BIOL 404 Ichthyology - the study of fishes

Fishes  Most numerous and diverse of the major vertebrate groups  More classes of fishes than all other vertebrates combined

Status of Fish “Humans are not the pinnacle of evolutionary progress but only an aberrant side branch of fish evolution.” - P.B. Moyle & J.J. Cech, Jr., 2004

Bony Fishes

Founders of Ichthyology

Aristotle  First known ichthyologist BC  Recognized 117 species of fish, distinguished fish from whales

Peter Artedi  “Father of Ichthyology”  Classification system of fishes  Standardized measurements and counts that remain basis of fish taxonomy today

Peter Artedi  Friend of Carolus Linneaus, who published his works after Artedi died by drowning in a canal in Amsterdam after a night of drinking

Carolus Linneaus  adapted Artedi’s system to use in his Systema Naturae - basis for all future classification systems  Extremely arrogant - some believe he may have been connected to Artedi’s death (competition between them)

Georges Cuvier  classified all known species of fishes  Conducted detailed studies of fish anatomy  Compiled early history of ichthyology

Constantine Rafinesque  produced the most detailed early account of fish in North America - Ichthyologia Ohiensis  Natural history of fishes of the Ohio River and its tributaries

Louis Agassiz  important volumes on classification based on fossil fishes  Strong non-believer of evolution, but work laid foundation for evolution studies of fish  Popularizer of science to American public

Johannes Muller  in Germany - revised Agassiz’s classification system to include most major groups still used today

Albert Gunther  British Museum - last person to attempt to describe all species of fishes in the world

David Starr Jordan  two major texts, plus president of Stanford  Fishes of North and Middle America  Guide to the Study of Fishes (ichthyology text)

Carl L. Hubbs  two important texts  Classification of Fishes (standard reference)  Fishes of the Great Lakes Region

Ichthyology Jobs  Applied research - state, federal agencies - fisheries management  University teaching/research  Museum research/curatorship  Collection management  Public aquaria & aquarium hobby  Conservation agencies (protection)  Applied research - state, federal agencies - fisheries management  University teaching/research  Museum research/curatorship  Collection management  Public aquaria & aquarium hobby  Conservation agencies (protection)

Position within Animal Kingdom  Phylum Chordata  Deuterostome branch along with echinoderms & hemichordates  Phylum Chordata  Deuterostome branch along with echinoderms & hemichordates

Within Phylum Chordata  Notochord  Dorsal, hollow nerve cord  Pharyngeal gill slits  Postanal tail  Notochord  Dorsal, hollow nerve cord  Pharyngeal gill slits  Postanal tail

Phylum Chordata  3 subphyla  Urochordata  Cephalochordata  Vertebrata  3 subphyla  Urochordata  Cephalochordata  Vertebrata

Subphylum Urochordata  Tunicates or sea squirts

Subphylum Cephalochordata  Lancelets

Subphylum Vertebrata  Vertebrates

Evolution & Major Groups: A Quick Overview

The First Fish  Ostracoderms appear in Cambrian fossils  Class Agnatha or Ostracodermi  Jawless, bony armor, many with bony endoskeleton  Most inhabited freshwater

The Next Fish  Ostracoderms disappear and placoderms appear in Devonian fossils  Class Placodermi  Jaws, paired fins, bony armor and endoskeleton  Not directly ancestral to higher fishes  May have given rise to cartilaginous fishes

First Chondrichthyes  Appeared in late Devonian  Differed from modern sharks  Terminal mouth  Pectoral fins broadly joined to body  No pelvic claspers  Appeared in late Devonian  Differed from modern sharks  Terminal mouth  Pectoral fins broadly joined to body  No pelvic claspers

Skates & Rays  Subclass Elasmobranchii (same as sharks)  Appeared in Mesozoic  Descended from primitive sharks

Chimaeras  Subclass Holocephali  Appeared shortly after primitive sharks, did not arise from them  Arose independently from placoderms?

Osteichthyes - bony fishes  Arose in late Silurian  Probably from freshwater  Followed two lines of development:  Sarcopterygii - fleshy-finned  Actinopterygii - ray-finned

Bony Fishes

Sarcopterygii: Crossopterygii  Lobe-finned fishes  Ancestral to first amphibians  Tetrapod-like bones in lobe fins  Thought extinct until coelocanth in Indian Ocean

Sarcopterygii: Crossopterygii

Sarcopterygii: Dipnoi  Lungfishes - air bladder modified into “lung”  Peaked in Paleozoic, then declined  3 living genera: Australia, Africa, South America

Bony Fishes

Actinopterygii: Chondrostei  Cartilaginous ganoids  Paddlefish and sturgeons  Became dominant during Paleozoic, then declined

Actinopterygii: Holostei  Bony ganoids  Gars and bowfin  Became dominant during Mesozoic, then declined

Actinopterygii: Teleostei  Higher bony fishes  Common modern fishes  Became dominant during Cenozoic, still dominant

Bony Fishes