BRACHIOSTOMA

BRACHIOSTOMA (Amphioxus)

P= Chordata
C= Cephalochordates
F= Branchiostomidae
G= Branchiostoma

amphioxus

- Commonly called 'lancelet'
- Total species =9 species
- Shape = laterally spindle shaped body
- Size = 4.5-7 cm
- Color = Whitish ,transparent
- Body division = trunk and tail
- Body Aperture = 3 aperture

Body Wall Branchiostoma

* Mouth
* Atriopore
* Anus
- Straight and complete Digestive system
- Skin consist outer epidermis and inner dermis
- These animal show metameric segmentation
- Presence of notochord in endoskeleton
- Main Feature of this animal are have notochord through out life
- This animal having true coelom
- Filter feeder feeding
- Presence of pharyx in alimentary canal
- pharynx have vertical oblique gill slits which are separted by gill bars

Gill Bar Branchiostoma

- Gill bar are of two type primary and secondary gill bars
- Having oesophagus are of small sized
- Tubular shaped intestine
- These animal are omnivorous in nature
- These animal are of holozoic type eat food by mouth
- Mainly survive on planktones or small organism
- Mouth part is called rostrum
- Mouth have oral cirri , tentacles like structure for capturing food particles
- Circulatory system is closed type
- Digestion is extracelluler
- Excretory particles through out by rectum
- Blood is colourless
- No haemoglobin pigment present
- Blood vessel divided into

Blood Vascular System Branchiostoma

* ventral aorta
* Afferent Branchial arties
* Efferent Branchial arties
* Lateral Dorsal Aorta
* Median Dorsal aorta
* Sub-intestinal vein etc
- Excretory organ protonephridia having numberous solenocytes

Protonephridium Branchiostoma

- Nervous sytem consist Nerve cord or CNS, peripheral nervous system , ANS
- Sense organ are
* EYe spot (OCelli)
* Cephalic Pigment spot
* Kollikers's pit
* Infundicular organ
* Hatschek's pit
* Sensory papillae and etc
- Gonads are in 26-27 in pair
- Sexes are separate
- Two types gamete spermatozoa (motile , small) and Ova (single, big , non-motile)
- Fertilization external