Kingdom: Animalia Phylum: Chordata Subphylum: Craniata Infraphylum: Vertebrata Classification
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) Evolutionary Perspective
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) Evolution of Fish
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 slimeHagfish 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 Infraphylum Hyperotreti Class Myxini Hagfish!!!
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 Infraphylum Vertebrata Class 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 Infraphylum Vertebrata Class Petromyzontida Lampreys!!!
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) Infraphylum Vertebrata Class Chondrichthyes Cartilaginous fish!!! NB #137
820 different species Sharks evolved from early jawed fishes ~375 million years ago Class Chondrichthyes Sublcass Elasmobranchii 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
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!!!! Class Chondrichthyes Subclass 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. Class Chondrichthyes Subclass Elasmobranchii Sharks!!!! For more shark facts visit www.sharkfacts.org
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 Class Chondrichthyes Subclass Elasmobranchii Rays & Skates!!!
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 Class Chondrichthyes Subclass Holocephali Chimaera or ratfish!!!