Goblet type mucous cells are large ovoid cells
that are composed mostly of large apical mucous
secretory granules (Figs. 3 and 7). The nucleus
and cytoplasm are usually flattened and in a basal
position. Within the cytoplasm is the cellular
machinery for producing the mucin (ER, Golgi,
mitochondria). The mucin granules are generally
electron lucent or only moderately electron dense
with some variability between granules within the
same cell. The mucous cells are commonly found
in the filament epithelium in the following
frequency: efferent edges 4 afferent edge 4
interlamellar space 4 base of lamellae outer
margin of lamellae. However, their distribution
and numbers do show variability from this
general plan. There tends to be a reduction in
the number of mucous cells in seawater versus
freshwater fish (Laurent and Hebibi, ’89).
Goblet cells have been found in all fishes with
the exception of the hagfishes (Mallatt and
Paulsen, ’86).