02 Sept. 2014Fishes.ppt1 FISHES

02 Sept. 2014Fishes.ppt2 Fishes All fishes retain four (4) primitive characters: Streamlined body Vertical tail fin Gills for gas exchange Lateral line system, No ears

02 Sept. 2014Fishes.ppt3 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.

02 Sept. 2014Fishes.ppt4 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

02 Sept. 2014Fishes.ppt5 Bony Fishes Fins paired fins: pectoral, pelvic median fins: dorsal, anal, caudal

02 Sept. 2014Fishes.ppt6 Bony Fishes Bony dermal scales covered by thin epidermis NOT homologous to reptilian scales. Operculum covers gills; one gill slit each side.

02 Sept. 2014Fishes.ppt7 Bony Fishes Lungs, often modified to swim bladder. Examples: sturgeons gars catfish trout bass Northern pike American eel note paired fins, jaw, operculum

02 Sept. 2014Fishes.ppt8 Class Cartilaginous Fishes spp. Skeleton of cartilage, bone lost.  Fossil placoderms and jawless fishes had bone tissue, prob. ancestral to both Cartilaginous & Bony fishes.

02 Sept. 2014Fishes.ppt9 Class Cartilaginous Fishes Cartilaginous skull poorly developed, esp. dorsal to brain Fins supported by cartilage or horn-like rays

02 Sept. 2014Fishes.ppt10 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.

02 Sept. 2014Fishes.ppt11 Cartilaginous Fishes Sharks, Rays  specialized flattened sharks  “wings” are pectoral fins

02 Sept. 2014Fishes.ppt12 Development of Jaws All animals studied so far are “Jawed Vertebrates” Jaws developed from an anterior gill arch,  Allowed diverse diet

02 Sept. 2014Fishes.ppt13 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.

02 Sept. 2014Fishes.ppt14 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

02 Sept. 2014Fishes.ppt15 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

02 Sept. 2014Fishes.ppt16 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

02 Sept. 2014Fishes.ppt17 Overview of where we have been All animals studied to date belong to: Phylum Chordata  notochord  dorsal nerve cord  pharyngeal arches/clefts bear gills in fishes, modified to other structures in terrestrial animals  postanal tail

02 Sept. 2014Fishes.ppt18 Review Subphylum Vertebrata  Notochord reduced, replaced by bony or cartilaginous vertebrae Some notochord tissue usually remains  Pharyngeal arches bear gills or developed into other organs: hyoid bone, larynx  Liver  Pancreas

02 Sept. 2014Fishes.ppt19 Review Subphylum Vertebrata 6 Classes: Jawless fishes Cartilaginous fishes Bony fishes Amphibians Reptiles including Birds Mammals

02 Sept. 2014Fishes.ppt20 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 02 Sept. 2014Fishes.ppt21

Subphylum Cephalochordata 02 Sept. 2014Fishes.ppt22 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