(hexactinellid sponge)

PHYLUM PORIFERA (= sponges) (tree & traits from Ruppert et. al. 2004, p. 93)

(calcareous sponge)

(demosponge)

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

Back to Zool 250 tree for animal phyla

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) pinacoderm (epithelium-like outer layer) lacking basal lamina & intercellular junctions e) dynamic tissue remodelling (reversible differentiation of most cell types) 2: a) calcareous spicules b) porocytes (pore cells) 3: a) silica spicules

4= HEXACTINELLIDA: a) distinctive 6-pointed spicule (hexactine) b) most cells, including collar cells, are part of an extensive syncytium (multinucleate fabric of cells) 5= DEMOSPONGIA: a) spongocytes & spongin fibers b) distinctive 4-pointed spicule (tetraxon) c) porocytes (pore cells)