Question

In Sycon, the larva is
A) Trochophore
B) Parenchymula
C) Redia
D) Amphiblastula

Answer 1

Hint:Animals which have indirect mode of development have a juvenile form which is known as the larval stage. There is no physical resemblance between the larva and the adult form.

Complete answer:
Let us first know more about sycon before finding the correct option. Sycons are a genus under Porifera and they are a group of small, tubular shaped organisms. They are mostly found in marine habitats and they are attached to solid substrata.

>Option A: Trochophore larva is seen in the phylum Annelida and Mollusca. As sycon belongs to porifera, this is the incorrect option.
>Option B: Parenchymula is the larval stage of Leucosolenia which is a sponge. But this larval stage is not seen sponge, therefore, this is the incorrect option.
>Option C: Redia is the larval stage of Fasciola hepatica but not sponge. Therefore, this is the incorrect option.
>Option D: Amphiblastula is the larval stage of Sycon. The larva is free swimming and it has small flagellated cells in one hemisphere. In the other hemisphere, there are large non flagellated cells. The flagellated cells help in swimming forward. Therefore, this is the correct answer.

Therefore, the correct option is (D) Sycon.

Note:The characteristics of amphiblastula larva is,
->It is oval in shape
->It is a free swimming larva
->The larva comes out of the sponge through an opening called osculum
->The front half of the larva consists of cylindrical and flagellated cells and the other half is made up of round cells without flagella