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Skelton & Muscles. Hagfish. No true vertebrae - sheath of cartilage surrounding notochord Few skull bones. Lamprey skeleton. Cartilaginous limited skull branchial basket. Chondrichthyes skeleton. Cartilaginous limited skull - 3 parts (chondrocranium, jaws, branchial cartilages).
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Hagfish • No true vertebrae - sheath of cartilage surrounding notochord • Few skull bones
Lamprey skeleton • Cartilaginous • limited skull • branchial basket
Chondrichthyes skeleton • Cartilaginous • limited skull - 3 parts (chondrocranium, jaws, • branchial cartilages)
Chondrichthyes skeleton • Cartilaginous • Pectoral, pelvic girdles, fin support
Osteichthyes skeleton • Solid bone with complete vertebral column • Simple vertebrae that lack interlocking processes • One vertebra per body segment - match with muscle masses for coordinated swimming movements
Osteichthyes skeleton Vertebrae modified anteriorly for skull articulation, posteriorly for caual fin articulation
Trunk vertebrae Vertebrae in middle are trunk vertebrae of two kinds: those with ribs and those without
Vertebrae • Vertebrae without ribs • Dorsal process • Neural arch with neural spine • Neural canal for spinal cord
Vertebrae • Ventral process • Hemal arch with hemal spine • Hemal canal for primary blood vessels (arteries, veins)
Spines provide support • Neural and hemal spines provide support for body musculature • Especially long in laterally compressed teleost fishes • “Double comb” appearance
Vertebrae • Vertebrae with ribs extending ventrally and dorsally • Extend between adjacent muscle masses • Dorsal ribs well developed in pike, suckers, minnows
Osteichthyes skull • >50 bones comprising 5 “groups” • Neurocranium • Suspensorium • Jaws • Opercular bones • Branchiohyoid apparatus
Neurocranium • Braincase • Most of the bones • Core of solid bone around the brain plus loosely articulated bones to permit feeding (suction) and respiratory (pump) movements
Suspensorium • Bones that connect (“suspend”) the braincase to the jaws
Jaws • Upper and lower jaws • Change from stiff, biting mouth to flexible, sucking mouth • Maxilla (primitive), premaxilla (advanced), dentaries
Opercular bones • No equivalent in jawless fishes or Chondrichthyes • Primary role in respiratory pumping • Advancements (from primitive condition) small, centered on improving efficiency
Branchiohyoid apparatus • Floor of the mouth, support for the gills • Includes the branchiostegal rays • Function in expansion of branchial chamber for respiration, suction feeding
Pectoral girdle • Fin rays articulate with radial bones (usually 5 radials) • Radials articulate with scapula, coracoid • These articulate with cleithrum, others • Cleithrum attached to skull
Pelvic girdle • Fin rays articulate with basipterygial bone • Basipterygials either united with each other, or with cleithrum/pectoral girdle complex in more derived teleosts
Dorsal, anal fin support Pterygiophores or interspinous bones
Segmental muscles -Right and left sides separated by vertical septum -Dorsal and ventral masses separated by horizontal septum
Epaxial, hypaxial muscles • Above horizontal septum - epaxials • Below horizontal septum - hypaxials
Red vs. white muscles -Red - rich in blood supply - aerobic swimming (slow) -White - poor in blood supply - burst swimming (fast) -Pink - intermediate -Color may be diet-based (carotenoids/crustaceans)