1. Chordata: Urochordata and Cephalochordata
Joycelin Luc
Michelle Chen

2. Intro to Chordata Have a notochord
Have a dorsal nerve cord => develops into central nervous system (brain and spinal cord)
Most have pharyngeal clefts and pharyngeal slits
Usually have a post-anal tail
Explain notocord (longitudinal flexible rod located between the digestive tube and the nerve cord; offers support for animals) and dorsal nerve cord
pharyngeal clefts: slits in the body that allows water entering the mouth to exit the body without passing through digestive tract
Michelle Chen

3. Common Names Urochordata Tunicate sea squirts sea pork Cephalochordata
Lancelets
amphioxus (means “both ends pointed”)
(left pic)
(right pic)
Joycelin Luc

4. Urochordata
Michelle Chen

5. Cephalochordata Michelle Chen

6. Body Cavity and Body symmetry
Coelom present in both the Urochordata and Cephalochordata subphlya
bilaterian (bilaterally symmetrical)
Body consists of myoepithelial and Epithelial cells
Myoepithelial = helps to expel secretions
Epithelium= line cavities; primary body tissue
Michelle Chen

7. Nervous System & Sensory Features
Present consisting of brain and spinal cord
in Urochordata, nervous system disintegrates when it reaches adult stage
Cephalochordates have a simple dorsal nerve cord enclosed in a sheath of collagen fibres which runs the length of the body below the notochord. From this arise a series of smaller nerves which serve the rest of the body. There is no brain or cranium such as we will find in the Vertebrata
Michelle Chen

8. Circulatory System Urochordata
Blood contains high concentration of vandium and lithium
Open circulatory system
Ventral heart
Cephalochordata
Closed blood system
Main ventral and paired dorsal aorta
No central heart, but consists of branches
lacks hemoglobin and is colorless
Has Atria cavity
Joycelin Luc

9. Digestive & Excretory System
Urochordata
Draws food through siphon into atrium from pharyngeal slits
Food filtered by mucous net
Moves to esophagus through cilia
Exits excurrent siphon
Cephalochordata
Uses cilia pumping to move food particles from slit
Trap food in pharynx
Atrium = chamber
Michelle Chen

10. Locomotion/ Musculature
Urochordata
Juvenile: tail muscles; gravity and light sensitive cells
Adult: attach to a substrate
sessile
Urochordata
Juvenile: tail muscles; gravity and light sensitive cells
Adult: attach to a substrate
sessile
Cephalochordata
Contraction of muscles arranged in a <<<< structure -> a side to side undulation to move forward
Somites
Somites = muscle segments developed from blocks of mesoderms; each side of notochord
Michelle Chen

11. Skeletal Type Urochordata Cephalochordata
Notochord (some have spicule when young)
adult: attach to rock
Cephalochordata
Develops dorsal, hollow never cord
Post-anal tail
Joycelin Luc

12. Reproduction Urochordata Hermaphrodites Eggs kept inside until hatch
Sperm released into H2O
Cephalochordata
Gonochoristic: sex separate
Sperm and eggs released into water
Fertilization is external
Cephalochordata are gonochoristic, meaning the sexes are separate. Both sperm and eggs are released into the water and fertilisation is therefore external
Joycelin Luc

13. Gas Exchange Uses cilia to regulate the gases
Pharynx and pharyngeal slits regulate the gas exchange (across external body surface)
Michelle Chen

14. Other unique features Urochordata = very few natural predators
Invasive species
Form colonies
Joycelin Luc

15. Quiz
1. What are the four basic features that separate Chordata from other phyla?
2. Name one difference between Urochordata and Cephalochordata.
3. How do adult sea squirts move? What about adult lancelets?
4. How are the reproductive methods for Urochordata and Cephalochordata different?
Joycelin Luc

16. THE END!!!