What is a Fish? Fishes are aquatic vertebrates. Most fishes have paired fins, scales, and gills.

What is a Fish? Fishes are aquatic vertebrates. Most fishes have paired fins, scales, and gills.

Feeding and Digestion Every mode of feeding is seen in fish herbivores, carnivores, parasites, filter feeders, and detritivores

Feeding and Digestion continued Complete Digestive Tract Food passes through the mouth and esophagus to stomach where digestion begins

Feeding and Digestion continued The pyloric ceca (cecum - singular)(fingerlike pouches) secretes digestive enzymes and absorbs nutrients from the digested food

Feeding and Digestion continued The liver secretes bile which helps break down fat The pancreas releases digestive enzymes into intestine The gallbladder stores bile and releases it to the intestine Gallbladder These are accessory organs, NOT part of the digestive tract

Feeding and Digestion continued The intestine completes the process of digestion and nutrient absorption

Feeding and Digestion continued Undigested material is eliminated through the anus Digestive Tract: M>E>S>I>A (write the words out) Accessory organs are not included.

Respiration Most fishes exchanges gases with gills located on either side of the pharynx Oxygen-rich water moves into the mouth and is pumped over gill filaments Oxygen-poor water is pushed out through openings in the sides of the pharynx

Circulation Closed system consists of heart, blood vessels, and blood (duh) Delivers oxygen and nutrients to body cells Single-loop Heart pumps blood to gills where it picks up oxygen and releases carbon dioxide Blood moves to all body tissues then back to heart through veins

Circulation continued Most Fish hearts have 4 parts: Sinus venosus Atrium Ventricle Bulbus arteriosis Sinus Venosus Atrium Ventricle Bulbus arteriosus

Circulation continued Oxygen-poor blood from the veins collects in the sinus venosus Blood enters the atrium (one-way compartment) and flows to the ventricle The ventricle pumps blood into the bulbus arteriosus The bulbus arteriosus moves blood into the ventral aorta and toward the gills

Excretion Kidneys filter chemical wastes from the blood Urine is formed in the kidneys and carried to urinary bladder where it is stored and later expelled Urinary bladder

Excretion continued Kidneys help maintain homeostasis by varying the amount of water and salts in urine Saltwater fish excrete very little urine but it is highly concentrated (little water) Freshwater fish excrete large amounts of diluted urine (a lot of water)

Response/Nervous Fishes have well-developed nervous systems organized around a brain

Response/Nervous continued The olfactory bulbs are involved with the sense of smell The cerebrum is responsible for the voluntary activities of the body primarily processes sense of smell The optic lobes process information from the eyes Cerebrum Optic lobe

Response/Nervous continued The cerebellum coordinates body movements The medulla oblongata controls the functioning of many internal organs Cerebellum

Response/Nervous continued Most have well-developed eyes and good color vision Good sense of taste and smell; may not hear sounds well Lateral line system allows fishes to sense vibrations in the water Some fishes can detect low levels of electric current

Movement Most fishes move by contracting paired sets of muscles on either side of backbone Force and action of the fins propel fish forward Fins are used to keep on course and adjust direction

Reproduction Separate sexes; most show external fertilization Spawning (reproductive behavior) varies among different species Most lay large numbers of eggs to ensure some will be fertilized and survive Most fish are oviparous (lay eggs that hatch outside of body) ex. salmon Some species are ovoviviparous (eggs stay in mother s body after internal fertilization) ex. guppies Some species are viviparous (give birth to live young) ex. sharks

Taxonomic Classification of Fishes Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Agnatha jawless fishes Class Chondrichthyes cartilaginous fishes Class Osteichthyes bony fishes

without jaws Most primitive class of fish Lack jaws, paired fins, and scales Skeleton is made of cartilage Retains notochord as adults External fertilization Only has 2 living members: hagfish and lamprey Class Agnatha

Hagfish Body Plan: Pinkish-grey wormlike bodies 4 or 6 short tentacles around mouths Found only in oceans (bottom dwellers) Detritivores use a toothed tongue to scrape a hole in the dead or dying fish s side Lack eyes but they have light-detecting sensors scattered around their bodies

Found in fresh water and salt water Feeding Filter feeders as larvae Parasites as adults - suck up tissues and body fluids of hosts They have small eyes beneath skin Lamprey

Class Chondrichthyes cartilage fish Sharks, skates, rays Have jaws, paired fins, and cartilage skeleton Most are covered with placoid scales feels like sandpaper Almost all live in saltwater Diverse feeding methods most are carnivores; some are detritivores or filter-feeders

Skates and Rays Flat body with paired pectoral fins behind heads Flat shape and coloration provide camouflage Mainly bottom dwellers Feed primarily on mollusks and crustaceans Largest rays are filter-feeders

Teeth are replaced throughout their lives Go through as many as 20,000 in a lifetime Use several senses to locate prey Smell chemicals in the water Sharp vision in little light Well-developed lateral line system detects vibrations in water Most are carnivores, but larger species filter-feed Sharks

Do not have swim bladders to control buoyancy (floating) Must keep moving (requires a lot of energy) OR Store lipids in liver to reduce density and provide buoyancy Internal fertilization Sharks continued Male uses claspers (modified pelvic fins) to transfer sperm to female Most are oviparous but some are ovoviviparous or viviparous

bony fish Catfish, salmon, perch, bass Have jaws, paired fins, and skeletons of bone 3 key features Skeleton of bone harder and heavier than cartilage Swim bladder used to control buoyancy Scales cover most bony fish; protects and helps reduce friction Largest class of fish (also largest class of vertebrates) Class Osteichthyes

2 Groups of Bony Fish Lobe-finned Fins are fleshy (like earlobes) Only 7 species exist today Includes lungfish

2 Groups of Bony Fish Ray-finned Fins are supported by long, flexible bony structures (rays) Very diverse group Includes most familiar fish eel, perch, bass, salmon

External Anatomy Operculum covers and protects gills Fins increase stability and movement through water Caudal fin (tail) moves from side to side helps swim 2 dorsal fins and anal fin keep fish upright and moving in straight line Pelvic and pectoral fins used to navigate, stop, move up and down Skin Most are covered with scales minimize friction as they swim Scales grow throughout life