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Lecture V. TheOsteichthyes
- - Common Characteristics
- - Class Actinopterygii
- - Class Sarcopterygii
Do bony fishes share any common characteristics?
- Osteichthyes has several defining characteristics:
- - bony ridge scales
- - fins supported by scales (vs.rods in Chondrichthyes)
- - skull (including jaws) and shoulder girdle composed largelyof dermal bone, with teeth rooted in jaws
- - gill slits covered by a bony operculum
- - swim bladder or lung for buoyancy and/or gas exchange
- - coiled intestine & ceca
- The 'ray-finned fishes' include approx. 1/3 of vertebrate species
- - fin rays form a "fan"
- - includes a few 'primitive' forms, with heavy scales and simple jaws (e.g. bichirs, sturgeons, bowfin)
- Actinopterygii also includes ~24,000 species of teleosts -e.g. tangs, triggerfish, suckers, bony-tongues, eels,pikes, tunas, perch, salmon, cod, sunfish, bass,haddock, barbs, angelfish....
Teleosts share several key adaptations:
- - a protrusible upper jaw
- - pharyngeal jaws with teeth
- - a homocercal tail
Teleosts are tremendously diverse:
- - habitats vary in terms of temperature, salinity, depth,dessication
- - scales vary in terms of size, shape, colour,modification
- - the skin includes many derivatives (flaps,barbels, poison glands...)
- - bodies vary in size and shape,and fins vary in size, shape,location and function
- - feeding habits vary widely
- - reproductive modesvary (courtship,fertilization, fecundity,parental care...)
- - migration habits vary (resident,anadromous [spawn in fresh water,mature in ocean], catadromous (spawnin ocean, mature in fresh water])
- - lifespan varies
- The ‘lobe-finned fishes’ includethe lungfishes and coelacanth:
- - heavy scales
- - fleshy fins with fin raysthat form a "feather"
- - lungs, and doublecirculation with a 3-chambered heart
- - may aestivate during droughts
- - early forms gave rise to the tetrapods...