Question

Bath sponge Euspongia has an endoskeleton of
A. Calcareous spicules
B. Siliceous spicules
C. Spongin fibres
D. Both A and B

Answer 1

Hint: There are water organisms that are helpful to us in many ways. They can be medicinal or used for cleaning purposes. Their dried exoskeleton can scrub and clean the surfaces. Some have sharp bristles while some have soft ones. The soft ones can be used on the body.

Complete answer:
Euspongia is commonly called a bath sponge. They belong to the phylum Porifera and hence are a very primitive organization. It belongs to the Demospongiae class. They are used for cleaning tools due to their bristles. It is found in the Meditteranean Sea.
It is globular in shape with projections called canals. It is found attached to the substratum. Their dried out outer skin is used as sponges.
Option A: Calcareous spicules: They are made of calcium carbonate. They are the endoskeleton of the sponges of the class Calcarea.
Option B: Siliceous spicules: They are made of silica and present as endoskeleton of sponges in class Hexactinellida and only some of Dempspongiae.
Option C: Spongin fibres: They are present as a skeleton in all sponges of class Demospongiae.

So the answer is option C: Spongin fibres.

Note: Euspongia is a zooplankton marine microorganism. Loofahs we use are made up of these sponges. Best quality loofahs are made from the dries sponges. They can exfoliate our skin. Sponges are woolly, sponge-like fibre bristles on them to be used for bathing and cleaning. There are more than 5000 sponge species under the Porifera phylum. They have 3 major groups- Dempspongia, Hexactinellida and Calcarea.