eversion, as a feeding strategy. Gastric eversion involves the stomach turning inside out, occasionally protruding from the shark's mouth. Unwanted items, such as turtle shells, bird feathers, and human trash, are then expelled before the stomach returns to its proper place.

Sharks often engage in gastric eversion under situations of extreme stress. Some scientists believe this is because it may lighten the shark, allowing it to swim more swiftly away from dangers. Fishermen who have caught sharks capable of gastric eversion will often see the practice in action; the act of being caught is incredibly stressful to shark species, and so they may be ejecting their stomachs as a defense mechanism in these instances.

Answer: cephalofoil

The cephalofoil, a unique hammer-shaped structure extending from the hammerhead shark, has multiple advantages, though scientists debate which purpose is most advantageous in terms of the evolution of this structure. The cephalofoil contains sensory organs known as ampullae of Lorenzini, which detect electrical signals emitted by prey, aiding in locating hidden prey such as rays and crustaceans.

In addition, the wide shape of the cephalofoil may provide hammerhead sharks with enhanced maneuverability and stability while swimming, allowing them to make quick turns and sharp movements. Some scientists also speculate that the cephalofoil may help improve the shark's vision and sense of smell.