BI256 Study Guide - Siphonophorae, Filter Feeder, Obelia
Document Summary
There are no organs, no systems, no mouths or digestive tract, but have a rudimentary nervous integration. Adult sponges have no germ layers and therefore are not diploblastic or triploblastic. Adult sponges are in the sessile form and can be either solitary or colonial. Some can have characteristic shape and radial symmetry, while majority have no regular form or symmetry. A simple sac with the spongocoel (atrium) lined by flagellates choanoctyes and the outside covered by flattened pinacocytes. Between these two layers is a mesohyl containing wandering amoebocytes. The wall is strengthened by a skeleton composed of inorganic compounds forming spicules and/or organic sponging fibers. A three grades of structure are found in this class: Asconoid forms: represent a stage through which the more complex syconoid and leuconoid sponges pass during their development. Found in shallow, coastal waters to a depth of 200m. Spicules are fused to form a glass-like skeleton.
