Transcript Document 7504064

Friday, September 12, 2008
1) Major evolutionary trends in fishes
a) caudal fin evolution
b) scales
c) swim bladders
d) guts
e) jaws
2) Character matrix for early Actinopterygiians & Teleostei
Tuesday - please wear pants out in the field. We
will be in some small ditches with scratchy weeds.
Gas/swim bladder
physostomous
physoclistous
Evolution of Jaws in Teleosts
• development of interopercular bone and
branchiostegal rays
interopercle
branchiostegals
braincase
premaxilla
premaxilla
maxilla
mandible
premaxilla
maxilla
note fixed premax.
& max.
Chondrostean
jaw condition
mandible
maxilla
note: maxilla acts as lever, in higher
teleosts, premaxilla can slide also
Amiiformes
(bowfin)
jaw condition
teleost
jaw condition
Evolutionary Trends in Bony Fishes
Ancestral
bony fish
Teleosts
Body
covering
heavy
scales
thin or no
scales
Respiratory
apparatus
rigid
branchial
cavity
lungs
Trait
branchiostegal
rays
swim bladder
Advantages
lighter,
flexible body,
maneuverability
more efficient,
suction feeding
hydrostatic
control, sound
Jaw
structure
holostylic
hyostylic,
premaxilla is
principal bone
flexible,
protrusible mouth
Tail
type
heterocercal
homocercal
fast swimming,
uniform thrust
Fin
position
pelvics
behind
pectorals
pelvics
below or
anterior to
pectorals
greater
maneuverability
88
Class Actinopterygii - the ray-finned fishes
Semiontiformes =
Lepisosteiformes
Order Polypteriformes - bichirs
Polypteriformes
Order Polypteriformes - bichirs
Unique characters
• 5 to 18 separate finlets- each with a spine and soft
rays
Order Acipenseriformes - sturgeons and paddlefish
Family Acipenseridae - sturgeon
Family Acipenseridae - sturgeon
link to Carol’s website
Family Acipenseridae
Family Acipenseridae
= grave conservation situation, several species
near extinction
Family Acipenseridae
• Sturgeons are the largest fishes found in
freshwaters
• beluga sturgeon -27 ft, 1,800 lbs.
• recreational fishery for more common
species still a viable industry
Family Polyodontidae - paddlefishes
Family Polyodontidae
Family Polyodontidae
• Snout not developed in juveniles
Family Polyodontidae
• Two species
• Polyodon spatula - Mississippi River
Drainage of eastern United States
•Psephurus gladius-China, Yangtze
Drainage
Family Polyodontidae
• Polyodon spathula - biology
• Filter feeder, zooplankton, mouth nonprotrusible
Class Actinopterygii - the ray-finned fishes
Family Lepisosteidae
• Fossils
Order Semiontiformes - gar
Order Semiontiformes - gar
Range
Order Semiontiformes - gar
•Heterocercal tail
Order Semiontiformes - gar
•Vascular air bladder
Order Semiontiformes - gar
• habitat
Family Lepisosteidae - biology
• Spawn in late spring over shallow
vegetated areas
• Female accompanied by multiple males,
eggs broadcast over substrate
• Eggs are large, adhesive, & poisonous.
Adhere to vegetation
• Larvae hatch with adhesive disk at tip of
lower jaw, attach to vegetation until yolk
sac is absorbed
Family Lepisosteidae - biology
•Reach maturity at 3 yrs, can live up to 20 yrs.
•Piscivores - lie-in-wait predators
•Most species average 2 - 3 ft. in size, alligator
gar can reach 10 ft.
Family Lepisosteidae - biology
• Of seven known species, four known to
occur in Illinois
Class Actinopterygii - the ray-finned fishes
Order Amiiformes
• One extant family, Amiidae
• one extant species - Amia calva
Order Amiiformes
• Amia calva
• Long dorsal fin, aids in propulsion
• Heterocercal tail
Order Amiiformes
Order Amiiformes
Amia calva - biology
• Life span ~10 years
• Can reach 2.5 - 3 ft. in length
Review Questions
1. (from the book) Explain why systematists at various times thought that Bichirs
(Polypteriformes) were most closely related to (a) Sarcopterygians, (b) lungfish,
(c) Actinopterygii. Which traits did they base these conclusions on?
2. Your book states that “The external gills (in bichirs) are only analogous to, not
homologous with, the gills of young lungfishes.” What do they mean by
“homologous” and “analogous”?
3. Describe the major patterns seen in (a) scale, (b) caudal fin, (c) swim
bladders, (d) guts, and (e) jaws. What do these changes in morphology
indicate about the changes in morphology? We used changes in the jaws
and the changes in the caudal fin as traits to support our phylogenetic tree.
Why didn’t we use the changes in scale type or swimbladder? Can you think
of any taxon that violates our general picture for the evolution of these traits?
4. Explain how the changes in jaw structure affected the manner in which fish
captured their prey.
5. An interesting pattern occurs. At the same time fishes are evolving increased
buoyancy control (swim bladders), they are evolving a more symmetrical tail which
provides less help with maintaining neutral buoyancy. How do you resolve this
apparent contradiction?
Review Questions (Cont’d.)
6. Sturgeons have a skeleton of cartilage. How can they be members of
Osteichthyes?
7. List 3 traits of sturgeon life-history that has led to them be endangered. What
human activities have led to a reduction in their numbers? How many species
occurred in the Aral Sea and why did they go extinct?
8. Where are paddlefish found today? Why does the paddlefish have such a long
snout? Describe their life-history.
9. How does the foraging behavior of gar differ from bowfin? How does parental
care vary between the two groups? In what ways are bowfin and gar similar?