Question

Gastrovascular cavity of coelenterates is partitioned in
a. Hydrozoa
b. Scyphozoa
c. Actinozoa
d. Both B and C

Answer 1

Hint: Gastrovascular cavity is an organ of digestion and circulation in Coelenterates (hydra, jellyfish, etc.) and Platyhelminthes (tapeworm, liver fluke, etc.). In coelenterates, the central gastro-vascular cavity has a single opening i.e. mouth, and is known as coelenteron.

Complete answer:
Actinozoa is a class of marine coelenterates in which the embryos are separated from the body and move out through oral aperture. Actinozoan includes corals, sea-anemones, etc. They are sessile (non-motile) and are solitary and colonial polyps. They have a cylindrical body, the oral end being suspended radially into an oral disc. All around the mouth, hollow tentacles are present. There are about 6000 species of actinozoa present worldwide.
In actinozoa, the gastro-vascular cavity is partitioned, and forms complete or incomplete septa or mesenteries (folds in the membrane).

Hence, the correct answer is option (C).

Additional information:
Hydrozoa is a class of phylum coelenterates and includes marine organisms such as hydra. They have tentacles to grasp food material. They feed on small organisms and have a simple gastro-vascular cavity covered with flagellated cells which help in circulation of food.

Scyphozoa are also marine and mostly free-swimming organisms. They are the true jellyfish having about 170 species. They live either solitarily or in colonies. They have four to eight arms suspended from the mouth. There is a single opening for both food and waste as they have no digestive tract.

Note: In actionzoa, the medusoid phase is suppressed completely and lives as polyps throughout their lives. However, they release eggs as well as sperms that attach to a substrate where they further grow. They can also reproduce asexually through the process of budding.