Little Ray Stingray and Shark Book displayed at 50% of viewport width
July 2018 by V. R. Duin


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 “Little Ray & Shark Patch Things Up” to show differences between stingrays and manta rays and sharks. Chondrichthyes, or cartilaginous fish, have no bones and have no swim bladders, like other fish, but they may have teeth and may have tongues.

Elasmobranchii is a subclass of Chondrichthyes. It includes rays, sharks, skates and sawfish. These cartilaginous fish are made of cartilage. Human babies have more cartilage than adults. It gradually is replaced by bone.

Elasmobranchs are ancient. Their cartilage endoskeletons date back hundreds of millions of years. Cartilage breaks and wears out, but it does not naturally repair like bone. They have no bones. Their skins are tooth-like.

Manta rays, Great White, Hammerhead, Mako and Whale sharks must keep swimming. If they stop, they sink. Most fish have swim bladders for up and down movement. These gas-filled sacs may aid survival in dirty water.

Cartilaginous fish have no swim bladders. Some sharks store fats and oils in their livers to make up for the absence. Rays and bottom-dwelling sharks have large, flat fins to control and maintain water buoyancy.

Fish breathe through gills. Before birth, people have gill-like parts. Gills are outside the body. They are behind the eyes on the heads of most sharks. They are under the heads of stingrays, rays and some sharks.

The large number of slit openings into the gills of Elasmobranchs is unique. Chondrichthyes have five to seven pairs of gill slits. Each of these opens into one gill. Bony fish have one opening to their many gills.

Fish have pectoral fins. Rays do not swim like most other fish. Their pectoral fins attach at the head. Some rays swim with a wavy motion. Others flap their pectoral fins like bird wings. Most fish steer with their pectoral fins.

Hammerheads swim on their sides. Most sharks, electric rays and bony fish move with tail “caudal fins”. The pectoral fins of angel sharks attach to the body as do those of other fish. They are behind the gills.

The dorsal fin keeps fish upright. The dorsal fin of a shark is on its back, where it may be visible when it breaks the water surface. It is small or missing in flat rays and sharks.

Sharks are the only fish that cannot go backwards. Pulled, they die. Rays move elegantly, except electric rays. The fastest ocean swimmers may be: Lamnid Sharks in GURPS.

Elasmobranch jaws are detached from the skull. During mating season, stingrays may develop points on their normally dull, flat teeth. Shark's teeth vary with their diet. Manta rays have no teeth.

Elasmobranchs are distinguished by continuous tooth replacement. Sharks shed and replace tens of thousands of teeth during their lifetimes. Divers and beachcombers often find them with a rare stingray tooth.

Cookiecutter sharks simultaneously replace rows of teeth. In most sharks, new teeth move forward to individually fill gaps. Similarly, stingray teeth push forward in bands for individual tooth replacement from behind.

Most fish have tongues or tongue-like parts. Stingrays and sharks have small tongues made of cartilage on the floor of their mouths. Bony fish, or osteichthyes, have bony tongues called “basihyals”.

All fish can taste. Taste is sensed by the body surface of some fish. Catfish and saw sharks taste with whiskers, called “barbels”. Stingrays and Sharks have taste buds throughout their mouths and throats.

The nose holes of fish are called nares. They give fish a sense of smell. The nose holes of cartilaginous fish are under their bodies. The nares of a fish are not connected to the mouth or throat or involved in breathing.

Hearing parts are internal. Some fish have ear-like parts with no outside openings. Others sense sound vibrations with lateral lines. Like sonar domes on vessels, sound helps fish locate and size up obstacles or targets.

Fish hear frequencies that people cannot. Fish can find their way with sound. They hear sounds over great distances. Learn more from DOSIT: What sounds can animals hear?.

Manta rays, whale sharks and most sharks have eyes on the side. According to Sphyrnid Sharks in GURPS have eyes at each end of hammer-shaped heads. Those of angel sharks and most rays are on top of their heads.

Sight requires light. Acuity varies by species and specimen. Some fish need periods of light and dark. Others live in darkness. They can be blind. Fish that glow may be attracting mates or giving warning.

Bioluminescent and biofluorescent sharks glow in the dark. Deep-sea viper dogfish, lantern sharks and cookie-cutter sharks emit light of their own making. Catsharks and swell sharks absorb light waves to cast a green glow.

Bony fish drink and leak water. Water enters via their mouths and their gills. They have a pore to release urine. Stingrays and sharks do not drink or leak water. This vital liquid comes from their food.

Most saltwater fish urinate via their gills. Elasmobranchs have no urinary tract. Rays and sharks can store urea. They release it through their skin. All fish have kidneys to filter wastes.

Elasmobranchii have placoid scales, or “denticles”. Most fish scales grow with the fish. “Denticles” do not get larger after a certain size. More are grown to fill the space in a regular pattern in sharks and irregular in stingrays.

Denticles may repel germs. Sharklet Technologies, Inc. is creating bumpy plastic medical wraps to ward infection. The CDC warns about water contamination and waterborne illness in: Healthy Pets, Healthy People.