BIO2231 Chapter Notes -Calcareous Sponge, Choanocyte, Hexactinellid
Document Summary
While sponges are multicellular, their organization is quite distant from other metazoans. A sponge body is an assembly of cells embedded in an extracellular matrix and supported by a skeleton of minute needle- like spicules and protein. Choanoflagelletes are solitary/colonial aquatic eukaryotes, with each cell carrying a flagellum surrounded by a collar of microvilli. Beating of the flagellum draws water into the collar, where microvilli collect tiny particles. Many choanoflagelletes are sessile and attached to hard surfaces. Choanoflagellete cells strongly resemble sponge feeding cells called choanocytes. Adult sponges have simple bodies; they are aggregations of several different cell types, including choanocytes, held together by an extracellular matrix. Most sponge bodies are not symmetrical, but some appear radial. A sponge body has neither a mouth nor a digestive system. Sessile sponges draw food and water into its body instead. A sponge uses a flagellated collar cell", the choanocytes to move water.
