Marine Fish • Fresh and saltwater fishes constitute about ½ of all vertebrate species • There are three classes of marine fish
Class Agnatha • Agnathans are jawless fish. • No paired appendages to aid in locomotion. Their thick snakelike bodies are pierced by gill slits. Their round, sucking mouths are surrounded by organs sensitive to touch and smell. • Hagfish live in colonies on continental shelf sediments, where they burrow for worms. • Lampreys are parasites that attach themselves to bony fish usually and will detach before they kill the host.
Class Chondricthyes • Cartilaginous fish • This class contains sharks, rays and skates • Shark characteristics include: cartilaginous skeleton, paired lateral fins, heterocercal tail (end of body turning up and continuing to the tip of the upper lobe), placoid scales, biting jaws with replaceable teeth, 5-7 gill slits, swim only one direction, an oily liver (aides in buoyancy).
Class Osteichthyes • Bony fish • Common characteristics of bony fish include: bony skeleton, leptoid scales two forms: cycloid (circular) or ctenoid (toothed), operculum (a flap covering the gills) and flexible fins. • They are the most diverse and numerous of all vertebrates and include all the common fish and eels found in salt water. • 90% of all living fish are contained in the order Teleostei.
Teleostei • Gas-filled swim bladder to assist in maintaining neutral buoyancy. • Movable fins for swimming and communication • Great speed • Effective camouflage (cryptic coloration) • Social organization (defensive schools, and orderly patterns of migration) • Some examples of fish in this order are: tuna, cod, halibut, perch and other familiar species.
What problems are unique to fish? • Drag (resistance to movement) active fish usually have a streamline body.
What problems are unique to fish? • Density of fish tissue is typically greater than that of salt water. Cartilaginous fishes have no swim bladder, bony fish do.
What problems are unique to fish? • Gas exchange the process of bringing oxygen into the body and eliminating carbon dioxide (countercurrent flow).
What problems are unique to fish? • Osmoregulation is the ability to adjust internal salt concentration.
What problems are unique to fish? • Feeding and Defense
Shark Dissection: External • Draw your shark and label and explain the function of all the following: • Mouth • Nostrils • Eyes • Spiracles • Snout • Gill Slits • Tails • Pectoral Fins
Shark Dissection: External • Caudal Fin • Anterior Dorsal Fin • Posterior Dorsal Fin • Pelvic Fins • Claspers (male only) • Sex your shark • Examine the placoid scales under the microscope and make a sketch of these scales.
Functions of External Parts of the Shark • Caudal Fin – Notice that the caudal fin is asymmetrical. This moves the shark forward. • Claspers – Found only on male sharks, they enable the transfer of sperm to the female during mating. • Eye – Enables the shark to see its surroundings. • Anterior Dorsal Fin – Allows shark to change direction and aids in stability and movement.
Functions of External Parts of the Shark • Gill Slits – Water passes through the slits effectively allowing the shark to breath. • Lateral Line System – Actually in the interior of the shark but visible from the outside, it helps the shark detect electromagnetic energy, aiding in the pursuit of prey. • Mouth – Food and water pass through to the body.
Functions of External Parts of the Shark • Nostril – Allows shark to smell. • Pectoral Fin – Paired and lift the shark as it swims. • Pelvic Fin – Paired and help stabilize the shark as it swims. • Second Dorsal Fin – Allows shark to change direction and aids in stability and movement.
Functions of External Parts of the Shark • Snout – Front of the sharks head. • Spiracles – These are the two openings on the dorsal side of the head . They allow water to pass through and provides oxygen directly to the brain and the eyes.
Function of the Internal organs of the Shark • Gall Bladder – produces bile. • Heart – pumps blood to the body, has two chambers, a ventricle and an artium. • Kidney – removes wastes from the blood • Liver – stores energy for the shark as well as bile and cleanses the blood, also provides buoyancy. • Pancreas – digestive gland, produces digestive enzymes for transport to spiral intestine • Spleen- lymphatic organ, part of the circulatory system
Function of the Internal organs of the Shark • Cloaca- chamber where the digestive, urinary and genital tracts all open to the outside. • Rectal Gland- salt gland, excretes excess salt from the blood. • Stomach- contains and digests food. • Spiral intestine- internally coiled organ that increases the surface area across which nutrients can be absorbed. • Gonads- reproductive organs, testes or ovaries