Gill. In the control snails, most of the epithelial lining of the
gills consisted of columnar cells with long cilia (Fig. 5G). Some
mucous cells were occasionally found in the gill filament (Fig. 5G).
In the sediment-exposed snails, the gills exhibited an increase in the
number of mucous cells, and reduction in length or loss of cilia
(Fig. 5H). Columnar cells became highly vacuolated, and some
degenerated