Question

Organisms with amphiblastula larva are?
A. Sycon
B. Euplectella and Sycon
C. Both A and B
D. None of the above

Answer 1

Hint: Larva of Scypha is known as Amphiblastula. The formation of the Amphiblastula takes place by inversion of the stomoblastula after they undergo gastrulation by invagination. It is a free-swimming larva and is partly flagellated and partly non-flagellated. It is also the characteristic larva of the Calcarea.

Complete answer:
> Option A- Sycon
Sycon is a genus of calcareous sponges of the family Cottidae. Its members are small, growing up to 7.5 cm, having a length from 2.5 to 7.5, are tube-shaped and often white to cream in color. They belong to Phylum- Porifera. The bodies of Sycon are arranged in the asconoid system, which is a simple tube with no folding of the outer body wall. They have Hairy, needle-like spines (called spicules) cover their bodies.

> Option B - Euplectella and Sycon
Euplectella is a genus of glass sponges including the well-known Venus' Flower Basket. Also, known as aspergillum. It is found in a small area of the sea near the Philippine Islands. It also occurs near Japan and in other parts of the western Pacific Ocean and the Indian Ocean. Their bodies, also known as an animal skeleton, or “basket,” is a curved tube about 25 cm (10 inches) long.

Option C- Both A and B
They belong to the phylum Porifera because they show all its characteristics. This is the wrong option because Euplectella does not have amphiblastula larvae.

Hence, the correct answer is option (A).

Note: Amphiblastula is also known as Pascarella. It is oval in shape and has a cavity in the middle. The front half of the larva contains cylindrical, flagellated cells and the other half contains round cells without flagella. The larva swims with the flagellated portion forward.