Marine Biology CHONDRICHTHYES and AGNATHA

Class Chondrichthyes Approximately 350 species Skeleton is made of cartilage. Have rows of teeth. Mouth is located on the ventral side. Body is covered with placoid scales. Body is fusiform in shape. Have 5 to 7 gill slits on each side of the body. Most need to swim to breathe.

Generalized Shark Anatomy

Squalus acanthias spiny dogfish Description: This shark is gray or brownish on top and pale gray or white on its ventral side with irregular white spots on the top or sides of the body. The average length is 30 to 40 inches. The second dorsal fin is smaller than the first and both fins have spines at their origin. The caudal fin is asymmetrical with the upper lobe being larger. The smooth edged short and oblique teeth are similar in both the upper and lower jaw. Habitat: The spiny dogfish is found in cold and warm temperate oceans at temperatures between 6 and 15 °C. However on the Scotian Shelf this shark has been caught in water temperature between 3 and 11 °C. The spiny dogfish is tolerant of a wide range of salinities and can be found in estuaries. It can be located in the water column from the surface to depths of 730 meters (2,400 feet).

Squalus acanthias spiny dogfish

Squalus acanthias spiny dogfish

Squalus acanthias spiny dogfish

Range: This species of shark occurs in the western Atlantic Ocean. Like M. canis, it ranges from the Bay of Fundy to Uruguay and is common in the waters off Cape Cod to Delaware Bay, overwintering from Chesapeake Bay to South Carolina. It is rare in Canadian waters – the Bay of Fundy representing the northern most part of its range. Comments: The spiny dogfish is an opportunistic feeder eating whatever prey is abundant. In general their diet is composed of small fishes such as capelin, cod, haddock, hake, herring, menhaden and ratfish. They also eat invertebrates such as krill, crabs, polychaete worms, jellyfish, ctenophores, amphipods, squid, and octopus. Squalus acanthias spiny dogfish

Sphyrna lewini scalloped hammerhead

Sphyrna lewini scalloped hammerhead

Sphyrna lewini scalloped hammerhead

Description: Grows to a length of 13’. The head is greatly expanded laterally (sphyrnid cephalofoil), with eyes on each end of the lateral expansion. Coloration is gray above and white below. Habitat: In oceans near surface, sometimes in estuaries. Comments: Several hypotheses are proposed to explain the evolution of the sphyrnid cephalofoil, but few have been empirically tested. Some suggest the cephalofoil acts like a canard to provide hydrodynamic lift and increased maneuvering capabilities. Others believe that the cephalofoil functions in prey manipulation. Other hypotheses involve the potential advantages of spacing sensory structures across the surface or at the lateral ends of the cephalofoil. Another such hypothesis is that the laterally expanded pores in the cephalofoil provide an electrosensory capability that maximizes search area coverage, thereby increasing the opportunity to detect food sources. Range: This species of shark occurs from New Jersey south to S. Brazil, including Gulf of Mexico and Caribbean. Sphyrna lewini scalloped hammerhead

Carcharodon carcharias white shark

Say “ahhhh” Carcharodon carcharias white shark

Carcharodon carcharias white shark

White shark Carcharodon carcharias Description: Grows to a length of 21’. The body is elongate and fusiform in shape. Coloration is gray or brown above and dirty white below. Snout is blunt. Caudal fin is nearly symmetrical. Habitat: Coastal surface waters. Comments: Juvenile white sharks normally eat squid and other fishes such as stingrays and other sharks. As the fish matures, its diet changes. Adults eat seals, sea lions, dolphins and dead whales, although some will continue to eat fishes such as snapper. These sharks have also been known to eat elephant seals, sea otters, turtles and sea birds. The white shark is a powerful predator, which provokes fear in many people. Range: Atlantic coast from Newfoundland to Brazil, including the Gulf of Mexico; on the Pacific coast from Alaska south to the Gulf of California.

Whale Shark Rhincodon typus

Whale Shark Rhincodon typus

Whale Shark Rhincodon typus Whale Shark Rhincodon typus

Whale Shark Rhincodon typus Description: Grows to a length of 60’. The body is very large and elongate. Three ridges begin on each side of the head and extend to the caudal peduncle. Coloration is dark grey or brown with yellow or white spots in a checkerboard pattern. Mouth is broad and at the end of a short snout. Habitat: The open sea Comments: R. typus are not whales, but sharks. The whale portion of their name was included to express the magnitude of their size. It is hypothesized that whale sharks have a maximum life span of around years. Scientists still know relatively little about them. Range: Atlantic from New York to Brazil, including the Gulf of Mexico; in the Pacific from S. California to the Gulf of California.

Clearnose Skate Raja eglanteria

Description: This skate, which reaches sizes up to 30 inches long and 19 inches wide. Coloration is light to dark brown above with darker brown or black round spots and irregular bars. White below. Spines are found down the center of its back. Dorsal fins are separate. The tail is half of the total length and is covered in spines. Habitat: Shallow shores. Comments: The Clearnose Skate earns its name from easily recognized translucent patches on either side of its "nose". As its downward-pointing mouth suggests, that it often swims close to the bottom searching for clams, mussels, shrimp, crabs and small fish to catch and crush in its broad teeth. Like many skates, the clearnose lays eggs inside a protective case often referred to as a mermaids purse--these black cases are often found washed up along beaches. Range: From Massachusetts to Florida and N. Gulf of Mexico. Clearnose Skate Raja eglanteria

Class Agnatha Approximately 65 species Mouth is round and muscular. Have rows of teeth. Feed by sucking the blood of its prey. Lack paired fins. Lack scales. Body is cylindrical and elongate.

Sea Lamprey Petromyzon marinus

Sea Lamprey Petromyzon marinus

Description: Grow to a length of about 3 feet. Eel-like in appearance, but have a soft, cartilaginous skeleton. They lack paired fins but have well developed dorsal and ventral finfolds. Large specimens usually are olive brown above, or of varying shades of yellow-brown, green, red, or blue, mottled with a darker shade of the same color, or sometimes nearly black if the dark patches are confluent. The lower surface is whitish, gray, or of a pale shade of the same hue as the ground color of the back. Habitat: It has been known from early times that the sea lamprey breeds in freshwater. Their requirements are a gravelly bottom in rapid water for their spawning beds, with muddy or sandy bottom in quiet water nearby waters, for the larvae. Range: Atlantic coasts of Europe and of North America; from the west coast of Greenland to Florida in the western side of the Atlantic; from northern Norway to the Mediterranean in the eastern; running up fresh rivers to breed, and landlocked in certain American lakes. Sea Lamprey Petromyzon marinus

Comments: In the adult the mouth is a longitudinal slit when closed, but forms an elliptical disk at the tip of the snout when open, and is armed with many horny, hooked teeth arranged in numerous (11 to 12) rows, the innermost the largest. Little is known of the habits of the lampreys while they live in the sea. Their mode of life centers around a fiercely predaceous nature. They are found fastened to fish, which they attack by "sucking on" with very effective mouths. The lamprey usually fastens to the side of its victim, where it rasps away until it tears through the skin or scales and is able to suck the blood. Its prey sucked dry, it abandons it for another. Probably lampreys are parasites and bloodsuckers pure and simple, for we cannot learn that anything but blood has been found in their stomachs, except fish eggs, of which lampreys are occasionally full.