Fishes

1. Fishes Chapter 39

2. Introduction to Vertebrates Section 39.1

3. Vertebrate Characteristics • Only 1 phylum: Chordata • Three distinguishing characteristics: • Vertebrae: bones or cartilage that surrounds and protects dorsal nerve cord (spine) • Cranium: skull that protects the brain • Endoskeletoncomposed of bone or cartilage

4. 3 Subphyla in Chordata • Subphylum Cephalochordata (ex. Lancelets) • Subphylum Urochordata (ex. Sea Squirts) • Subphylum Vertebrata (ex. all other familiar animals) • All contain: notochord, dorsal nerve cord, pharyngeal pouches, and postanal tail at some stage of life • video

5. Vertebrate Classification • Nine Classes: • Hagfishes- Myxini: elongated, eel-like bodies, lack jaws, paired fins & bones, no vertebrae • Lamprey- Petromyzontida: same as hagfish except they have a primitive vertebrae • Sharks, Rays, & Skates- Chondrichthyes: jaws, paired fins, cartilage skeleton • Ray-finned Fish- Actinopterygii: jaws, bony skeleton

6. Classification Continued 5. Lobed-finned Fish-Sarcopterygii: fins on main axis of body 6. Amphibians:thin & permeable skin, eggs & larval stage in water 7. Reptiles:dry & scaly skin, eggs on land 8. Birds:flight, feathers, hollow bones, unique respiratory system 9. Mammals: hair, mammary glands

7. Vertebrate Evolution • 560 million years ago • First vertebrae = tadpole like, jawless fish

8. Origin of Jaws • 450 million years ago • Evolved from first pair of gill arches: • skeletal elements that protect pharynx • Jaws aid in food seizure and manipulation

10. Jawless & Cartilaginous Fishes Section 39.2

11. Characteristics for the Water: • Streamline body shape • Strong muscular tail for propulsion • Paired fins to maneuver in multiple directions • Secreted mucus to reduce friction • Stored fat to help float • Gills for respiration

12. Homeostasis • Maintain homeostasis through osmosis • osmoregulation • Waste removal organs: kidneys & gills • Kidneys filter wastes from blood & removes excess water as urine • Out through the cloaca • Gills remove waste gases (CO2) directly into the water

13. Jawless Fishes Video • Hagfish (Class Myxini): • Bottom dwellers, marine habitat • No vertebrae • Mouth with two movable plates & rough tongue-like structure • Burrow into body eat from the inside out • Lamprey (Class Petromyzontida) : • Some are parasitic on other fish • Disk-shaped mouth with rough tongue that scrapes a hole into host Video

14. Cartilaginous Fishes • Class Chondrichthyes • Examples: Sharks, rays, & skates • Skeletons made of cartilage: • Flexible, lightweight material made of cells surrounded by tough fibers of protein • Carnivores • Skin covered with placoid scales: • Small, tooth-like spines that feel like sandpaper

15. Sharks Video • 20,000 teeth during lifetime! • Multiple rows • Fusiform: smooth, torpedo-shaped bodies that reduce turbulence • Typically dark color on dorsal side and lighter color on ventral side to blend with enviro.

16. Liver • Store lipids in liver for energy and to maintain buoyancy • 25% body mass

17. Nervous System • Brain= olfactory bulb (smell), cerebrum (thought processing), optic tectum (visual, auditory, and lateral line system info. processing), cerebellum (muscle coordination, mvt., balance), medulla (coordinate muscle control), spinal cord (carries nerve impulses from brain to rest of body)

18. Ampullae of Lorenzini- detect electrical signals to locate prey • Chemoreception- detect chemicals in the enviro. (smell or taste_ • Nostrils

20. Circulatory • Blood closed in heart & blood vessels (arteries, capillaries, veins) • 2 chambered heart = Atrium and Ventricle

21. Respiration • Gills • Gill slits on side of head • Fast swimming or pumping water over gills • Spiracles (openings behind eye) and mouth draw in water

22. Fins: • Caudal (tail)- move forward • Pectoral- lift • Pelvic- stabilize • Dorsal- stabilize, may have spines • Anal- stabilize

23. Digestive system • Mouth, pharynx, esophagus, J-shaped stomach (rugae- internal folds aid in movement and churning of food), duodenum (U-shaped spiral small intestine), valvular large intestine, colon, cloaca (collects waste from colon and extratory sys.)

24. Other organs… • Pancreas: digestive gland • Spleen: dark, triangle-shaped, creates rb cells, • Rectal gland: end of intestine, removes excess ions from the blood and releases into rectum for elimination (osmoregulation) • Kidneys: make and transport urine

25. Digestive Tract

26. Reproduction • Internal fertilization • Male inject sperm into female with modified pelvic fins called claspers • Many cartilage fish have live birth • No parental care once born

28. Reproductive Organs Dissection video

29. Rays & Skates Video • Dorso-ventrally flattened fish • About 500 species • Wing-like pectoral fins • Bottom dwellers • Most feed on mollusks and crustaceans Ex) manta rays, electric ray, guitarfish, sawfish

30. Differences between rays (left) and skates (right) • Reproduction: Rays are live bearing while skates are egg laying • rays are kite-shaped with whip-like tails posessing one or two stinging spines while • skates have fleshier tails and lack spines

31. Bony Fishes Section 39.3

32. Characteristics • Bone: harder & heavier than cartilage • Lungs or swim bladder: early fish have lungs, most have a swim bladder(gas filled sac used to control buoyancy) • Scales: protect fish & reduce water resistance

33. Lobed-Finned Fishes: Sarcopterygii • Paired lobe fins, fleshy that extend away from its body • 2 major groups exist today… Example 1) Coelacanth • Carnivores, deep-sea of coast of Indian Ocean and Indonesia • Ancestors of amphibians & other terrestrial vertebrates • Endangered, most went extinct 65 m.y.a. • video

34. Example 2) lungfish • Live in shallow tropical ponds of Africa, S. America, & Australia • Omnivores • Breath through lungs and gills • video

35. Ray-Finned Fish: Actinopterygii • Rays: long, segmented, flexible bony elements that support the fins • Evolved from scales • Diverse in appearance, behavior, & habitat • Familiar fish • 30, 000 species

36. External Anatomy • Distinct head, trunk, & tail regions • Operculum: hard plate that opens toward the rear and covers & protects gills • Caudal fin: extends from tail & moves side to side • Dorsal fins: anterior & posterior • Pelvic fins & pectoral fins: help navigate fish • Scales: skin of fish that grow quickly when food is abundant • Growth rings

37. Caudal Fin Dorsal Fin Operculum Pectoral Fin Anal Fin Pelvic Fin

38. External Anatomy Anterior Dorsal Fin Lateral Line Caudal Fin Nares Posterior Dorsal Fin Eye Anal Fin Pectoral Fin Operculum Pelvic Fin

39. Internal Anatomy • Skeleton = skull, spinal column, pectoral girdle, pelvic girdle, & rib • Pectoral girdle: where pectoral fins attach • shoulders • Pelvic girdle: where pelvic fins attach • hips

43. Circulatory System • Delivers oxygen & nutrients and removes waste carbon dioxide & ammonia • Consists of heart, blood vessels, capillaries, veins, & arteries

44. The Heart • Two chambers in a row • Sinus venosus: deoxygenated blood empties into this collection area • Atrium: contractions move blood to the ventricle • Ventricle: main pumping chamber • Conus arteriosus: valves to prevent backflow of blood

45. Sinus venosus Atrium Conusarteriosus Ventricle

46. Respiratory System • Water goes into mouth, past gill filaments and out the operculum • Blood flows in a countercurrent flow opposite of water flow • Allows for more O2 diffusion

47. Reproduction • Spawning: reproductive behavior of fish • Eggs & sperm released into water through opening behind anus • Most fish use external fertilization • video

48. Excretory System • Kidneys: dissolve chemical wastes from blood resulting in urine (with ammonia) • Urinary bladder: holds urine until expelled

50. Swim Bladder • Thin walled sac in abdominal cavity • Contains a mixture of O2, CO2, and N2 • Enables movement up and down