Behavioural and anatomical observations of the amphibious snail Pirenella conica (Gastropoda: Potamididae)

The coastal snail Pirenella conica (Gastropoda: Potamididae) was observed and photographed in its mud flat habitat (Alaçati Bay, Karaburun Peninsula, Türkiye) and in the laboratory. The snails were amphibious; they moved about in damp sediment when the sea had receded and readily left the water in the laboratory to move on dry surfaces. The siphon, normally used for the intake of oxygenated water in submerged snails, remained open when snails were out of water, suggesting that they can also breathe air. Videos of snails taken from below explained  the mechanics of their stop-and-go locomotion. Close-up photographs also revealed the presence of a pallial eye at the top of the  siphonal canal. When a snail was partially buried in soft sediment, its pallial eye remained above the sediment. The pallial eye may orient the snail and help it detect potential dangers when its tentacular eyes are obstructed.