FISHES Agnatha Chondrichthyes Osteichthyes General Characteristics l l

FISHES Agnatha Chondrichthyes Osteichthyes

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

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

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

Fish Anatomy

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

Scale Types l Placoid – Look like tiny teeth, feel like sandpaper, on cartilagenous fish Sharks – Rays –

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

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

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

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

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

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

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 l Freshwater fishes never drink – Lots of nephrons – Ions are reabsorbed – l Marine fishes Drink constantly – Less blood is filtered – Water is reabsorbed –

Senses l Hearing – sound conducted through skull l Lateral line system – senses movement of other organisms around them l Electroreception – sense electrical impulses generated by muscle twitches

Reproduction l Oviparous (most fish) – l Ovoviviparous (some cartilaginous fishes) – – l 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 l Counter shading l Mimic l Camouflage l Bioluminescence

There 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 l Simplest and oldest vertebrates l Jawless l No scales l Scavengers or parasites l Lamprey, hagfish l

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

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

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

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

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