Little Ray Stingray and Shark Book
July 2018 by V. R. Duin

COMPARE STINGRAYS AND SHARKS,
FISHY FISH RELATIVES

Sometimes when we trip or fumble,
Teamwork may just stop our stumble.
That's why we must always show respect
To help that comes as we least expect.
(“Little Ray & Shark Patch Things Up”)

“Fishy Fish” expands the information in the children's book,“Little Ray & Shark Patch Things Up”, to help children compare stingrays and sharks. Adults also enjoy exploring the differences between these cartilaginous fish.

“Little Ray & Shark Patch Things Up” is a stingray and shark book for children. Like Fishy Fish, the book helps children compare stingrays and sharks. Although there are differences between these cartilaginous fish, stingrays and sharks are relatives with a lot in common. It is the differences that make it hard for stingrays and sharks to get along. Little Ray and the shark in his adventure work hard to develop and encourage teamwork. The illustrations and the biologically sound content in Little Ray's stingray and shark book for children make a lot of things clear about the similarities and differences in the lives of these fishy fish. There are many different species of stingrays and sharks. The appearance and activities of electric rays and of manta rays are unlike those of stingrays.

Stingrays and sharks are cartilaginous fish. Most fish are vertebrates. However, stingrays and sharks do not have bones. They are made of cartilage. Sawfish, guitarfish and skates are in the same family as sharks and stingrays. Most fish have swim bladders to help maintain buoyancy. Rays and sharks do not have swim bladders. Stingrays and some sharks sink to the bottom when not swimming. Swim bladders enable fish to move up and down, without uncontrolled sinking or floating. Swim bladders may help fish survive in dirty water. Some sharks gulp air to push water over their gills to breathe while not swimming. This exhausting ram-ventilation effort can be used for short periods. Other sharks store fats and oils in their livers to help maintain buoyancy. Unlike sharks and other fish, stingrays do not pump water from their mouths to their gills.

Except for lungfish, which have gills and lungs, fish are characterized by the gills they use for breathing. Lungs are internal. Gills are external. Gills are located in the head area. Most rays and sharks have five pairs of gill slits, which are individual openings to gills. This structure differs from the single opening to the multiple gills in bony fish. Bony fish pump water through their mouths to their gills. Humans also develop gill-like structures during the embryonic stage. In addition to gills, stingrays and bottom dwelling sharks have openings for breathing similar to those of spiders, insects and whales. The spiracles are used to breathe while not swimming. The spiracles also may aid in identifying the presence of prey. Great White, Hammerhead, Mako and Whale sharks do not have them, and must move to breathe. Manta rays also must keep moving, because their spiracles are small and nonfunctional.

Fish are characterized with their paired fins, which are generally used for movement through the water. Stingrays do not look or swim like sharks, or most other fish. Stingrays swim with their fins. Some stingrays move their flat, rounded bodies through the water in a wavy motion. Others flap their fins like bird wings, and soar through the water. Stingrays are elegant movers. Sharks are the only fish that cannot swim backwards. When pulled backward by their tails, their gills fill with water and they die. Sharks use their tail fins to propel themselves through the water. Sharks generally cruise at a leisurely speed. Since sharks do not thrive in captivity, their speeds are hard to measure. Stingrays and sharks in captivity have no cause for speed. Hammerhead sharks swim on their sides. Electric rays tend to be slow and sluggish swimmers. Electric rays propel themselves with their tail fins.

A stingray's mouth is under its body, as are its nostrils and gills. The eyes are on the top of the body. Although their eyesight is weak, this eye position helps stingrays keep watch while they are partially hidden in the ocean floor. This is how these fishy fish spend most of their time. Sharks spend most of their time on the move, hunting for prey. All fish have a head, with a mouth and eyes. These fish parts do not look or work alike in different fish. Not all fish have teeth in their mouths. Some fish have modified teeth in their throats to filter plankton or to grind food. Unlike the eyes of stingrays, sharks' eyes are on the sides and very useful for spotting food. A shark's mouth also is located below its skull, but it is generally larger and more destructive than that of a stingray. Electric currents can be detected by electric rays, stingrays and sharks on the prowl for hidden prey.

These fishy fish relatives have tongue-like structures, but their taste buds are located throughout their mouths. These structures are called “basihyals”. They are positioned on the floor of the mouth, but they are generally small and made of cartilage. Fish do not have salivary glands to begin digestion. Taste buds help stingrays and sharks decide whether to swallow prey. Taste buds are located throughout the mouths and throats of these cartilaginous fish. Stingrays and sharks are food tasting and processing machines. These fishy fish also can vomit to rid themselves of indigestible food or to make room for the next meal. As children compare stingrays and sharks and explore the differences between them, they also learn how cartilaginous fish compare to and differ from other fish and people. Some bony fish have teeth on their tongues. These tongue teeth are used to hold prey or suck blood from prey. Unlike most fish, the lamprey can stick out its horny tongue.

Humans and most other land animals cannot drink saltwater. It makes them thirstier and the concentrations of salt cause deadly dehydration. Bull Sharks, River Sharks and some species of stingrays can live in fresh water. See freshwaterstingrays.co.uk for interesting facts about the adaptation of some stingrays to freshwater. This adaptation is fortunate, because survival in salt water is complicated. Marine sharks and rays do not drink water like their bony fish cousins. Sea animals have developed different means of pumping or excreting excess salt back into their environment. Stingrays and sharks obtain water from their food. Water also can pass into their bodies through their gills. These fishy fish do not drink water like other fish, because they do not leak water like other fish. To offset salt concentrations, sharks produce urea. Excess urea is discharged by a gland near the anus. The digestive systems of rays and sharks are similar.

Sharks spend most of their time on the prowl for food. Their hunts take them to shallow and deep waters. Along the way, sharks eat a variety of foods, including fish, squid, sea turtles, sea stars and mammals, be these living, dying or dead. Sharks can handle large bites and deep ocean depths. Bull sharks eat other sharks and almost anything else in the water. Hammerhead sharks dine on stingrays. Sharks often work as scavengers. However, the hagfish is among the most morbid of scavengers in the fish family. It has teeth, but it does not need them to eat. The hagfish absorbs the bulk of its nutrients through its skin. Like sharks, some stingrays are swimmers that hunt for prey in the water. However, most stingrays are bottom feeders that poke around in the sand or wait for food to come their way. Stingrays are masters of ambush. Stingrays can dig trenches with their fins to locate prey under the sandy ocean floor.

Unlike sharks, stingrays generally prefer shallow waters. Fortunately, there are plenty of fish in this hunting ground. These fishy fish dine on snails, shrimps, crabs, worms, clams and other creatures, including fishes, stirred up from the ocean floor. The freshwater species also eat insects, including mosquitoes and their larvae. Stingrays crush food with hard plates. Stingrays are not scavengers. Unlike sharks, which eat dead prey and gobble up non-food objects, stingrays prefer small, fresh, live catches. In captivity, stingrays will eat processed foods. As children compare stingrays and sharks, exploring the differences between these cartilaginous fish, they learn about fish habits and survival. Stingrays, electric rays and sharks improve hunting effectiveness with electro-receptors to detect electrical charges emitted by prey. Rays use their teeth for chewing food, not for self-defense. Rays are opportunistic feeders. Whether swimming or resting in the sand, they are alert for prey.

The bites of a stingray are fairly mild and may not leave any marks. Sharks dine on flying, swimming, floating and resting animals, as well as those felled by death. The bites of a shark may not leave anything behind. The bite of a shark can be very dangerous to humans. Sharks hunt and catch prey in the water and in the air. Sharks are in serious need of a tooth fairy, as they shed tens of thousands of teeth in their lifetimes. Lost shark teeth are replaced. Divers and beachcombers commonly find shark teeth. Stingray tooth findings are rare. A stingray might shed an occasional tooth, while crunching food with hard shells. That tooth will be replaced. As children compare stingrays and sharks and explore the differences between these fishy fish relatives, they learn the lifespan of stingrays is significantly shorter than that of their shark relatives.

The lifetime of sharks can span one hundred years or more. Greenland sharks smash longevity records. The lifespans of these sharks may reach 400 years. Humans don't live long enough to accurately count the number of years passed or the number of shark teeth shed. Stingray and shark teeth, denticles and taste buds are genetically linked. These cells regrow. Sharks' teeth are longer versions of the tooth-like projections covering their bodies. Shark teeth are arranged in rows that slowly move forward from the back of the jaw to the front. As the front teeth wear out or fall out, new rows move from behind to replace them. These shark teeth replacements happen about every two weeks. Tooth damage and replacement can be accelerated by snacking on cans, tires and other garbage that humans toss into sharks' habitat. Sharks have huge appetites.

Different sharks have different shaped teeth depending on what food they eat. Sharks that eat shellfish and crabs have flat crushing teeth. Sharks that eat fish have pointed teeth and those that sometimes eat seals and sea lions have razor sharp teeth. The teeth of some sharks are non-functional. Some rays and sharks use sucking mouth parts instead of their downsized teeth. Stingray teeth are small and flat. Their teeth also are replaced much like sharks' teeth. There is a strong association between chewing and tasting for hunger satisfaction. Despite the presence of teeth, sharks and rays may swallow their food whole. Many people also take this short cut for immediate satisfaction. Ancient members of this species may have had jaws that evolved into the formation of teeth. Electric rays have rows of small teeth that are sharper than those of most stingrays.

Most fish have scales for protection. Sharks and stingrays have skin projections that are made of the same structure as their teeth and the stinging spines in those species that have them. The location of the tooth-like stinging structures in sharks is different from that of stingrays. The skin of a shark feels like sandpaper to human touch. The projections on the skin of these cartilaginous fish are called dermal “denticles”. The denticles are arranged in a regular pattern in sharks and in an irregular pattern in stingrays. Because the bumps in sharkskin tend to repel germs, a company named Sharklet Technologies, Inc. is creating plastic wraps designed with bumpy sharkskin-like scales to fend off sources of infection in medical settings. The skin of electric rays is smooth and untextured.

Fish scales developed from the same genes as hair and teeth in humans and other mammals. Unlike other types of fish scales, the dermal denticles of stingrays and sharks do not get larger as the fish grows. Instead, these cartilaginous fish grow more dermal denticles to fill in the larger space. In primitive times, shark skin was used as sandpaper. However, it can be hazardous to produce, so it is no longer commonly used for this purpose. If the dermal denticles are removed, shark skin may be used to make leather products. Unsurprisingly, the dermal denticles of a shark can injure prey. The skin of electric rays is soft and flabby without denticles or horns. Other fish without scales include clingfish, eels and anglerfish. Some fish are coated with a slimy mucous that reduces friction for swimming.

A few fish can live out of water for brief periods, such as eels, snakefish, climbing perch, mudskippers or walking catfish. Lungfish can survive for long periods out of the water, which is particularly helpful when their habitat goes dry. Few fish can survive when their gills remain out of water. The time that it takes to photograph a trophy fish before release often results in rapid death. Life in the water is a characteristic of most fish. Stingrays prefer shallow waters that are near shore. They migrate to warm parts of the world. Sharks also migrate to warmer temperatures, but they are known to swim to deep, dark, cold depths. Stingrays and sharks are typically lone hunters, but they do come together for group migrations, group hunts and mating purposes. Like stingrays, sharks may come close to shore and some species cruise along the water surface. Electric rays are widely distributed from shallow waters along shorelines to oceanic waters of great depth. Like stingrays, these cartilaginous fish are largely bottom-feeders.

Since most fish are cold-blooded, they take on the temperature of their environment. A few fish can regulate their body temperature. As any swimmer or scuba diver knows, water drains body heat faster than air does. Wet suits and heated pools are used for human protection. Some sharks can raise the temperature of some body parts. Tunas also can do this to provide some protection and improve performance during deep, cold hunts. Stingrays do not have this ability, but they generally stay in warm, shallow waters. As children compare stingrays and sharks and explore the differences between these fishy fish relatives, they learn a lot about the ocean environment. The differences between these shark relatives help bust some myths about Sharks and Rays. Once rays and sharks are understood, children might want to further study electric rays, about which little is known.

Cartilaginous Fish

  • cartilaginous fish admin says:

    Cartilaginous fish can be purchased from tropical fish stores, but stingrays and sharks don't belong in the same aquarium.

  • stingray and shark book for children admin says:

    In Little Ray's book about stingrays and sharks for children, these cartilaginous fish travel together, so children can compare them.

    • encouraging teamworkadmin says:

      Encounters with sharks generally require protective equipment and procedures encouraging teamwork.