Post on 13-Jan-2017
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 pectoralsRays 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