FISH PART TWO:

AGNATHACHONDRICHTHYES

OSTEICHTHYES

Phylum ChordataSubphylum Vertebrata

Fish: General

24,000-30,000 species of fish 15,000 marine

95% Osteichthyes 1,000 Chondrichthyes

~350 known shark sharks

Osteichthyes and Chondrichthyes

General Characteristics seen in these groups:o Highly efficient gillso Scales cover the bodyo Streamlined o Paired fins o A wide variety of jaw and feeding typeso Lateral line and other sensory organs

show the position of fins in cartilaginous and bony fish

Osteichthyes

95% of all fish species ~23, 000 species

Skeleton composed of bone

Paired finsHinged jawsHomocercal tail

lobes equal sizeFlat bony scales

Ctenoid-tiny spines on borders (b)

Cycloid-smooth (a)

Fins

Caudal Fin Forward movement

Dorsal and anal fins provide steering and stability – keep it from rolling

Pectoral and pelvic fins help it turn, balance, and brake

Osteichthyes

NaresBony operculum covers

gills protection

Lateral line Sensory and

communicationSwim bladder

Air-filled bladder Buoyancy control Lacking in sharks

Varied Body shape

Dependent on their environment

Soles and Flounder Flat shape Bottom dwellers Bury themselves in

sand as camouflauge

Varied Body shape

Tuna and BillfishFusiform =streamlined,

strong, fast swimmers Long Fins as rudders-not

flexible Caudal fin flexible Predators

caudal peduncle (area just before the tail) is very thin – this allows all the muscles to concentrate in this area allowing for greater thrust of the caudal fin = FAST

Varied Body shape

Reef fishCompressed body shapeThin, quick, short bursts

of speed. Ex: Angelfish

Do not inhabit open oceans

Coral, oyster reefs Feather like fins

Flexibility Allows for greater control

around features

Varied Body shape

EelsElongated body

Live in crevices Live among rocks

Body shape for Camouflage

Shape allows for camouflage, Ex: Kelp fish, Pipe fish, trumpetfish, stone

fish,

camouflage fish

Coloration

Warning coloration Using colors to advertise danger, poison, bad tasting

Cryptic coloration Blending with environment to deceive prey and predators

Some can change color

Disruptive coloration Presence of stripes, bars, spots to break up outline of fish

body In groups, hard to distinguish just one fish

Countershading Light bellies (blend with sun when looking up) Dark backs-blend with depths/bottom when looking down

Swimming Patterns

“s-shaped” swimming patternBands of muscle along the body, myomeres,

drive this swimming motionDepending on the type of fish, different fins

may be used primarily for the forward movement

Sharks: Swimming, Oily liver

In sharks, swim bladder absent a large lipid-rich liver to help in buoyancy

Sharks tend to sink when not in motion and there is no lift from the swim bladder while swimming either

While swimming, sharks aided by the “lift” provided by the position and stiffness of pectoral fins

Bony fish: Swimming

Pectoral fins are not needed for lift therefore normally not stiff in construction Exception: fast swimming species like tuna, billfish

Pectoral fins are often flexible and used for maneuverability

In some slower-swimming species, forward movement provided by pectoral fins

Respiration

Gills Covered by

operculum for protection

Exchange of oxygen and carbon dioxide takes place on gill filaments

Feeding

Mouth size and location reveals dietary preferences

“Beak” (fused teeth) in parrotfish scrape algae and other

organisms off of hard surfacesButterfly fish

long tube-like mouth to feed on corals

Barracuda uses rows of sharp teeth and a wide

mouth to capture its prey – other fish

Forward mouth-chase preyHerring

Larger mouth-filter feeder

Regulating Internal Environment: Bony Fish

Salt water solute-rich, blood less saltier than water

Salt water fish lose water through osmosisOsmoregulation = the process of managing

internal water/solute balanceA variety of ways to osmoregulate include:– Many fish swallow seawater – expel the solutes through kidneys and

special cells on gills called chloride cells. – Kidneys conserve water-small amounts of

urine.

Regulating Internal Environment: Cartilaginous fish

• Blood is kept at about the same concentration as seawater• Keep urea in the bloodstream (this toxin is

filtered out of the blood by other organisms)• Urea—product made when proteins broken down

• This means no solutes are gained or water lost because the concentration internally and externally match

Reproduction

Both sexes have paired gonads in the body cavity

Spawning happens during the most favorable conditions , timed with sex hormones

The release of them is triggered by environmental factors-many unknown Day length, temperature, food availability

Nassau Grouper spawning

Reproductive Behavior

Many species migrate to breeding or spawning grounds at certain times

Color change to advertise readiness to breedCourtship--series of behaviors to attract mates

Dances, displaying colors, swimming upside down Each species has a unique courtship; this keeps them from mating

with other speciesSome fishes have internal fertilization

Mainly cartilaginous fishes, using the claspersMost have external fertilization – gametes are releases

into the water to fertilize (broadcast spawning)Female can release millions of eggs

Most of the eggs released into the plankton don’t survive, but some do

Billfish spawning

Early Development

Most fishes spawn eggs – oviparous The yolk sac provides energy during development After a few days they hatch into free-swimming

larvae, or frySome fishes give birth to live young (the

eggs hatches inside) - ovoviviparous Mostly cartilaginous fishes

Some live embryos get nourishment from the uterus before born –Viviparous

Secret Lives of Baby Fish-TED Ed