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Home , Ampullae of Lorenzini, Evolution of fish, Sarcopterygii

Fish What is a ? •: Chordata •Subphylum: Vertebrata •Key Features: • Aquatic • Paired - movement • Scales - protection • – gas exchange • Endoskeleton – made of or

Evolution of •Fish where the first vertebrates •They arose from a common ancestor with or •First fish were small and jawless • Some developed heavy armored plates. •They evolved in the late period •The Age of Fishes – period •Key Features of the of Fish: • • Paired fins Evolution

•Evolved from jointed arches. Gill arches used for support of the gills. Gill arch attached to cranium forming top jaw. The joint/hinge created a lower jaw. First used to prevent backflow of water over gills. Allowed to hold on to prey.

• Jaws increase the food options for fish.

• Jaws allow for muscle attachment and true teeth.

• Jaws allow for defense.

Evolution of Fishes • Paired pectoral and pelvic fins developed at same time as jaw. Allowed for more control in movement.

• Tail is used for thrust and propulsion in the water.

The combination of jaws and paired fins allowed for more complex movement for attack and evasion.

• Cartilage is flexible tissue that supports the body and is softer than and more flexible than bone.

• Modern fish groups: • • Jawless fish • Bony fish – two groups – lobe fined and ray fined fish Form and Function • Key feature: • to aquatic included various modes of: • Feeding • Specialized structures for gas exchange • Paired fins for locomotion • Feeding • All modes of eating are seen in fish. • From carnivores to parasites • The movement of food: • – esophagus – stomach – pyloric ceca – intestine – out anus • Other organs that aid in digestion – liver and pancreas • Excretion • Two ways to remove ammonia: • Diffusion through gills • Kidneys – excretory that filters wastes from the blood. • Waste removed as urine Form and Function

• • Gills are used for gas exchange • Covered in Boney fish by • Made of feathery, thread like structures called filaments • Contain a network of fine capillaries that provide a large surface area for exchange of O2 and CO2. • Countercurrent flow – blood flows in opposite direction of water flow. Increases the O2 exchange. • Process:

1. O2 rich water enters mouth. 2. Water moves over gills filaments

3. O2 poor water out of openings on side of pharynx.

Form and Function •Circulation • Fish have a closed circulatory system • Two chambered heart • Single loop circulatory system. • Heart has 4 parts • Sinus venosus • Atrium – (Chamber) • Ventricle – (Chamber) • Bulbus Arteriosus

Form and Function •Response • Well organized nervous system • Parts of Fish Brain: • Olfactory bulb – smell (olfaction) • – Fish smell – other verts – voluntary functions • Optic lobe – sight • Cerebellum – coordination • Medulla Oblongata – functions of many internal organs Form and Function System Sensitive receptors along body used to detect movement in the water.

• Most fish active at Daytime

• Well developed Eye

Senses electrical currents in water

Found in sharks and their relatives. Form and Function •Movement •Fish move by alternating paired sets of muscles on either side of the backbone.

•Forms an S – shape •Fins are used for stabilization in the water and control course and direction. Swim bladder is an organ that adjusts buoyancy.

Found in Bony fish.

Fish are denser than water which means they would sink if not for swim bladder. Relax-air in-float Muscles tighten-air out-sink

Sharks and relatives use large oil-filled liver for buoyancy. Lift is generated by swimming. •Reproduction • Both internal and external •Oviparous • Eggs laid and hatch outside the body of female. • Ex: •Ovoviviparous • Eggs are retained in body after internal fertilization • “Born Alive” • Ex: Guppies •Viviparous • Live birth – mother attached to offspring – no egg – • No fish examples

Form and Function • Integuments • Skin covered with scales -Thin, round disks of highly modified bone that grow from pockets of skin -Overlap like roof shingles, all pointing toward tail to minimize friction

Grow during entire life of fish -Adjusting growth pattern to food supply • Scales grow quickly when food is abundant and slowly when scarce • Skin contains pigmented -Create various color patterns Form and Function Some Types of Fish Scales: • Ganoid – found in , diamond-shaped, shiny, and hard. • Placoid – found in sharks and relatives. Structure similar to teeth. • Leptoid – found in high bony fish. As they grow form concentric rings. Overlapping- head to tail (roof tiles). Less drag. • Two types of Leptoid scales • Cycloid – smooth outer edges. Primitive fish with soft rays. • Salmon and • Ctenoid – toothed outer edges. Advanced fish with spiny fin rays. • Bass and crappie Ganoid Scales Placoid scales

Cycloid Leptoid Scales Ctenoid scale

Body Plan

•Jawless Fish •Oldest of vertebrates •Lack true teeth and Jaws and Paired Fins •Skeleton made of cartilage •Keep during life • •Contains Lampreys and • Class: Cephalospidomorphi • Long and slender w/ no paired fins. • Filter feeds as larva. • Parasite as adult. • Can live in Fresh and Salt water • Breed in and lakes but move into sea as adults Feeding process: Attaches to organism with suction cup mouth. Use strong, rasping tongue and toothlike structure to scrape skin away. Sucks up blood, tissue and body fluid.

Hagfish Class: Myxini Pinkish gray, wormlike body w/ four or six short tentacles around mouth Feeds on dead or decaying fish, may eat from inside out Called Slime Eels Peculiar Traits Creates a lot of slime that suffocate prey Ties itself into knots Cartilaginous fishes Sharks and their Relatives • Class: • Skeletons made of cartilage • like scales – sandpaper like • Skates, Rays, , • ~ 760 • Ventral mouth • Dermal denticles • Called living Two types: • Holocephalans • - • Elasmobranchs • All other sharks and relatives Holocephalans Chimaeras-

• HAVE SKIN OVER GILLS LIKE AN OPERCULUM • TAKE WATER THROUGH NOSTRILS AND OUT OF GILLS Characteristics • Elasmobranchs • Teeth most notable feature for sharks. • Acute olfactory -2/3 of cells in the brain used for smell • Nictitating membrane over eye • Gills not protected (Gill Slits) Shark Characteristics Pectoral Fins (Bernouli’s Principle) and oily liver for lift Continue to swim for oxygen and lift (Nurse shark exception) Lateral Line System and AMPULLAE OF LORENZINI Largest Fishes Whale Shark (60 ft) and Basking Shark (60 ft) both are filter feeders DIGESTION • TAKES CHUNKS OF PREY, NO CHEWING • -aids in digestion by adding surface area OSMOREGULATION • RETAIN UREA (maintains solute concentration equal or greater than sea water • RECTAL GLAND AND GILLS GET RID OF EXCESS SALT • SOME SHARKS CAN GO INTO RIVERS REPRODUCTION • Claspers insert into for internal fertilization SHARKS MAY BE: • OVIPAROUS (Lay eggs; Mermaid’s Purse) • VIVIPAROUS (Live young) • OVOVIVIPAROUS (internal eggs and live birth)

RAYS VS. SKATES • Flat bodied bottom dwellers (Demersal) • Gill slits on ventral side of body • -like pectoral fins • Stingrays have stinging barbs at base of tail • Electric Rays= up to 220 volts with organs on head • Skates don’t have whip tail or sting, and have wave-like motion with pectoral fins instead of flapping Bony Fish • Class: • Skeleton made of calcified bone • Two groups • – Lobe finned fish – and • – Ray finned fish – all other fish Most fish are bony (98%); half of all vertebrates Bony skeleton Cycloid (round) scales Operculum (gill cover) Terminal Swim bladder (pressure and lift) Maneuverable fins

Subclass sarcopterygii (lobe-finned) • (thought to have been extinct until discovered off the coast of madagascar) Coelacanths are thought to be a link between fish and because of their lobe fins (homologous structures) Coelacanths have fat-filled swimbladder They are ovoviviparous Jelly-filled rostral organ-electroreceptive fish (have primative instead of swim bladder) Subclass actinopterygii (ray finned fish)

• Have ray fins and comprise all fish other than lung fish and coelacanths • Contain a swim bladder • Most diverse and numerous subclass of fish • Body shape directly related to the habitat the fish in • Fast fish are hydrodynamic (fusiform body shape; and marlin) • Reef fish are built to turn and maneuver (laterally compressed; butterfly fish and tang) • Flat fish are built for bottom dwelling (flounder) • Some fish are shaped for camo. (Stone fish, pipe fish)

Coloration • Chromatophores are color cells (sacks of pigment) • Iridophores reflect light (crystals inside) • Cause fish to look shiny • Colors advertise reproduction, danger, bad taste (poster colors)

• Reef fish have cryptic coloration (camo) • Open water fish = obliterative counter shading, darker on the upper side and lighter on the underside of the body Schooling

• About 4000 species school as adults

• Keep a consistent distance using lateral line

• Lateral line is a series of fluid filled pits that pressure changes in the water Reproduction • Cartilaginous fish have internal fertilization: claspers are inserted into female cloaca

• Cloaca is a common opening for waste and reproduction • Spawning is a fishes fertile time • Sex hormones ready the gametes and fish for spawning

• Some are hermaphrodites

• Some have sex reversal triggered by hormones turned on by environmental factors, like loss of dominant male or maturity to a certain age or size Migration of Fish

•Anadromous – Life cycle goes from salt water to . • Ex: Salmon and Lampreys

•Catadromous – Goes from freshwater to saltwater. • Ex: European Eel