The document provides an overview of the phylum Porifera, which is classified into three classes: Calcarea, Hexactinellida, and Demospongia, based on the types of spicules. Each class has distinct characteristics, such as skeleton formation and symmetry, with notable examples like Clathrina and Euplectella. Demospongia is highlighted for its economic importance, with species such as Spongilla and Cliona.

1. PORIFERA
DR.V.JEYANTHI KUMARI
ASSISTANT PROFESSOR OF ZOOLOGY
A.P.C.MAHALAXMI COLLEGE FOR WOMEN
THOOTHUKUDI-628002

2. Phylum porifera is divided into 3 classes based on types of
spicules. They are
1.CALCAREA
2.HEXA’ACTI’NELLIDA &
3.Demospongia.

3. CALCAREA
1.Skeleton is formed of
calcareous spicules
2.Radially symmetrical
animals
3.Choanocyte cells are large
and conspicuous (easily
seen or notice)
4.They have usually a single
cavity called spongocoel
opening to the exterior
through a single opening
called osculum. Example
Clathrina, Leucosolenia.

5. HEXACTINELLIDA
1.Skeleton is formed of six
rayed triaxon, silicius
spicules.
2.Canal system is
branched or
unbranched
3.Radially symmetrical
4.These are also known as
glass sponges.
Examples Farrea,
Euplectella

7. DEMOSPONGIA
1.Skeleton either absent or
present.
2.If it has skeleton, it is
formed of spongin fibres
or combination of
spongin fibres and
silicious spicules.
3.The canal system is
complicated Rhagon type
4.These sponges are of
great economic
importance.
5.Ex. Spongilla, Cliona