Skelton Muscles Hagfish w No true vertebrae sheath

Skelton & Muscles

Hagfish w No true vertebrae sheath of cartilage surrounding notochord w 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

Osteichthyes skeleton w Solid bone with complete vertebral column w Simple vertebrae that lack interlocking processes w 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

Specialized anterior vertebrae

Posterior vertebrae

Better view of posterior vertebrae

Trunk vertebrae Vertebrae in middle are trunk vertebrae of two kinds: those with ribs and those without

Vertebrae without ribs w Dorsal process w Neural arch with neural spine w Neural canal for spinal cord

Vertebrae w Ventral process w Hemal arch with hemal spine w Hemal canal for primary blood vessels (arteries, veins)

Spines provide support w Neural and hemal spines provide support for body musculature w Especially long in laterally compressed teleost fishes w “Double comb” appearance

Vertebrae with ribs extending ventrally and dorsally w Extend between adjacent muscle masses w Dorsal ribs well developed in pike, suckers, minnows

Nice photo

Vertebrae in various fishes

Osteichthyes skull

Osteichthyes skull w w w >50 bones comprising 5 “groups” Neurocranium Suspensorium Jaws Opercular bones Branchiohyoid apparatus

Neurocranium w Braincase w Most of the bones w Core of solid bone around the brain plus loosely articulated bones to permit feeding (suction) and respiratory (pump) movements

Suspensorium w Bones that connect (“suspend”) the braincase to the jaws

Jaws w Upper and lower jaws w Change from stiff, biting mouth to flexible, sucking mouth w Maxilla (primitive), premaxilla (advanced), dentaries

Opercular bones w No equivalent in jawless fishes or Chondrichthyes w Primary role in respiratory pumping w Advancements (from primitive condition) small, centered on improving efficiency

Branchiohyoid apparatus w Floor of the mouth, support for the gills w Includes the branchiostegal rays w Function in expansion of branchial chamber for respiration, suction feeding

Advanced fish skull

Pectoral, pelvic girdles

Pectoral girdle w Fin rays articulate with radial bones (usually 5 radials) w Radials articulate with scapula, coracoid w These articulate with cleithrum, others w Cleithrum attached to skull

Pelvic girdle w Fin rays articulate with basipterygial bone w Basipterygials either united with each other, or with cleithrum/pectoral girdle complex in more derived teleosts

Dorsal, anal fin support Pterygiophores or interspinous bones

Fish musculature

Segmental muscles -Right and left sides separated by vertical septum -Dorsal and ventral masses separated by horizontal septum

Epaxial, hypaxial muscles w Above horizontal septum - epaxials w Below horizontal septum - hypaxials

W-shaped myotomes

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)