Transcript Chapter 18
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: HyperoartiaClass 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 – – 2. 3. 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