Sitka periwinkle • Littorina sitkanaIdentification
Sitka periwinkles have variable shell colouration and shell texture. Colour can be light brown, red-brown, grey or black and can include yellow, orange or white bands. Like other periwinkles (Littorinids), the shell is globose, with a short spire. Sitka periwinkles are the largest of the Central Coast periwinkles; they can be up to 22 mm tall with a nearly equal diameter, giving them a rather squat appearance. Some individuals have sculpturing on their shells, such as ridges or furrows that spiral around the shell, while others are smooth. The fleshy body and tentacles of this species are black. |
Sitka periwinkles. Note the globose shape, short spire and distinct shell ridges that spiral around the shells. However, not all individuals have ridges. Photo by Jenn Burt.
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Similar Species
This species is the most circular and globose of the Central Coast periwinkles. The Sitka periwinkle has a less streamlined shape than the checkered periwinkle (L. scutulata). The shell of L. scutulata is taller than it is wide, and often has a white checkered pattern. The shell interior of the Sitka periwinkle is brown or orange, whereas that of L. scutulata is purple.
Habitat and Range
This species is a common intertidal grazer and can be found in sheltered to moderately exposed areas on rocky substrates in the very high (splash zone) to low intertidal zones. It lives among Fucus distichus, eelgrass (Zostera marina), and other algae. Sitka periwinkles are generally quite sedentary, with most individuals moving less than 1 m per month. Numerous Sitka periwinkles often aggregate in tidepools and in moist, shady crevices in bedrock to avoid desiccation. This species is also susceptible to suffocation if it remains underwater for too long. Its range extends from Alaska to southern Oregon, and also includes Japan and Siberia.
Intriguing Information
This species is herbivorous, and uses its radula to scrape diatoms and algae growing on rocks and on Fucus distichus. This species also consumes Verrucaria maura – a lichen that grows in the highest intertidal/splash zone.
Sitka periwinkles have a number of predators, including Nucella lamellosa (frilled dogwinkle), Cancer productus (red rock crab), numerous species of sea stars (including Leptasterias hexactis and Evasterias troschelii), as well as many species of fish, ducks, and shore birds. Hairy hermit crabs (Pagurus hirsutiusculus) often occupy empty shells.
This species is able to protect itself from desiccation by attaching itself to the substrate using a glue-like mucus that essentially seals the operculum shut to preserve moisture, until the next high spring or wave re-moistens the substrate. Sitka periwinkles can survive attached like this for many days.
This species has separate sexes, with females laying 50-400 eggs after copulation occurs. Eggs are enclosed in a thick, transparent gelatinous mass that is typically attached to the underside of rocks or seaweed in the upper intertidal zone. As Sitka periwinkle larvae develop, they feed on yolk and emerge from the egg cases as tiny juveniles that are capable of crawling away. This strategy contrasts with other species, such as L. scutulata, L. plena and L. littorea that have pelagic larval stages that later settle. Sitka periwinkles live about 2 years.
iNaturalist
https://www.inaturalist.org/taxa/129298-Littorina-sitkana
This species is the most circular and globose of the Central Coast periwinkles. The Sitka periwinkle has a less streamlined shape than the checkered periwinkle (L. scutulata). The shell of L. scutulata is taller than it is wide, and often has a white checkered pattern. The shell interior of the Sitka periwinkle is brown or orange, whereas that of L. scutulata is purple.
Habitat and Range
This species is a common intertidal grazer and can be found in sheltered to moderately exposed areas on rocky substrates in the very high (splash zone) to low intertidal zones. It lives among Fucus distichus, eelgrass (Zostera marina), and other algae. Sitka periwinkles are generally quite sedentary, with most individuals moving less than 1 m per month. Numerous Sitka periwinkles often aggregate in tidepools and in moist, shady crevices in bedrock to avoid desiccation. This species is also susceptible to suffocation if it remains underwater for too long. Its range extends from Alaska to southern Oregon, and also includes Japan and Siberia.
Intriguing Information
This species is herbivorous, and uses its radula to scrape diatoms and algae growing on rocks and on Fucus distichus. This species also consumes Verrucaria maura – a lichen that grows in the highest intertidal/splash zone.
Sitka periwinkles have a number of predators, including Nucella lamellosa (frilled dogwinkle), Cancer productus (red rock crab), numerous species of sea stars (including Leptasterias hexactis and Evasterias troschelii), as well as many species of fish, ducks, and shore birds. Hairy hermit crabs (Pagurus hirsutiusculus) often occupy empty shells.
This species is able to protect itself from desiccation by attaching itself to the substrate using a glue-like mucus that essentially seals the operculum shut to preserve moisture, until the next high spring or wave re-moistens the substrate. Sitka periwinkles can survive attached like this for many days.
This species has separate sexes, with females laying 50-400 eggs after copulation occurs. Eggs are enclosed in a thick, transparent gelatinous mass that is typically attached to the underside of rocks or seaweed in the upper intertidal zone. As Sitka periwinkle larvae develop, they feed on yolk and emerge from the egg cases as tiny juveniles that are capable of crawling away. This strategy contrasts with other species, such as L. scutulata, L. plena and L. littorea that have pelagic larval stages that later settle. Sitka periwinkles live about 2 years.
iNaturalist
https://www.inaturalist.org/taxa/129298-Littorina-sitkana
References
Alaska Department of Fish and Game (2006). Sitka periwinkle. Accessed 2015-10-30.
Carefoot, T. Littorina plena (Gould, 1849) In Klinkenberg, Brian. (Ed.) E-Fauna BC: Electronic Atlas of the Fauna of British Columbia. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Accessed 2015-10-30.
Cowles, D. (2006). Littorina sitkana (Philippi, 1845). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 2015-10-30.
Harbo, R. M. (1997). Shells & Shellfish of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P.199-200.
Lamb, A., and Hanby, B. (2005). Marine Life of the Pacific Northwest [electronic version]. Madeira Park, BC: Harbour Publishing.
Lindberg, M. and Lindstrom, S. (2010). Verrucaria maura. Seaweeds of Alaska. Accessed 2015-03-11.
Authors and editors of page
Beatrice Proudfoot and Kelly Fretwell (2015)
Alaska Department of Fish and Game (2006). Sitka periwinkle. Accessed 2015-10-30.
Carefoot, T. Littorina plena (Gould, 1849) In Klinkenberg, Brian. (Ed.) E-Fauna BC: Electronic Atlas of the Fauna of British Columbia. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Accessed 2015-10-30.
Cowles, D. (2006). Littorina sitkana (Philippi, 1845). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 2015-10-30.
Harbo, R. M. (1997). Shells & Shellfish of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P.199-200.
Lamb, A., and Hanby, B. (2005). Marine Life of the Pacific Northwest [electronic version]. Madeira Park, BC: Harbour Publishing.
Lindberg, M. and Lindstrom, S. (2010). Verrucaria maura. Seaweeds of Alaska. Accessed 2015-03-11.
Authors and editors of page
Beatrice Proudfoot and Kelly Fretwell (2015)
