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. 2 classes: cartilaginous and bony fish

3. 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