FISHES Agnatha Chondrichthyes Osteichthyes
General Characteristics! Ectothermic! Vertebrates! Have scales! Swim with fins! Almost all exclusively aquatic! Filter oxygen from water over gills
Classes of Fish! Agnatha Jawless Fish! Chondrichthyes Cartilagenous Fish! Osteichthyes Bony Fish
Question #1:! What is the name for a person who studies fishes?! Ichthyologist
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
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
Why are fish so slimy?! To slip away from predators! As an anti-abrasive to slip over rocks! Lubricant to enable easy swimming through the water! An "envelope" for protection from fungus, parasites and disease
Maintaining Buoyancy! Swim bladder Uses air to keep the fish afloat Can adjust the amount of air to go deeper or rise Most bony fishes have them Can be used as a second lung
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
Locomotion--Fins! What are fins for?! Not for swimming, but for steering. The muscles of the entire body of the fish are used for propulsion, and even if the fish had no fins at all it could still make progress through the water; however it would not be able to right itself well.
Gills! Obtain oxygen! Give off carbon dioxide! Most have an operculum (cover over outside)! Oxygen dropped into circulatory system pumped by 2-chambered heart
Gas Exchange! 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
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
Reproduction (cont.)! Most fish use external fertilization female lays eggs in water and male fertilizes them in water! Some use internal fertilization
Class Agnatha! Cartilagenous! Simplest and oldest vertebrates! Jawless! No scales! Scavengers or parasites! Lamprey, hagfish
Lamprey (Class Agnatha)
Hagfish (Class Agnatha)
Class Chondrichthyes! Hinged jaw! Paired fins! Scales! Muscles attached to skin, not skeleton! Cartilagenous skeleton no bones
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
Shark (Class Chondrichthyes)
Skates and Rays! Wing-like pectorals! Most live on sea beds! Some have poison spines on backs or tails (stingrays)
Skates and Rays (Class Chondrichthyes)
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
Subclass Sarcopterygii (Lobe-finned fish)
Subclass Actinopterygii (Ray-finned fish)