FISHES

Phylum Chordata Contains ALL fishes, amphibians, reptiles, birds, and mammals ALL chordates have a notochord; - a flexible rod that supports a chordates back (all embryonic, some retain, some change)

CHARACTERISTICS Cold blooded Paired Fins Gills, Scales EVOLUTION OF FISHES Agnathans – jawless, 1st vertebrae, round mouth for sucking or filter feeding Jaws (from gill arches) = Gnathostomes! & Paired fins improved swimming and feeding Cartilage Skeletons (Sharks, Rays, Skates – still considered vertebrates) – Class Chondrichthyes Bony Skeletons (Modern Fish) – Class Osteichthyes

FORM & FUNCTION Feeding Everything you can imagine – carnivores (“big teeth”), herbivores (pharyngeal bone – small “teeth” on jaw, omnivores (random), detritivores (mouth on bottom), parasitic (“suckers”) Respiration Hard bony flap covering the gills - operculum Air breathers Obligate – must breathe air or will die (African Lungfish) Facultative – whatever is convenient (some Catfish) Usually found in tropical waters – because… Circulation Closed Circulatory System, Single Loop Atrium --Ventricle -- Gills -- Body -- Back to Atrium

Osmoregulation – balance of water levels in body - Salt water fish tend to lose water & gain salt - Fresh water fish tend to gain water & lose salt - Homeostasis maintained by the kidneys Brain Responses - Cerebrum - thinking, voluntary activities - Cerebellum - coordination - Medulla Oblongata - functions of internal organs - Lateral Line System - senses vibrations Movement - Very muscular – make great swimmers and good food - Swim Bladder - buoyancy

Reproduction Ovoviviparous (eggs stay in mom) Oviparous (lays eggs) Ovoviviparous (eggs stay in mom) Viviparous (babies get nourishment from mom. Ex. Humans, cats, some fish)

Classes of Fish Class Myxini: “Jawless Fish” EX: hagfish and lampreys Class Chondreichthyes: “Cartilaginous fish” EX: sharks, rays, chimaeras Class Osteichthyes: “Bony Fish”

Class Myxini Hagfish and Lampreys (Mis-zini) Hagfish and Lampreys Slow enough metabolism that they can eat once every 6 months! (metabolism control) They are scavengers (eat dead organisms) Tie themselves into a knot to A) clean themselves, B) escape prey, C) pull on food Hagfish Lamprey’s oral disk Lamprey Hagfish knot

Class: Chondrichthyes Means “Cartilage fish” Skeleton composed entirely of cartilage – still considered a vertebrate Contains ALL sharks, stingrays, skates, and chimaeras Characteristics: jaws, paired fins, skin covered w/ placoid scales (armored fish) Denticles: teeth-like scales, feels like sandpaper

2 Subclasses Elasmobranchs: Sharks and rays Holocephalans: chimaeras (ratfish) Whale shark World’s Largest Fish Sand tiger Shark Manta Ray Blue Spotted Stingray Chimaera

Class Osteichthyes Means “bony fish” About 25,000 spp. of bony fish Characteristics: swim bladder, bony scales, and fin rays 2 sub-classes of fish Sarcopterygii: Lobefin fish Actinopterygii: Ray-finned fish

Sub-class: Sarcopterygii Lobefin Fish; have round fleshy-lobes EX: Coelacanth and Lungfish Coelacanth: is over 400 million years old Thought to be extinct; found in 1938 Lungfish: Lives in Africa & South America Facultative air breathers Lungfish gave rise to land vertebrates Can live out of water for short time periods Coelacanth Lungfish link Lungfish Lungfish walking!

Sub-class: Actinopterygii Ray-finned fish; most numerous group Fusiform body shape: stream-lined allows fish to move through watch w/ great efficiency Scale types Ganoid: Thick bony scales that don’t overlap Cycloid: Thin, smooth overlapping scales Ctenoid: Thin, spiny overlapping scales Perch Lookdown

Fins ___________: on the top of fish used for stability _________: tail fin used for locomotion & stability ____________: bottom of fish used for stability ___________: used for steering (anterior) ____________: used for steering (posterior)

Functions Bony fish are Oviparious: (reproduce by laying eggs) Air Bladder: gas-filled sac used to maintain buoyancy Fish have a closed cardiovascular system Lateral line system: canals on the side of the fish used to detect movement in the water

Coloration *Chromatophore: specialized cells that contain pigments Countershading Iridophore *Chromatophore: specialized cells that contain pigments *Iridophore: crystals that produces a mirror-like silver color *Countershading: camouflage where top of fish is dark, and bottom of fish is light, used to blend into the ocean