Contents • Phylum: Chaetognatha • Phylum: Hemichordata • Phylum: Chordata • Subphylum: Urochordata • Subphylum: Cephalochordata • Subphylum: Vertebrata (Craniata) • Superclass Agnatha • Class: Myxini • Class: Cephalaspidomorphi
Phylum Chaetognatha • Arrow worms • Stratified skin along sides of body.
Phylum Hemichordata • Acorn worm • Proboscis, collar and trunk • Like Chordata • Gill slits and a hollow, dorsal nerve chord • Have stomochord rather than a notochord • Like Echinodermata • Tornaria larva resembles bipinnaria larva of echinoderms. • Coelomic pouches • Nerve plexus
Urochordata Phylum Chordata Cephalochordata Vertebrata • Notochord • Dorsal tubular nerve cord • Pharyngeal gill slits (pouches) • Post anal tail • Ventral heart
Chordata Subphylum Urochordata • Tunicates (sea squirts) • Larva has all chordate characteristics • Adult sessile, encased in tunic • Ventral heart with a large vessel on each side. Heart pumps blood through one vessel—, stops, then pumps blood through other vessel. • Endostyle present
Chordata Subphylum Cephalochordata • Branchiostoma -the lancelets or Amphioxus • Retain all the chordate characteristics throughout life. • Shows the basic diagnostic chordate characteristics very clearly. • Also possesses several features that suggest the vertebrate plan • Endostyle present
Chordata Subphylum Vertebrata Myxini Cephalaspidomorphi • Chordate characteristics present at some stage of life cycle. • Integumentary - with stratified epidermis and an inner dermis present. • Skeletal -Notochord at least partly replaced by vertebrae. A cranium present. • Nervous- 10 to 12 pairs of cranial nerves • Excretory - vertebrate kidney (at least mesonephric in adults)
Class: Myxini Vertebrata • Hagfishes • Naked skin containing slime glands • No paired appendages • No jaws • Notochord and other chordate characters persistent • Systems • Representative pictures
Myxini Myxini systems • Systems • Circulatory - Two chambered heart with aortic arches in gill region have accessory hearts in caudal region. • Excretory - pronephric with independent mesonephric kidney posteriorly, isosmotic to sea water. • Respiratory - 5 to 16 pairs of gills (one pair or more gill openings) • Digestive -complete, with no jawsor stomach present • Nervous- they have 10 pair of cranial nerves, no cerebellum. Dorsal and ventral nerve roots united. • Integumentary- No scales, skin with slime glands • Skeletal - cartilaginous with persistent notochord. • Reproductive - both male and female gonads found in some animals, but one one gonad is functional. No larval stage. Life cycle largely unknown • Endocrine - pineal gland present, there are islets of pancreas cells around the bile duct • Muscle - myomeres alternate
Myxini Myxini representatives Ventral view Lateral view
Class: Cephalaspidomorphi Vertebrata • Lampreys • Slender eel-like body without scales • No paired appendages • Cartilaginous skeleton, notochord persistent • No jaws—Sucker-like oral disc, has teeth and tongue. • Ammocoete larvae • Systems • Representative pictures
Cephalaspidomorphi Lamprey Systems • Integumentary- No scales , stratified skin • Skeletal- Cartilaginous, notochord persistent, no paired appendages. • Circulatory- Two chambered heart, aortic arches in gill region. • Respiratory - seven pairs of gills each with and external opening. • Excretory- Mesonephric kidney, hypotonic sea water, have to osmotically and ionic regulate. • Nervous- 10 pairs of cranial nerves, dorsal and ventral nerve roots separated, small cerebellum present. • Endocrine- pineal structure, pituitary body present, endostyle present in larvae is thyroid gland present in adult. • Muscle - short segmental muscles as in other fishes • Digestive-complete, no stomach, liver does not have a bile duct, pancreas cluster of cells near liver. • Reproductive - dioecious, larvae= Ammocoete, look much like amphioxus, are freshwater filter feeders.
Ammocoete larvae Juvenal lampreys Adult lamprey mouth with tongue and teeth Adult lamprey - lateral view Cephalaspidomorphi Cephalaspidomorphi examples