diversity of fishes
DESCRIPTION
Also some vertebrate background.TRANSCRIPT
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1. Diversity of Fishes
Kingdom - AnimaliaPhylum - Chordata
3 Classes: Agnatha, Chondrichthyes, Osteichthyes
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Vertebrates:
• Ex: fish, amphibians, reptiles, birds, & mammals • Have a notochord (slim, flexible rod) present in early
stages that may be replaced by backbone in adults • Contain a dorsal, hollow bundle of nerves called the
nerve or spinal cord • Respire through pharyngeal or gill pouches during
early development • Have post-anal tail in early stages • Endoskeleton made of bone &/or cartilage • Anterior head with well developed brain & sensory
organs (Cephalization) • Closed circulatory system
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Taxonomy: 1. Class Agnatha: hagfish & lamprey-long,
eel-like bodies without jaws or paired fins & cartilage skeletons
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Agnatha (Jawless Fish): • Hagfish& lampreys• Circular mouths that can’t close• Sharp teeth & strong, raspy tongue-tears hole in
prey & sucks out blood & body fluids• Eel-shaped body • Skeleton made of cartilage • No paired fins • Gills – no operculum• Hagfish: benthic in cold marine waters-burrow in
mud, scavenge on dead & dying fish, & have tentacles around their mouth
• Lampreys: usually parasitic with keen sense of smell to locate prey, lay eggs in freshwater streams, & are covered with a poisonous slime
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Lamprey with Prey
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2. Class Chondrichthyes include sharks, rays, & skates also with cartilage
skeletons, paired fins, & jaws
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Characteristics of the more advanced fishes:
• Streamlined body & muscular tail for swimming (know the differences between tail shapes!)
• Most have paired fins for maneuvering • Body covered with protective scales & mucus layer to reduce
friction when swimming • Have less dense body tissues & store less dense lipids to
help them float • Respire through gills • Most have lateral line system or sensory structures running
down each side of the organism to detect changes in water temperature, pressure, current, etc.
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• Most w/ well-developed sense of sight & smell
• Most can detect electrical currents
• Ectotherms (body temperature close to envtl.)
• Two chambered heart (upper atrium receives blood & lower ventricle pumps blood)
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Class Chondrichthyes
• Includes sharks, rays, & skates
• Endoskeleton of cartilage
• Hinged jaws & paired fins
• Placoid scales & tooth-like dermal spines on scales
• Most Marine
• Most Carnivorous
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Sharks vs. Rays
• Sharks are torpedo shaped=“fusiform”
Rays & skates have broad, flat bodies with wing-like fins and a tail
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Shark Characteristics:• Large, oily liver (20% of body weight) makes them buoyant• Have protective coloration (darker top & lighter bottom)
(AKA countershading)• Whale shark is largest & filter feeds on plankton• Ventral mouth with 6-20 rows of sharp, replaceable teeth • Short, straight intestine with spiral valve to slow food
movement • 5-7 pairs of gills for gas exchange • Kidneys remove wastes & maintain water balance • Electroreceptors on head help find prey & navigate • Lateral line along side of body contains sensory cells to
detect vibrations & pressure • Separate sexes with external fertilization
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Ray & Skate Characteristics:
• Usually harmless to humans • Broad, wing-like pectoral fins used to glide
through water • Flattened bodies with ventral mouth • Both eyes on top of head • Have protective coloration (darker on top &
lighter on bottom) - countershading• Feed on fish & invertebrates • Stingray with poison spine by tip of tail• Electric ray gives off strong, electric shock • Manta ray is largest
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Traits of Bony Fish (Class Osteichthyes)
• Skeleton made of bone • Hinged jaws • Paired fins • Gills for gas exchange • Lateral line • Body covered with scales & mucus coating • Includes lobe-finned, ray-finned, and lung fish
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Ray-finned Fish:• Fan-like fins supported by rays • Includes salmon, perch, catfish, tuna, etc. • Have movable fins • Dorsal fin (s) located on top-keep fish upright & used
for defense • Caudal fin (tail) moves side to side to help steer • Pectoral fins (paired) on each side behind the
operculum • Pelvic fins (paired) on ventral surface near the head • Anal fin (single) behind anus
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Ray-finned Fish (cont.):
• Swim bladder thin-walled sac in abdomen that creates buoyancy from diffusion of dissolved gas from blood
• Kidneys filter blood & help maintain water balance • Ectothermic - body temperature regulated by envt.• Keen sense of smell (nostrils) & have chemical
receptors over the body • Can detect the earth's magnetic field as a guide to
navigate oceans • Have separate sexes & external fertilization • Eggs hatch into fry
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Body covered with round, overlapping cycloid or ctenoid scales & mucus
Four sets of gills covered by bony operculum
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External Anatomy of a Bony Fish
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Guess What These Are:
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Sites for Help on Vertebrates & Fish in Particular
• http://www.infovisual.info/02/033_en.html
• http://kentsimmons.uwinnipeg.ca/16cm05/1116/chordate.htm
• http://www.fishbase.org/home.htm