Chapter 18 Fishes

Characteristics Phylum: Craniata (describes the skull that surrounds their brain Much evolution occurred in freshwater Much evolution involved the movement of fish between fresh and marine environments Over 41% of fish live in freshwater even though only small percentage of the Earth’s water resources is freshwater

Subphylum Hyperotreti: Hagfishes 20 species Heads are supported by cartilage and brains enclosed in a fibrous sheath Retain a notochord 4 pairs of sensory tentacles surrounding their mouths Cold water marine habitats Most primitive group in the craniata Live buried in the sand and mud Feed off of soft bodied invertebrates and scavenge dead and dying fish Slimy skin

Subphylum Vertebrata: Ostracoderms Extinct agnathans Had bony armor as a defense Bottom dwellers Filter feeders

Subphylum Vertebrata: Hyperoartia- Class Cephalaspidomorphi Lampreys Found in freshwater and marine environments Prey on other fish and their larvae as filter feeders Mouth of an adult lamprey is suckerlike with lips that have sensory attachments Have salivary glands with anticoagulant secretions and feed mainly on the blood of their prey

Lampreys Adult lampreys live in the ocean or the Great lakes, at the end of their lives they migrate to freshwater to spawn They build spawning nests in shallow water, a female attaches to a rock with her mouth, male use their mouth to attach to the female head and wrap themselves around the female Eggs are shed in batches and fertilized externally and then covered in sand

Gnathostomata 1. 2 important evolutionary developments Jaws: allowed for more efficient gill ventilation Paired appendages: used to counteract the tendency to roll during locomotion and control the pitch of the the swimming fish 2 classes: cartilaginous and bony fish Contain the armored fish which are extinct and acanthodians which are also extinct

Class Chondrichthyes Includes sharks, skates, rays and ratfishes Most are carnivores or scavengers Have biting mouthparts and paired appendages

Subclass Elasmobranchii About 820 species no swim bladders Cartilaginous skeleton Born with full sets of teeth

Tiger Sharks Found in tropical and temperate waters Can grow up to 16 ft. Solitary, nocturnal Wide spectrum of food http://www.discovery.com/tv-shows/shark-week/videos/tiger-sharks-snack-on-birds.htm

Whale Shark Slow moving filter feeding shark Largest: 41 feet and 47000 pounds Found in warm oceans Life span of 70 years

Whale Shark Feed mainly on plankton Docile Does not pose a threat to humans http://www.youtube.com/watch?v=uQrBwN39LJI

Hammerhead Shark Utilize electroreception http://video.nationalgeographic.com/video/worlds-deadliest/deadliest-hammerhead-shark

Distribution Hammerhead sharks Tiger sharks

Stingray http://video.nationalgeographic.com/video/stingray http://video.nationalgeographic.com/video/sting-rays-doubilet?source=searchvideo

Subclass Holocephali About 30 species Have an operculum: gill cover Lack scales

Class Osteichthyes Bony fish Have swim bladders: an internal gas filled organ that contributes to the buoyancy of fish

Subclass Sarcopterygii Have muscular lobes associated with fins and use lungs in gas exchange They survive stagnation by breathing with lungs but normally use gills

Coelacanths Rare order of fishes that were thought to have been extinct but rediscovered in 1938

Osteolepiforms Prehistoric lobe finned fish Extinct

Subclass Actinopterygii Ray finned fishes Possess swim bladders Sturgeons, paddlefishes

Sea Horses 54 species Class actinopterygii Female deposits up to 1500 eggs in a male seahorses pouch who then carries them for up to 45 days till they emerge from pouch

Sea horses http://www.youtube.com/watch?v=C1XYg4km7Yk