Question

Which of the following Urochordate animal is known as Sea squirt?
A. Tunicate
B. Branchiostoma
C. Balanoglossus
D. Sacoglossus

Answer 1

Hint: The Urochordata are marine organisms. They are invertebrates belonging to the kingdom Animalia. They possess very basic or primitive features of vertebrates.

Complete answer:
The Seasquirt belongs to the class Tunicata. They are sessile organisms, that is, they are attached permanently to solid surfaces. They are called so because of their unique shape. The body of these organisms has an outer covering that is composed of a substance that is similar to cellulose. The body is composed of two pores, one through which the water enters into the body cavity and the other through which the entered water exits. These cavities are also known as siphons. Their body resembles a swollen sac.

Considering the other given options:
Branchiostoma is also protochordate, which is less evolved and less complex than other invertebrates. They are also known as gill-mouth. They do not possess a true head.
Balanoglossus are the organisms that exist as an evolutionary link between invertebrates and vertebrates. They are Hemichordates. Being deuterostome, they resemble sea squirts but are not true sea squirts.
Saccoglossus are aquatic organisms that belong to the class Hemichordata. They are soft cylindrical worms.
Thus the most appropriate option among the given ones is A. That is, Tunicates are the Urochordates that belong to Sea Squirts.

Note: Sea squirts are a very important source of chemicals that are involved in new drug discoveries. They secrete a substance known as trabectedin, which has cancer-curing or anti-cancer properties. It is used in the treatment of different sarcomas or soft tissue tumors.