Question

The characteristic larva of phylum coelenterata is
A. Planula
B. Cysticercus
C. Rhabditiform
D. Wriggler

Answer 1

Hint: Phylum coelenterata is having that larva which is free-living type and its body shape is cylindrical or egg shaped where there are presence cilia for locomotion.

Complete answer:
Phylum coelenterata is a group of aquatic or marine organisms which are found usually attached to the rocks at the bottom of the sea. They are diploblastic organisms which means that their body is made up of two layers of cells i.e., Ectoderm and Endoderm.

If we look at options now,
> Option A -
Planula is a free-living type of larvae and it is commonly found in many species of coelenterates. The shape of the planula body is cylindrical or egg-shaped and its body bears many cilia which are required for locomotion. There are some other types of larvae too i.e., ephyra, hydrula and scyphistoma. Planula are produced by the polyp form and also by the medusa form in some cnidarians. It is clear that this option is correct.

> Option B -
Cysticercus is a scientific name given to young tapeworms at a stage where the scolex is inverted in a sac and found encysted in the muscle tissue of the host. This larva belongs to phylum Platyhelminthes.

> Option C - Rhabditiform.
A roundworm infects humans when an ingested fertilized egg becomes a larval worm and that is termed rhabditiform larvae. Rhabditiform larva is characteristic to nematodes.

> Option D -
Wiggler larvae is the larva of mosquito and it is characteristic of phylum arthropods.

Hence, the correct answer is option (A).

Note: Planula is the characteristic larva of phylum coelenterata and planula is a free-living type of larvae which are produced by the polyp form and by the medusa form. Since this larva is a characteristic larva of phylum coelenterata, Hence planula becomes the right answer.