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

• O2 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 A History of Fishes 7 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 Placodermi - first jawed Class Chondrichthyes - cartilaginous fishes fishes No apparent descendants Subclass Elasmobranchii - Subclass Holocephali - sharks, skates, & rays ratfishes Subclass Sarcopterygii - lobe-finned fishes

Class Present day lungfishes and coelcanth Osteichthyes - Infraclass Chondrostei - sturgeons & paddlefishes bony fishes Subclass Actinopterygii - Infraclass Neopterygii - A History of Fishes ray-finned 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 A History of Fishes 28