Fish Form & Funcon Heyer Axial endoskeleton of a bony fish Fish Axial skeleton: Cranium & vertebral column • Fishes — aquatic vertebrates; axial skeleton only – Closed, single-circuit circulatory system • Class- Aganatha — jawless fishes • Class- Chondrichthyes — cartilaginous fishes Vertebra • Class- Osteichthyes — bony fishes Figure 3.02 Locomoon with an axial skeleton Fishes Class- Aganatha — jawless fishes • ~120 extant species (lampreys; hagfish) • Inner layer of mesoderm bloc becomes skeletal • Cartilaginous skeleton vertebrae • Jawless, suctorial mouth with many teeth • Outer layer becomes & protrusible toothed tongue myomere (muscle band) • Medial fin fold; No lateral (paired) fins • Proximal edge of myomere aaches to vertebrae • Distal edge of myomere projects posterio-laterally to insert into connecve ssue of skin • ... Contracon of muscle → lateral flexing body Fishes Fishes Class- Chondrichthyes — cartilaginous fishes Class- Chondrichthyes — cartilaginous fishes • Cartilaginous skeleton, but unique bone tissue present • Cartilaginous skeleton, but unique bone tissue present • Semi-rigid paired lateral fins connected across ventral body wall Subclass- Holocephali — ~ 40 spp. (chimeras) Subclass- Elasmobranchii — ~1,000 spp. (sharks; rays) • 5–7 gill slits [elasmo-branch: “strap gills”] • Protrusible upper jaw not fused to skull • Thick skin with dermal denticles Fins supprted by cartilagenous rods 1 Fish Form & Funcon Heyer Fishes Fishes Class- Chondrichthyes — cartilaginous fishes Class- Chondrichthyes — cartilaginous fishes • Cartilaginous skeleton, but unique bone tissue present Subclass- Elasmobranchii — ~1,000 spp. (sharks; rays) • Semi-rigid paired lateral fins connected across ventral body wall • Protrusible upper jaw not fused to skull CAT scan of a great white shark Lateral fins 1. Jaw opens (pectorals & pelvics) 2. Hyoid arch located ventrally springs jaw forward 3. Jaw protrudes Pelvic fins located near vent & closes 4. Hyoid & jaw Modified for copulatory organs (claspers) in males retract Fishes Class- Chondrichthyes — cartilaginous fishes Subclass- Elasmobranchii — ~1,000 spp. (sharks; rays) • Thick skin with dermal denticles Dermis packed with collagen fibers • Tough body wall • Semirigid aachement for swim muscles Goblin shark 1. Jaw opens 2. Hyoid arch springs jaw Dermal dencles (“skin teeth”) forward 3. Jaw protrudes • Armor & closes • Enlarge to make spine or sng 4. Hyoid & jaw • Streamlining retract in 1.4 seconds! • Anbacterial Fishes Fishes Class- Chondrichthyes Class- Osteichthyes — bony fishes Subclass- Elasmobranchii Subclass- Sarcopterygii — lobe-fin fishes • Jaws with oral denticles • 8 extant spp. (2 coelacanths + 6 lungfishes) • Dermal, not fused to jaw • Multiple rows Subclass- Actinopterigii — ray-fin fishes • Continually shed and replaced • ~30,000 extant spp. (more than all other vertebrates combined) Dynamic Lobe-fin fishes Ray-fin fishes membranous fin supported by flexible, segmented Fleshy fin rays with with bony individual supports acve control Fin margin supported by rigid rays 2 Fish Form & Funcon Heyer Ray fins can be raised and lowered; contorted into variable shapes; Fishes or even undulated or flapped like wings Class- Osteichthyes — bony fishes Subclass- Actinopterigii — ray-fin fishes • ~30,000 extant spp. (more than all other vertebrates combined) Swim: Thrust >> Drag • Body / Caudal fin propulsion • Other fin propulsion Fish Morphology Fish morphology tells us how fish body structures meet the specific demands of their habitats. It includes: • body forms • jaw shapes • fin shapes • tail shapes • coloration 3 Fish Form & Funcon Heyer Fish Form & Funcon Fish Form & Funcon 1. Perciform: “perch form” — generalist 2. Fusiform: bullet-shape; extremely streamlined; low turbulence; efficient long-distance cruiser; not so maneuverable Fish Form & Funcon Fish Forms & Funcon 4. Compressiform: laterally compressed; oval profile 3. Sagiform: “arrow form” — elongated, cylindrical body; — slow but highly maneuverable reef fish broad tail — fast acceleraon, but high drag — burst predator Fish Forms & Funcon Fish Forms & Funcon 6. Taeniform: “ribbon form” — (anguilliform) elongated, laterally 5. Depressiform: dorso-ventrally flaened; usually with large compressed body; usually with connuous fin fold and pectorals & upturned mouth — boom dwellers reduced/absent paired fins i. Crevice dwellers ii. Low energy, slow undulang swimming in low food systems 4 .