I. BIOLOGY OF FISHES
A. BODY SHAPE
i. Directly related to the fish’s lifestyle ii. Fast swimmers are streamlined: helps move through water. Laterally compressed bodies: leisurely swimming, efficient enough to allow speed. Flatfishes; adapted to live on bottom, laterally compressed. Lie on one side, both eyes on top, born with one on each side, migrates to the other side. Elongated bodies; live in narrow spaces or among vegetation iii. Useful for camouflage
B. COLORATION
i. Some use for camouflage ii. Colored pigments found in special cells in skin called chromatophores (irregular in shape, branches radiating from center). Variety of colors and hues results from combinations of chromatophores with varying amounts of different pigments. iii. Many can rapidly change color by contracting and expanding pigments in chromotophores. iv. Structural colors result when special surface only reflects certain colors of light. Consequence of crystals contained in iridophores. Iridescent, shiny quality produced by structural colors in combination with pigments.
v. Warning coloration: advertise they are dangerous, poisonous, taste bad. vi. Can change color with mood or reproductive conditions. vii. Cryptic coloration: blending with environment to deceive predators or prey viii. Disruptive coloration: presence of color stripes, bars, or sports that help break outline of fish. ix. Countershading use to disguise in open water (silver/white bellies, dark backs)
C. LOCOMATION
i. Swim to obtain food, escape predators, find mates. ii. Some swim to flush gills with water and obtain oxygen. iii. Rhytmic side-to-side motion of body or tail. S-shaped waves of contraction produced by muscles (myomeres, which run along the side of the body) moving from head to tail push against water and force body forward. iv. Fins used for maneuverability. Dorsal and anal fins used as rudders to steer and provide stability. Paired pelvic fins help turn, balance, and brake. Many don’t use body, only fins.
D. FEEDING
i. Most sharks are carnivores. ii. Most cartilaginous fishes are filter feeders. iii. Many sharks filter the water with their gill rakers, slender projections on inner surface of the gill arches. iv. Bony fish have protrusible jaws allowing flexibility in feeding habits. Most are carnivores. Capture prey from sediment, water column, surface of rocks, or other organisms, some chase their prey, others sit and wait.
v. Carnivorous bony fish have well-developed teeth for catching, grasping, and holding their prey. Roof of mouth, gill rakers, pharynx may also have teeth to help hold prey. vi. Fishes that feed on seaweeds and plant are grazers. Front teeth fused to form beak-like structure. Use beaks to scrape off bits of live coral. vii. Some filter planktons with gill rakers. Strain food by swimming with large mouths open. Most abundant.
E. DIGESTION
i. After being swallowed, food passes through pharynx and esophagus into the stomach. Digestion begins. Stomach to intestine. ii. In bony fish, anterior portion of intestine has pyloric caeca which secrete digestive enzymes. Other digestive enzymes secreted by inner walls of intestine and pancreas. iii. Liver secretes bile needed for breakdown of fat. iv. Intestines of cartilaginous fishes have spiral valve which increases internal surface area of intestine.
v. Intestine absorbs nutrients from digestion; they pass into blood to be distributed through body. vi. Undigested materials exit through anus or cloaca, the common passage for the digestive, excretory, and reproductive organs in cartilaginous fishes.
F. CIRCULATORY SYSTEM
i. Two-chambered heart below gills. Deoxygenated blood enters first chamber. Blood is pumped to second chamber, which then pumps it to the gills where gas exchange takes place. ii. Oxygenated blood is carried to body by arteries. Arteries branch out into thin-walled capillaries, which allow oxygen and nutrients to reach every cell. iii. Other capillaries collect into veins, which carry