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Exploring the Diverse World of Fishes: An Overview

Dive into the fascinating world of fishes, the oldest vertebrate group with over 27,000 species. Learn about jawless fishes, cartilaginous fishes, bony fishes, and their unique characteristics. Discover the feeding habits, habitats, and reproduction mysteries of these aquatic creatures.

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Exploring the Diverse World of Fishes: An Overview

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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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