Pond mud snail Omphiscola glabra

The pond mud snail is a very small freshwater aquatic snail. It is dark brown with an elegant spire that has slightly flattened whorls, but with a blunt tip. The aperture opens on the right side. Typically, these snails live in temporary nutrient-poor habitats like ponds, marshes, swampy meadows and small ditches.


The species is typically found in very clean water and survives on a diet of algae and decaying plants.

A key characteristic of their habitat is that water levels are significantly reduced in the summer months. This ensures they have few competitors (other molluscs), as only specialists can survive these variable and harsh conditions. The pond mud snail can survive dry conditions by burying itself in the mud (up to 6cm) and storing a little water in a cavity in its shell, from which oxygen is extracted, until water returns to the pool.

The pond mud snail is hermaphroditic; it can lay and fertilise its own eggs. This makes the species a prolific breeder, with an individual laying between 10-30 eggs in February, taking around 25 days to hatch. It typically has two generations per year.


  • Length: 14-25mm in length
  • Width: 4-7mm
  • Average lifespan: 1 year (approx.)


Listed as a vulnerable species in the UK Red Data Book. This species has become extinct over large parts of lowland England and continues to decline. The pond mud snail is listed under section 41/42 of the 2006 Natural Environment and Rural Communities (NERC) Act and is a priority species for conservation.

The pond mud snail is on the UK Biodiversity Action Plan Priority List and the Scottish Biodiversity List.


Formerly widely distributed throughout acidic lowland areas of England, Wales and Scotland, as far north as Perth. They have been lost from 64% of former sites in Scotland due largely to habitat loss and pollution. Their distribution is now limited to a handful of sites in Scotland.

When to see

January to December. They can often be found on the underside of logs or tree roots, especially during the summer months when water levels are low.


  • The pond mud snail plays a key role in the ecosystem, by eating dead vegetation and turning it into nutrients that go back into the wider food chain.
  • The pond mud snail is able to fill the pallial cavity (in its shell) with water and acquire oxygen from it, despite being lung-breathing.
  • The Royal Zoological Society’s (RZS) Edinburgh Zoo and Buglife Scotland released (captivity bred) pond mud snails into the Scottish Wildlife Trust’s Red Moss of Balerno Reserve, where the population is being monitored and where there are plans for annual releases.

Common name

Pond mud snail

Species name

Omphiscola glabra

IUCN Red List status

Listed as vulnerable in the UK Red Data Book

When to see in Scotland

January to December. They can often be found on the underside of logs or tree roots, especially during the summer months when water levels are low.

Where to see in Scotland

The Red Moss of Balerno Nature Wildlife Reserve in the Pentlands, south west of Edinburgh, is one of the sites where this rare species of snail is clinging on. The seven known sites are in North Lanarkshire, East Dunbartonshire, Edinburgh, West Lothian, Falkirk, Clackmannanshire and the Scottish Borders.

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