Question

A sponge that contains a sieve plate in the region of its osculum is:
(a) Hyalonema
(b) Spongia
(c) Euplectella
(d) Cliona

Answer 1

Hint: Sponges of the class hexactinellida are also known as ‘glass sponges’. Like all other sponges, they have a completely perforated body. The special feature of sponges of this family is the presence of a sieve plate towards the upper end of the body i.e. osculum.

Complete step by step answer:
Euplectella belongs to the class hexactinellida. It is popularly known as the ‘Venus flower basket’ due to its appearance. Their body is made up of triaxon spicules and is tubular. The body has numerous perforations like all other sponges but these are just parietal gaps and not true Ostia. The canal system present is of syconoid type. Their body is composed of silica entirely and has 6 pointed siliceous spicules. The osculum which is the upper open end of the body is covered with an ocular sieve plate in euplectella.

So, the correct answer is ‘Euplectella.’

Additional information: Canal systems in sponges are similar to circulatory systems in humans. Water enters the body of a sponge from various openings and leaves through the other. A particular path is followed by water which in easy words is referred to as a canal system. In the syconoid type of canal system, Ostia communicates with internal canals which in turn communicate with the radial canals through structures called prosopyles. The prosopyles open into the spongocoel which finally opens into the osculum and hence water which enters from Ostia is given out from the osculum. Sponges of different families have different canal systems and hence different paths are followed by water.

Note: ‘Venus flower baskets’ are very popular sponges and are widely used as ornamental sponges due to their beautiful external appearance. In order to attract planktons, these sponges are known to show bioluminescent activity. Their fibers are the thickness of a human hair and hence are currently a subject of optic fiber research.