Question

Give a brief account on the characters of Tunicates.

Answer 1

• They are exclusively marine and are commonly called sea squirts, Mostly sessile,
• Some pelagic or free swimming, exist as solitary and colonial forms.
• Body - unsegmented and covered by a test or tunic.
• ***** forms are sac like.
• Coelom is absent, but has an atrial cavity surrounding the pharynx.
• Notochord -present only in the tail region of the larval stage, hence named urochordata.
• Digestive system : complete
• Circulatory system - open type.
• The heart is ventral and tubular.
• Respiration is through gill slits and clefts.
• Dorsal tubular nerve cord is present only in the larval stage and a single dorsal ganglion is present in the adults.
• Mostly hermaphrodites,
• Development indirect and includes a free swimming tadpole larva with chordate characters.
• Declining metamorphosis is seen. eg. Ascidia.