Icthology study of fish

1. Icthologystudy of fish

6. Phylum Chordata • Subphylum Vertebrata • Superclass Agnatha (jawless) • Class mixini – hagfish • Class cephalaspidomorphi – lamprey HAGFISH LAMPREY

7. Subphylum Vertebrata • Superclass Gnathostomata (jaw mouth) • Class Chondrichthyes – cartilage fish • Subclass Elasmobranchi – sharks, rays, skate • Class Osteoichthyes – bony fish SKATE

8. SUPER CLSS AGNATHA • Superclass Agnatha – 70 species General Characteristics 1. Body – long, cylindrical (eel like) 2. No scales, jaws, or paired fins 3. Two chambered heart 4. 3-16 pairs of gills 5. poikilothermic – having a body temperature that varies with the temperature of its surroundings

9. Hagfish • Marine, feed on dead or dying organisms (not parasitic) • When caught, secretes enormous quantities of slimy mucus • Enters body of an animal through gills, mouth, or anus and eats the contents of the body leaving a sack of bones and skin • Lamprey • 40 species, fresh and marine water, parasitic

10. Reproduction (Hagfish and Lamprey) • Both ovaries and testes present, but only one is functional • Males build nests in spring and fertilization is external (2-65,000 eggs) • Adults die after spawning • Eggs hatch into larvae and burrow into sand or mud • Emerge at night to feed, blind and toothless • Larval form for 3-7 years • Metamorphosis into adult takes about 4-11 months

11. Economic importance • Fish bait • Lamprey is food for humans • FYI… • Portuguese and Spanish diners prize sea lamprey as a gourmet treat for which they're willing to pay up to $25 a pound. European fishers harvested local lamprey so much that populations on that side of the Atlantic are crashing, allowing demand for this prehistoric boneless fish to exceed supplies. • So what does lamprey taste like? "I would have to say it tastes like lamprey," says Chef Bob Bennett, "because it does not have a flavor that you can associate with anything else." • When pushed further, he volunteered that "its taste is not offensive. A lot of delicacies that I've been introduced to over the course of my career are a lot less palatable - such as the sea urchin." • Hagfish will damage fish caught in net or line

12. Some differences between sharks and fish Sharks Fish Made of cartilage Made of bones and cartilage Can only swim forward Can swim forwards and backwards Uses oil for buoyancy Uses gas-filled swim bladder for buoyancy Eggs fertilized in females body Eggs fertilized in water Skin is rough like sandpaper Slippery scales on skin

13. CLASS CHONDRICHTHYES • External features • Head, trunk, tail

14. Dorsal fins – keep upright • Caudal fins – forward thrust • Heterocercal - dorsal lobe is larger than ventral • Homocercal – dorsal and ventral lobes are the same size • Pectoral and pelvic fins – steering

15. They use one at a time • After communicating its intentions to a receptive female shark through ritualized swimming and gentle 'love nips' along her back or flanks, the male grasps one of her pectoral fins and docks next to her. • If the male happened to dock along the left side of the female, he flexes his right clasper across the mid-line of his body and inserts it into her vent (genital opening). • Clasper – (male) on pelvic fin used in mating MALE FEMALE

16. Mouth – ventral • Eyes – lower lids to cover eye when feeding • Gill slits – 5-7 pairs; used for water to exit • Spiracle – modified gill slit on top of head • Purpose: provide oxygenated blood directly to the eye and brain through a separate blood vessel. • Absent or reduced in many sharks, especially the fast swimming sharks and is usually larger and present in bottom dwelling sharks.  • In the rays, the spiracle is much larger and more developed and is used to actively pump water over the gills to allow the ray to breathe while buried in the sand.

17. Vent- opening to cloaca; analogous to anus • Latin: “sewer” • Cloaca - common chamber that intestinal, urinary, and genital tracts open. • FYI: It is present in amphibians, reptiles, birds, sharks, and monotremes. A cloaca is not present in placental mammals or in most bony fishes.

18. Lateral line – sensory system detecting and locating objects • Made of cells called Nematocysts (sensitive gel filled cells that transmit signals to nerves) • Sensitive to vibrations and currents

19. Ampullae of Lorenzini – gel-filled pores on face • sense bioelectric fields • A biolelectric field surrounds all animals. Sharks can even detect animals under the sand! • It looks like a 5 o’clock shadow

20. Placoid scales – backward pointing spine covered by enamel

21. Skeleton – cartilage • Axial – skull and vertebral column • Appendicular – pectoral girdle (front fins) and pelvic girdle (pelvic fins)

22. Digestive system • Mouth • Teeth -replaced throughout life of fish • Tongue -immobile • Esophagus -short • Stomach -J shaped • Pylorus -valve • Intestine -spiral valve • Cloaca -common chamber • Vent -anus • Liver -very large, oily, purifies blood • Gall bladder -near top of liver, stores bile collected from liver and passes bile to intestines through bile duct • Pancreas – between stomach and intestine, secretes digestive enzymes that are released into intestine • Rectal gland – located near most posterior part of abdominal cavity; regulates excess salt received from food and water

23. Coelom • Peritoneum – lining the abdominal cavity • Made of layers • Outer layer - parietal peritoneum, is attached to the abdominal wall • Inner layer - visceral peritoneum, is wrapped around the internal organs located in inside the abdominal cavity • Mesenteries – membranes that attach organs to the abdominal wall, hold intestine in place

24. Circulatory System • Sharks have a two-chambered heart, with an atrium (aka auricle) and a ventricle. • Heart is covered by a visceral pericardium • The heart is S-shaped • ventral aorta transports blood to the gills • dorsal aorta takes blood back to the heart • Vessels • Carotids – carry blood to and from head • Subclavians – carry blood to and from pectoral fins • Meaning “subclavical”, under the clavical • Renal – carry blood to and from kidneys • Have you ever heard of renal failure in cats? Renal is from the Latin word renes which means kidneys • Iliacs – carry blood to and from pelvic fins • From the Latin word ilia describing the bones that make up the pelvis

25. Some Review

26. Sketch a shark: LABEL the • Anterior dorsal fin • Posterior dorsal fin • Homocercal caudal fin • Pelvic fin • Pectoral fin

27. 2. What is the function of the spiracle? 3. What is the function of the ampullae of lorenzini? 4. Why do sharks have a large liver? 5. What is the function of the clasper? 6. What is the function of the cloaca?

28. 9. What kind of fish eats out the insides of a dead organism? 10. What class do sharks belong to? 11. What class do bony fish belong to? 12. What shape is the sharks stomach? 13. How many chambers are in a sharks heart?

29. Sketch a shark: LABEL the Anterior dorsal fin Posterior dorsal fin Homocercal caudal fin Pelvic fin Pectoral fin

30. 2. What is the function of the spiracle? Provide oxygenated blood directly to eyes and brain 3. What is the function of the ampullae of lorenzini? Sense bioelectric field 4. Why do sharks have a large liver? Produces oil 5. What is the function of the clasper? Reproduction (male part) 6. What is the function of the cloaca? Common chamber for intestines, urinary, and genitial

31. 9. What kind of fish eats out the insides of a dead organism? hagfish 10. What class do sharks belong to? Chondrichthyes 11. What class do bony fish belong to? Osteoichthyes 12. What shape is the sharks stomach? J 13. How many chambers are in a sharks heart? two