CH 8 Marine Fishes

Vertebrates (Subphylum Vertebrata) Backbone enclosing a nerve cord, or spinal cord Phylum Chordata Notochord Pharyngeal pouches Postanal tail Dorsal Nerve Chord

Phylum Chordata Subphylum Vertebrata Class Agnatha, Jawless fishes, (Hagfishes and Lampreys) Class Chondrichthyes, Cartilaginous fishes, (Sharks, Sharks and Rays, Ratfishes) Class Osteichthyes, Bony fishes

Fig. 8.1

Tab. 8.1

Class Agnatha: Jawless Fishes Hagfishes and lampreys lack jaws, most primitive of living fishes Feed by suction Lack paired fins and scales Hagfish (slime eels) Lampreys, freshwater

Class Chondrichthyes: Cartilaginous Fishes Sharks, rays, skates, and ratfishes Endoskeleton of cartilage Paired fins, movable jaws, gill slits Rough sandpaper – like skin placoid scales pointed tip that is directed backward same composition as teeth

Fig. 8.3

Class Osteichthyes: Bony Fish Largest group of living vertebrates Gills covered by operculum Usually swim bladder Highly maneuverable fins Cycloid scales

Biology of Fishes Body Shape Directly related to its lifestyle Predator or prey Streamlined, flattened, elongated, etc Used for camouflage

Fig. 8.4

Coloration Locomotion Feeding Biology of Fishes Chromatophores Swim using a sideways movement of the body and tail Pectoral fins and tail Aid sharks with buoyancy Aid bony fish maneuver/swim Feeding Carnivorous, herbivorous, filter feeders

Fig. 8.11

Fig. 8.10

Fig. 8.12

Digestion Respiratory System Same set up as all vertebrates Obtain oxygen filtered from the water Cartilaginous Fish First pair of gill slits modified into spiracles (pull water in) Gill filaments, fleshy projections Lamellae, increase surface area Diffusion, countercurrent system of flow

Fig. 8.6

Regulation of Internal Environment Marine fishes keep a constant internal environment Kidneys, gills, “drinking” water, rectal gland Cartilaginous fishes increase their solute concentration in their blood Urea Created by breaking down proteins.

Nervous System and Sensory Organs Central Nervous System Olfactory sacs, sense of smell, opens to nares Taste buds Barbels Nictitating membrane Lateral line, detect vibrations in the water (neuromasts)

Behavior Biology of Fishes Territoriality Schooling Migration Anadromous, fishes spend most of their lives in the sea but migrate to fresh water to breed Catadromous, fishes spend most of their lives in fresh water but migrate to salt water to breed

Reproduction and Life History Urogenital Opening sperm or eggs Hermaphrodites Courtship Internal fertilization Copulation Males cartiliginous fishes have claspers External fertilization

Oviparous Ovoviviparous Viviparous Parthenogenesis Biology of Fishes Spawn eggs Ovoviviparous Eggs are retained in reproductive tract Viviparous Live – bearers, nutrition comes from reproductive tract Parthenogenesis Development of an egg without fertilization

Fig. 8.30

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