Biology 450: Fish Week Lecture 2: Scott Heppell Department of Fisheries and Wildlife Oregon State University 042 Nash Hall , What is a fish?

Fish [fIS] (1) n. & v.. (pl. same or fishes) 1 a vertebrate cold-blooded animal with gills and fins living wholly in water. 2 any animal living wholly in water, e.g. cuttlefish, shellfish, jellyfish. 3 the flesh of fish as food. 4 colloq. A person remarkable in some way (usually unfavorable) ( an odd fish)

What is a fish? fish /f ɪʃ / plural (especially collectively) fish, (especially referring to two or more kinds or species) fish·es, verb –noun 1.any of various cold-blooded, aquatic vertebrates, having gills, commonly fins, and typically an elongated body covered with scales. 2.(loosely) any of various other aquatic animals. 3.the flesh of fishes used as food. 4.Informal. a person: an odd fish; a poor fish. 5.a long strip of wood, iron, etc., used to strengthen a mast, joint, etc. 6.to catch or attempt to catch (any species of fish or the like). 7.to try to catch fish in (a stream, lake, etc.): Let's fish the creek. 8.to draw, as by fishing (often fol. by up or out): He fished a coin out of his pocket for the boy. 10.Nautical. a. to secure (an anchor) by raising the flukes, b. to reinforce (a mast or other spar) by fastening a spar, batten, metal bar, or the like, lengthwise over a weak place. –verb (used without object) 11.to catch or attempt to catch fish, as by angling or drawing a net. 12.to search carefully: He fished through all his pockets but his wallet was gone. 13.to seek to obtain something indirectly or by artifice: to fish for compliments; to fish for information. 14.to search for or attempt to catch onto something under water, in mud, etc., by the use of a dredge, rake, hook, or the like. 15.to attempt to recover detached tools or other loose objects from an oil or gas well. fish. (n.d.). Dictionary.com Unabridged (v 1.1). Retrieved April 30, 2008, from Dictionary.com website:

What is a fish? Our working definition: Member of any of the several craniate groups of mostly gill- breathing, finned ectotherms considered phylogenetically more primitive than amphibians.

Fishes in context Five extant groups of vertebrates – Fishes, amphibians, reptiles, birds, mammals Fish comprise 3/5 of all vertebrate species Current estimates are between 24,000 and 28,000 species – 22,000 of those in one small group

Fish extremes Size – The largest fish is the whale shark 15 meters in length – The smallest fish is the carp Paedocypris Sexually mature at 8-10 mm – That’s a 2000x size range! Speed – The fastest fishes are the tunas and billfishes Burst speeds in excess of 50 mph Sailfish recorded at 68 mph!

Fish extremes Morphology

Life history – Lifespan Less than one year for very small teleosts 205 years for shortraker rockfish 200+ for white sturgeon? – Feeding Omnivores, herbivores, carnivores, parasites Swallow hole, bite, filter, crush – Reproduction Modes: Oviparous, gonochoristic, parthenogenic Hermaphroditic, gonochoristic, parthenogenic Fecundity: 1-2 every few years to millions per year – Respiration and thermal biology Antarctic ice fish at -1 0 C (and no hemoglobin) to bluefin tuna at 38 0 C in 4 0 C water. A successful life history strategy represents a “solution” of how to persist in a given environment.

Phylogeny Still under debate – Mostly at the lower divisions (Genus, species) – Some at the upper levels as well (Class, Division, Family)! Evans (1993) splits agnathans and gnathostomes as two groups Moyle and Cech (2004) place hagfish as separate from the lampreys or the gnathostomes I’ll follow the conventions of Moyle and Cech

Evolutionary timeline The evolutionary timeline of fishes extends back at least 550 million years. Complete fossils don’t exist prior to ~425 mya The Devonian period is considered “The Age of Fishes” – Elasmobranchs, actinopterygiians, sarcopterygiians arose during that time

Evolutionary timeline

Ostracoderms (Shell-skinned) First fossil remains appear during upper Cambrian (550 mya) First whole skelotons during Silurian (425 mya) Features – No jaws – No true teeth – No paired fins – Complete notochord in adults – Multiple gill openings – Extinct Probably related to the extant cyclostomes (hagfish and lampreys)

Agnathans (Without teeth) Two extant lineages – Hagfish – Lamprey Often lumped together – similar body form – Probably separate lineages from ostracoderms Hagfish – Stenohaline – Lack larval stage Classification (Agnatha superclass): – Hagfish –Myxini – Lamprey –Cephalospidimorphi Classification (new subphylum) – Hagfish as Craniata, outside Vertebrata subphylum

Agnathans (Without teeth) Characteristics – 70 living species 42 lamprey 28 hagfish – Elongate body – Persistent notochord throughout life – No vertebrae (hagfish) – Multiple gill openings 7 in lamprey 1-14 in hagfish – Silly fact for the day: Henry I died after over-indulging on a dish of cooked lamprey Divergence of Agnathan lineage ends here

Placoderms (Plate skinned) Next major group to arise Dominant class during Devonian Features – Internal skeleton – Paired fins – Jaws – Dorso-ventrally compressed bodies – Looked like ostracoderms w/jaws – Extinct

Acanthodians (Spiny sharks) Oldest jawed vertebrates W/ Placoderms formed two of four major classes of gnathostomes Small part of total fish fauna

Acanthodians (Spiny sharks) Features – Large eyes – Flexible, streamlined bodies – Fins hard, immovable spines – Predecessor to modern fins? – Extinct Relationship to other fishes unresolved. – Some place acanthodians with placoderms – Some place them as offshoot of osteichthyes – Some place them with chondrichthyes

Chondrichthyes (Cartilaginous fishes) Appear during late Silurian, common during Devonian Primarily marine Features – 800+ species of sharks and rays (subclass Elasmobranchii) – 30 species of ratfishes/chimerids (subclass Holocephali) – Cartilaginous skeleton – Teeth not fused to jaw – Un-segmented fins – Single nostrils – Spiral valve intestine – Pelvic fins modified as claspers (males) – Holocephali have tooth “plates” for crushing invertebrates – Lack a swim bladder

Osteichthyes (Bony fishes) Slight misnomer – Absent in some Osteichthyes – Present in agnathans First appear during Devonian Two major subclass – Sarcopterygiians – Actinopterygiians All Osteichthyes share – Lungs (swim bladder in derived forms) – Bone (lost in derived forms) – Flexible scales – Lepidotrichia (soft fin rays)

Sarcopterygiians (Lobe-finned fishes) Features – Seven extant species Six lungfihs (infraclass dipnoi) One coelacanth (infraclass coelacanthimorpha) – Two extinct subclasses (physiologically uninteresting) – Vascularized scales – Epichordal lope on heterocercal caudal fin – Paried fins with fleshy/bony central axis – Choanae present Tetrapods are an infraclass of this subclass

Actinopterygiians (Ray-finned fishes) 24,000+ species Features – Lack vascularized scales – Paired fins comprised only of rays – Single dorsal fin with single girdle – Hetero- or homocercal tail – Choanae absent

Actinopterygiians (Ray-finned fishes) Subdivided into – Infraclass Chondrostei (25 species, all in order Acipenseriforms) Family Acipenseridae (sturgeons Family Polyodontidae (paddlefishes) – Infraclass Neopterygii Order Lepisosteiformes (Gars, 7 species) Order Amiiformes (Bowfins, 1 species) Teleostei Division (Remaining ~24,000 species)

Neopterygiians (New-finned fishes) Subdivided into – Order Osteoglossomorpha (bony tongues) – Order Clupeomorpha (herrings, anchovies) – Order Elopomorpha –linked by leptocephalus larvae Elopiformes (tarpon, bonefish) Anguilliformes (true eels) – Order Notocanthiformes (spiny eels – Order Euteleostei (22,00 species)

The Lineage according to Evans (1993)

The Lineage according to Moyle and Cech (2004) SubphylumMyxiniVertebrata ClassChondrichthyes Class PlacodermAcanthodiiOsteichthyes Infraclass Superorder CoelocanthimorphaChondrosteiNeopterygii Tetrapods