Download Ichthyology Fall 2000

Reading Assignment:
• Chapter 2--form & movement
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Living Fishes:
• Numerous--23,250 valid spp.
(Eschmeyer) est. 25,000 valid spp.
• 200 new species described/yr
• possibly 30,000 or more
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Named & Valid Species of fishes
30000
21,700
25000
24,600 25,000
18,818
2000
20000
15000
1988
1996
1976
10000
5000
0
1970
1975
1980
1985
1990
1995
2000
2005
Moyle & Cech
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Examples of new species:
New species of shark (500 m; near Galapagos Is.)
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New species of wrasse (Labridae) (near Galapagos Is.)
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New species of sea bass (Serranidae) (near Galapagos Is.)
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New species of pipefish—orange hairy ghost pipefish
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Fish or Fishes?
• Fish -- singular
• Fish -- plural
• Fishes -- plural (groups of fishes)
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Diversity of Form:
brook trout
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sea horse
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flounder
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deepsea anglerfish
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sand tiger shark
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barred moray eel
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Diversity of Habitats:
•
•
•
•
•
•
•
intermittent streams
desert springs
oceanic trenches
saline bays
caves
open oceans
sub-zero water
•
•
•
•
•
hot springs
swift streams
continental shelves
estuaries
underground
aquifers
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Freshwater vs. Saltwater
• 58 % of fishes are marine
• 41 % freshwater
• Earth’s waters:
– 97% saltwater; 70% of surface of Earth
– 0.0093 % freshwater; 1% of Earth surface
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Diversity of Life Styles:
• nekton (self mobile)
• Plankton (drifters)
• bottom dwellers
(benthic)
• Pelagic (open water)
• surface oriented
(epipelagic)
•
•
•
•
•
•
carnivorous
omnivorous
herbivorous
filter feeders
parasites
diadromous
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Why do we recognize fish?
• Constraints & Characteristics of water
– density (800 x denser than air)
– support (lighter skeleton, diminished limbs)
– viscosity (streamlined shapes)
• Evolutionary convergence
• Absence of divergence
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Thoughts on the Evolution of Fishes
• What are general characteristics of fishes
and vertebrates? (consider their protist and
invertebrate ancestors)
• size
• mobility
• bilateral symmetry
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Evolutionary race among
predators and prey:
size
energetic
efficiency
locomotion
guidance
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Advantages of size:
• Survivability:
predator avoidance
prey availability
environmental selection and
avoidance
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Requirements for size:
• support (skeletal system)
• mechanisms of locomotion
• systems
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Simplest form of locomotion in verts.
Notochord--flexible, incompress.
Direction of locomotion
sinusoidal movement
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Vertebral column:
vertebrae
discs
Flexible
incompressible
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Dorsal fin--spines
Dorsal fin--rays
Caudal fin
Caudal peduncle
Pectoral fins
Pelvic fins
Anal fin
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Thought experiment:
Engineer a new species:
• Given a certain biomass to work with, how
many individuals would you make? Why?
– Considerations related to size
• extremes
• survivability versus cost of losing an individual
• What characteristics would you choose?
Why?
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Evolutionary History:
Phylum
Chordata
Subphylum Myxini
Superclass
Class
Vertebrata
Gnathostomata
Myxini Cephalaspidomorphi Chondrichthyes Osteichthyes
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