Question

Spicules are formed by
A) Calcoblasts
B) Scleroblasts
C) Spongioblast
D) Silicon Blasts

Answer 1

Hint: The organizational components found in sponges are known as Spicules. Spicules can be seen in the shape of spines or form of rays that are being emerged from the centre. They are vital as they provide the salient structural support as well as they protect the sponge from the attacks of the predators. They are mainly divided into megascleres and microscleres. The megascleres are noticeable in naked eyes but the microscleres can’t be seen.

Complete Answer:
- Calcoblasts, Spongioblasts and Silicon Blasts are made by thescleroblasts.
- The spicules are secreted from mesenchyme cells, which are called ‘Scleroblasts’.
- The Scleroblast Are the main manufacturing cells in spicules.

Additional Information:
- Spicules can be divided into three types as Monaxon, triaxon and polyaxon. It is distinguished depending on the number of axes as present in the rays spicules.
- In Monaxon, the single axis can be seen. If spicule shows a single point, then it is called ‘Monoactinal’ and when it is showing two points, it is called ‘Diactinal’.
- In Triaxon and Tetraxon, we can see respectively three and four axes. And, in the Poly Axons, from the central point, several equal rays emerge.

Note: When scleroblasts discharge calcareous spicules, they are termed as Calcoblasts. When they secrete spongin fibres, they are called Spongioblasts. Silicon Blasts are formed when scleroblast discharge siliceous spicules. In primary development of spicules, the single mother cell or scleroblast is being responsible and in secondary development, more than one scleroblasts work.