Porifera: The Sponges

Found at all depths and latitudes, sponges are among the most ubiquitous of marine organisms. With the advent of modern laboratory and field techniques (e.g., electron microscopy, histochemistry, the development of molecular biology and biochemistry, and the use of SCUBA for collection purposes) our knowledge of sponge biology has mushroomed (see reviews by Fell, 1974; Bergquist et al., 1979). The phylum Porifera is divided into four classes, three of which occur off the coast of the Pacific Northwest. Of the three classes present locally, this chapter deals only with the classes Calcarea (Table 1) and Demospongiae (Table 2). It does not present the Hexactinellida, which are found only in deep water. Of the two classes of sponges presented here, the class Demospongiae is the larger; indeed, containing 80% of the known sponges, it is the largest of all the classes (Fell, 1974).