Alex Mustard / Spiral wrack (Fucus spiralis) with fruiting bodies photographed in a rock pool, with common periwinkle (Littorina littorea). Looe, Cornwall, England, United Kingdom. English Channel, North East Atlant...

Alex Mustard / Aggregation of Common periwinkles (Littorina littorea) gather in a rock pool. Looe, Cornwall, England, United Kingdom. English Channel, North East Atlantic.

Nick Upton / Common / Edible periwinkle (Littorina littorea) crawling over a rockpool floor, The Gower Peninsula, UK, August.

Alex Hyde / Common Hermit Crab (Pagurus bernhardus) in shell of Edible Periwinkle (Littorina littorea). This close up shows the compound eyes. Northumberland, UK. May.

Alex Hyde / Common Hermit Crab (Pagurus bernhardus) in shell of Edible Periwinkle (Littorina littorea). Photographed on a white background in mobile field studio. Northumberland, UK. May.

Alex Hyde / Common Hermit Crab (Pagurus bernhardus) in shell of Edible Periwinkle (Littorina littorea). Photographed on a white background in mobile field studio. Northumberland, UK. May.

Nick Upton / Common brittle star (Ophiothrix fragilis) moving over floor of rockpool encrusted with red algae past Common periwinkles (Littorina littorea) and Flat / Purple Top shell (Gibbula umbilicalis) low on a...

Alex Hyde / Selection of gastropods commonly found in rockpools, clockwise from top left: Periwinkle (Littorina compressa / nigrolineata), Dogwhelk (Nucella lapillus / Thaius lapillus), Common Flat Periwinkle (Li...

Nick Upton / Beadlet anemone (Actinia equina) with tentacles spread out, alongside adult and young Common periwinkles (Littorina littorea) in a rockpool, North Berwick, East Lothian, UK, July

Nick Upton / Dense gathering of Common periwinkles (Littorina liitorea) of all ages in a rockpool lined with Coralweed (Corallina officinalis) and Irish moss (Chondrus crispus), North Berwick, East Lothian, July

Nick Upton / Dense aggregation of Common periwinkles (Littorina littorea) in a rockpool, North Berwick, East Lothian, UK, July

Nick Upton / Adult Common periwinkle (Littorina liitorea) with well worn shell on rocks encrusted with Common barnacles (Semibalanus balanoides) exposed at low tide, Crail, Fife, July

Nick Upton / Dense gathering of adult and young Common periwinkles (Littorina liitorea) on red sandstone rocks exposed at low tide, North Berwick, East Lothian, July.

Nick Upton / Dense gathering of adult and young Common periwinkles (Littorina liitorea) on red sandstone rocks exposed at low tide, North Berwick, East Lothian, July.

Nick Upton / Dense aggregation of adult and young Common periwinkles (Littorina littorea) in a rockpool, North Berwick, East Lothian, UK, July.

Nick Upton / Dense aggregation of Common periwinkles (Littorina littorea) in a rockpool alongside a variety of red algae, Crail, Fife, UK, July

Nick Upton / Two Common periwinkles (Littorina littorea) crawling over a boulder in a rockpool, Crail, Fife, Lothian, UK, July

Nick Upton / Common periwinkle (Littorina littorea) crawling over rockpool floor, North Berwick, East Lothian, UK, July

Nick Upton / Common periwinkle (Littorina littorea) grazing on Kelp frond in a rockpool, North Berwick, East Lothian, UK, July

Nick Upton / Common periwinkles (Littorina liitorea) alongside yellow and brown Rough periwinkles (Littorina saxatilis) nestled in a crevice in sandstone rocks at low tide, Crail, Fife, July

Nick Upton / Common periwinkles (Littorina liitorea) alongside yellow and brown Rough periwinkles (Littorina saxatilis) nestled in a crevice in sandstone rocks at low tide, Crail, Fife, July

Alex Mustard / 2020VISION / Common edible periwinkle (Littorina littorea) on submerged rocks covered in barnacles and limpets. This species in an important herbivore in this habitat. Note that eyes are visible in this photo. Loc...

Laurie Campbell / Split level view into rockpool showing Edible periwinkles (Littorina littorea) grazing on kelp, Berwickshire Coast, Scotland

MYN / Jerry Monkman / Common periwinkle (Littorina littorea) Rye, New Hampshire, USA, September. meetyourneighbours.net project

MYN / Jerry Monkman / Common periwinkles (Littorina littorea) (left and top) and Dogwhelk (Nucella lapillus). Rye, New Hampshire, USA, August. meetyourneighbours.net project

Robert Thompson / Periwinkles {Littorina saxatilis} and {Littorina littorea} and Barnacles exposed on rock at shoreline, Killough, County Down, Northern Ireland, UK, December

Robert Thompson / Common periwinkle {Littorina littorea} and Barnacles on rock, Ballyhenry Point, Strangford Lough, County Down, Northern Ireland, UK, September

Simon Colmer / Common periwinkle (Littorina littorea) shell, underwater, captive UK

Simon Colmer / Common periwinkle (Littorina littorea) underwater, viewed from the underside showing foot, captive UK

Gary K. Smith / Common periwinkles (Littorina Littorea) attached to rock with bladderwrack (Fucus vesiculosus), Norfolk, UK

Simon Colmer / Green shore crab (Carcinus maenas) in rock pool with Beadlet anemone (Actinia equina), Common limpet (Patella vulgata), American slipper limpet (Crepidula fornicata), flat top shell (Gibbula umbilical...

Ingo Arndt / Common periwinkle {Littorina littorea} viewed from underside, from North Sea, Europe FOR SALE ONLY IN UK

Ingo Arndt / Common periwinkle {Littorina littorea} viewed from underside, from North Sea, Europe FOR SALE ONLY IN UK

Christophe Courteau / Common periwinkle feeding {Littorina littorea} Brittany France

Bernard Castelein / Common periwinkles {Littorina littorea} + seaweed Scotland, UK

Ingo Arndt / Common Periwinkle (Littorina littorea) underside shell length is approximately two centimeters, Helgoland, Germany

Ingo Arndt / Common Periwinkle (Littorina littorea) underside shell length is approximately two centimeters, Helgoland, Germany

Jason Smalley / Common periwinkles {Littorina littorea} + Barnacles on rock Pembrokeshire, Wales

Nick Upton / Common prawn (Palaemon serratus) foraging among boulders and shells of Comon periwinkles (Littorina littorea), Rhossili, The Gower Peninsula, UK, July.

Paul D Stewart / Chromolithograph illustration of perforated Cromagnon 30,000 ybp ornaments (shell, ivory), by Edouard Lartet and Henry Christy. 'Reliquiae Aquitanicae' 1865-1875, Williams and Norgate, London 1875. Th...

Duncan Usher / Flat Topshells (Gibbula umbilicalis), Common Northern Whelk (Buccinum undatum), and Common Periwinkle (Littorina littorea) shells