Left or right snail other than crab
2006/03/23 Rementeria Argote, Nagore - Elhuyar Zientziaren Komunikazioa
The crab of the species Calappa flammea feeds on sea snails, among which are species of the figure. But not all: those on the left of the image have to discard them. These shells are made from left to right (they are levógiras) and the right arm of the crab (the one who uses it to eat) cannot fulfill its function.
Apparently, the crab would only have to turn around a levógiro snail to place the opening of the shell on the right side, but it seems that it always holds the snail from behind when eating crabs.
Fortunately, the shell of most snails is dextrogyre, that is, from right to left.
This question has brought biologists a question: if marine snails with levógira shell have this advantage, why are they not more abundant?
