BIOL 2003 Lecture Notes - Lecture 17: Dermal Bone, Fish Scale, Osteichthyes
Osteichthyes
November 4 2015
Gnathostomata
• Chondricthyes – sharks and rays
• Teleostomi
o Osteichthyes
o Acanthoids
o Tetrapods
Osteichythes – Bony fish
• Dermal bone in humans inherited from bony fish
Internal Skeleton:
• Vertebrae with centrum
• Braincase
• Ribs
• Fin girdles
Dermal Skeleton:
• Outer skull – where human face structure is derived
o Could be found in ancestor of chondricthyes
• Operculum
• Fin rays – derived from dermal bone
• Scales – part of external dermal skeleton
• Teeth – external armour *chondricthyes
Central vertebrae (bony) is not an ancestral trait in osteichthyes and cephalo..?
Bones within a human arm are part of endoskeleton
Complex skull is associated with complex feeding mechanisms.
Scales in Chondrichthyes and Osteichthyes:
• Placoid scales – cartiligenous fish
• Ganoid scale – nonteleost bony fishes
• Cycloid scales – teleost fishes
• Ctenoid scales – teleost fish
Soma many contain dentine and enamel. Therefore, scales derived from armour of early armour agnathan
fish (as are teeth).
• Scales in osteichthyes are living bone – not external covering
• Bony scales overlap with mucous glands and epidermis for preventing infection and balancing ion
concentration/water
• Therefore, all wet hands before touching fish to prevent osmotic shock
Life in Water: Differences from land/air
• Respiration: oxygen is less abundant
• Water and ion balance: exchanges with eater
• Buoyancy: swim bladder for neutral buoyancy
• Hearing: lateral lines (pick up vibrations), Weberian ossicles
o Transmitted in low vibrations within a dense medium
• Locomotion: push against water
• Feeding: suction
o Through series of complex bones within the head
o Suction occurs efficiently due to water medium
• Use electricity to see through electroreception
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