In the test of Herdmania two types of calcareous spicules are Present. They are:
- Microscleres: These are 40 to 80 microns in length. They are minute.
- Megascleres: These are long spicules. They show different shapes. They are 1.5 to 3.5 mm in length. They are two types.
a) Spindle shaped Megascleres. They are 1.5 to 2.5 mm in length.
b) Pipette shaped Megascleres. They are 3.5 mm in length.
The microscleres are present only in the test. But the megascleres occur in the test, body wall, and viscera.
FUNCTIONS OF SPICULES
- They give support to the test.
- They protect the animal from predators.
- They fix mantle with test.