Jurgen Freund / Timelapse of Periwinkle snails (Littoraria) climbing up Mangrove (Rhizophora) roots at lowtide, Daintree, Wet Tropics World Heritage Area, North Queensland, Australia.

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.

Nick Upton / Flat periwinkle (Littorina obtusata / littoralis) yellow form crawling over rocks exposed at low tide, Cornwall, UK, March.

Heather Angel / Winkles clustering in empty Oyster shells to avoid drying out when exposed to air at low tide. On rocky shore, Dalian, Liaoning Province, China.

Nick Upton / Flat periwinkle (Littorina obtusata), yellow form crawling over Spiral wrack (Fucus spiralis). Treyarnon Bay, Cornwall England, UK. September.

Nick Upton / Flat periwinkle (Littorina obtusata), yellow form from Atlantic Ocean. Cornwall, England, UK. September.

Jurgen Freund / Timelapse of Periwinkle snails (Littoraria) climbing up Mangrove (Rhizophora) roots at lowtide, Daintree, Wet Tropics World Heritage Area, North Queensland, Australia.

Alex Hyde / Common Hermit Crab (Pagurus bernhardus) in Flat Periwincle shell (Littorina obtusata). Isle of Mull, Scotland, UK. June.

Sue Daly / Smooth periwinkles (Littorina obtusata) on kelp, Derrible Bay, Sark, British Channel Islands.

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.

MYN / Carsten Krieger / Flat Periwinkle (Littorina obstusata) from rock pool, County Clare, Ireland, August. Meetyourneighbours.net project

MYN / Carsten Krieger / Flat Periwinkle (Littorina obtusata) from tide pool, County Clare, Ireland, August. Meetyourneighbours.net project

MYN / Carsten Krieger / Flat Periwinkle (Littorna obtusata) on Bladderwrack (Fucus vesiculosus) from tide pool, County Clare, Ireland, December. Meetyourneighbours.net project

Alex Mustard / Wide lacuna snail (Lacuna vincta) lays a chain of doughnut shaped egg clutches on a kelp leaf. Browning Pass, Port Hardy, Vancouver Island, British Columbia, Canada. Pacific Ocean

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

MYN / Paul Marcellini / Mangrove / Angulate periwinkle (Littorina angulifera) Florida, USA, March . meetyourneighbours.net project

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

Vincent Grafhorst / Periwinkle (Littorina sp) snails gathering, Belo sur Mer, Madagascar

Vincent Grafhorst / Periwinkle (Littorina sp) snails gathering, Belo sur Mer, Madagascar

Vincent Grafhorst / Periwinkle (Littorina sp) snails, Belo sur Mer, Madagascar

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