Chordates and VertebratesChordates and Vertebrates

ChordatesChordates The The notochordnotochord is an elongate, rod- is an elongate, rod-

like, skeletal structure dorsal to the gut like, skeletal structure dorsal to the gut tube and ventral to the nerve cord. tube and ventral to the nerve cord.

The notochord should not be confused The notochord should not be confused with the backbone or vertebral column with the backbone or vertebral column of most adult vertebrates.of most adult vertebrates.

The notochord appears early in the The notochord appears early in the embryo and plays an important role in embryo and plays an important role in promoting or organizing the embryonic promoting or organizing the embryonic development of nearby structures.development of nearby structures.

In most adult chordates the notochord In most adult chordates the notochord disappearsdisappears

In some non-vertebrate chordates and In some non-vertebrate chordates and fishes the notochord persists as a fishes the notochord persists as a laterally flexible but incompressible laterally flexible but incompressible skeletal rod that prevents telescopic skeletal rod that prevents telescopic collapse of the body during swimming.collapse of the body during swimming.

Primitive Jawless FishPrimitive Jawless Fish Lamphrey and Hag fishLamphrey and Hag fish The most primitive of the The most primitive of the

chordates evident in the fossil chordates evident in the fossil record are the jawless record are the jawless OstracodermsOstracoderms. .

They were jawless, bottom feeders They were jawless, bottom feeders

Their endoskeleton was cartilaginous Their endoskeleton was cartilaginous but the are covered with small bony but the are covered with small bony

platesplates They use a muscular pharynx to They use a muscular pharynx to

suck food into their mouths and to suck food into their mouths and to exchange gases in respiration. exchange gases in respiration.

Their gill slits were permanently Their gill slits were permanently open open

Jawless Fish cont.Jawless Fish cont. As the fish swam, this fin As the fish swam, this fin

configuration drove the animal configuration drove the animal down into the bottom where its down into the bottom where its food was located. food was located.

The bony plates were useful for The bony plates were useful for protection but inhibiting when rapid protection but inhibiting when rapid swimming was required. swimming was required.

They still had no axial skeleton They still had no axial skeleton These animals are long, slender eel These animals are long, slender eel

like organisms. like organisms.

These animals exist either as These animals exist either as bottom scavengers or parasites of bottom scavengers or parasites of other fish. (Hag fish top right)other fish. (Hag fish top right)

Jawed cartilaginous fishJawed cartilaginous fish The Chondrichthyes are the The Chondrichthyes are the

modern cartilaginous fish modern cartilaginous fish The present Chondrichthyes The present Chondrichthyes

include the sharks, skates and include the sharks, skates and rays. (Top left: skate Bottom rays. (Top left: skate Bottom leftleft

A ventral A ventral jawjaw with replaceable with replaceable teethteeth. The limited mobility of . The limited mobility of the jaw means that the shark the jaw means that the shark must thrash around to break must thrash around to break up its prey up its prey

Sharks must continually swim Sharks must continually swim to avoid sinking. (Thought this to avoid sinking. (Thought this was interesting!)was interesting!)

The gills are not protected by The gills are not protected by an operculum an operculum

Cartilagenous FishCartilagenous Fish

Cartilage is a soft, Cartilage is a soft, flexible materialflexible material End of your nose, earsEnd of your nose, ears

Cartilagenous fish Cartilagenous fish have an entire have an entire skeleton made of itskeleton made of it

Class ChondrichthyesClass Chondrichthyes Sharks, skates and Sharks, skates and

raysrays First jawed fishFirst jawed fish

Cartilagenous FishCartilagenous Fish Placoid Scales: tiny Placoid Scales: tiny

“teeth” that point towards “teeth” that point towards posterior of animalposterior of animal

Gill Slits: openings to the Gill Slits: openings to the gills gills Skates, rays and some Skates, rays and some

bottom-dwelling sharks bottom-dwelling sharks have gill slits on ventral have gill slits on ventral sideside

Spiracles: openings that Spiracles: openings that allow water to enter gill allow water to enter gill chamberchamber Behind eyeBehind eye

Mouth can be used to Mouth can be used to help spiracles pump help spiracles pump water over gillswater over gills

Cartilagenous FishCartilagenous Fish

FinsFins More rigid than bony More rigid than bony

fishfish Pectoral fins in sharks Pectoral fins in sharks

provide liftprovide lift In skates and rays In skates and rays

pectoral fins are more pectoral fins are more developeddeveloped

Skates and RaysSkates and Rays

Many species are Many species are bottom-dwellersbottom-dwellers

Stingrays have a Stingrays have a spine at the base of spine at the base of the tail that can inflict the tail that can inflict a stab wounda stab wound

Skates do not have Skates do not have spinesspines

Both eat crustaceans Both eat crustaceans and mollusksand mollusks

SharksSharks Group is more than 300 million years oldGroup is more than 300 million years old Lateral line organLateral line organ

Used to detect motion in the waterUsed to detect motion in the water Ampullae of LorenziniAmpullae of Lorenzini

Sense electric fields generated by fishSense electric fields generated by fish TeethTeeth

Constantly replacedConstantly replaced Many sharks have to swim as they can not pump water over their gills Many sharks have to swim as they can not pump water over their gills

SharksSharks

ReproductionReproduction ClaspersClaspers

Males use claspers to Males use claspers to transfer sperm to transfer sperm to femalesfemales

Located between the Located between the pelvic fin and bodypelvic fin and body

EggsEggs All sharks have eggsAll sharks have eggs Some species have Some species have

eggs that hatch eggs that hatch internally and are then internally and are then born liveborn live

Some species lay an Some species lay an egg case known as a egg case known as a Mermaid’s PurseMermaid’s Purse

Bony FishBony Fish

Bony fishBony fish Skeleton made of Skeleton made of

bonebone Have vertebraeHave vertebrae Have scales covered Have scales covered

with mucuswith mucus Barrier against infection Barrier against infection

and reduces friction and reduces friction with the waterwith the water

Found in every aquatic Found in every aquatic environmentenvironment

Bony FishBony Fish

Obtaining oxygenObtaining oxygen

Use gillsUse gills Located under a Located under a

protective flap called protective flap called the operculumthe operculum

Mouth and operculum Mouth and operculum open at the same time open at the same time as water is drawn in by as water is drawn in by the mouth and passed the mouth and passed over the gillsover the gills

Bony FishBony Fish LocomotionLocomotion

NektonNekton As opposed to planktonAs opposed to plankton

FinsFins Some are paired, others Some are paired, others

are singleare single Paired: pectoral and pelvicPaired: pectoral and pelvic

movementmovement Single: dorsal, anal and Single: dorsal, anal and

caudalcaudal Stabilization and thrust Stabilization and thrust

(power)(power)

PedunclePeduncle Used as a major marker Used as a major marker

for determining speciesfor determining species Base of caudal finBase of caudal fin

Bony FishBony Fish

Pelagic v. BenthicPelagic v. Benthic Pelagic refers to those Pelagic refers to those

living in the middle of the living in the middle of the water column, open oceanwater column, open ocean

Benthic refers to those Benthic refers to those living on the bottomliving on the bottom

SpeedSpeed Depends on shapeDepends on shape Faster fish have more Faster fish have more

sharp angles and bigger, sharp angles and bigger, forked caudal finsforked caudal fins

Bony FishBony Fish

TemperatureTemperature Bony fish are ectothermicBony fish are ectothermic Their body temperature Their body temperature

depends on the depends on the temperature of the temperature of the environmentenvironment

BuoyancyBuoyancy Swim bladderSwim bladder Neutral buoyancy is when Neutral buoyancy is when

the fish neither sinks or the fish neither sinks or floatsfloats

Swim bladder contracts Swim bladder contracts and fish sinks, bladder and fish sinks, bladder expands and fish risesexpands and fish rises

Bony FishBony Fish FeedingFeeding

Parasitic (lamprey)Parasitic (lamprey) PredatoryPredatory Strainers (plankton-Strainers (plankton-

eaterseaters Suckers (use change Suckers (use change

in volume to suck prey in volume to suck prey into mouth)into mouth)

DigestionDigestion One-way digestive One-way digestive

system coupled with a system coupled with a closed circulatory closed circulatory system and 2-system and 2-chambered heartchambered heart

Bony FishBony Fish

ReproductionReproduction Takes place during spawningTakes place during spawning Sperm and eggs are released into the water or fertilization takes Sperm and eggs are released into the water or fertilization takes

place internallyplace internally Eggs develop either floating or attached to a substrateEggs develop either floating or attached to a substrate