A History of Fishes Evolutionary History Fish have adapted to a - PowerPoint PPT Presentation

A History of Fishes

Evolutionary History  Fish have adapted to a wide range of environmental parameters • Temperatures -1.8°C - 40°C • pH 4 - 10 • O 2 Concentrations 0 - Saturation • Salinity 0 - 90 • Depths 0 - 7000m A History of Fishes 2

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 A History of Fishes 3

Evolutionary History

Conodonts A History of Fishes 6

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Ostracoderms Characteristics:  1. Lack of jaws 2. Lack of paired fins 3. Bony armor 4. Internal cartilaginous skeleton Modern day representatives of this group:  • Class Pteraspidomorphi (hagfishes) • Class Cephalaspidomorphi (lampreys) A History of Fishes 8

Ostracoderms A History of Fishes 9

Early Jawed fishes  Gnathostomes • Jaws are probably the greatest advancement in vertebrate evolution o This allowed for an explosion in diversity due to the different prey items that can be processed A History of Fishes 10

Placoderms Diverse group with a bizarre  appearance 1. Jaws 2. Dermal body plates 3. Internal skeleton 4. Paired fins Some were over 6 meters in size and  possessed a craniovertebral joint A History of Fishes 11

Dinichthys Placoderms Craniovertebral joint A History of Fishes 12

Placoderms Gemuendina Bothriolepis A History of Fishes 13

Class 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 o Fossil record is poor, since cartilage does not readily fossilize  Characteristics A History of Fishes 14

Class Chondrichthyes A History of Fishes 15

Class Chondrichthyes Two distinct evolutionary lines  1. Subclass Elasmobranchii o Sharks, skates, and rays A History of Fishes 16

Class Chondrichthyes Two distinct evolutionary lines  2. Subclass Holocephali o Ratfishes or chimaeras A History of Fishes 17

Class Osteichthyes Bony Fishes

Subclass 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 A History of Fishes 19

Subclass Actinopterygii (Ray-finned fishes)  The most successful of all the modern fishes 1. Triangular dorsal fin 2. Paired fins without fleshy lobes 3. Ray-finned A History of Fishes 20

Subclass Actinopterygii (Ray-finned fishes)  Infraclass Chondrostei • Sturgeons, and paddlefishes A History of Fishes 21

Subclass Actinopterygii (Ray-finned fishes)  Infraclass Neopterygii • Remaining 27,000+ bony fishes A History of Fishes 22

Evolutionary Review Ostracoderms - primitive jawless fishes No living representatives, possible relatives include hagfish and lamprey Class Chondrichthyes - cartilaginous fishes Class Placodermi - first jawed fishes No apparent descendants Subclass Elasmobranchii - Subclass Holocephali - sharks, skates, & rays ratfishes Subclass Sarcopterygii - lobe-finned fishes Present day lungfishes and coelcanth Class Infraclass Chondrostei - Osteichthyes - sturgeons & paddlefishes bony fishes Subclass Actinopterygii - Infraclass Neopterygii - ray-finned fishes A History of Fishes 23 remaining bony fishes

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 A History of Fishes 24

Physical Properties of Water  Water is 800x denser than air!  Water is incompressible  Water is a universal solvent A History of Fishes 25

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 A History of Fishes 26

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 o Rhinichthys - nose-fish o cataractae - the fast water in which it lives A History of Fishes 27

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