Table 1 Cell types in Ephydatia muelleri

Epithelial layer

I

Pinacocyte

Exopinacocyte

Covering outer surface

Flat pentagonal, central nucleus, pinching cell junctions, no clear tubulin label, actin at periphery of cells

Figure 2

Pinacocyte

Endopinacocyte I

Lower lining of 'dermal layer' forms surface of subdermal space

Flat elongated or polygonal, with actin tracts diagonally across cell; plaque-like cell junctions

Figures 2,3

Pinacocyte

Endopinacocyte II

Lines canals

Polygonal, peripheral actin—no clear actin tracts across cells

Figure 9

Pinacocyte

Basopinacocyte

Lines base of sponge

Pentagonal/polygonal, actin tracks as in endopinacocyte I, tubulin cytoskeleton is well-developed forming star like array

Figures 10, S6

Porocyte

Porocyte

In exopinacoderm

Flat with one or more central opening, hook-like junctions

Figure 4

Porocyte

Sieve cell

Incurrent canal

Basket-shaped cell at entrance to incurrent canal

Figure 5

Choanoderm (feeding epithelium)

Porocyte

Endopinacocyte III (prosopyle cell)

Incurrent canal

Flat cell with holes, support base of choanocytes, form the openings into chambers

Figure 7

II

Apopylar

Apopyle cell (cone cell)

Choanocyte chamber

Make up the exit out of chambers, bear a single cilium

Figure 7

III

Choanocyte

Choanocyte

Choanocyte chambers

Squat cells with collar of microvilli surrounding single flagellum, form chambers

Figures 7,8

Motile cells

IV

Polyblast

Type 1 polyblast

Mesohyl, canal, osculum

Large flat ameboid, broad pseudopodia

Figure 10

Polyblast

Type 2 polyblast

Mesohyl, canal, osculum

Flat amoeboid, small pseudopodia

Figure 10

V

Archaeocyte

Archaeocyte

Mesohyl, canal, osculum

Spherical, large central nucleus with nucleolus, ameboid

Figure 10

VI

Cystencyte

Big cystencyte

Mesohyl, canal, osculum

Large central inclusion, travels with broad anterior pseudopodium "foot"

Figure 10

Cystencyte

Small cystencyte

Mesohyl, canal, osculum

Small central inclusion, travels with small anterior pseudopodium "foot"

Figure 10

VII

Thesocyte

Thesocyte

Mesohyl, canal, osculum

Globular cells with birefringent storage inclusions; give rise to archaeocytes at hatching

Not shown

VIII

Sclerocyte

Sclerocyte

Mesohyl, canal, osculum

Spicule secreting cells

Figure 10

IX

Collencyte

Lophocyte/collencyte

Mesohyl, canal, osculum

Secrete collagen fibrils

Figure 2

X

Spongocyte

Spongocyte

Mesohyl, canal, osculum

Secrete spongin fibres (not identified in this work but assumed present due to spongin attaching spicules)

Not shown