Any of numerous aquatic, chiefly marine invertebrate animals of the phylum Porifera. Sponges characteristically have a porous skeleton, usually containing an intricate system of canals, that is composed of fibrous material or siliceous or calcareous spicules. Water passing through the pores brings food to the organism. Sponges live in all depths of the sea, are sessile, and often form irregularly shaped colonies attached to an underwater surface. Sponges are considered the most primitive members of the animal kingdom, since they lack a nervous system and differentiated body tissues or organs. Adults do not have moving parts, but the larvae are free-swimming. Sponges have great regenerative capacities, with some species able to regenerate a complete adult organism from fragments as small as a single cell. Sponges first appear during the early Cambrian Period and may have evolved from protozoa. Also called poriferan. See Note at regeneration.
The light, fibrous, flexible, absorbent skeleton of certain of these organisms, used for bathing, cleaning, and other purposes.
A piece of porous plastic, rubber, cellulose, or other material, similar in absorbency to this skeleton and used for the same purposes.