BIOL 371 Lecture Notes - Lecture 5: Pinacoderm, Choanocyte, Spongin
Document Summary
Made up of collar cells: cell body, a ring of microvilli and then a long flagella. Water enters ring of microvilli due to beating flagellum creating a water current. Relationship to porifera (sponges) unclear but probably have a common ancestor. No head, no mouth, many with no defined shape, no anterior-posterior and no left right symmetry. Have genes homologous to other metazoans for axes of symmetry though. Shape can be determined by substrate and/or environment. Choanocytes, like collar cells of choanoflagellates move water and capture food particles via micropinocytosis. Located inside the sponge in canals of pockets. Makes up the pinacoderm, which covers the mesohyle. Some pinacocytes can shorten= myocytes can change sponge shape. Archeocytes, ameboid cells that can differentiate into cells that make spicules of different types. Inside the sponge are canals lined with choanocytes. Water enters via tiny pore (ostia) in pinacoderm. Passes into central cavity- spongocoel, lined with choanocytes which absorb nutrients.
