M. myosotis has a mantle cavity that functions as a lung for breathing atmospheric air, suitable for its habitat in the supralittoral zone which is only covered by water for about an hour on each of 2 to 6 days each month. When first submerged, a bubble of air may be retained in the mantle cavity (see image 19Mm 19 Myosotella myosotis. Adult. Height 7.5 mm. Salting on Severn Estuary, Gloucestershire, England. August 2011. Left: in water. Right: same specimen in air. ), but Gittenberger (2004) states, “Long submersion is well tolerated if the oxygen content remains high. The animals then take water into their breathing cavity” [translated]. The submerged specimen above has a small bubble of air escaping from the partially open pneumostome (1) which indicates that some water has entered the mantle cavity.