Phylum Porifera

Sponges…weird - in a good way.

 
  1. Unifying Characteristics
    1. Predominantly marine except for two freshwater families
    2. Metazoan, with loosely aggregated cells
    3. Adults sessile, commonly encrusting.
    4. Asymmetrical or radially symmetrical.
    5. Body permeated with pores, canals, and chambers through which water current flows
    6. Internal cavities are, at least partially, lined with flagellated cells (choanocytes)
    7. Possess an internal skeleton of spicules and/or organic fibers.
    8. A nervous system is absent.
    9. Possess high regenerative powers.
    10. Exhibit cellular differentiation, but no tissue layers
      1. 3 cell layers

      epidermis - outer layer

      mesenchyme - middle layer

      endodermis - inner layer

    11. Canal systems extend surface area of sponge
      1. asconoid, syconoid, leuconoid
    12. Skeletal systems - all sponges possess spicules
      1. spongin - fibrous, similar to collagen
      2. calcium carbonate
      3. silicate
  1. Porifera Classification
    1. Class Calcarea
      1. calcareous spicules
      2. asconoid and syconoid canal systems

      Examples:

      Leucosolenia (asconoid); Scypha (=Grantia) (syconoid)

       
    2. Class Hexactinellida - glass sponges
      1. silicaceous spicules (6-rayed)
      2. syncold and leuconoid canal systems

      Examples:

      Venus flower basket (Euplectella)

       
    3. Class Demospongiae
      1. silicon or spongin spicules, or both
      2. (spicules never six-rayed)
      3. all leuconoid

Examples:

Spongia; bath and basket sponges