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Fig. 10-1

Fig. 10-1. Fishes – Overview Oldest group of vertebrates (530 mya) 27,000+ species (15,600+ marine spp.) Four major groups Agnatha (Jawless fishes) Hagfishes, lampreys Chondrichthyes (Cartilaginous fishes) Sharks, rays, skates, ratfishes Actinopterygii/Osteichthyes (Bony fishes)

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Fig. 10-1

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  1. Fig. 10-1

  2. Fishes – Overview • Oldest group of vertebrates (530 mya) • 27,000+ species (15,600+ marine spp.) • Four major groups • Agnatha (Jawless fishes) • Hagfishes, lampreys • Chondrichthyes (Cartilaginous fishes) • Sharks, rays, skates, ratfishes • Actinopterygii/Osteichthyes (Bony fishes) • Most familiar fish species • Sarcopterygii • Coelacanths, lungfishes

  3. Fishes – Overview • Agnatha • Four chordate characteristics • Brain protected by skull made of bone or cartilage • Myxini (subphylum) – Hagfishes • Unpaired fins • Lack jaws • Round, muscular mouth with dental plates • Predators and scavengers (max length ~80 cm) How do they feed? video • Dig burrows in mud bottoms, usually cold water • Attack hooked or trapped fish • Capable of producing slime!! • Very flexible (can tie selves into knots) – Why? • Little known about reproduction • Exploited commercially – Eelskin wallets

  4. Fig. 10-3

  5. Fishes – Overview • Agnatha • Four chordate characteristics + vertebral column • Spine encloses and protects nerve cord • Petromyzontida – Lampreys • Unpaired fins • Lack jaws • Round, muscular mouth with dental plates • Most live in fresh water as adults • Marine species are anadromous, semelparous (ammocoete larvae) • Attach to other fishes, rasp away sides and suck blood • Also feed on benthic invertebrates

  6. Fig. 10-4

  7. Fishes – Overview • Chondrichthyes (Cartilaginous fishes) • Skeleton of cartilage (more flexible than bone) • Movable jaws (upper & lower) • Often contain well-developed teeth • Mouth usually ventral • Paired and unpaired fins • Unpaired • Dorsal • Caudal • Anal • Paired • Pectoral • Pelvic • Placoid scales • Similar to teeth (pulp, dentine, vitrodentine) • Liver (lipid-rich) used for buoyancy

  8. Fig. 10-5

  9. Fishes – Overview • Chondrichthyes (Cartilaginous fishes) • Sharks • Fusiform body • Heterocercal tail • Typically two dorsal fins • Pectoral fins usually large and pointed • Five to seven gill slits • Most sharks swim continuously to ventilate gills • Whale shark = Largest fish species (to 14+ m) • Planktivorous (zooplanktivorous) – How? • Most prevalent in tropical coastal waters • Reproduction • Internal fertilization (claspers) • Viviparous • Ovoviviparous • Oviparous

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