Introduction To Chordates 9. Chordata: Urochordata and Cephalochordata James Hake & Eden Berdugo

Introduction To Chordates

9. Chordata: Urochordata

and Cephalochordat

aJames Hake & Eden Berdugo

What is a chordate?

• Vertebrates are a subphylum of the phylum Chordata (the chordates)

• Chordates are bilateral• Belong to a clade of animals

known as Deuterostomia

James Hake & Eden Berdugo

Derived Characteristics of Chordates

• Notochord– a longitudinal, flexible

rod; provides flexible skeletal support

• Dorsal Hollow Nerve Chord– develops into central

nervous system (brain/spinal cord)


•Pharyngeal Slits or Clefts–grooves that develop into slits that open to the outside of the body; used in gas exchange and feeding

•Muscular, Post-Anal Tail–A tail extending posterior to the anus that contains skeletal elements and muscles; propelling force in aquatic species

http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb7pg1_files/34-02-ChordateCharacters-L.gif

Tunicates (subphylum Urochordata)

Sea Tulips

http://en.wikipedia.org/wiki/File:Sea-tulip.jpghttp://upload.wikimedia.org/wikipedia/commons/9/98/Bluebell_tunicates_Nick_Hobgood.jpg

Bluebell Tunicates


Categories• Body Cavity

– Coelemate– Body cavity lost in adults

• Body symmetry– Bilateral

• Nervous System– Simple brains with ganglion

clusters• Circulatory System

– Closed circulatory system in which blood is transported

– Blood circulation powered by heart


http://www.mun.ca/biology/scarr/142007_Urochordata.jpg

Categories [Continued]• Digestive System:

– Suspension feeders; feed by filtering sea water through pharyngeal slits, where food gets caught in a mucus lining

– Two openings in body cavity: in-current and ex-current siphon

• Excretory System– None

• Locomotion/Musculature– Sperm are mobile, but adults

are immobile• Skeletal Type

– None– Invertebrate



Categories [Continued]• Sensory Structures

– Light/gravity sensing cells in the larvae

• Reproduction– Hermaphrodites (ie asexual

reproduction)• Gas Exchange

– Absorb through pharynx• Unique Features

– As larvae, they move around until they find a suitable environment to become permanently fixed to.



Urochordata Review



Adult Tunicate Larvae Tunicate

Cephalochordata (Lancelets)

http://www.bethel.edu/~johgre/bio114d/LowerVerts.html http://www.mun.ca/biology/scarr/142007_Urochordata.jpg


Branchiostoma

Categories• Body Cavity

– Coelomate• Body Symmetry

– Bilateral Symmetry• Nervous System

– Dorsal, hollow nerve cord – Hox genes control

development of brain– No full-fledged brain; only

have swollen tip on the anterior end of the nerve cord

• Circulatory System– Contains heart– Closed Blood System


http://www.mun.ca/biology/scarr/Cephalochordata.html

Categories [Continued]• Digestive System

– Use pharyngeal slits lined with mucous to remove tiny food particles

• Excretory System– Composed of paired nephridia (a

tubule open to the exterior; has ciliated or flagellated cells and absorptive walls)

• Locomotion/Musculature– Simple swimming mechanism– Coordinated contractions of muscles

in chevrons (<<<) produce movement

– Muscle segments called somites• Skeletal Type

– No solid skeleton, but has flexible notochord

– Invertebrate



Categories [Continued]• Sensory Structures

– Poorly developed• Reproduction

– Separate Sexes– Males and females have multiple

paired gonads– External Fertilization

• Gas Exchange– Pharynx and pharyngeal slits aid

gas exchange, which occurs across the external body surface

• Other Unique Features– Lancelets’ bodies aren’t hard, so

little fossil evidence– Adult lancelets live in the sand with

their anterior ends exposed to remove tiny food particles



A Review of Cephalochordata (Lancelets)

http://www.bethel.edu/~johgre/bio114d/LowerVerts.html


Quiz1. Which is not a characteristic of all chordates?A. Notochord B. Radial Symmetry C. Nerve Cord D. Pharyngeal Slits

2. True or false: Urochordates are mobile throughout their entire lives.


3. Urochordates and cephalochordates feed by:A. ChemosynthesisB. PhotosynthesisC. Pharyngeal Slits and CleftsD. All of the Above

4. Regarding their notochords…A. Urochordates keep theirs for their entire lives, and

Cephalochordates do not.B. Cephalochordates keep theirs for their entire lives,

and Urochordates do not.C. Both Urochordates and Cephalochordates do NOT

keep theirs for their entire lives.D. Both Urochordates and Cephalochordates keep theirs

for their entire lives.


Answers1. B2. False3. C4. B


Documents

Introduction To Chordates 9. Chordata: Urochordata and Cephalochordata James Hake & Eden Berdugo