Fig. 10-1

I. I.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

I. I.Fishes – Overview A. A.Agnatha Four chordate characteristics Brain protected by skull made of bone or cartilage 1. 1.Myxini (subphylum) – Hagfishes Unpaired fins Lack jaws Round, muscular mouth with dental plates Predators and scavengers (max length ~80 cm) How do they feed? videovideo 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

Fig. 10-3

I. I.Fishes – Overview A. A.Agnatha Four chordate characteristics + vertebral column Spine encloses and protects nerve cord 2. 2.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

Fig. 10-4

I. I.Fishes – Overview B. B.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

Fig. 10-5

I. I.Fishes – Overview B. B.Chondrichthyes (Cartilaginous fishes) 1. 1.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