Marine FishesMarine FishesRead Chapter 9 Pages 154- 178Read Chapter 9 Pages 154- 178

ChordatesChordates

All chordates have (at least during some All chordates have (at least during some period of their life)period of their life)– Dorsal nerve cordDorsal nerve cord– Gill slitsGill slits– NotochordNotochord– Post-anal tailPost-anal tail

These are the 4 basic characteristics of all These are the 4 basic characteristics of all chordates.chordates.

Bridging the gapBridging the gapChordates w/o backboneChordates w/o backbone

TunicatesTunicates– Not fish but chordatesNot fish but chordates

Lancelets: Not a Vertebrate, but a ChordateLancelets: Not a Vertebrate, but a Chordate– Chordate characteristics throughout life-Chordate characteristics throughout life-– But no backboneBut no backbone– Subphylum CephalochordataSubphylum Cephalochordata

The FishesThe Fishes

Note: The term Note: The term fish fish refers to a single fish or a refers to a single fish or a group of the same species of fish.group of the same species of fish.

FishesFishes refer to more than one species of fish. refer to more than one species of fish.

FishFish

Structurally simplest living vertebratesStructurally simplest living vertebrates Probably ~30,000 speciesProbably ~30,000 species At least half of all known vertebrate species At least half of all known vertebrate species

are fishesare fishes At least half of all known fishes are marine At least half of all known fishes are marine First appeared about 500 million years ago First appeared about 500 million years ago

and were the first vertebratesand were the first vertebrates– every other vertebrate has ultimately descended every other vertebrate has ultimately descended

from a fish-like ancestorfrom a fish-like ancestor

Three major groups of FishThree major groups of Fish

Jawless fishes (Agnatha)Jawless fishes (Agnatha) Cartilaginous fishes (Chondrichthyes)Cartilaginous fishes (Chondrichthyes)

– Sharks and rays (elasmobranchs)Sharks and rays (elasmobranchs)– Ratfishes (chimeras) (Holocephalins)Ratfishes (chimeras) (Holocephalins)

Bony fishes (Osteichthyes)Bony fishes (Osteichthyes)– Lobe-finned fishesLobe-finned fishes– Ray-finned fishesRay-finned fishes

Jawless FishesJawless Fishes

Most primitive living fishesMost primitive living fishes Feed by suction with a round, muscular Feed by suction with a round, muscular

mouth and rows of teethmouth and rows of teeth Long, cylindrical bodyLong, cylindrical body No paired fins or scalesNo paired fins or scales Lampreys are parasites on other fishes and Lampreys are parasites on other fishes and

suck on their blood; hagfish typically feed on suck on their blood; hagfish typically feed on dead animalsdead animals

Jawless FishJawless Fish

Cartilaginous FishesCartilaginous Fishes

Sharks, rays, skates, chimeras (ratfishes)Sharks, rays, skates, chimeras (ratfishes)– Skeleton is made of cartilage, which is lighter Skeleton is made of cartilage, which is lighter

and more flexible than boneand more flexible than bone– Moveable jaws with well-developed teethMoveable jaws with well-developed teeth– Paired lateral fins for efficient swimmingPaired lateral fins for efficient swimming– Rough skin due to placoidscalesRough skin due to placoidscales

SharksSharks In some form, sharks have In some form, sharks have

been around for about 400 been around for about 400 million years. million years.

Even before dinosaurs Even before dinosaurs roamed the earth, sharks roamed the earth, sharks hunted through the hunted through the oceans! They're such oceans! They're such good survivors that they've good survivors that they've had little need to evolve in had little need to evolve in the last 150 million years. the last 150 million years.

Scientific Information: Scientific Information: Sharks belong to the class Sharks belong to the class of fish, Chondrichthyes.of fish, Chondrichthyes.

More on Sharks to come More on Sharks to come in a later lecture!!!in a later lecture!!!

Skates vs. RaysSkates vs. Rays

SkatesSkates– Oviparous (lay eggs)Oviparous (lay eggs)

Mermaids purseMermaids purse

– Do not have barbs, Do not have barbs, have thorns on their have thorns on their dorsal area or tailsdorsal area or tails Placement and number Placement and number

varyvary

– Small teethSmall teeth

RaysRays– Viviparous (bare Live Viviparous (bare Live

young)young)– Have BarbsHave Barbs

Above tailAbove tail

– In general, largerIn general, larger Tail almost 2x’s as long Tail almost 2x’s as long

as bodyas body

– Plate Like TeethPlate Like Teeth

Skates and RaysSkates and Rays

Flattened bodyFlattened body Large pectoral finsLarge pectoral fins

Rat Fishes (Chimeras)Rat Fishes (Chimeras)

Bizarre-looking, primarily deep-sea, Bizarre-looking, primarily deep-sea, cartilaginous fishescartilaginous fishes

Have only one pair of gill slits instead of 5-7Have only one pair of gill slits instead of 5-7 Have a long rat-like tailHave a long rat-like tail Feed on crustaceans and molluscsFeed on crustaceans and molluscs

Cartilaginous vs. Bony FishCartilaginous vs. Bony FishCartilaginousCartilaginous skeleton made of cartilage skeleton made of cartilage possess movable jaws mostly with possess movable jaws mostly with

powerful teeth. powerful teeth. mouth is located ventrally (under mouth is located ventrally (under

the head). the head). presence of paired lateral fins presence of paired lateral fins

allows for efficient swimming. allows for efficient swimming. skin is covered with small scales skin is covered with small scales

that have the same composition as that have the same composition as teeth.teeth.

BonyBony Skeleton made (at least partially) of Skeleton made (at least partially) of

bone bone Thin, flexible, overlapping scales Thin, flexible, overlapping scales

along the body along the body A flap of bony plates and tissue A flap of bony plates and tissue

known as the gill cover, or known as the gill cover, or operculum, that protects the gills operculum, that protects the gills

Protruding jaws with more freedom Protruding jaws with more freedom of movement than cartilaginous fish of movement than cartilaginous fish

The presence of a swim bladder The presence of a swim bladder – helps buoyancy and compensates helps buoyancy and compensates

for the relatively heavier bony for the relatively heavier bony skeleton skeleton

Highly maneuverable fins Highly maneuverable fins

Cartilaginous Vs. Bony – ExternalCartilaginous Vs. Bony – External

Cartilaginous vs. BonyCartilaginous vs. Bony

Cartilaginous vs. BonyCartilaginous vs. Bony

Cartilaginous vs. BonyCartilaginous vs. Bony

Cartilaginous vs. BonyCartilaginous vs. Bony

Extinct No MoreExtinct No More

Subclass Sarcopterygii-Once known only for Subclass Sarcopterygii-Once known only for fossils and thought to be extinct for 60 fossils and thought to be extinct for 60 million years-Named Latimeriachalumnaemillion years-Named Latimeriachalumnae

Preserved specimen of the Coelacanth is Preserved specimen of the Coelacanth is located in the HMNHlocated in the HMNH

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Fish Form and FunctionFish Form and Function