Chapter 16 Fishes

2 Fish  Fish/fishes  Characteristics: –gill breathing –ectothermic –aquatic –fins –scales on epidermis –larger the fish, faster it can swim

3 2 Superclasses:  A. Superclass Agnatha –Class Myxini (Slime) hagfishes (70 species)  Agnathans- lack jaws  Marine  live buried in the sand and mud  No paired appendages (fins)  cartilaginous skeleton  No vertebrae  Naked skin

4  Eel-like  4 pair of barbels on mouth  Keratinized teeth  10 cranial nerves  Three accessory hearts  No distinct stomach  Able to produce lots of slime through glands  Food in Asian cultures

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6 Figure 24.03b

Hagfish mouth 7

Hagfish slime 8

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11  Class Petromyzontida “stone” “sucking” lampreys lampreys  marine and freshwater  Move pebbles to build nest  suckerlike mouth with teeth  Neural arches present  feeds on other fish  1950’s destroyed trout industry in G.L.s

12 Figure 24.06

Lamprey mouth 13

Lamprey attached to trout 14

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17  B. Superclass Gnathostomata – “jaw” “mouth” –7 Classes:  1. Class Chondrichthyes – cartilaginous –(1000 species) –most marine –most carnivores or scavengers –placoid scales –cartilaginous endoskeleton

18 Subclass Elasmobranchii – Sharks, skates and rays (930 species)  Sharks: –Tough skin covered with placoid scales –teeth are modified placoid scales –carnivores –Good vision (far-sighted) –keen sense of smell –Lateral line system  Neuromasts are special receptor organs that sense vibrations –Ampullae of Lorenzini are electroreceptors in the head –no swim bladder – most have to keep moving  Heavier than water so sink if not swimming “sinkers”

19 –internal fertilization:  male has a modified pelvic fin called a clasper  Ovoviviparous (yolk sac)  oviparous (egg laying)  Viviparous (placenta) –Size:  Smallest: Pygmy ribbontail catshark (6-7 inches) Pygmy ribbontail catshark (6-7 inches) Dwarf Lanternfish (7 - 8 inches) Dwarf Lanternfish (7 - 8 inches) Spined pygmy shark (7- 8 in.) Spined pygmy shark (7- 8 in.)  Largest: Whale shark (50 feet) (50 feet)

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24 Placoid scales

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26 Ancient Megalodon

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29 Spined Pygmy Shark

30 Whale Shark

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32  Skates and rays: –live on ocean floor in shallow water –pectoral fins are winglike –Large spiracles on dorsal side where water enters –Teeth adapted for crushing –Stingrays have one or more spines on the tail to wound prey –Electric rays have powerful electrical organs which can stun prey –Skates are usually more boxy in shape

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36 Little Skate

37 b. Subclass Holocephali (35 species) Chimaeras, ratfish, rabbitfish, elephant fish “monster” “ghostsharks”  Long fossil record  Deep sea  Operculum over gills  No spiracle  Three pair of teeth plates (grind)  No stomach  No ribs  Not usually commercial  Pearly iridescence colors

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40 Elephant fish

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42 2. Class Sarcopterygii - “fleshy” “fin” (8 species) Lungfish –Paired muscular lobes with fins –lungs for gas exchange –Skeleton with bone from endochondral –Embedded dermal scales –Teeth covered with true enamel –Operculum –Double circulation –Dioecious, fertilization external or internal

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44 African lungfish

45 Australian lungfish

46 South American lungfish

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48 Figure 24.23

49Coelacanth

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51 3. Class Actinopterygii – “ray” “fin or wing” 3. Class Actinopterygii – “ray” “fin or wing” (20,000 species) (20,000 species) Bony fish Bony fish –most diverse class of all vertebrates –characteristics  Endochondral bone replaces cartilage  operculum covering gills  swim bladder for buoyancy  have ganoid, cycloid or ctenoid scales  Single circulation, nucleated erythrocytes

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53 a. Subclass Chondrostei (50 species) (50 species) Sturgeons, Paddlefish Sturgeons, Paddlefish –Primary cartilage –Lack scales on most of body –Caudal fin heterocercal like sharks (sturgeon) –Rostrum extending past mouth –Spiracle present –Endangered (sturgeons) because of caviar  Black caviar—Beluga most expensive  $3,000 for 16 oz.

54 Sturgeon

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57 Gathering caviar

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59 Paddlefish

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63 b. Subclass Neopterygii “new” “fins” b. Subclass Neopterygii “new” “fins” (27,000 sp) Characteristics: Characteristics:  Primarily bone  Move rapidly  Lighter  Jaws more powerful  Caudal fin usually homocercal –Two groupings:  a. Non-teleosts: gars, bowfins  b. Teleosts: “complete” “bone” –all the rest of the fish (96%) –38 orders ending in “formes”

64 Gars

65 Bowfins

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67 Teleost

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70 A Few Interesting Fish Facts  Tail Shapes: –Heterocercal  Sharks  Sturgeons –Homocercal  Bony fish –Diphycercal  Lungfish  Hagfish

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72  Migration: –Anadromous – live in marine but will spawn in freshwater (Salmon) –Catadromous – live in fresh but will spawn in marine (Freshwater eels)

73 Figure 24.37

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75 Figure 24.33

76  Growth: –1. Fish will grow as long as they live –2. Scale rings show number of years just like trees

77 Figure 24.38

78  Egg production: –produce huge numbers – 4-6 million –more marine, more eggs –some have nests that are watched over –adhesive eggs stick to rocks –bury in sand –keep in mouth –male seahorses carry in pouches –450 kg sturgeon will produce 45 kg of caviar

79 Figure 24.35

80 Figure 24.36