Other Anatomy


Pallial Water

Walter C. Blinn also studied the water that is contained within the mantle cavity of land snails and he particularly looked at Mesodon thyroidus (Say) and Allogona profunda (Say).  He found that when snails retract into their shells they expel, what Blinn came to call, pallial water through the pneumostome (Blinn, 1964).
The source of this pallial water is most likely from ingestion or osmotic uptake, but it can also come from the entry of water into the pneumostome. This water can also be replenished by body tissues (Blinn, 1964).
Now, however, rapid withdrawal into the snail’s shell is not very common in nature. It may occur in the presence of the predator, but in most cases when a snail withdraws into its shell, the process is very gradual. Also, withdrawal and even epiphragm were only completed after most of the pallial water had disappeared or diminished. Blinn did not observe any emission of liquid from the snails so he concluded that the pallial water passed into the tissues of the animal (Blinn, 1964).
This pallial water in the mantle cavity of the snail is considered to be a water reservoir if the snail seems to be under any conditions in which water is scarce. This water can be used to help keep the snail hydrated and help with the production of mucus (Blinn, 1964).

The shell of Allogona profunda (Say) is described as having a thin, smooth coating on both parietal and basal regions with microprojections completely to partially covered (Emberton, 1996).