• 1) Metazoa=Animalia: capable of movement (most, contrasts with fungi and multicellular plants), heterotrophic, truly multicellular, pass through a blastula stage, possess collagen

• 2) Porifera (sponges) are sessile, show the least cellular differentiation & integration of metazoans

  • lack true tissues, endoderm, mouth & gut (cellular level of organization), hence sometimes placed in subkingdom Parazoa

• 3) Three classes to note: Calcarae (calcareous spicules), Demospongiae (silica spicules, with spongin in some), Hexactinellida (syncytial, silica spicules)

• 4) Common features of the water-canal system are: multiple (small) incurrent pores (ostia), one or a few (large) excurrent pores (oscula)

• 5) Colony form varies from simple to complex

  • ascon type- single flagellated pumping cavity
  • sycon type- multiple radial flagellated pumping canals
  • leucon type- many distinct flagellated chambers
  • all three forms are found in the Calcarae, but only the leucon type is seen in the Demospongiae

• 6) Specialized cells include: pinacocytes (form pinacoderm), choanocytes (pumping, feeding), porocytes (incurrent pores), mesenchyme cells (make spicules, spongin), contractile cells (encircle oscula)

• 7) Choanocytes feed like choanoflagellates, they phagocitize tiny particles (bacteria, spores, gametes, fine organic debris, etc.) trapped on 'collar' of microvilli

• 8) Reproduction: sponges are hermaphroditic (sperm from choanocytes, eggs from choanocytes or mesenchyme cells), fertilization internal!, early cleavage is radial and yields a blastula larva that may be simple or complex

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