Phylum Chordata subphylum Vertebrata Share the 4 chordate

Phylum Chordata, subphylum Vertebrata • Share the 4 chordate characters with lancelets and sea squirts • Backbone, vertebral column, spine – Series of hollow vertebrae – Protects nerve cord (spinal cord) • Bilateral symmetry • endoskeleton

Agnatha (jawless fishes) • Lack: paired fins, scales, & well developed vertebrae • Hagfish (slime eels) – Mucus for protection – Feed on decaying flesh • Lampreys – Parasitic – Anadromous • Marine adults, breed in freshwater

Chondrichthyes (cartilagenous fishes) • Sharks, rays, skates, & ratfishes • Movable jaws of ventral mouth • Paired fins • Placoid scales – Dentricles (same composition as teeth)

Sharks • • Heterocercal caudal fin Two dorsal fins Paired pectorals 5 -7 gill slits Many rows of teeth Oily liver Diverse examples: hammerhead, sawfish, thresher, whale sharks

Rays, Skates, & Ratfishes • Flattened • Demersal • 5 prd ventral gill slits • Expanded pectorals Rays vs. skates rays: reduced or no dorsal fin – Stingrays • Venomous defensive spine – Electric rays • Upto 200 volts for defense and predation – Ratfishes (chimaeras) • Deep, bottoms, long skinny tail • Paired (pelvic) & unpaired (forehead) male claspers for copulation & holding female --seen in rabbitfish

Osteichthyes (bony fishes) • • Swim bladder Operculum (gill cover) Homocercal tail Scales of bony origin – Smooth cycloid – Spiny ctenoid

• Diverse morphologies, habits, & behaviors • Tear flesh; most swallow whole by: snout; protrusible; beak-like; large filtering mouths • Undulating entire body; muscular caudal flex; fins only; caudal fin only

Digestive systems • • Mouth Esophagus Stomach Intestine w/ increased SA – spiral valve – pyloric caeca • Pancreas – Digestive enzymes • Liver – Bile to breakdown fats • cloaca or anus

Circulatory system: 2 chambered heart (“one way flow”) …atrial chamber to gills, “fresh” blood to tissues, back to ventricle chamber

a. ) Water across gills through mouth and spiracles in cartilagenous fishes – Why are spiracles significant? b. ) Opercula of bony fishes opens and closes with mouth; greater suction; more efficient

Gill function and diffusion of gas • High surface area from many folds or lamellae of gill filaments • The water : blood relationship is in a counter-current orientation -enhances diffusion – higher [Oxygen] in water than blood

Osmosis a. ) concentrated urea prevents dehydration to deal with excess salts; excrete via rectal gland b. ) to compensate for tissue water loss: drink sea water, conserved by kidneys, excrete urine

Fish reproduction & development • Internal fertilization – w/specialized copulatory structures • External fertilization – Broadcast spawning • Millions of eggs released as part of plankton – Some fishes deposit eggs on bottoms – Some bury in sandy shores • Unique examples: – Male carriers • • e. g. At Birch aquarium Oviparous – Eggs released, fertilized, developed externally, lots of yolk • Viviparous – Internal development, direct nourishment; birth live young • Ovoviviparous – Internal egg development; yolk; birth live young