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Contents Lesser Deuterostome Phyla and Phylum Chordata(through agnathans) Contents Contents • Phylum: Chaetognatha • Phylum: Hemichordata • Phylum: Chordata Subphylum: Urochordata Subphylum: Cephalochordata Subphylum: Vertebrata (Craniata) • Superclass Agnatha Class: Myxini Class: Cephalaspidomorphi Contents Phylum Chaetognatha • Arrow worms Stratified skin along sides of body. Contents 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 Contents Phylum Chordata Urochordata Cephalochordata Vertebrata • • • • • Notochord Dorsal tubular nerve cord Pharyngeal gill slits (pouches) Post anal tail Ventral heart Contents 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 Contents Chordata Contents Subphylum Vertebrata Chordata 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) Contents Class: Myxini • Hagfishes Naked skin containing slime glands No paired appendages No jaws Notochord and other chordate characters persistent Systems Representative pictures Vertebrata Contents Myxini systems Systems Myxini • 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 jaws or 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 Contents Myxini representatives Ventral view Myxini Lateral view Contents Class: Cephalaspidomorphi • 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 Vertebrata Lamprey Systems • • • • • • • • • • Contents Cephalaspidomorphi 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. Cephalaspidomorphi examples Contents Cephalaspidomorphi Ammocoete larvae Juvenal lampreys Adult lamprey mouth with tongue and teeth Adult lamprey - lateral view