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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
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