Amphibola crenata

Amphibola crenata (titiko in the Māori language or mud-flat snail in English) is a species of air breathing snail with an operculum, a terrestrial pulmonate gastropod mollusc. It is the only member of its genus, Amphibola.

This is not a true land snail, but it is also not a true sea snail. Unlike almost all other snails that have opercula, this species breathes air. It is common in New Zealand.

Distribution

This species is endemic to New Zealand.

Habitat

This snail is found on tidal mudflats, often in great numbers.

Shell description

The thick shell of this species is about 20 mm in size and has a coarsely wrinkled surface. The whorls are shouldered with a spiral ridge, and there is a crescentic umbilicus, also bounded by a ridge. The colour is yellowish-brown externally and purplish-brown within the aperture, but the peristome is whitish.

Life habits

Amphibola crenata is interesting as it seems to represent a transitional state between marine and terrestrial gastropods. The mantle is employed as a lung, and therefore immersion of the animal in sea water is of secondary importance, and occurs for not more than an hour at each high tide.

This is one of very few air-breathing marine snails with an operculum and a veliger larva.

Feeding

This snail is a detritus or deposit feeder. It extracts bacteria, diatoms and decomposing matter from the surface sand. It egests the sand and a slimy secretion that is a rich source of food for bacteria.

Human use

In the past this species was an important food for the Māori.

References

• Powell A W B, William Collins Publishers Ltd, Auckland, New Zealand 1979 ISBN 0-00-216906-1
• 1966 Te Ara encyclopedia entry and
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