Question

Chordata, Urochordata Questions

1. Copy the drawing of the tadpole larva and label each of the parts that make a tunicate a chordate.

2. Which organ systems are elaborated and which are atrophied during metamorphosis in tunicates?

3. Explain how tunicates feed.

4. Tunicates are often part of the fowling community. What makes them “fowling” organisms and why is that group of organisms economically important?

Answer 1

Ans 1

A tunicate is a marine invertibrate animal, a member of the subphylum Tunicata. it is a part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords, The subphylum was at one time Urochordata. Presence of notochords makes it to comes under Chordata.

Refer Picture 1

Ans 3:

Tunicates are filter feeders, Basic part used for feedings are

1. Sipon

2. Atrial cavity

3. Pharynx

4. Exhalent siphon

5. Epicardium or Visceral Cavity

• The tunicate body is shaped like a small barrel with two large openings called Siphons. The inhalent siphon brings water into saclike, central cavity which is called as atrial cavity, which is distinct from the coelom, and then through the pharyngeal slits where food is foltered into the digestive system, the water then exits the cavity through an exhalent siphon. The tunicate coelom is reduced to a small compartment surroundings the heart. The majority of the organs lie within a body cavity below the atrial cavity called the epicardium or the visceral cavity. The visceral cavity contains the digestive tract.
• Tunicates are suspension feeders, capturing planktonic particles by filtering sea water through their bodies, water is drawn into the body through the buccal siphon by the action of cilia. To obtainenough food, it need to process one body volume of water per second. This is drawn through a net lining the pharynx which is being continuously secreted by the endostyle. The net is rolled up on the trapped particles are drawn into the oesophagus.
• The gus is U shaped and also ciliated to move the contents along. the stomach is an enlarged region at the lowest part of the U bend. Here digestive enzymes are secreted and a pyloric gland further secretions.
• After digestion, the food is moved on through the intestine, where absorption takes place, and the rectum, where undigested remains are formed into faecal pellets or strings, the outlet part open into the dorsal or cloacal part of the peribranchial cavity near the atrial siphon.
• Daeces are caught up by the conatant stream of water which carries the waste to the exterior. The animal orientates itself to the current in such a way that the buccal siphon is always upstream and doesnot draw in contaminated water.

Refer Diagram 3