BIOL 337 Study Guide - Midterm Guide: Chemoreceptor, Microvillus, Mechanoreceptor
Document Summary
Fresh water sponges use water expulsion vesicles for osmoregulation. Particles are trapped in mucus of choanocyte collar, and then endocytosed. Partial digestionin choanocyte, then transfer to archaeocyte for final digestion and transport. Rigid, perforated bag with inner surface lined with flagellated cells (choanocytes). Water flows into spongocoel through ostia and out through oscula. Choanocytes make water current, capture food particles and sperm. Closing ostia or oscula ; constricting canals. Asexual: fragmentation / budding gemmules = small spherical structures produced at the beginning of winter in freshwater sponges aggregate of archaeocytes. & food reserves, coated with spongin and spicules, resistant to freezing/drying. Most sponges are hermaphroditic, but produce sperm & eggs at different times. Choanocytes capture sperm; transport to mesophyll for fertilization. Sponge larvae are lecithotrophic (feed on yolk; non-feeding) Trap prey on hook- or freshwater shaped spicules. Hexact inellida spicules = silica and chitin, six-rayed. Syncytial single plasma membrane with many nuclei.
