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Urochordates and Cephalochordates
2,420
Body Type
- 1-3 inches long
- translucent body tapered at both ends
no head, no paired fins
Lacks
- Brain
- Paired fins
- Heart
- Hard parts
Subphylum: Cephalochordata
The Lancelet
-Asymmetric living fossil
Physiology
Chordates
Digestive System
Life Style
Mouth
Nephridia
Wheel Organ
- Live buried in shallow, sandy environments
- Can swim
- Rarely exceed 5cm
- Up to 5,000 per square meter
- Filter feeders
- pharyngeal basket
- Eggs laid and fertilized externally yearly
Oral Cirri
Intestines
1. Single, hollow nerve cord
Atrium
Gill slits
-in vertebrates, it differentiates
into brain and spinal cord
2. Notochord
-flexible rod on dorsal side of gut
-in vertebrates: displaced by vertebral column that forms around the nerve cord
3. Pharangeal slits
-connect pharynx with the outside-present in terrestrial animal embryos
-Eustachian tube
4. Post-anal tail
-similar to tailbone
5. Segmentation
-arrangement of muscles and vertebral column
Kingdom: Animilia
Phylum: Chordata
Sea Squirts
Urochordata
The Lancelet
(Amphioxus)
Cephalochordata
Subphylums:
Cephalochordata
&Urochordata
Urochordates
Kayla Ventura and Giovanni Crimi
Subphylum: Urochordata
The Tunicate
"Sea Squirt" or "Sea Vase"
Physiology
- Soft body surrounded by barrel- like tunic
- Live at bottom of barrel
- 2 siphons: water enters through top, exits through side
- Gill slits
- Most organs enclosed in Epicardium
- Usually sedentary, filter-feeding
- Heart & Circulatory system
- Controlled by blood vessles
- No kidneys
- Large clear vesicles
Digestive System
Life Cycle
- Suspension feeders
- Plankton
- Some reproduce by budding
- Some are hermaphrodites
- Most follow typical life cycle:
Incurrent
Siphon
Expelled via
syphion
External fertilization
Tadpole-like
larva
Eggs held in
tunicate
Entangled in mucus
in pharynx, the
bronchial sac
Anus
Uses muscular tail to swim with plankton until
finds a place to settle
Digests tail, grows
tunicate, and
begins feeding