![]() ![]() ![]() Used water is passed into the spongocoel and eventually out the osculum. Water enters canals through ring-shaped pinacocytes, propelled by the flagellae of numerous choanocytes (in this sponge, the choanocytes are organized into distinct chambers). The outer surface of the sponge is covered with pinacocytes. Note: Arrows show water flow patterns through the body. Palo Alto: Blackwell Scientific Publications. Hexactinellids are quite different and will be discussed separately.Īlthough some species are consistently tube- or vase-shaped, the bodies of manyįigure 1 Source: Pearse, Vicki, et al. Members of the first two groups make up the vast majority of known species, and much of what follows will describe these groups. Living sponges are divided into three classes: the Calcarea, Demospongiae, and Hexa-ctinellida. Sponges play vital ecological roles in many aquatic habitats, especially coral reefs, and because they are thought to be the most primitive living animals, they also play an important role in studies of animal phylogeny. Despite this simplicity of form and function, sponges are an important component of animal diversity in marine and freshwater habitats (with at least 5,000 living species)-and they have been since they appeared as fossils in the late Pre- cambrian. Sponges are also relatively uniform in manner of life-they are all sessile, aquatic, and feed on particles suspended in water. Sponges contain few different cell types, and these are not organized into the distinct tissues that characterize members of other animal phyla. The body plan of members of the Phylum Porifera, known as sponges, is perhaps the simplest among living animals. ![]()
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