Chapter 12 Marine Fishes. Section 12.1 Protochordates and Jawless Fishes
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- Chapter 12 Marine Fishes
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- Section 12.1 Protochordates and Jawless Fishes
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- Objectives List the distinguishing features of the
protochordates and the jawless fishes Explain the importance of
studying protochordates Discuss the differences between the
protochordates and jawless fish.
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- Classification Phylum Chordata (Chordates) Hollow dorsal nerve
cord Notochord (flexible, rodlike, supports spinal cord) Pharyngeal
gill slits Protochordates first chordates Subphylum Vertebrata
(Vertebrates) Skeleton Backbone Skull Brain
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- protochordates Agnatha vertebrates
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- An evolutionary Connection Vertebrates include fish,
amphibians, reptiles, birds, and mammals. Vertebrates differ from
protochordates: Both have a notochord, but in vertebrate embryos it
develops into a backbone The ancestors of protochordates are the
link between invertebrate animals and vertebrates!
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- Protochordates Sea squirts (tunicates) Covered by a clear tough
membrane Incurrent/excurrent siphon Hermaphrodite with no self
fertilization External fertilization Larva is fishlike, with dorsal
nerve cord, a notochord, and gill slits Adult lives attached to
substrate and these structures dissappear
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- Tunicate Larva
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- Protochordates Lancelets (Amphioxus) Tiny, transparent,
fishlike Lives buried in sand, filter feeds plankton Adult retains
dorsal nerve cord, notochord, and gill slits Separate sexes
External fertilization and development
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- Lancelet
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- Jawless Fishes Superclass Agnatha without jaws The most
primitive of the vertebrates Lack jaws and a true backbone Adults
retain the larval notochord Two extant groups Hagfish Lamprey
Hagfish
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- Jawless Fish Sea Lamprey (Petromyzon marinus) parasitic Lives
in estuaries from Maine to Florida Uses sucking disk on its mouth
to attach to living trout and other host fish Uses teeth and
rasping tongue to make a hole, then sucks out blood and tissue
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- Sea Lamprey Damage
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- Jawless Fish Pacific and Atlantic Hagfish Use sharp teeth in
their rounded mouth to burrow into bodies of dead or dying fish
devour prey from the inside Secrete mucus (slime) when captured to
evade predators
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- Jawless Fish
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- Cartilaginous Fishes 12.2
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- Cartilage Cartilage is a flexible connective tissue composed of
cells and proteins Your ears, nose, and joints contain
cartilage!
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- Cartilaginous Fishes Class Chondrichthyes cartilage fishes
Contains Sharks, Skates, and Rays
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- Characteristics First Jawed fish Have placoid scales tiny teeth
embedded in the skin (feels like sandpaper) ventral gill slits
(breathing) with no flap Spiracles breathing holes behind each
eye
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- Characteristics Ventral mouth Rigid fins Pectoral fins provide
lift to prevent sinking and to glide
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- Rays and Skates Highly developed pectoral fins for swimming
Many are bottom dwellers Ventral mouth for bottom feeding
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- Rays Stingray (Dasyatis) Lives in the sand in the Gulf of
Mexico and from Carolinas to Brazil Sharp spine on tail for
defense
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- Skates Skate (Raja) No spine on tail Found in temperate waters
along the Atlantic and pacific coasts Eat crustaceans and mollusks
in subtidal zone
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- Sawfish Unusual Cartilaginous fish Virginia to Brazil, and the
Gulf Long bladelike snout full of teeth Uses snout as weapon to
stun and kill prey fish
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- Sharks! About 350 known species
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- Structure and Behavior Sharks are called living fossils because
they resemble some early ancestral forms Sharks have very sensitive
sensory receptors
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- Lateral line Organ A faint line along each side of a sharks
body Picks up sound vibrations over long distances
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- Sense of Smell Can detect small amounts of blood over half a
kilometer away 2/3 of the sharks brain is dedicated to
smelling!
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- Ampullae of Lorenzini Tiny pores in the sharks snout (rostrum)
Sense the electric fields generated by the muscles of fish and
other prey How might this be beneficial at night?
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- Body shape and Movement Sharks are streamlined for quickly
moving through water Accelleration accomplished by powerful muscle
contractions along the sides of body Move the caudal fin and
generate thrust
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- Teeth Predatory sharks have several rows of teeth Lost teeth
are replaced by new teeth from behind Hunneds of teeth!
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- Reproduction Internal fertilization Male sharks have claspers
between pelvic fins Transfer sperm into females reproductive tract
Claspers
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- Gestation and Birth Vivipary Live young develop inside mother
Ovovivipary Eggs hatch within mother Oophagy Hatched young eat
unhatched eggs Ovipary Eggs are laid and hatch externally
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- Mermaids Purse Egg casing produced by some sharks and skates
Black and leathery 1 or more embryos develop within (>1
year)