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Phylum Mollusca > Class Gastropoda
Periwinkles
Family Littorinidae
updated Sep 12
if you learn only 3 things about them ...
Don't take them off the rocks! They will wash away with the tide and may die.
Periwinkles do move! But only at high tide or in cool weather.
The area around a periwinkle is often grazed bare of algae.

Where seen? Periwinkles sprinkle the rocks on many of our shores. They appear dead but are very much alive. At low tide, they are usually wedged into crevices and cracks in rocks and even inside the empty shells of dead oysters and barnacles. Small but resilient snails, periwinkles can breathe air so they are among the most common snails seen on the rocks above the high tide line. Large groups of periwinkles often form a horizontal band on the rocks as they move with the tides. Some larger periwinkles are found on mangrove trees, clinging on to roots, trunk and even leaves. Among the hardiest of these must be the tiny Knobbly periwinkles (Echinolittorina trochoides).

Features: 2-5cm. The periwinkle's shell is thin. The operculum is thin, circular and made of a horn-like material.

Some very similar species are difficult to positively identify without close examination. On this website, they are grouped by external features for convenience of display

Surviving the low tide: At low tide, periwinkles attach the lip of the shell to the surface with mucus then seal the shell opening tightly with a thin, horny operculum. Don't pick periwinkles off a rock! Left unattached, they may wash away when the tide comes in and they will die.

What do they eat? Periwinkles graze on tiny algae growing as a film over the rocks. Some species even eat algae growing within the rock, and rasp off some rock as they graze!

Periwinkle Babies: In periwinkles, the genders are separate and they practice internal fertilisation. The males have a prong-like male organ. Some females shed their eggs directly into the water where these drift with the plankton as they develop. Others lay gelatinous egg masses or retain their eggs until these hatch. Free-swimming larvae hatch from the eggs, only later developing into snails.

Human uses: In our region, they are collected for subsistence food by coastal dwellers and for shellcraft. Large periwinkles are eaten in temperate countries such as England. In fact, the name 'periwinkle' comes from the Old English for 'penny winkle' as they were then sold for a penny per handful. They were also used as jewellery.

Status and threats: There are indications that the temperate Edible periwinkle (Littorina littorea) is being over-collected in some places.


None of our Periwinkles are listed among the threatened animals of Singapore. However, like other creatures of the intertidal zone, the rest of our Top shell snails are affected by human activities such as reclamation and pollution. Trampling by careless visitors and overcollection can also have an impact on local populations.

Several kinds of periwinkles
may be found together.
Chek Jawa, Aug 05


Like other snails, they have
a broad foot and tentacles.
Chek Jawa, May 05


A thin operculum.
Labrador, May 05


Laying eggs on leaves?
Labrador, May 05

Family Littorinidae recorded for Singapore
from Tan Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist of The Molluscs of Singapore.

  Periwinkle snails seen awaiting identification
Species are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of display
  Mangrove periwinkles
Rock periwinkles
Round periwinkles

  Family Littorinidae
  Echinolittorina malaccana (Knobbly periwinkle snail)=Nodilittorina trochoides
Echinolittorina melanacme
Echinolittorina vidua


Littoraria ardouiniana
Littoraria articulata
Littoraria carinifera

Littoraria conica

Littoraria intermedia
Littoraria lutea
Littoraria melanostoma
(Black-mouth mangrove periwinkle snail)
Littoraria pallescens
Littoraria scabra
Littoraria strigata
Littoraria undulata
Littoraria vespacea

Mainwaringia leithii
Mainwaringia rhizophila

Peasiella lutulenta
Peasiella patula
Peasiella roepstorffiana

Links

References

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