A History of Fishes

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A History of Fishes

• Where did they come from?

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Evolutionary History

• Fish have adapted to a wide range of
  environmental parameters
• Temperatures -1.8C - 40C
• pH 4 - 10
• O2 Concentrations 0 - Saturation
• Salinity 0 - 90
• Depths 0 - 7000m

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Diversity and Evolution

• The diversity of fishes reflects their long
  evolutionary history
• A major challenge to ichthyologists involves
  unraveling the evolutionary pathways of both
  extant (living) and extinct taxa

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Evolutionary History
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Ostracoderms

• Characteristics
• Lack of jaws, lack of paired fins, bony armor,
  and internal cartilaginous skeleton
• Modern day representatives of this group include
  the classes Pteraspidomorphi (hagfishes) and
  Cephalaspidomorphi (lampreys)

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Early Jawed fishes

• Jaws are probably the greatest advancement in
  vertebrae evolution
• This allowed for an explosion in diversity due to
  the different prey items that can be processed

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Placoderms

• Diverse group with a bizarre appearance
• Jaws, dermal body plates, internal skeleton, and
  paired fins
• Some were over 2 meters in size and possessed a
  craniovertebral joint (increased prey size)

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Placoderms
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Chondrichthyes

• Arose during the early Paleozoic and followed a
  very different line of evolution
• Cartilaginous fishes, 2 distinct lines of
  evolution, the connection between the two is
  poorly understood
• Since cartilage does not readily fossilize not a
  very good fossil record
• Characteristics

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Chondrichthyes

• Two distinct evolutionary lines
• Elasmobranchii
• Sharks, skates, and rays
• Holocephali
• Ratfishes and chimaeras

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Sarcopterygii (Lobe-finned fishes)

• Present day lungfishes and coelacanths
• This group has paired fins which actually have
  muscle in the fin itself
• It is this class which is believed to have given
  rise to the amphibians

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Actinopterygii (Ray-fined fishes)

• The most successful of all the modern fishes
• Distinguished form sarcopterygians triangular
  dorsal fin, paired fins without fleshy lobes, and
  ray finned
• As this class flourishes the previous groups
  decline or disappear, which may show possible
  ecological interactions

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Actinopterygii (Ray-fined fishes)

• Chondrostei
• Sturgeons, and paddlefishes

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Actinopterygii (Ray-fined fishes)

• Neopterygii
• Remaining 23,000bony fishes

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Osteichthyes Lineage
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Evolutionary Review

• Ostracoderms - primitive jawless fishes
• No living representatives, possible relatives
  include hagfish and lamprey

• Placoderms - first jawed fishes
• No apparent descendants

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Population Distributions

• By volume 97 of all water on earth is found in
  the worlds oceans
• 58 of all fish species are marine
• 41 are freshwater species
• 1 move between the two habitats
• Marine Habitat
• 13 of marine species associate in open water
• 78 live over the continental shelf

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Physical Properties of Water

• Water is 800x denser than air!
• Water is incompressible
• Water is a universal solvent

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Have you hugged your Ichthyologist?

• Ichthyology - study of fishes
• Describing new taxa
• Understanding evolutionary relationships
• Taxonomy and systematics
• Ecology, physiology, and behavior

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Nomenclature

• The most frustrating aspect of ichthyology is the
  constant changing of scientific names
• These names change for several reasons
• Changes are necessary as new information is
  discovered concerning evolutionary history

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Species Names

• Each spp. is assigned a unique two part
  scientific name
• Longnose Dace Rhinichthys cataractae
  (Valenciennes 1842)
• Names are usually descriptive in some way
• Rhinichthys - nose-fish
• cataractae - the fast water in which it lives

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