Transcript Lesser Deuterostome Phyla and Invertebrate members of

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