Vertebrates!!

1. Vertebrates!!

2. Classification • Kingdom: Animalia • Phylum: Chordata • Subphylum: Craniata • Infraphylum: Vertebrata

3. Evolutionary Perspective • Largest and most successful group of chordates • Notochord: replaced by bony or cartilaginous vertebrae (the backbone) • Anterior end • Develops into a three-part brain • Forebrain, midbrain, & hindbrain • Sense organs • Display high degree of cephalization • Large number of fossils (thanks to the endoskeleton)

4. Evolution of Fish • Began evolving 500 million years ago • Display a variety of colors, shapes, & sizes • Occupy all aquatic environments • Divided into two infraphyla: Hyperotreti (hagfish) & Vertebrata (all other fish) • Until recently, hagfish & lampreys were classified together • Lampreys actually are closely related to cartilaginous fish • Zoologists are still unaware if fish were the first craniates (animals with skulls) • (more than likely hagfish were the first to evolve)

5. InfraphylumHyperotretiClass Myxini Hagfish!!! • 20 different species • Brains enclosed by a fibrous sheath • Body is supported by cartilaginous bars • Mouth is surrounded by sensory tentacles • Slime glands produce a large amount of slime (hard to grab the animal if it is covered in slime) • * Hagfish slime • Live in cold-water marine habitats • Both Northern & Southern hemispheres • Bury themselves in the sand and mud • Eat soft-bodied invertebrates & dead/dying animals • Can also swim into a fish’s mouth and eat the organs while the fish is still alive • Some hagfish are endangered due to overfishing for their soft, tough skin

6. InfraphylumVertebrataClass Petromyzontida Lampreys!!! • Found in marine & freshwater environments • Temperate regions • Adults prey on other fishes • Larvae filter feed • Mouth is modified into suckers • Surrounded by lips with sensory & attachment functions • Teeth line the mouth & cover a movable tongue • Lampreys use their mouths to scrape away scales • Secrete an anticoagulant to suck blood from their prey • Lamprey video

7. InfraphylumVertebrataClass Petromyzontida Lampreys!!! • Not all lampreys are predators • Brook lampreys feed only as larvae (for 3 years) • As adults, they do not eat. They simply reproduce and then die. • Adult lampreys live in either the ocean or the Great Lakes • Lampreys travel to freshwater streams to spawn (mate & lay eggs) • Once they have constructed their nest, the females attach to stone with their mouths • The males attach to the female heads with their mouths during mating. • Eggs are shed in batches over the course of a few hours- External fertilization

8. InfraphylumVertebrataClass Chondrichthyes Cartilaginous fish!!! NB #137 • Includes sharks, skates, rays, & ratfishes • Mostly carnivores or scavengers • Usually marine • Skeleton- made out of cartilage • Mouths are highly developed for BITING!!! • Skin- covered in “placoid” scales • Gives the skin a tough, sandpaper feel • Some dried shark skin is used as sandpaper • We use this same design for some swim wear (designed to add speed)

9. Class ChondrichthyesSublcassElasmobranchii Sharks, skates & rays!!! • They are sometimes considered to be more primitive fish • Lack swim bladder, gill cover, & bony skeleton • They are not primitive, but they simply adapted to different selection pressures • 820 different species • Sharks evolved from early jawed fishes ~375 million years ago

10. Class ChondrichthyesSubclass Elasmobranchii Sharks!!!! • Successful predators in the ocean • Teeth- several rows of teeth • As the teeth become useless, newer teeth move into the position from the inside jaw to replace that tooth • Rapid teeth replacement in young sharks (new row every seven or eight days) • Adapted to the shark’s prey • possibly shearing prey or crushing • Range in size from 1 m (dogfish sharks) to over 10 m (whale sharks) • The largest sharks are filter feeders • *Fiercest and most feared sharks are….the GREAT WHITE SHARKS and the MAKO SHARKS!!!!

11. Class ChondrichthyesSubclass Elasmobranchii Sharks!!!! • Shark Facts • The bull shark is known for swimming into rivers. One was even found as far as Alton, Illinois in the Mississippi River. • The oceanic whitetip sharks are responsible for more shark attacks than any other species • You are 1,000 times more likely to drown in the sea than you are to be bitten by a shark. • The chance of being killed by a shark is one in 300 million. The chance of being killed by airplane parts falling from the sky is one in 10 million. • Sharks’ wounds heal quickly and they rarely get tumors. • Sharks can smell one drop of blood in a million drops of water. For more shark facts visit www.sharkfacts.org

12. Class ChondrichthyesSubclass Elasmobranchii Rays & Skates!!! • Specialized for life on the ocean floor • Usually live in shallow water • Use their blunt teeth to feed on invertebrates • Pectoral fins are modified into “wings” • Move through dorsoventral muscular waves • Can camouflage with the ground • Sting rays have a tail modified into a defensive lash (contains venom) • Manta rays have horn-shaped cephalic fins • Electric rays produce an electric discharge for defense that ranges from 8-220 volts

13. Chimaera or ratfish!!! Class ChondrichthyesSubclass Holocephali • 30 different species • Possess a gill cover (called an operculum) • Have teeth modified into plates for crushing shells of mollusks • Ratfish do NOT have scales