2 General featuresany gill-bearing aquatic vertebrate (or craniate) animal which lacks limbs with digitsmost fish are ectothermic (Tuna, swordfish, and some species of shark are homoiothermic)has a streamlined bodyhas gills or an accessory breathing organhas two sets of paired finshas skin that is usually covered with scalesFishes are divided into two main classes: chondrichthyes(fishes with cartilaginous skeletons) and osteichthyes(bony fishes)
3 Fish Chondrichthyes Osteichthyes Elasmobranchii Sarcopterygii HolocephaliActinopterygii
4 Chondrichthyes (Cartilaginous fishes) jawed fish with paired finspaired naresscalestwo-chambered heartsskeletons made of cartilage rather than bonelarge, oily liver for buoyancyswim bladder and lungs are absentforward swimming only2 subclasses -Elasmobranchii (includes sharks , rays and skates)-Holocephali.
5 (A) Skeleton cartilaginous (cartilage is often partly calcified ) notochordlack ribsdo not have bone marrow (red blood cells -> spleen , epigonal organ , Leydig’s organ
6 (B) Scales (placoid scales or dermal denticles) covered with dermal teethtoothlike ( feel like sandpaper)protectionin most cases streamlining(C) Respirationbreathe through 5-7 gills (D)Excretionexcrete urea as nitrogen waste (they are ureotelic,like adult amphibians and mammals).Tuna gills
7 (E) Reproduction (Three types) OVIPAROUS like fish-- external fertilization of eggOVOVIVIPAROUS -embryos develop inside eggs - no placental connectionVIVIPAROUS - oppose to laying eggs
10 Osteichthyes (Bony fish) head and pectoral girdles are covered with large dermal boneeyeball is supported by a sclerotic ring of four small bonesa lung or swim bladderGas-filled swim bladder for buoyancyno fin spines (has lepidotrichia)an operculumbones are much heavier and less flexible than cartilageboth forward and backward swimming2 subclasses -Sarcopterygii-Actinopterygii
11 (A) Scales ( 2 types ) 1 . Ganoid scales covered by enamel like substance called ganoinfound in primitive bony fishes such as garsdiamond-shapedthicknon-overlapping
12 2 . Leptoid scalesfound on higher-order bony fishoverlap in a head-to-tail direction2 sub-groups- Cycloid scales Ctenoid scales*scaleless fish -sacrifice protection of scales presumably for added flexibility
13 (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 specieslobed paired fins, joined to the body by a single bonetwo dorsal fins with separate bases.3 subclasses - Coelacanthimorpha — Coelacanths- Dipnoi — Lungfishes- Tetrapodomorpha — Tetrapods and their extinct relatives
14 A specimen of Latimeria Chalumnae Queensland Lungfishes
15 (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 mouth2 subclasses - Chondrostei- Neopterygii
17 Excretion Reproduction excrete nitrogen as ammonia, NH3, (they are ammoniotelic)Reproductiongenerally is externalgametes are released in the water, where they can fecundate their counterpart andform the zygote.
18 Osteichthyes VS Chondrichthyes Chondrychthyes Osteichthyes