Icthology study of fish

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Icthologystudy of fish
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Phylum Chordata

• Subphylum Vertebrata
• Superclass Agnatha (jawless)
• Class mixini hagfish
• Class cephalaspidomorphi lamprey

HAGFISH
LAMPREY
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• Subphylum Vertebrata
• Superclass Gnathostomata (jaw mouth)
• Class Chondrichthyes cartilage fish
• Subclass Elasmobranchi sharks, rays, skate
• Class Osteoichthyes bony fish

SKATE
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SUPER CLSS AGNATHA

• Superclass Agnatha 70 species
• General Characteristics
• 1. Body long, cylindrical (eel like)
• 2. No scales, jaws, or paired fins
• 3. Two chambered heart
• 4. 3-16 pairs of gills
• 5. poikilothermic having a body temperature
  that varies with the temperature of its
  surroundings

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• Hagfish
• Marine, feed on dead or dying organisms (not
  parasitic)
• When caught, secretes enormous quantities of
  slimy mucus
• Enters body of an animal through gills, mouth, or
  anus and eats the contents of the body leaving a
  sack of bones and skin
• Lamprey
• 40 species, fresh and marine water, parasitic

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• Reproduction (Hagfish and Lamprey)
• Both ovaries and testes present, but only one is
  functional
• Males build nests in spring and fertilization is
  external (2-65,000 eggs)
• Adults die after spawning
• Eggs hatch into larvae and burrow into sand or
  mud
• Emerge at night to feed, blind and toothless
• Larval form for 3-7 years
• Metamorphosis into adult takes about 4-11 months

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• Economic importance
• Fish bait
• Lamprey is food for humans
• FYI
• Portuguese and Spanish diners prize sea lamprey
  as a gourmet treat for which they're willing to
  pay up to 25 a pound. European fishers harvested
  local lamprey so much that populations on that
  side of the Atlantic are crashing, allowing
  demand for this prehistoric boneless fish to
  exceed supplies.
• So what does lamprey taste like? "I would have to
  say it tastes like lamprey," says Chef Bob
  Bennett, "because it does not have a flavor that
  you can associate with anything else."
• When pushed further, he volunteered that "its
  taste is not offensive. A lot of delicacies that
  I've been introduced to over the course of my
  career are a lot less palatable - such as the sea
  urchin."
• Hagfish will damage fish caught in net or line

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Some differences between sharks and fish
Sharks Fish Made of cartilage Made of bones
and cartilage Can only swim forward Can swim
forwards and backwards Uses oil for
buoyancy Uses gas-filled swim bladder for
buoyancy Eggs fertilized in females body Eggs
fertilized in water Skin is rough like
sandpaper Slippery scales on skin
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CLASS CHONDRICHTHYES

• External features
• Head, trunk, tail

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• Dorsal fins keep upright
• Caudal fins forward thrust
• Heterocercal - dorsal lobe is larger than
  ventral
• Homocercal dorsal and ventral lobes are the
  same size
• Pectoral and pelvic fins steering

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• Clasper (male) on pelvic fin used in mating

• They use one at a time
• After communicating its intentions to a receptive
  female shark through ritualized swimming and
  gentle 'love nips' along her back or flanks, the
  male grasps one of her pectoral fins and docks
  next to her.
• If the male happened to dock along the left side
  of the female, he flexes his right clasper across
  the mid-line of his body and inserts it into her
  vent (genital opening).

MALE
FEMALE
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• Mouth ventral
• Eyes lower lids to cover eye when feeding
• Gill slits 5-7 pairs used for water to exit
• Spiracle modified gill slit on top of head
• Purpose provide oxygenated blood directly to the
  eye and brain through a separate blood vessel.
• Absent or reduced in many sharks, especially the
  fast swimming sharks and is usually larger and
  present in bottom dwelling sharks. 
• In the rays, the spiracle is much larger and more
  developed and is used to actively pump water over
  the gills to allow the ray to breathe while
  buried in the sand.

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• Vent- opening to cloaca analogous to anus
• Latin sewer
• Cloaca - common chamber that intestinal, urinary,
  and genital tracts open.
• FYI It is present in amphibians, reptiles,
  birds, sharks, and monotremes. A cloaca is not
  present in placental mammals or in most bony
  fishes.

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• Lateral line sensory system detecting and
  locating objects
• Made of cells called Nematocysts (sensitive gel
  filled cells that transmit signals to nerves)
• Sensitive to vibrations and currents

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• Ampullae of Lorenzini gel-filled pores on face
• sense bioelectric fields
• A biolelectric field surrounds all animals.
  Sharks can even detect animals under the sand!
• It looks like a 5 oclock shadow

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• Placoid scales backward pointing spine covered
  by enamel

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• Skeleton cartilage
• Axial skull and vertebral column
• Appendicular pectoral girdle (front fins) and
  pelvic girdle (pelvic fins)

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• Digestive system
• Mouth
• Teeth -replaced throughout life of fish
• Tongue -immobile
• Esophagus -short
• Stomach -J shaped
• Pylorus -valve
• Intestine -spiral valve
• Cloaca -common chamber
• Vent -anus
• Liver -very large, oily, purifies blood
• Gall bladder -near top of liver, stores bile
  collected from liver and passes bile to
  intestines through bile duct
• Pancreas between stomach and intestine,
  secretes digestive enzymes that are released into
  intestine
• Rectal gland located near most posterior part
  of abdominal cavity regulates excess salt
  received from food and water

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• Coelom
• Peritoneum lining the abdominal cavity
• Made of layers
• Outer layer - parietal peritoneum, is attached to
  the abdominal wall
• Inner layer - visceral peritoneum, is wrapped
  around the internal organs located in inside the
  abdominal cavity
• Mesenteries membranes that attach organs to the
  abdominal wall, hold intestine in place

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• Circulatory System
• Sharks have a two-chambered heart, with an atrium
  (aka auricle) and a ventricle.
• Heart is covered by a visceral pericardium
• The heart is S-shaped
• ventral aorta transports blood to the gills
• dorsal aorta takes blood back to the heart
• Vessels
• Carotids carry blood to and from head
• Subclavians carry blood to and from pectoral
  fins
• Meaning subclavical, under the clavical
• Renal carry blood to and from kidneys
• Have you ever heard of renal failure in cats?
  Renal is from the Latin word renes which means
  kidneys
• Iliacs carry blood to and from pelvic fins
• From the Latin word ilia describing the bones
  that make up the pelvis

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Some Review
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• Sketch a shark LABEL the
• Anterior dorsal fin
• Posterior dorsal fin
• Homocercal caudal fin
• Pelvic fin
• Pectoral fin

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• 2. What is the function of the spiracle?
• 3. What is the function of the ampullae of
  lorenzini?
• 4. Why do sharks have a large liver?
• 5. What is the function of the clasper?
• 6. What is the function of the cloaca?

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• 9. What kind of fish eats out the insides of a
  dead organism?
• 10. What class do sharks belong to?
• 11. What class do bony fish belong to?
• 12. What shape is the sharks stomach?
• 13. How many chambers are in a sharks heart?

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• Sketch a shark LABEL the
• Anterior dorsal fin
• Posterior dorsal fin
• Homocercal caudal fin
• Pelvic fin
• Pectoral fin

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• 2. What is the function of the spiracle?
• Provide oxygenated blood directly to eyes and
  brain
• 3. What is the function of the ampullae of
  lorenzini?
• Sense bioelectric field
• 4. Why do sharks have a large liver?
• Produces oil
• 5. What is the function of the clasper?
• Reproduction (male part)
• 6. What is the function of the cloaca?
• Common chamber for intestines, urinary, and
  genitial

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• 9. What kind of fish eats out the insides of a
  dead organism?
• hagfish
• 10. What class do sharks belong to?
• Chondrichthyes
• 11. What class do bony fish belong to?
• Osteoichthyes
• 12. What shape is the sharks stomach?
• J
• 13. How many chambers are in a sharks heart?
• two