02 Sept. 2014 Fishes.ppt 1
FISHES
02 Sept. 2014 Fishes.ppt 2
Fishes
• All fishes retain four (4) primitive characters:• Streamlined body
• Vertical tail fin
• Gills for gas exchange
• Lateral line system, • No ears
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Fishes
• Three traditional vertebrate classes that remain aquatic. Class Bony Fishes Class Cartilaginous Fishes Class Jawless Fishes
• All three classes well adapted to aquatic environment.
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Class Bony Fishes
• Also called “Ray-finned Fishes” • ~30,000 species.
Majority of living vertebrate species. Bony skeleton, well developed skull Fins supported by cartilage or bony “rays”
and minute scales (=lepidotrichia) • paired fins:
• pectoral, pelvic
• median fins: • dorsal, anal, caudal
02 Sept. 2014 Fishes.ppt 5
Bony Fishes• Fins
• paired fins: • pectoral, pelvic
• median fins: • dorsal, anal, caudal
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Bony Fishes• Bony dermal scales• covered by thin epidermis
• NOT homologous to reptilian scales.
• Operculum covers gills; one gill slit each side.
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Bony Fishes
• Lungs, often modified to swim bladder.• Examples: • sturgeons• gars• catfish• trout• bass• Northern pike• American eel
• note paired fins, jaw, operculum
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Class Cartilaginous Fishes • 400 - 600 spp. • Skeleton of cartilage, bone lost.
Fossil placoderms and jawless fishes had bone tissue, prob. ancestral to both Cartilaginous & Bony fishes.
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Class Cartilaginous Fishes
• Cartilaginous skull poorly developed, esp. dorsal to brain
• Fins supported by cartilage or horn-like rays
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Cartilaginous Fishes
• No ribs.
• No lungs or swim bladder.
• Separate gill slits, usually 5
• Placoid scales, – tiny, tooth-like
• Enlarged at edge of mouth teeth – Homologous to teeth in all
other vertebrates.
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Cartilaginous Fishes• Sharks, • Rays
specialized flattened sharks
“wings” are pectoral fins
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Development of Jaws
• All animals studied so far are “Jawed Vertebrates”• Jaws developed from an anterior gill arch,
Allowed diverse diet
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Class Jawless Fishes
• Survivors of earliest vertebrates• No jaws,
can not close mouth
• No scales• No paired fins, only median caudal fin
(continues dorsal & ventral to anus)• Single median nostril on top of head • Circular gill slits
7 or 12 pairs on sides of pharynx.
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Jawless Fishes
• Hagfishes tentacles around mouth predators on worms,
mollusks scavengers 20 spp. in 4 genera
• Lampreys circular mouth, no tentacles filter feeders, or external parasites of bony
fishes 30 spp. in 10 genera
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Jawless Fishes
• Life cycle of sea lamprey• Adult parasitic, feeding
stage
• Adults swim into small freshwater streams to breed
• Larvae live in sediment as filter feeders up to seven years
• Metamorphosis, migration to lake or sea to become parasitic adults
02 Sept. 2014 Fishes.ppt 16
Jawless Fishes• Sea lamprey in the Great Lakes
• Lake Ontario since end of last Ice Age, prevented from entering upper lakes
• Welland canal• Sea lamprey devastated commercial fishing• Control
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Overview of where we have been
• All animals studied to date belong to:
• Phylum Chordatanotochorddorsal nerve cordpharyngeal arches/clefts
• bear gills in fishes,
• modified to other structures in terrestrial animals
postanal tail
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Review
• Subphylum VertebrataNotochord reduced, replaced by bony or
cartilaginous vertebrae• Some notochord tissue usually remains
Pharyngeal arches bear gills • or developed into other organs: hyoid bone, larynx
LiverPancreas
02 Sept. 2014 Fishes.ppt 19
Review• Subphylum Vertebrata• 6 Classes:• Jawless fishes
• Cartilaginous fishes
• Bony fishes
• Amphibians
• Reptiles including Birds
• Mammals
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Invertebrate Chordates
• Two more subphyla of Chordata, lack distinguishing characters of Vertebrates:
Subphylum Urochordata • tunicates, sea squirts
Subphylum Cephalochordata • lancelets, amphioxus
Subphylum Urochordata
• Adult is sessile filter-feeder
• Larva shows all characters of Phylum Chordata
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Subphylum Cephalochordata
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• Adult and larva show characters of Phylum Chordata
• Live in holes in sandy or muddy bottoms• Ciliated pharynx pulls in
water
• Filtered water exits atriopore
• Food directed to intestine , feces disposed through anus