Scypha Dr. Shivani Gupta, PGGCG-11,Chandigarh

Morphology Body wall: The body wall of a common sponge consists of following layers. Pinacoderum (= dermal layer). It is outer cellular layer which consist of (i) flattened Pinacocytes and (ii) oval porocytes. Choanoderm (= gastral layer). It is inner cellular layer which consists of highly specialized flagellated cells called choanocytes (collar cells). They are the characteristic cells of this phylum. Responsible for injestion of food, secretion of mesohyaland differentiation of sex cells.

Body Wall c) Mesohyl layer (= mesenchyme). Basically, it is a non cellular layer found in between pinacoderm and choanoderm. It has fine dispersed sponging fibres and numerous spicules. It also contains amoebocytes (amoeba-like-cells) of both pinacoderm and choanoderm. Amoebocytes are modified into the following types: -Archaeocytes: They may be converted into other types of cells and are also called undifferentiated "totipotent" cells. -Trophocytes: They provide food to developing cells and are called nurse cells. -Thesocytes: They store food granules. -Gland cells: They secrete a slimy substance. -Spongioblasts: They secretes spongin fibres of the mesohyl layer. -Scleroblasts: They secretes spicules. In calcareous sponges. They are called calcoblasts.

Body Wall -Collencytes: They secretes collagen fibres. -Myocytes: They form a circular ring around the osculum and help in closing and opening of the osculum. -Germ cells (Sex cells). They form sperms and ova and develop during breeding season. -Chromocytes. They contains pigment granules and excretory substance. -Phagocytes. They collect food from choanocytes through their pseudopodia and also engulf excreta and damaged tissues.

Physiology The central body cavity of a sponge is called spongocoel or paragastric cavity. The continuous body current flowing through the canal system is very important for the life of a sponge. It brings in food and oxygen and carries away carbon dioxide, nitrogenous wastes and reproductive bodies. Thus the canal system helps the sponge in nutrition , respiration, excretion and reproduction. Skeleton: Almost all sponges possess an internal skeleton. It may consist of calcareous or siliceous spicules or fine sponging fibres or of both, location in the mesohyl layer.

Physiology Digestion: It is intracellular and takes place inside food vacuole as in protozoans Circulation: Distribution of food from the ingesting cells to others is brought about by wandering amoebocytes of mesohyl layer. 7.In case of Sycon pinacoderm is divided into exopinacoderm and endopinacoderm. Endopinacoderm lines the incorrect canal. Respiration: Exchange of gases occurs by diffusion through the plasma membranes of the cells as in protozoans. Excretion: Removal of metabolic wastes also occurs by diffusion through the plasma membranes of the cells as in protozoans. Ammonia is chief excretory waste.

Scypha Osculum Spongocoel Radial Canal Incurrent Canal Choanocytes Ostium

Canal System Sycon type.

Reproduction Both asexual and sexual reproduction occur in sponges. Asexual reproduction occurs by budding and gemmules. In fresh water sponges and a few marine sponges gemmules (internal buds) are formed. Each gemmule has the mass of archaeocytes surrounded by protective covering to tide over seasonal drought or adverse environmental conditions. Gemmule formation is also called internal budding. Sponges have a great power of regeneration. Most forms are hermaphrodite. Sperms leave one sponge and enter another with water current to fertilize the ova(eggs) in situ. Thus fertilization is internal.