02 Sept. 2014Fishes.ppt1 FISHES. 02 Sept. 2014Fishes.ppt2 Fishes All fishes retain four (4) primitive characters: Streamlined body Vertical tail fin Gills

02 Sept. 2014 Fishes.ppt 1

FISHES


Fishes

• All fishes retain four (4) primitive characters:• Streamlined body

• Vertical tail fin

• Gills for gas exchange

• Lateral line system, • No ears


Fishes

• Three traditional vertebrate classes that remain aquatic. Class Bony Fishes Class Cartilaginous Fishes Class Jawless Fishes

• All three classes well adapted to aquatic environment.


Class Bony Fishes

• Also called “Ray-finned Fishes” • ~30,000 species.

Majority of living vertebrate species. Bony skeleton, well developed skull Fins supported by cartilage or bony “rays”

and minute scales (=lepidotrichia) • paired fins:

• pectoral, pelvic

• median fins: • dorsal, anal, caudal


Bony Fishes• Fins

• paired fins: • pectoral, pelvic

• median fins: • dorsal, anal, caudal


Bony Fishes• Bony dermal scales• covered by thin epidermis

• NOT homologous to reptilian scales.

• Operculum covers gills; one gill slit each side.


Bony Fishes

• Lungs, often modified to swim bladder.• Examples: • sturgeons• gars• catfish• trout• bass• Northern pike• American eel

• note paired fins, jaw, operculum


Class Cartilaginous Fishes • 400 - 600 spp. • Skeleton of cartilage, bone lost.

Fossil placoderms and jawless fishes had bone tissue, prob. ancestral to both Cartilaginous & Bony fishes.


Class Cartilaginous Fishes

• Cartilaginous skull poorly developed, esp. dorsal to brain

• Fins supported by cartilage or horn-like rays


Cartilaginous Fishes

• No ribs.

• No lungs or swim bladder.

• Separate gill slits, usually 5

• Placoid scales, – tiny, tooth-like

• Enlarged at edge of mouth teeth – Homologous to teeth in all

other vertebrates.


Cartilaginous Fishes• Sharks, • Rays

specialized flattened sharks

“wings” are pectoral fins


Development of Jaws

• All animals studied so far are “Jawed Vertebrates”• Jaws developed from an anterior gill arch,

Allowed diverse diet


Class Jawless Fishes

• Survivors of earliest vertebrates• No jaws,

can not close mouth

• No scales• No paired fins, only median caudal fin

(continues dorsal & ventral to anus)• Single median nostril on top of head • Circular gill slits

7 or 12 pairs on sides of pharynx.


Jawless Fishes

• Hagfishes tentacles around mouth predators on worms,

mollusks scavengers 20 spp. in 4 genera

• Lampreys circular mouth, no tentacles filter feeders, or external parasites of bony

fishes 30 spp. in 10 genera


Jawless Fishes

• Life cycle of sea lamprey• Adult parasitic, feeding

stage

• Adults swim into small freshwater streams to breed

• Larvae live in sediment as filter feeders up to seven years

• Metamorphosis, migration to lake or sea to become parasitic adults


Jawless Fishes• Sea lamprey in the Great Lakes

• Lake Ontario since end of last Ice Age, prevented from entering upper lakes

• Welland canal• Sea lamprey devastated commercial fishing• Control


Overview of where we have been

• All animals studied to date belong to:

• Phylum Chordatanotochorddorsal nerve cordpharyngeal arches/clefts

• bear gills in fishes,

• modified to other structures in terrestrial animals

postanal tail


Review

• Subphylum VertebrataNotochord reduced, replaced by bony or

cartilaginous vertebrae• Some notochord tissue usually remains

Pharyngeal arches bear gills • or developed into other organs: hyoid bone, larynx

LiverPancreas


Review• Subphylum Vertebrata• 6 Classes:• Jawless fishes

• Cartilaginous fishes

• Bony fishes

• Amphibians

• Reptiles including Birds

• Mammals


Invertebrate Chordates

• Two more subphyla of Chordata, lack distinguishing characters of Vertebrates:

Subphylum Urochordata • tunicates, sea squirts

Subphylum Cephalochordata • lancelets, amphioxus

Subphylum Urochordata

• Adult is sessile filter-feeder

• Larva shows all characters of Phylum Chordata


Subphylum Cephalochordata


• Adult and larva show characters of Phylum Chordata

• Live in holes in sandy or muddy bottoms• Ciliated pharynx pulls in

water

• Filtered water exits atriopore

• Food directed to intestine , feces disposed through anus

Documents

02 Sept. 2014Fishes.ppt1 FISHES. 02 Sept. 2014Fishes.ppt2 Fishes All fishes retain four (4) primitive characters: Streamlined body Vertical tail fin Gills