Agnatha Chondrichthyes Osteichthyes FISHES Agnatha Chondrichthyes Osteichthyes

General Characteristics Ectothermic Vertebrates Have scales Swim with fins Almost all exclusively aquatic Filter oxygen from water over gills

Chondrichthyes – Cartilagenous Fish Osteichthyes – Bony Fish Classes of Fish Agnatha – Jawless Fish Chondrichthyes – Cartilagenous Fish Osteichthyes – Bony Fish

What is the name for a person who studies fishes? Ichthyologist Question #1: What is the name for a person who studies fishes? Ichthyologist

Early Fish Earliest - Filter feeders, no jaws, no fins Ostracoderms – jawless, heavy bony plates Lobe finned fishes – Coelocanths

Fish Anatomy

Fins Caudal – propels fish forward Dorsal – stabilizer Anal – stabilizer Pectoral – hold fish steady, maneuvering Pelvic – hold fish steady, maneuvering

Scale Types Cycloid – smooth surface, on bony fish Carp Salmon Ctenoid – teeth along ridge (rough to touch), on bony fish Bass Bluegill Perch

Ganoid – hard, interlocking, diamond-shaped, on primitive fish Scale Types Placoid – Look like tiny teeth, feel like sandpaper, on cartilagenous fish Sharks Rays Ganoid – hard, interlocking, diamond-shaped, on primitive fish Gar

Question #2: What is the purpose of a fish’s scales? Shield against injury, help to move through the water

Maintaining Buoyancy Swim bladder Liver Uses air Most bony fishes Can be used as a second “lung” Liver Uses oil Sharks Most sharks must constantly swim to avoid sinking

Use fins and body wall to push against water Locomotion Use fins and body wall to push against water Forked tails reduce drag in the water Muscles in a zig-zag shape Each contraction moves large parts of the body wall

Gills Obtain oxygen Give off carbon dioxide Most have an operculum Oxygen dropped into circulatory system pumped by 2-chambered heart

Gas Exchange Pump ventilation Ram ventilation Exchange of gases occurs in capillary network in gill lamellae; water and blood flow in opposite directions over lamellae = Countercurrent Exchange

Countercurrent Exchange System

Excretion and Osmoregulation Freshwater fishes never drink Lots of nephrons Ions are reabsorbed Marine fishes Drink constantly Less blood is filtered Water is reabsorbed

Limited vision, focus by moving lens back and forth Senses Limited vision, focus by moving lens back and forth Olfactory receptors Magnetic receptors Touch

Sense (cont.) Hearing – sound conducted through skull Lateral line system – senses movement of other organisms around them Electroreception – sense electrical impulses generated by muscle twitches

Reproduction Oviparous (most fish) Release eggs, young develop outside mom Ovoviviparous (some cartilaginous fishes) Eggs remain inside mom Eggs at a later stage of development before they are released Viviparous (a few sharks) Young born alive

Class Agnatha Cartilagenous Simplest and oldest vertebrates Jawless No scales Scavengers or parasites Lamprey, hagfish

Class Chondrichthyes Hinged jaw Paired fins Scales Muscles attached to skin, not skeleton Cartilagenous skeleton

Jaws not attached to brain case Sharks Jaws not attached to brain case Can protrude during attack 20 tons per square inch for an 8’ shark Size varies (few inches to over 40 feet) Variable body shapes

Skates and Rays Wing-like pectorals Most live on sea beds Some have poison spines on backs or tails (stingrays)

Class Osteichthyes Largest group of fishes Skeleton made of bone and cartilage Hinged jaws Paired fins Hard, protective scales Covered gills (operculum)

Major Groups of Osteichthyes Subclass Sarcopterygii Lobe-finned fishes (Coelocanth) Lungfishes Subclass Actinopterygii – Ray-finned fishes Bass Tuna Guppies