Life History

Taxonomy: (adapted from the "Tree of Life")

        Kingdom: Animalia

                Phylum: Mollusca

                        Class: Gastropoda

                                Order: Mesogastropoda

                                        Family: Littorinidae

                                                Genus: Littorina

                                                        Species: obtusata

Picture from the Marine Life Information Network for Britain and Ireland

        As their taxonomy shows L. obtusata are mollusks (phylum Mollusca).  Periwinkles have an un-segmented body exhibiting bilaterally symmetry and have a hard carapace composed of calcium carbonate secreted from an organ called the mantle (Castro and Huber).  L. obtusata have a muscular foot used for locomotion and attaching to substrates to prevent being moved by wave action and a tongue like radula used for feeding.  Periwinkles feed by scraping the alga from the substrate where the radula pulls the food toward it’s mouth where it is surrounded by mucus and pulled into their digestive system, which consists of a digestive gland, stomach, and intestine (Castro and Huber).  Work by Geoffrey Trussell in 1996 and 2000 have discovered that the foot size is phenotypically plastic with wave action and the carapace thickness increases when predators (Carcinus maenas) are present. 

            As this study shows, there are a wide variety of color morphologies of the carapace.  L. obtusata are often found living on or under the Ascophyllum nodosum canopy for food and protection.  This relationship is not one-sided since L. obtusata may graze microalgae and remove epiphytes from the Ascophyllum nodosum decreasing the likelihood of it becoming dislodged due to wave action.  Aside from matching substrate color, their size and shape is virtually identical to that of the air bladders, aiding in their camouflage from visual predators like C. maenas (Wilbur and Steneck 1999).  This study delves into seeing if some relationship exists between the phenotype and color morphology of the carapace and substrate color. 

Read on for further information

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