Fishes

What is a chordate? At some point in life, they have: –Notocord –Dorsal hollow nerve cord –Post-anal tail –Pharyngeal slits At some point in life, they have: –Notocord –Dorsal hollow nerve cord –Post-anal tail –Pharyngeal slits

Invertebrate Chordates? Protochodates –Lancelets and tunicates –Have all other characteristics but no vertebrae Protochodates –Lancelets and tunicates –Have all other characteristics but no vertebrae

Fishes First and most abundant vertebrates Evolve about 500 MYA Minimum species (half of all verts) Major groups: –Jawless (Agnatha) –Cartilaginous (Chondrichthyes) –Bony (Osteichthyes) First and most abundant vertebrates Evolve about 500 MYA Minimum species (half of all verts) Major groups: –Jawless (Agnatha) –Cartilaginous (Chondrichthyes) –Bony (Osteichthyes)

Agnatha Jawless fishes Lack true vertebrae Hagfish and lampreys NYRr_MrjebAhttp:// NYRr_MrjebA Jawless fishes Lack true vertebrae Hagfish and lampreys NYRr_MrjebAhttp:// NYRr_MrjebA

Chondrichthyes Cartilaginous fishes Sharks, rays, skates and ratfish Cartilaginous fishes Sharks, rays, skates and ratfish

Characteristics Cartilaginous skeleton Ventral mouth with moveable jaws Paired lateral fins Rough skin (Placoid scales) Cartilaginous skeleton Ventral mouth with moveable jaws Paired lateral fins Rough skin (Placoid scales)

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Sharks

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Are Sharks Dangerous?

Are Sharks Dangerous?

Who’s number one?? 1.Great White 2.Tiger 3.Bull Others: Sand Tiger, Hammerhead, Shortfin Mako 1.Great White 2.Tiger 3.Bull Others: Sand Tiger, Hammerhead, Shortfin Mako

Why do sharks attack?

Other explanations?

Fear the... Deer?? Animal Fatalities (avg/yr) –Deer = 130 (vehicular) –Dogs = 18 –Snakes = 15 –Mountain lions = 0.6 –Sharks = 0.4 (statistics from International Shark Attack File) Animal Fatalities (avg/yr) –Deer = 130 (vehicular) –Dogs = 18 –Snakes = 15 –Mountain lions = 0.6 –Sharks = 0.4 (statistics from International Shark Attack File)

Who is the bigger threat?

Rays and Skates

Characteristics Dorsoventrally flattened Ventral gill slits Expanded pectoral fins Few scales Small or plate-like teeth Dorsoventrally flattened Ventral gill slits Expanded pectoral fins Few scales Small or plate-like teeth

What’s the difference? Rays –Viviparous –Whip-like tail with stinging spine Rays –Viviparous –Whip-like tail with stinging spine Skates –Oviparous –Broader tail with apparent dorsal fins Skates –Oviparous –Broader tail with apparent dorsal fins

Ratfish (Chimaeras) Mostly deep water Prey on crustaceans and mollusks Mostly deep water Prey on crustaceans and mollusks

Bony Fishes (Osteichthyes) 96% of fishes Fresh and saltwater 96% of fishes Fresh and saltwater

Sensory/Nervous System CNS - Brain w/ spinal cord Olfactory sacs Complex moveable eyes (adjust position to focus) Lateral line Ampullae of Lorenzini Inner ears - hearing and equilibrium CNS - Brain w/ spinal cord Olfactory sacs Complex moveable eyes (adjust position to focus) Lateral line Ampullae of Lorenzini Inner ears - hearing and equilibrium

Territoriality Some establish permanent homes More common with crowding (ex. Reefs) Agonistic encounters Some establish permanent homes More common with crowding (ex. Reefs) Agonistic encounters

Schooling Coordination maintained by vision, lateral line, olfaction, etc. Advantages? Disadvantages? Coordination maintained by vision, lateral line, olfaction, etc. Advantages? Disadvantages?

Migration Periodic mass movements Daily, yearly, once in a lifetime Vertical or horizontal Why migrate? Guidance? Anadromous vs. Catadromous Periodic mass movements Daily, yearly, once in a lifetime Vertical or horizontal Why migrate? Guidance? Anadromous vs. Catadromous

Reproduction/Development Internal vs. external fertilization Male, female or both? Courtship behavior Oviparous, ovoviviparous, viviparous Larval metamorphosis Internal vs. external fertilization Male, female or both? Courtship behavior Oviparous, ovoviviparous, viviparous Larval metamorphosis