Using longitudinal and transverse anatomical sections, we observed that
the three cristae of the mantle of Biomphalaria glabrata (renal,
rectal and dorsolateral cristae) divide the mantle cavity into three
chambers which we designated air or pulmonary chamber, water inflow chamber
and water outflow chamber. Using videotape filming, we observed the inflow
and outflow of air and water into and from the mantle cavity and we related
their probable functions such as flotation, oxygen reservoir and transport,
excreta circulation and elimination, water skeleton, and modification of
specific weight. To determine whether the air bubble may function as a
physical gill in this species we submitted three groups of snails to
different systems in which water contained the same level of dissolved
oxygen whereas the gas phases were atmospheric air, pure nitrogen or pure
oxygen. We observed the following parameters: time of permanence on the
surface, time of immersion, and frequency at which the snails reached the
surface. These results did not demonstrate a physical gill function;
morphological analysis of the mantle cavity indicates this possibility.
