information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Looping snail (Truncatella subcylindrica)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.
Only coastal and marine records shown



A buff-coloured snail that grows up to 5 mm high. The animal has a cylindrical snout ending in a rounded mouth disc. It has a peculiar looping gait.

Recorded distribution in Britain and Ireland

Recorded from Pagham Harbour, West Sussex; The Solent, Isle of Wight, The Fleet, Dorset and St Mawes Bay, Cornwall.

Global distribution

From the Channel coasts of France and Britain to the Mediterranean, the Black Sea, and on the Canaries, Madeira and Azores.


Found in shingle amongst rotting vegetation and fine sediment at a depth of 15 cm, at high water mark and more rarely in muddy habitats under stones at the high water mark. It is often associated with the plants Suaeda maritima, Suaeda vera and Atriplex (Halimione) portulacoides.

Depth range


Identifying features

  • The juvenile has a typical spire-shaped shell; later whorls are parallel-sided until maturity when the tapered part is broken off, leaving a suture line. The adult shell is thus truncated and more or less cylindrical.
  • Buff-coloured, 5 mm high.
  • Animal with cylindrical snout ending in a rounded mouth disc.

Additional information

Abscission of the earlier part of the shell is presumably an adaptation to an interstial habitat.
The taxonomy of the Gastropoda has been recently revised (see Ponder & Lindberg 1997, and Taylor 1996). Ponder & Lindberg (1997) suggest that Mesogastropoda should be included in a monophyletic clade, the Caenogastropoda.

Listed by

- none -

Further information sources

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Biology review


Authority(Linnaeus, 1767)
Recent Synonyms


Typical abundanceModerate density
Male size rangeup to 5mm
Male size at maturity
Female size rangeVery small(<1cm)
Female size at maturity
Growth formCylindrical
Growth rateData deficient
Body flexibility
Characteristic feeding methodSub-surface deposit feeder, Surface deposit feeder
Diet/food source
Typically feeds onVegetable detritus and small algae
Environmental positionEpifaunal
SupportsNot relevant
Is the species harmful?Data deficient

Biology information

It has a peculiar looping gait and moves along by alternately attaching the foot and snout to the substratum (Seaward, 1988). The species is found at moderate densities in narrow, linear habitats.

Habitat preferences

Physiographic preferencesEstuary, Isolated saline water (Lagoon)
Biological zone preferencesLower littoral fringe, Upper littoral fringe
Substratum / habitat preferencesGravel / shingle, Mud
Tidal strength preferencesVery Weak (negligible)
Wave exposure preferencesSheltered
Salinity preferencesVariable (18-40 psu)
Depth range
Other preferencesNo text entered
Migration PatternNon-migratory / resident

Habitat Information

Formerly known from 12 sites in Britain, from Porthcurno along the south coast to the rivers Orwell and Deben, Suffolk. Presently known to be living in only five locations. It is a southern species which reaches its most northerly distribution in Britain. Paludinella globularis (as littorina), Ovatella myosotis and Leucophytia bidentata are associates.

Life history

Adult characteristics

Reproductive typeGonochoristic (dioecious)
Reproductive frequency No information
Fecundity (number of eggs)No information
Generation timeInsufficient information
Age at maturityInsufficient information
SeasonInsufficient information
Life spanInsufficient information

Larval characteristics

Larval/propagule type-
Larval/juvenile development Oviparous
Duration of larval stageNot relevant
Larval dispersal potential <10 m
Larval settlement periodInsufficient information

Life history information

Egg capsules are laid of 0.75-0.80mm diameter, which are spherical and surrounded by a thick wall. Each capsule contains one egg and they are attached singly to pieces of detritus in the habitat in which the adults live. Small snails are hatched with a shell of 0.65mm (Fretter & Graham, 1978)

Sensitivity reviewHow is sensitivity assessed?

Physical pressures

High Low High Very low
The species would be removed with substratum loss and may be damaged during the process. It has low recoverability as it lacks an aquatic dispersal phase and living populations are only known from three locations in the UK.
High Low High Very low
Smothering could block shingle interstices and prevent movement of the snail and reduce the level of oxygenation. Recovery would be low because it lacks an aquatic dispersal phase and living populations are only known from five locations in the UK.
Tolerant* Not relevant Not sensitive* Very low
Truncatella subcylindrica lives in estuaries and lagoons amongst fine muddy sediment so would be able to tolerate increased siltation. Indeed, some increased siltation may be beneficial to feeding as it is a deposit feeder, so long as interstices remain clear.
No information
Low Moderate Low Very low
The mollusc is adapted to avoid desiccation by having a hard shell and operculum. Where it is interstitial, the species would also be protected from desiccation by the depth of sediment above it and where the species is epifaunal would avoid desiccation by hiding in crevices or under stones.
Low Moderate Low Very low
Increased or decreased emergence is likely to occur on a relatively long time scale, during which the habitat and animals will probably be able to re-adjust.
No information
Low Moderate Low Very low
Living at high water mark, the species is inundated for only short periods, so that increased water flow is unlikely to have a significant effect unless it is so great as to erode materials and animals.
No information
Intermediate Moderate Moderate Very low
The degree of temperature tolerance of Truncatella subcylindrica is not known. The species will be sheltered from temperature extremes to some extent by its hard shell and by its interstitial habitat. However, the species may be intolerant of decreases in temperature as it is at the northern limit of its distribution.
No information
Tolerant Not relevant Not sensitive Very low
The species is unlikely to be affected by a change in turbidity as it does not depend on light availability for feeding and some populations are found interstitially where light cannot penetrate.
No information
Intermediate Low High Very low
The high water mark habitat means that the species is only subject to wave action for short periods. However, increased wave action may damage or wash it away, or move shingle damaging the animal by abrasion.
No information
No information Not relevant No information Not relevant
No information Not relevant No information Not relevant
High Very High Very low
Any factor causing movement of shingle where the animal lives, by natural (e.g. wave action) or human (e.g. trampling) means would be likely to damage infauna by abrasion and crushing.
High Low High Very low
Habitat displacement would cause damage to animals.

Chemical pressures

High Low High Moderate
Exposure of spermatocytes of the species to dibutyltin(IV) and tributyltin(IV) caused structural damage in the chromosomes in 24 hours at 0.0001 moles per litre (Vitturi et al., 1992).
Heavy metal contamination
No information Not relevant No information Not relevant
Hydrocarbon contamination
No information Not relevant No information Not relevant
Radionuclide contamination
No information Not relevant No information Not relevant
Changes in nutrient levels
No information Not relevant No information Not relevant
Low Low Moderate Very low
The species occurs in lagoons and estuaries so is tolerant of reduced and fully saline conditions. However, the species may not be tolerant of low salinities for long periods of time.
No information
No information Not relevant No information Not relevant

Biological pressures

No information Not relevant No information Not relevant
No information Not relevant No information Not relevant
Not relevant Not relevant Not relevant Not relevant
High Low High Very low
Would cause huge disturbance and damage but is unlikely.

Additional information

Importance review




Importance information

The assemblage is of low diversity and biomass occupying only a small proportion of the space available. It is unlikely to provide a unique food source, although a nemertean predator Prosorhochmus claparedii is recorded from the same niche at the Fleet (R.S.K. Barnes, per. comm.)


  1. Barnes, R.S.K., 1994. The brackish-water fauna of northwestern Europe. Cambridge: Cambridge University Press.

  2. Fretter, V., & Graham, A., 1978. The Prosobranch Molluscs of Britain and Denmark. Part 3. Journal of Molluscan Studies, Supplement 5, 137.

  3. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  4. Killeen, I.J. & Light, J.M., 1998. A discovery of Truncatella subcylindrica living in Cornwall. Journal of Conchology, 36, 50-51.

  5. Ponder, W.F. & Lindberg, D.R., 1997. Towards a phylogeny of gastropod molluscs: an analysis using morphological characters. Zoological Journal of the Linnean Society, 119, 83-265.

  6. Seaward, D.R., 1988. Locomotion in Truncatella subcylindrica Journal of Conchology, 33, 49.

  7. Seaward, D.R., 1991. Caecum armoricum. In British Red Data Book. 3. Invertebrates other than Insects (ed. J.H. Bratton). Peterborough: Joint Nature Conservation Committee. 253p.

  8. Taylor, J.D.(ed.), 1996. Origin and Evolutionary Radiation of the Mollusca. Oxford: Oxford University Press.

  9. Vitturi, R., Mansueto, C., Catalano, E., Pellerito, L., & Girasolo, M.A., 1992. Spermatocyte chromosome alterations in Truncatella subcylindrica following exposure to dibutyltin (IV) and tributyltin(IV) chlorides Applied Organometallic Chemistry, 6, 525-532.


This review can be cited as:

White, N. 2008. Truncatella subcylindrica Looping snail. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 16-08-2018]. Available from:

Last Updated: 03/06/2008