The pillar cell is a type of modified endothelial
cell, which defines the blood spaces within the
lamellae and is a cell type unique to the fish gill.
They give the lamellae the appearance of a string
of beads when viewed in cross section (Fig. 3c,f,g).
The pillar cell body spans the lamellar blood space
and has a centrally located polymorphic nucleus
(Fig. 5).