Phylum: Chordates

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Phylum Chordates

• Subphylum Urochordata and Cephalochordata
• AA SS
• Period 1

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http//www.bio.miami.edu/dana/160/chordatephylogen
y.gif
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Chordates

• Chordates are organisms that possess
• A structure called a notochord at some part of
  their development.
• A dorsal, hollow nerve cord
• Pharyngeal slits
• Muscular post-anal tail.

http//instruct1.cit.cornell.edu/courses/biog105/l
abs/deuts/chordates.html
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Chordates

• Notochord a rod that extends most of the length
  of the body that provides support during
  locomotion.
• Nerve cord- dorsal hollow nerve cord that is
  unique to chordates animals from other phyla
  have solid nerve chords.
• The nerve cord of a chordate is the central
  nervous system brain and spinal cord.

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Chordates

• Pharyngeal slits allow water to exit from the
  mouth without going through the entire digestive
  tract. Slits have become modified for gas
  exchange, jaw support, hearing, and other
  functions during vertebrate evolution.
• Chordates have a tail. Usually, non-chordates
  have a digestive tract that extends the whole
  length of the body. The chordate tail has
  muscles, and skeletal elements and provides
  propulsion in water.

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Invertebrates

• Invertebrates are animals that lack a backbone.
• Invertebrates include 98 of the animals on
  Earth.
• Invertebrates usually have a shell or a hard
  exoskeleton for protection

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Invertebrate Chordates

• The adults of Urochordates have neither a
  notochord nor a dorsal tubular nervous system So
  how can they be chordates?
• These animals disperse themselves with
  free-swimming larvae that have
• a dorsal tubular nervous system
• notochord
• gill slits

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Invertebrate Chordates

• Chordates include two subphyla of invertebrates
• -UROCHORDATES -CEPHALACHORDATES

http//instruct1.cit.cornell.edu/courses/biog105/l
abs/deuts/media/urochadult.jpg
http//www-biol.paisley.ac.uk/courses/Tatner/biome
dia/pictures/amphi8.htm
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Invertebrate Chordates

• Tunicate larva - free-swimming and exhibits all
  chordate characteristics
• notochord, a dorsal nerve cord, pharyngeal slits,
  and a post-anal tail.
• The larvae swims until it eventually attaches to
  a hard substrate
• it loses its tail and ability to move, and its
  nervous system disintegrates.

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Urochordates

• Commonly called tunicates
• Most are marine animals
• Some adhere to rocks while others are planktonic.
• Seawater enters through an incurrent passes
  through the pharyngeal slits into atrium and
  exits through an excurrent siphon (Atriopore).
  The food that is filtered from this water is
  passed by cilia into the intestine. The anus
  empties into the excurrent siphon.

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Urochordates
http//www.talkdesign.org/faqs/evimmune/ei_animal0
03.jpg

• Have a notochord that extends from just behind
  the head to the tail
• Urochordata means "tail-cord
• There are three classes within this subphylum
  Ascidiacea, Thaliacea, and Larvacea.

http//www.animalshow.hpg.ig.com.br/tunic_ascid.jp
g
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Class Ascidiacea

• Adult ascidians are commonly called "sea squirts
• Ascidiacea are inhabitants of the intertidal zone
• they may be either solitary or colonial.
• All are filter feeders.

http//upload.wikimedia.org/wikipedia/commons/1/16
/Ascidias.jpg
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Class Thaliacea

• barrel-shaped
• Known as "salps".
• They are surrounded by circular muscle bands and
  both ends of their cylindrical body are open.
• Contractions of the circular muscles make the
  body pulsate
• This creates a form of jet propulsion and a
  mechanism for filter-feeding (suspended food is
  removed from the water by the pharyngeal gill
  slits).

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Class Larvacea

• Larvacians resemble ascidian larvae
• Most specialized urochordates.
• Build a home that is mobile within which they
  travel through the course of their lives.
• The walls of their mobile homes give little
  protection.
• Their pharyngeal gill slits are used for feeding.

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Urochordata

• There are roughly 1,600 species of urochordates
  most are small solitary animals but some are
  colonial, organisms.
• Tunicates
• Sea Squirts

http//www.dscc.edu/bwilliams/Biology2/bio2animcon
t.htm
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Physiology

• No coelom - has been replaced by proliferation of
  connective tissue
• Complex nervous system
• Locomotion propulsion
• Reproduction
• Most are hermaphrodites, producing both eggs and
  sperm hat are either free-spawned or brooded.
  Most species are self-sterile, but some are self-
  fertile

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Physiology

• Urochordates have
• dual nervous system - different nerves segmented
  (somatic nerves) unsegmented (visceral nerves)
  regions
• segmented muscles.
• locomotion by contraction of alternate sides as
  in vertebrates

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Physiology

• Brain is functions similarly to the vertebrate
  brain
• segmented muscle (myomeres) pull alternate sides
  (stiffened by notochord.)
• Pharynx gills used only for filter feeding.
• Circulation limited, but has a ventral pump
  major dorsal artery.
• No hemoglobin oxygen carried in solution
• no kidney, but similar excretory cells.
• No connection between segmented unsegmented
  nerves.
• Semi-sedentary filter feeder Both
  Cephelochordata and Urochordata trap detritus in
  mucus water moved by cilia mouth and gut have
  little or no musculature.
• No paired fins therefore less coordination.

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Anatomy Urochordata
http//bio.classes.ucsc.edu/bio136/urochordata/uro
chordata.html
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Cephalochordata

• Derived from Greek meaning both ends pointed
• The Cephalochordata subphylum commonly includes
  vertebrates, tetrapods, and amniotes
• Lampreys and hagfish are the only agnathans
  (jawless fish) that are not extinct today
• They are commonly known as lancelets

http//io.uwinnipeg.ca/simmons/16cm05/1116/34-09a
-Lamprey.jpg
http//lemonodor.com/scruz-2003-01-24/med/130-lo-h
agfish.jpg
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Lampreys (Cephalaspidomorphi)

• Feed upon fish blood from the flank
• Born in fresh water streams and remain there
  until they reach maturity in lakes or open sea
• Larva (ammocoete) are scavengers since their
  mouths are not developed for rasping

http//upload.wikimedia.org/wikipedia/en/thumb/e/e
5/Lamprey_illustration_side.png/800px-Lamprey_illu
stration_side.png
http//io.uwinnipeg.ca/simmons/16cm05/1116/34-09a
-Lamprey.jpg
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Hagfish (Myxini)

• Hagfish secrete slime, then tie themselves in a
  knot to scrape it off, to clean themselves
• Pair of horizontal structures that have
  projections that pick up food
• Feed on alive/dead fishs insides
• Tie themselves in a knot and slide towards the
  mouth, the knot pulling the mouth off

http//newport.pmel.noaa.gov/heceta/source_files/s
ource_jpegs/logbook_images/r609hagfish_link.jpg
http//lemonodor.com/scruz-2003-01-24/med/130-lo-h
agfish.jpg
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Anatomy of Cephalochordata

• 1 brain-like blister
• 2 notochord
• 3 dorsal nerve cord
• 4 post anal tail
• 6 food canal
• 10 gill slit

http//upload.wikimedia.org/wikipedia/commons/thum
b/b/b1/Lancetnikinside.png/800px-Lancetnikinside.p
ng
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Physiology I

• Chordates generally have bilateral symmetry that
  is differentiated into head, trunk, and tail
• All have notochord, nerve cord, visceral clefts
  and arches (gills)
• Notochord rod-like structure found in
  cephalochordata embryos gives axial support.
  Made from mesoderm cells.

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Physiology II

• Nerve cord develops above the notochord as a
  hollow tube. Differentiates brain anteriority and
  spinal cord from the trunk to the tail. Makes up
  central nerve system.
• Visceral clefts arches (gills) appears as
  pouches that push out to make clefts, connecting
  the pharynx to the exterior. Site of major gas
  exchange.

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Quiz

• Of which of the following features does a
  cephalochordata not possess?
• I notochord
• II jaws
• III nerve cord
• I only
• II only
• I and II
• I and III
• I, II, and III

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Quiz

• Which classes are not extinct in jawless
  vertebrates today?
• A) Myxini and Cephalaspidomorphi
• B) Lancelets
• C) Agnatha
• D) Cephalaspidomorphi and Mammalia
• E) Amphibia and Reptilia

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Quiz

• How do the adults of Urochordates and
  Cephelochordates belong to the group chordates?
• What are the three classes within the subphylum
  Urochordata?

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QUIZ

• These animals disperse themselves with
  free-swimming larvae that have
• a dorsal tubular nervous system
• notochord
• gill slits
• There are three classes within this subphylum
  Ascidiacea, Thaliacea, and Larvacea.