Transcript Marine Fishes - Somerset Academy

Marine Fishes
Chapter 8
Page 154
Vertebrates
• Subphylum Vertebrata
• Four fundamental characteristics:
– Have a backbone (Vertebral Column or spine with
vertebrae
– Nerve Cord (Spinal Cord) which is protected by
vertebrae.
– Bilaterally symmetical body
– Endoskeleton
Fishes
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Oldest, simplest vertebrates
Total of 30,000 species
24,000 known to science (15,300 are marine).
Make up half of the vertebrates on earth.
Three groups:
– Jawless (Agnatha) – Hagfish and Lampreys
– Cartilagenous (Chondricythes) – Sharks, Rays,
Skates, Ratfishes (Chimaeras).
– Bony Fishes (Osteichthyes)
Examples
Agnatha
• Considered Jawless fishes, as they
feed by suction with no jaws.
• Round mouth with rows of teeth.
• Body like an eel
• Do not have true vertebrae.
Hagfishes (Myxine)
• Also called Slime Eels (as produce slime
against predators.
• Feed on dead or dying fish
• Live in burrows in cold waters
• 20 species known
• Skin used to manufacture leather goods
• Will attack bait lines
Lampreys (Petomyzon)
• Freshwater fishes
• Breed in freshwater, move to the sea as
adults
• Parasitic – attach to other fish and suck their
blood or feed on invertebrates.
• 30 species
Cartilagenous Fishes (Chondricthyes)
• Cartilage – lighter and more flexible than
bone.
• Moveable jaws with well-developed teeth
• Mouth ventral, or underneath head
• Paired lateral (side) fins for efficient swimming
• Placoid skin scales – sandpaper like with a tip
pointed backwards (can cause bleeding)
Sharks
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Similar to species from 100 million yrs ago.
Very agile
Tail (Caudal fin) is well developed,powerful.
Tail is heterocercal (upper lobe longer)
Two dorsal (upper) fins – first triangular
Paired pectoral (chest or breast) fins – large
and pointed
• Five to seven gill slits (behind the head and on
each side of the body).
• Numerous rows of teeth that shift forward like
a conveyor belt
Example of body structure
Example of teeth
Body plan
• Hammerhead head serves as a rudder
(directional) with eyes on edges
• Sawsharks – mouth is under a blade with
teeth on the edge.
• Thresher sharks – large tail kills fish to eat
Size variations
• Spined pygmy shark – Only 10 inches long
• Whale shark – largest fish of all – filter feeder
– feeds on plankton – 60 feet long
• Basking shark – filter feeder – 30-40 feet long
• Great White – Up to 20 feet in length
Locations
• Throughout all oceans
• Mostly in tropical coastal waters (Florida) –
definitely during breeding
• Bull shark can travel up rivers and lakes in the
tropics (salt and fresh water)
• Larger sharks found in deep water.
Reproduction
• Are being overfished in many areas of the world,
so reproduction numbers are very reduced.
• Whitetip sharks are only at 1% of population in
1950 (60 years).
• Killed for shark oil and skin (used to make
shagreen (leather) and sandpaper.
• Finning is common for shark fin soup – animal
caught, fins cut off while alive, animal dumped
back into water to attract other sharks.
• People believe that the cartilage can help with
arthritis
• Fishing of sharks is now managed in most
countries, and certain species are illegal to fish.
Examples
Attacks
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25 species of shark have attacked humans
Most dangerous: Great White, Tiger, Bull Sharks
Average of 61 attacks, with 2/3 in U.S.
Portrayed as hideous creatures, but just looking for food.
Most sharks inflict bites, then leave and wait for prey to
weaken before eating.
• No known shark repellent
• What attacts them?
– Garbage, seals, sea lions, blood, urine, feces.
– More active at night
– Attracted to splashing, as think it is fish or mammals in distress.
**They eat most of the dead biomass in the oceans, so they are a
vital predator for the oceans.**
Rays and Skates
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Approximately 500 species
Flattened bodies
Live on ocean floor (Demersal)
Some look like sharks, but are not classified that
way.
Five pairs of gills slits on underside (ventral) of
body.
Pectoral fins expanded to look like wings.
Eyes on top of the head
Rays are Vivaprous – give birth to live young.
Stingrays
• Also Eagle ray, Bat ray, and Cow Nosed Ray
• Whip-like tail with stinging spine at base
• Wounds caused by the venom (injected) by whiplike action or stepping on them.
• Most wounds caused by mishandling or
accidental encounters, as under the sand.
• Eat clams, crabs, small fish and invertebrates.
• Teeth are grinding plates that crush their prey
Electric Rays (Torpedo)
• Special organs that produce electricity on each
side of the head.
• Deliver shocks of up to 200 volts to stun fish and
discourage predators (Electrical outlets produce
110 – 120 volts – Appliances take 220-240 volts).
• Considered the original shock treatment used by
the Greeks and Romans to cure headaches.
Skates (Raja)
• Similar to rays in appearance and feeling
• Lack a whip-like tail and stinging
apparatus.
• Some do give an electric shock
• They lay egg cases (oviparous) in which
their young mature before being born.
• Are fished for food in some parts of the
world.
Ratfishes (Chimaeras)
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30 species
One pair of gill slits (Operculum)
Some have a tail
Feel on bottom dwelling crustaceans and
molluscs.
Bony Fishes (Osteichthyes)
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Skeleton made partially of bone
23,000 species – 96% of fishes
More than half live in the ocean.
Cycloid (ctenoid) scales – can be smooth or have
tiny spines. Covered by a thin layer of skin and
mucus.
• Operculum – A gill cover that is a flap of tissue
and plates to protect the gills.
Bony Fish (Con’t)
• Caudal Fin (tail) lobes are Homocercal (same size)
• Fins have fin rays or bony spines in them for support
• The finds can protect, steer, maneuver, or move them
forward.
• Mouth terminal (located at one end)
• Teeth attached to jawbone and are replaced, but not
like a conveyor belt.
Bony Fish (Con’t)
• ** Swim Bladder** - This is a gas filled sac just
above the stomach and intestines that helps
the fish to adjust their buoyancy.
• Helps to compensate for a heavy bony
skeleton.
• How they seem to float in the water.
• Helps them also stay deeper if they need to.
Body Shape
• Directly related to lifestyle
• Streamlined – Open water fish
• Laterally compressed – Inshore fish (snapper,
damselfishes, etc..)
• Demersal – Flattened – Rays and Skates
• Flatfishes – Live on bottom – Flounder, Halibut **Body is actually laterally (on one side)
compressed – Both eyes on top (Eye migrates
from the side to the top during their lifetime)!!
• Distinctly Elongated – Narrow spaces – Eels and
Pipefishes.
• Useful for camouflage.
Examples
Coloration
• Can be used for camouflage (cryptic coloration),
breeding, mood, warnings of venom, break up
outline (Disruptive coloration), Disguise in open
water (Countershading – sharks have).
• Color found in chromatophores (special cells in
the skin that can contract and expand to change
the fishes color).
• Structural colors – Are constructed of crystals
that reflect light called Iridophores – Why some
fish are so shiny.
Coloration Examples
Locomotion
• Used to get food, escape from predation, breeding, and
oxygenation.
• See Page 162 – Mostly swim in an S-pattern (like snakes).
• Move forward using muscle contractions with bands
muscle called Myomeres.
• Most bony fish are mostly muscle.
• Sharks have to keep swimming constantly, as they do not
have a swim bladder. The oil in the liver, the fins, and the
tail compensate.
• Most bony fish can maneuver, as have swim bladder. Some
can hover or move backwards, as fins not needed for
bouyancy.
• Tails and pelvic fins mostly used for rudder control.
• Some fish now “walk” on their fins on the bottom of the
ocean.
• Remoras get around by attaching to other fish.
Locomotion Examples
Feeding
• Most sharks are carnivorous – A tiger shark
caught off South Africa had eaten the front half of
a crocodile, find leg of a sheep, three seagulls,
and two cans of peas.
• Cookie cutter sharks cut out chunks of flesh from
still living organisms (they have even attacked
submarines).
• Filter feeders – Whale shark, basking shark,
manta ray, megamouth shark. They filter the
water through their gill arches, and the spaces in
between the arches determines how much they
catch.
Feeding (Con’t)
• Most bony fish are carnivorous – can catch prey
in sediment, on rocks, or on the bottom.
• Some chase prey, others lie in wait.
• Usually have well-developed teeth to hold prey or
a very large mouth to hold, chew, then swallow.
• Some eat only sponges, some eat only coral,
some eat sea cucumbers, some eat dead material
only.
• Grazers – fish that eat seaweed and plants only.
(algae off of coral).
• Some fish eat only plankton (herring, sardines
and anchovies).
Digestion
• Digestion begins for fish in their actual stomach.
• The stomach may be curved into a J-shape, may be a
grinding structure, or there may not be one.
• Then, in the intestine, there are Pyloric Caeca which
secrete digestive enzymes.
• The pancreas also secretes enzymes and the liver
secretes bile to break down the fats.
• If the fish is a grazer, their intestines are coiled , or
there may be a Spiral Valve, which increases surface
area to help fully digest meals.
• Any digestible nutrients get passed into the blood.
• All other waste passes out the Cloaca (handles all
waste and reproductive systems).
Digestion Example
Circulatory System
• Two Chambered heart (below the gills)
• Blood flows from body (de-oxygenated) into
first chamber. Then pumped backwards to
second chamber , then pumped to gills for
oxygenation, then out to rest of body.
Respiratory System
• Paired gills are where fish obtain oxygen and
release carbon dioxide – the gills lie in the
pharynx (chamber behind the mouth).
• Gills have to be constantly irrigated or ventilated
with water flow for fish to get oxygen.
• Irrigation occurs through swimming and opening
and closing of the mouth (some sharks).
• When fish are caught in a net, they drown, as
they cannot swim to force water over the gills
(that is why they open and close their mouths
continuously).
Respiratory System (Con’t)
• For sharks, there is expansion and contraction
of the pharynx walls and gill slits.
• Each gill has its own chamber and separate gill
slit.
• The first pair of gills behind the eye is
modified into spiracles (round openings that
help cartilaginous fishes take in water no
matter the circumstances).
Respiratory System Example