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Fish Ho Suet Ying 6S (8)
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General features any gill-bearing aquatic vertebrate (or craniate) animal which lacks limbs with digits most fish are ectothermic (Tuna, swordfish, and some species of shark are homoiothermic) has a streamlined body has gills or an accessory breathing organ has two sets of paired fins has skin that is usually covered with scales Fishes are divided into two main classes: chondrichthyes(fishes with cartilaginous skeletons) and osteichthyes(bony fishes)
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Fish Chondrichthyes Osteichthyes Elasmobranchii Sarcopterygii
Holocephali Actinopterygii
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Chondrichthyes (Cartilaginous fishes)
jawed fish with paired fins paired nares scales two-chambered hearts skeletons made of cartilage rather than bone large, oily liver for buoyancy swim bladder and lungs are absent forward swimming only 2 subclasses -Elasmobranchii (includes sharks , rays and skates) -Holocephali.
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(A) Skeleton cartilaginous (cartilage is often partly calcified )
notochord lack ribs do not have bone marrow (red blood cells -> spleen , epigonal organ , Leydig’s organ
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(B) Scales (placoid scales or dermal denticles)
covered with dermal teeth toothlike ( feel like sandpaper) protection in most cases streamlining (C) Respiration breathe through 5-7 gills (D)Excretion excrete urea as nitrogen waste (they are ureotelic, like adult amphibians and mammals). Tuna gills
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(E) Reproduction (Three types)
OVIPAROUS like fish-- external fertilization of egg OVOVIVIPAROUS -embryos develop inside eggs - no placental connection VIVIPAROUS - oppose to laying eggs
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Bullhead and its egg Catfish and its egg
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Osteichthyes (Bony fish)
head and pectoral girdles are covered with large dermal bone eyeball is supported by a sclerotic ring of four small bones a lung or swim bladder Gas-filled swim bladder for buoyancy no fin spines (has lepidotrichia) an operculum bones are much heavier and less flexible than cartilage both forward and backward swimming 2 subclasses -Sarcopterygii -Actinopterygii
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(A) Scales ( 2 types ) 1 . Ganoid scales
covered by enamel like substance called ganoin found in primitive bony fishes such as gars diamond-shaped thick non-overlapping
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2 . Leptoid scales found on higher-order bony fish overlap in a head-to-tail direction 2 sub-groups - Cycloid scales Ctenoid scales *scaleless fish -sacrifice protection of scales presumably for added flexibility
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(A) Sarcopterygii (fleshy-finned fish)
2 subclasses : Sarcopterygii & Actinopterygii (A) Sarcopterygii (fleshy-finned fish) a clade (traditionally a class or subclass) of fleshy-finned or lobe-finned vertebrates. only eight living species lobed paired fins, joined to the body by a single bone two dorsal fins with separate bases. 3 subclasses - Coelacanthimorpha — Coelacanths - Dipnoi — Lungfishes - Tetrapodomorpha — Tetrapods and their extinct relatives
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A specimen of Latimeria Chalumnae
Queensland Lungfishes
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(B) Actinopterygii ( ray-finned fish )
possess lepidotrichia or "fin rays" Considered more “advanced” than (A)Sarcopterygii – increased caudal symmetry - trend toward homocercal tail – fin membranes with fewer rays – reduction in dermal armor – loosening of maxillary and premaxillary bones, leading to a rounded mouth 2 subclasses - Chondrostei - Neopterygii
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Gar Fish (Neopterygii) Nile Bichir (Chondrostei)
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Excretion Reproduction
excrete nitrogen as ammonia, NH3, (they are ammoniotelic) Reproduction generally is external gametes are released in the water, where they can fecundate their counterpart and form the zygote.
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Osteichthyes VS Chondrichthyes
Chondrychthyes Osteichthyes
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Sources http://en.wikipedia.org/wiki/Osteichthyes
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