Phylum Porifera

20.6.1

PHYLUM PORIFERA

Unique characteristics of porifera

•        From Latin porous for pore and ferre to bear, hence an animal with pores.

•        Sponges have an asymmetric body with no true tissues, or organs.

•        Sponges often are shaped like vases with a central cavity.

•        They have two layers of cells. Flattened cells cover the exterior.

•        Collar cells line the interior chambers.

•        Numerous pores in body wall.

•        The porocytes, cells that make up the pores of the sponge.

•        Epidermal cells form the skin on the outside of the sponge.

•        Finally, the amoebocytes exist between the epidermal and collar cells.

•        They carry out functions of the sponge and help transport nutrients. They also form spicules, which are the sponge’s skeletal fibers. They work together with the collar cells to digest the food for the sponge and produce gametes for sexual reproduction.

•        Sponges are sessile and aquatic.

•        They feed by drawing water into their body cavity (spongocoel) through pores and pushing it out through the osculum.

•        Collar cells move large volumes of water through body pores by their beating flagella.

•        They filter-feed from this water by trapping food particles with choanocytes, or collar cells.

•        All energy and oxygen are obtained through simple diffusion across each cell membrane (i.e. no special circulatory or respiratory system).

•        Small spicules, made of calcium carbonate, project out of the body surface, giving support and protection to the sponge.

•        Sponges are hermaphrodites.

•        Sponges can reproduce asexually (by budding or from fragments) or sexually.

Sponges produce eggs and sperm that are released into a central cavity of the sponge, in which the zygote develops into a ciliated larva. The larval stage is able to move