Fish and Amphibians

1. Fish and Amphibians Chapter 30 TURBOBLAST Edition!

2. What is a fish?? • All fish are: • Chordates, vertebrates, bilaterally symmetrical coelomates • Have endoskeleton, closed circulatory systems, nervous systems with complex brains & sense organs, efficient respiratory systems • Ichthyology: the study of fish (Gr: icthyes = fish)

3. Four classes of Fish • Cephalaspidomorphi • lampreys • Myxini • hagfish Agnatha “without jaws” (Gr: gnatho = jaw) • 2 classses: Chondrichthyes “cartilage fish” Osteicthyes “bony fish” Chimaerasharksskates & rays

4. Fishes breath using gills Fish takes in water through its mouth, water passes over gills and out side slits Oxygen & carbon dioxide are exchanged through capillaries in gill filaments

5. Fish have hearts, too! • All fishes have two-chambered heart • One chamber receives deoxygenated blood, the second chamber pumps blood directly to gills • Blood takes up oxygen in gills, pumped around the body, then back to the heart *This circulation allows fish to efficiently make ATP through cellular respiration!

6. Sexual reproduction • External fertilization in most fishes • Simultaneous release of gametes into water • Sometimes deposited in protected areas (plants, rocks, etc.) • Most fishes produce large #s of eggs at once, some produce small # of larger eggs • Cartilaginous fish have internal fertilization • Skates deposit fertilized eggs on ocean floor • Some sharks & rays carry developing young inside bodies • Spawning – bony fish (external fertilization & development), produce millions of eggs, provide little to no care for young, only a few survive until adulthood (ex. Salmon, cod) https://www.youtube.com/watch?v=Jgp6OjpfrQo • Some adults protect young fry when threatened by danger (Ex. Gouramis, cichlids, tilapia http://youtu.be/QkmmpSrbbjM

7. Pairs of fins & Movement • Fish in Chondrichthyes and Osteichthyes have paired fins • Fins are fan-shaped membranes used for balance, swimming, steering • Lobe-finned vs. Ray-finned fishes • Lobe-finned fishhave sturdy bone structure and stronger pectoral muscles, foreshadow the evolutionary development of all tetrapods on land • Ray-finned fish have webbed spines, comprise 99% of all fish species

8. Sensory systems in fish • Lateral line system • Enables fish to sense objects and changes in their environment • System of fluid-filled canals running along sides of fish, detect vibrations & movement in the water • Complex eyes • Can see objects and contrast in water • Vision varies greatly among fishes (some in darker waters have reduced, almost nonfunctional eyes • Sense of smell • Can detect extremely small amounts of chemicals in water, helps locate prey

9. Most Fish Have Scales • Cartilaginous & bony fishes have skin covered by overlapping scales (like roofing tiles) • Can be classified by the types of scales • Scales are thin bony plates formed from the skin

10. Evolution of the Jaw • Jaws evolved in fishes • Have the advantage of grasping & crushing prey • Fish with jaws could feed on greater variety of food • Sharks have up to 20 rows of razor-sharp teeth, pointing back into their mouth (stops prey from escaping)

11. Bony, flexible skeletons • Osteichthyes are most successful fish group • Skeletons are mineralized (w/ calcium) & rigid • Development of bone allowed fish to adapt to variety of aquatic environments, and eventually to land • Bony fishes have separate vertebrae for flexibility

12. Swim Bladders • Swim bladder is a thin-walled internal sac that fish can contract to change gas/liquid concentration • Squeeze  higher pressure, gas dissolves into liquid, fish can descend deeper • Relax  lower pressure, gas accumulates into bubbles, fish can rise toward water surface

13. Fish Diversity • Hagfish & Lampreys are jawless, and feed with a rasping, suckerlike mouth http://youtu.be/tKTRv3hx1s0http://youtu.be/-SYhOD1Yx10 • Skeletons are made of flexible cartilage • Hagfish create thick slime to avoid predators, tie into knots to slip out of tight spots while feeding http://youtu.be/pmaal7Hf0WAhttp://youtu.be/5kS64P-o5mU • Sharks, skates and rays are cartilaginous fishes • Similar to 100,000 year old fossils, considered “living fossils” • Sharks are most well-known predators of the oceans http://youtu.be/iLHTtDbtDFA • Rays & skates have flat bodies, feed near ocean floor http://youtu.be/9D06j__CZHs • Lobe-finned fishes – 6 species (ex. lungfish, coelacanth) • Ray-finned fishes - ~30,000 species (ex. catfish, perch, salmon, cod) http://youtu.be/cIgHEhziUxU

14. Origins of Fish • Fossils from the Cambrian Period 500 mya show the existence of fishes • Ostracoderms (early jawless fish) were dominant vertebrates • Possessed a cartilage skeleton and bony head plate • Most were extinct by the end of Devonian Period 354 mya • Present-day agnathans appear to be direct descendants • Ostracoderms swam sluggishly (weighed down by heavy, bony external armor) • Development of calcified bone in early vertebrates was important for muscle attachment, improved locomotion • Jawless ostracoderms are considered common ancestors of all fishes (and subsequent tetrapods) • Lobe-finned fishes appeared 395 mya (ex. Coelacanth http://youtu.be/NzzxOlFJtzg, lungfish http://i306.photobucket.com/albums/nn263/headbanger_jib/protopterus%20annectens/DSC_7437.jpg

15. Amphibians • What is an amphibian? • Gr: Amphi = “both,” bio = life  “double life” • Transition from aquatic larvae to air-breathing, semi-terrestrial adult is unique in amphibians • 3 orders in class Amphibia: • Caudata (salamanders & newts) • Apoda (caecilians) • Anura (frogs & toads) • All have moist skin, most have 4 legs, capable of terrestrial existence, rely on water for reproduction

16. Rely on external temperature • Amphibians are ectotherms, whose body temps depend on external sources • Usually found in warmer habitats • Become dormant when temperature ranges become too cold or too hot • Often bury themselves & wait out the harsh season

17. Metamorphosis Tadpoles have fins, gills, 2-chambered heart like fish Can avoid competition with adults by occupying a completely separate niche Eventually develop legs, lungs, and a 3-chambered heart (needed for life on land) • Fertilized egg  tadpoles (aquatic stage of most amphibians) • Young salamanders resemble adults but have gills and tail fins as larvae, while adults breathe only through skin • Most salamanders have 4 legs, but some have just 2 front legs

18. Walking takes energy! • Early amphibians required lots of food and oxygen to get around on land (they were uncoordinated on land) • 3-chambered heart enabled oxygen-rich blood to reach body tissues more efficiently • Some mixing of oxygen-rich & oxygen-poor blood happens, so as blood is pumped near skin, more gas exchange occurs across the moist skin • Most amphibians are limited to life on water’s edge or moist areas • Toads live in drier areas but still return to water to reproduce

19. Amphibian diversity • Not always easily seen, but numerous worldwide (Must complete part of life cycle in water) • Frogs & Toads (Anura) http://youtu.be/Tz1vyIavi_M • Salamanders & Newts (Caudata) http://youtu.be/jX3TGK1Ey9w • Caecilians (Apoda) http://youtu.be/DMvL4zOLSeM

20. What’s that sound? • Acoustic communication is essential for the frog's survival • Territorial defense and in localization and attraction of mates • Frogs can hear above and below water • Tympanic membrane (eardrum) size & distance apart is related to frequency of calls • The call or croak a frog makes is unique to its species, some species do not vocalize • Pass air through larynx (“voice box”) in throat, often amplified inflated with vocal sacs • Ex. Bullfrog http://youtu.be/M02_dnl9zCA, treefroghttp://youtu.be/080Dv8pV2y8wood frog http://youtu.be/BaTret-W7DASpotted toad http://youtu.be/j5vGZsCP1Co

21. Amphibian origins • 360 mya freshwater seas filled with carnivorous fishes • Early tetrapods may have used limbs to move among marshlands • Later fossils show ability to lift body off the ground • Ability to breathe air with lungs evolved • Adaptations necessary to provide support to land-heavy bodies, efficient respiration, membrane protection from dryer air (prevent water loss) • Challenges of life on land: • More O2, large food supply, shelter, no predators • But air changes temperature faster, bodies are clumsier on land • Some early amphibians had legs at right-angles to body • Became dominant terrestrial predators during warm, wet Carboniferous period 345 mya