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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
24-1
Superclass Osteichthyes: Bony Fishes n 2 major classes
n Ray-finned fishes, class Actinopterygii, radiated to form modern bony fishes
n Lobe-finned fishes, class Sarcopterygii, include lungfishes and the coelacanth
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
24-2
n Modern Day Bony Fish n Constitute 96% of all living
fishes and half of all vertebrates
n Range from 10 millimeters to 17 meters long, and up to 900 kilograms in weight
n Some can live in hot springs at 44o C (111.2oF) while others survive under Antarctic ice at - 2o C (28.4oF)
n Some live in salt concentrations three times seawater
n Others found swamps devoid of oxygen
Class Actinopterygii: Ray-finned Fishes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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n Heavy dermal armor replaced by light, thin, flexible cycloid and ctenoid scales n Some eels, catfishes, and others
lost scales n Increased mobility to avoid
predators and improve feeding efficiency
n Provide greater mobility and serve a variety of functions n Braking, streamlining, and social
communication n Homocercal tail allowed greater
speed and buoyancy n Jaw changed to increase suctioning
and protrusion to secure food
Class Actinopterygii: Ray-finned Fishes
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24-4
Structural and Functional Adaptations of Fishes
Locomotion in Water n Mechanism
n Trunk and tail musculature propels a fish using undulations and/or the fins.
n Muscles are arranged in zigzag bands called myomeres n Have the shape of a W on the side of fish n Internally the bands are folded and nested n Each myomere pulls on several vertebrae
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24-5
Neutral Buoyancy and the Swim Bladder
n Fish are slightly heavier than water
n To keep from sinking, a shark must continually move forward
n Shark liver has a special fatty hydrocarbon, or squaline, that acts to keep the shark a little buoyant
n Swim bladder, as a gas-filled space, is the most efficient flotation device n Fish controls depth by
adjusting volume of gas in swim bladder
Structural and Functional Adaptations of Fishes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
24-6
Hearing and Weberian Ossicles
n Fish, like other vertebrates, detect sounds as vibrations in the inner ear.
Structural and Functional Adaptations of Fishes
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24-7
Respiration n Fish gills are filaments with plate-
like lamellae n Gills are covered with a movable
flap, the operculum for protection and to streamline the body
n Pumping action by operculum helps move water through gills
n Water flow over gills is continuous n Water flow is opposite to the
blood flow to maximize gas exchange
n Some active fishes use ram ventilation to force water across gills
Structural and Functional Adaptations of Fishes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
24-8
Osmotic Regulation n Freshwater fish have tissue with a
high salt concentration n Kidney works to pumps excess
water out n Special salt-absorbing cells
actively move salt ions from water into fishes’ blood
n Marine bony fishes have tissue with low salt concentration n Tend to lose water and gain
salt n Risks “drying out”
n To compensate for water loss, a marine fish drinks seawater n Brings in more unneeded
salt n Carried by blood to gills
and secreted by special salt-secretory cells
Structural and Functional Adaptations of Fishes
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24-9
Feeding Behavior n Most fish are carnivores
n Feed on zooplankton, insect larvae, and other aquatic animals
n Most fish do not chew food which would block water flow across the gills
n A few can crack prey items teeth or have molar-like teeth
n Most swallow food whole n Easy with water pressure that
sweeps food in when the mouth opens
n Others are herbivores, suspension feeders, omnivores, scavengers, detritivores, or parasites
Structural and Functional Adaptations of Fishes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
24-10
Reproduction and Growth n Most fishes are dioecious with external
fertilization and external development n Guppies and mollies represent ovoviviparous
fish that develop in ovarian cavity n Some sharks are viviparous with some kind
of placental attachment to nourish young n Most oviparous pelagic fish lay huge
numbers of eggs n Female cod may release 4–6 million eggs
Structural and Functional Adaptations of Fishes