Transcript FISHES
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 – Jawless Fish Chondrichthyes – Cartilagenous Fish Osteichthyes – Bony Fish Agnatha Question #1: What is the name for a person who studies fishes? Fish Anatomy Fins Caudal – propels fish forward Dorsal – stabilizer Anal – stabilizer Pectoral – hold fish steady, maneuvering Pelvic – hold fish steady, maneuvering Scale Types – Look like tiny teeth, feel like sandpaper, on cartilagenous fish Placoid Sharks – Rays – Scale Types Cycloid – smooth surface, on bony fish – – Carp Salmon Ctenoid – teeth along ridge (rough to touch), on bony fish – – – Bass Bluegill Perch Question #2: What is the purpose of a fish’s scales? Shield against injury, help to move through the water Maintaining Buoyancy Swim bladder – – – Uses air Most bony fishes Can be used as a “lung” Liver – – – Stores oil Sharks Most sharks must constantly swim to avoid sinking 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 Counter-current exchange system Circulation The heart of a fish is simple when compared to our heart. They have a two cambered heart that follows a heart-gillsbody-heart path. 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 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) – Ovoviviparous (some cartilaginous fishes) – – Release eggs, young develop outside mom Eggs remain inside mom Eggs at a later stage of development before they are released Viviparous (a few sharks) – Young born alive Internal Anatomy Color and Pattern Counter shading Mimic Camouflage Bioluminescence There are also many patterns. Many open water fish like this tuna show countershading. Mimicry Camouflage Many mid-depth fish are often red while lots of the deep water fish are black and may have luminescent organs. 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 Sharks Jaws not attached to brain case Can protrude during attack – 20 tons per square inch for an 8’ shark – Size feet) varies (few inches to over 40 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