2. Phylum Chordata
• Class Actinopterygii
– “modern bony fish”
– 25,000 species or ½ of all vertebrate species
– So diverse no one characteristic can differentiate
them from sharks, skates, and rays (cartilaginous
fish)
• Taxonomy of fishes is concentrated on order or family
rather than phylum or class (b/c phylum is too broad)
– Taxonomy of fishes are still changing as new
technology and research reveal new characteristics
3. Phylum Chordata
• Class Actinopterygii
– Characteristics
• Presence of swim bladder: gas filled
sac; add and remove to adjust
buoyancy
• Bones
• Bony scales
• Fin rays
4. Coelacanths “primitive fish”
• Historic fish that give rise to modern day amphibians
• Were thought to be extinct 65 million years ago until
living specimens were discovered in 1938 and as
time goes on finding more and more individuals
“living fossils”
• Live at depths 150-250 meters
• Bony skeleton but vertebrae is almost all cartilage
(like sharks)
• Maintain high amount of urea to maintain
homeostasis
• Reproduction: ovoviviparous
5. Ray-finned Fishes
• Most numerous and diverse of ALL vertebrates
in ocean
• Characteristic-fins attached to body by fin ray
– Webs of skin connected by bony plates
6. 2 major groups
• Subclass Chondrostei
– Heterocercal tail
– Skeleton made mostly of
cartilage
– Ganoid scales
– Atlantic Sturgeon
• Subclass Neopterygii
– Successful b/c bodies
lighter; jaws stronger
– Homocercal tails
• Backbone does not
extend into tail
– Cycloid OR Ctenoid
scales
• Both are thinner and
more flexible than ganoid
scales
– Salmon; seahorses
7. Body Shapes-determined by habitat
• Fusiform (torpedo)-
streamlined shape for
active swimmers
• Laterally compressed-
flattened so can
maneuver though corals
• Flattened: bottom-
dwellers
• snakelike: burrowing
fish
8. Respiration
• Gills: receive oxygen and
remove CO2, and maintain
salt balance
– Made of gill filaments: blood
flows in opposite direction of
incoming H2O
• Water must continuously
pass over gills
– Meets with blood with lower
O2 and higher CO2
• Diffusion moves from where to
where?????
– Fish actually “pump” H2O
over gills
9. Cardiovascular
• Close circulatory system: Heart, veins, arteries
– Most complex we’ve seen so far!
– 4 chambered heart
• Draw Heart diagram in your notes
10. Nervous System
• Brain, spinal cord, nerves
• Senses
– Olfaction: sense of smell: olfactory pits
(nostrils)
– Taste: receptors on head, jaws, tongue,
mouth and barbels on some fish
(catfish)
– Eyes Lack eyelids
• Most set on sides of face: each eye see
own independent view.
11. Reproduction
• Vast: species specific
– Change Sex
– Female to Male: Blue headed
wrasse can change sex ; also
form Harems
– Male to Female: Moray Eels
– Seahorses: males carry eggs
– French Angelfish: mate for life:
Monogamous
– Perch: Spawners separate
sexes: No parental care for
young
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