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Fig. 6. Closure of a field of porocytes in the apical pinacoderm correlates with
contraction of the choanosome after stimulus by agitation. (A–C) Stereo
microscope images show that individual ostia (arrows) close within 50 s, and a
field of 20 porocytes closes over a period of 83 s. Scale bar, 100 µm. (D)
Constriction (closing) of eight ostia in the field shown in A is correlated
with the contraction of the choanosome (broken line). Shortly after the sponge
was stimulated the ostia closed and the choanosome contracted. A few ostia
opened briefly at 1200 s during an expansion of the choanosome, but these
closed again as the choanosome contracted. The field opened again with the
expansion of the choanosome at t=1500 s (here approximately 22 min
later), and again closed just prior to contraction of the choanosome at 2400
s.