brainpop | fish. marine fishes structurally simplest of all living vertebrates probably evolved from...

BrainPOP | Fish

Marine Fishes• Structurally simplest of all

living vertebrates• Probably evolved from sea

squirt larvae• About 24,000 species known

(most abundant vertebrates!)• Lateral line: clusters of

sensory cells that detect vibrations

• Usually swim with sideways undulations (“s” wriggle)

1. Jawless Fishes

Class: Agnatha

• Most primitive

• Lack paired fins and scales

• Many covered with thick mucus

• Feed mostly on dead/dying fish

• Ex. Hagfishes (slime eels), lampreys

Life Cycle

Ex. Hagfishes

Hagfish Video

Hagfish Slime

2. Cartilaginous Fishes!

CLASS: Chondrichthyes

• Cartilaginous skeleton and rough skin covered by “placoid” scales with a pointed tip

• Possess moveable jaws and paired fins

• Most have well-developed teeth and a ventrally facing mouth (underneath head)

Ex. SHARKS• About 350 species

• Caudal fin (tail) heterocercal: the upper lobe is longer than the lower lobe

• Pectoral fins large and pointed

• 5-7 gill slits behind the head

Range in size from 25 cm: Pygmy Shark to…

…to 60 feet: Whale shark!

RAYS / SKATES• About 500 species• Dorsoventrally flattened• Gill slits on the underside of body• Pectoral fins flat and expanded (wings)• Skates: lack a whip-like tail and stinging

spines, lay eggs, usually smaller• Rays: possess stinging spines on tail,

give live birth, usually larger

RATFISHES• About 30 species

• Feed on bottom dwelling crustaceans and mollusks

• One pair of gill slits covered by a flap

3. Bony Fishes

• 23,000 species, 96% of all fishes

• Skeleton: made at least partially of bone

• Ctenoid scales: thin, flexible, overlapping

• Operculum: protective cover over gills

• Lobes of caudal fin are homocercal (relatively same size)

• Most have a terminal mouth (at the end of the head)

• Swim bladder: gas-filled sac above the stomach which adjusts buoyancy

Anatomy of a shark

TAIL FIN

External Fish Anatomy

DORSAL

VENTRAL

ANTERIOR

POSTERIOR

BODY SHAPE & Coloration

●Epipelagic: streamlined, strong muscles, large eyes, countershading common

Coral Reef: laterally compressed (to fit into small spaces) also allows for speed

Color: many species, helps in identification of species/mate & for warning

Bottom Dwellers: Dorsoventrally flattened, both eyes on top

Ex: flounder, fluke, halibut, rays, skates

Coloration:

Usually cryptic (camouflaged)

Rock Dwellers:

●moray eels, trumpetfishes, pipefishes

●Distinctly elongated

Slow-moving bottom dwellers:

●Sculpin, blennies

●Cryptic with projections to resemble seaweed

Ex. Stone Fish

Deep Sea Fishes: relatively small, weak & flabby muscles, eyes small/absent, black, red or lack coloration, bioluminescence common

Ex. Deep Sea Anglerfish

Parasitic Male!!!

Small parasitic male attaches to female for the rest of its life, obtaining nutrients from female’s blood & providing sperm

• Many have very large mouths

Shark structure

Sharks typically have a fusiform body (rounded and tapered at both ends). This

shape reduces drag and requires a minimum amount of energy to swim.

Most stripes and other markings are juvenile colors that fade or disappear with age, as in the case of the

tiger shark

Shark eyes

• Sharks have nictitating membrane– Clear eyelid is deployed

during attack to protect eyes from thrashing

• Like its relatives, rays and skates, the shark's jaw is not attached to the cranium. The jaw's surface, like its vertebrae and gill arches, is a skeletal element that needs extra support due to its heavier exposure to physical stress and its need for extra strength. It has therefore a layer of unique and tiny hexagonal plates called "tesserae", crystal blocks of calcium salts arranged as a mosaic

• The Ampullae of Lorenzini are the electroreceptor organs of the shark, and they vary in number from a couple of hundred to thousands in an individual

Tonic immobility – YouTube

Sharkman - Tonic Immobility - YouTube

Fish Structure

Gills• composed of a gill arch (gives the gill rigid support), gill filaments (always paired), and secondary lamellae (where gas exchange takes place

 The blood flows through the lamellae in the opposite direction from the water passing the gills. This is a counter current exchange system ( very important for getting all of the available oxygen out of the water and into the blood)

By having the blood flow in the opposite direction, the gradient is always such that the water has more

available oxygen than the blood, and oxygen diffusion continues to the place after the blood has acquired more than 50% of the water's oxygen content. The

counter current exchange system gives fish 80-90%

efficiency in acquiring oxygen.

Gills pump oxygen to the 2-chambered heart

Vision

• lens of a fish eye is almost spherical (high curvature) and has a relative high refractive index

• this allows more light to enter the lens and produces a wide field of view

•Tapetum lucidum amplifies light–Can see in varying light conditions