Armiger crista


Armiger crista, commonly known as the Nautilus ramshorn, is a minute species of freshwater snail, an aquatic pulmonate gastropod mollusk in the family Planorbidae, the ram's horn snails.

Distribution

The distribution of this species is Holarctic. The distribution type is circumpolar wide-temperate, and the range includes:

Shell description

The minute shell is nearly planispiral in its coiling, but the spire is actually considerably sunken rather than raised.
The shell has regular transverse ridges which form points extending beyond the main curve of the periphery of the shell.
The shell color is a translucent yellowy-brown. The maximum shell dimension is about 3 mm.

Ecology

This snail lives on water plants in clear still freshwater.
In Ireland it is common in medium to very small habitats including slow streams, drains and marsh and fen pools
It is occasionally found in very acid waters.
This minute species, although technically a pulmonate gastropod, does not use air for respiration but instead absorbs oxygen through its mantle cavity which is full of water.