(hexactinellid sponge)

PHYLUM PORIFERA (= sponges) (tree & traits from Ruppert et. al. 2003, Ed. #7)

(calcareous sponge)

(demosponge)

        ==2======== Hexactinellida (glass sponges; no regular canal system)
        |
        |========== Sclerospongia (coralline sponges; leucon type, silica & calcareous spicules)
<<===1==|
        |    ==4=== Calcarea (includes ascon, sycon & leucon grades)
        ==3==|
             ==5=== Demospongia (most living sponge species; leucon type)

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade):

1: a) adult is sessile b) water canal system with pumping choanocytes** (monociliated cells with diplosome) c) extensive mesenchyme (gelatinous proteinaceous matrix containing skeletal material & amoeboid cells) d) silica spicules, initiated intracellulary e) pinacoderm (epithelium-like outer layer) lacking basal lamina & intercellular junctions f) dynamic tissue remodelling (reversible differentiation of most cell types) 2 (Hexactinellida): a) silica spicules** b) distinctive 6-pointed spicule (hexactine) c) most cells part of extensive syncytium

3: a) porocytes (pore cells) b) transport of sperm to egg via choanocyte 4 (Calcarea): a) loss of silica spicules b) calcareous spicules 5 (Demospongia): a) silica spicules** b) spongocytes & spongin fibers c) distinctive 4-pointed spicule (tetraxon)