Often, sponges are distinguished by the level of complexity exhibited by their bodies. The simplest form consists of a single tube two cell layers thick. Poriferans with this type of architecture are necessarily very small due to surface area to volume constraints. In order for a sponge to attain greater size, the sponge wall must be folded in on itself. A simple folding of the wall yields a sponge body with sycon organization. The vast majority of sponges are organized in a more complex way, the leucon condition, with folds upon folds, resulting in a series of flagellated chambers connected by canals. Ascon, sycon, and leucon are levels of complexity that grade one into the other.
Sponge bodies are diverse in form, ranging from encrusting sheets, to volcano-shaped mounds, to tubes as small as one millimeter or as large as one meter, and to upright sheets reminiscent of elephant ears. In all
cases, poriferans have a canal system, through which they pump water.
Water enters through pores called ostia, flows through canals to a
spacious chamber called a spongocoel, and finally exits through large
openings called oscula.
What's going on inside sponges?