Littorina Plena Class: Gastropoda Order: Littorinomorpha the Checkered Littorine Or Periwinkle Family: Littorinidae
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Phylum: Mollusca Littorina plena Class: Gastropoda Order: Littorinomorpha The checkered littorine or periwinkle Family: Littorinidae Taxonomy: Although originally described as visceral mass (e.g. anus, mantle cavity) is separate species by Gould in 1849, Littorina directly above the foot (rather than posterior scutulata (see description in this guide) and to) (McLean 2007). The Littorinidae are Littorina plena were synonymized in 1864 and small-shelled snails with a rounded peristome only became recognized as two separate (Plate 378, Reid 2007). Two local species in species again in 1979 (Murray). Illustrations the family Littorinidae, Littorina scutulata and in this guide utilize the same figures for both. L. plena, are morphologically very similar and L. plena and L. scutulata. Readers should require examination of penis morphology for refer to supplemental materials on our differentiation (Fig. B2, supplemental images website to differentiate the two species (e.g., on our website and Possible photos of shell shading and penis shape). Misidentifications in this text). Shell: The checkered shell pattern of L. Description plena is composed of smaller checks than L. Size: Littorina plena is smaller than the scutulata. They are usually black/dark brown morphologically similar congener, L. and white. Individuals exhibit a range of shell scutulata, and has an average height of ~9 patterns and colors including a solid mm and rarely exceeds 11 mm (Reid 1996); purple/black (Reid 1996). Other reported the illustrated specimen (from Coos Bay) is 9 differences include the presence of a basal mm in length (Fig. 1). At settlement, ridge and a distinct light-colored basal band in individuals are ~ 350 µm. the body whorl of L. scutulata which is absent Color: Color and patterns can be variable in L. plena (Rugh 1997; Hohenlohe and but shell exterior is most commonly Boulding 2001). Shells should be wet to fully checkered, and can include a range of colors examine colors and patterns. including dark brown, purple, green, black Shape: The overall shell shape is and white. Other possible patterns include conical, with four whorls, and lacking a splotches, zig-zags, fine vertical and/or columellar groove (inner lip) or chink. Shell horizontal etched banding, or various shape is known to vary depending on local combinations of these. Shells are never with conditions and snails on wave-exposed strong spiral shape and the exterior sculpture shores have shorter, thinner shells with a is often encrusted with algae depending on larger aperture (allows a larger foot to help the local habitat (e.g., protected shore vs. prevent dislodgment) whereas snails on wave-exposed shore). The Interior of the protected shores have larger, thicker shells shell is nearly always purple (Keep and with a smaller aperture, which may reduce Longstreth 1935). predation by crabs (Rugh 1997) General Morphology: Shelled gastropods Interior: Littorina spp. lack posterior can crawl and burrow using a muscular foot or metapodial tentacles, having only cephalic and have a head with eyes and tentacles, a tentacles (Carlton and Roth 1975) (see mantle (which secretes the shell) and a dissection, Fig. A3). radula that is composed of many teeth for Exterior: tearing and rasping algae. Gastropods are Aperture: characterized by torsion, where the body Inner (Columella) and Outer Lip: rotates early in development such that the Umbilicus: Tentacles: Littorina. plena tentacles typically have a mostly-unbroken longitudinal stripe Valley, J. and T.C. Hiebert. 2015. Littorina plena. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/19870 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Valley, J. and T.C. Hiebert. 2015. Littorina plena. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. with or without transverse bands, but they can species can be strongly striped, or rough also be all-dark (Fig. B3). and striated. It is fairly common in salt Eyes: marshes, and can be up to 15 mm tall Siphons: (Kozloff 1974a). Foot: Littorina (Algamorda) Operculum: Solid, horny, and brown newcombiana (= subrotundata) is a small, operculum with spiral lines originating in the rare salt marsh littorine originally thought bottom half (Fig. A1a). to be a freshwater snail. It is light colored, Radula: with four rounded whorls, and usually striped. The shell is smooth, thin and Possible Misidentifications covered with a brown periostracum and Snails in the genus Littorina (family the aperture is almost circular. It is only Littorinidae) are very common members of about 5 mm long, and has a simple gap, the intertidal, however their similarity in (not a groove) between the whorl and the shell morphology renders species difficult columella (Keen and Coan 1974). It is to differentiate. Species level found quite high in the intertidal area of identification requires examination of the the marsh. penis and pallial oviduct (Reid 1996, Littorina littorea, is an Atlantic 2007). A similar but smaller genus of species that was introduced into California another family is Lacuna, the small 'chink' bays 100 years ago. It is quite thick- shell, which has a groove, or chink, shelled, globose and brown to black, with between the large whorl and the fine dark spiral bands (Abbott 1968). It columella. Littorina lacks this groove. The has not yet been reported in Oregon Lacunidae are often found in eelgrass, (Carlton and Roth 1975). (Littorina is not), and are never in the upper intertidal area, as Littorina often is Ecological Information (Kozloff 1974a). Range: Type locality is San Francisco, There are seven species in the California (Mastro et al. 1982), with known genus Littorina locally. Of those species, range from Sitka, Alaska to Cabo San Lucas, at least three also have the solid shell and Baja California. absence of columellar groove found in L. Local Distribution: Local distribution in plena. Littorina planaxis is an inhabitant outer coast and bays including Coos Bay, of the outer shore intertidal although South Slough, and the Siuslaw River, near individuals are also found in Puget Sound, Florence (Matthews 1979). Washington and, occasionally in more Habitat: Snails are often found on rocks and marine parts of Oregon's estuaries. It is pilings on both the rocky outer coast and stout and globose, and usually larger than protected shores. Littorina plena is most L. scutulata (Brusca and Brusca 1978), abundant on sheltered shores and can often with a broad, flat, polished columella be found in salt marshes (Reid 1996), but (Keep and Longstreth 1935). Littorina rarely found in eelgrass (Kozloff 1974a). planaxis is essentially a southern form, Individuals are very tolerant of near-terrestrial although it does occur occasionally in conditions (Brusca and Brusca 1978). Puget Sound (Kozloff 1974a), and its Salinity: Individuals ae found near full sea niche is generally taken over northwards water (e.g., salinities of 30) on the open at about Cape Arago, Oregon, by L. coast, as well as in conditions of somewhat sitkana (Ricketts and Calvin 1971). reduced salinity (Carlton and Roth 1975). Littorina sitkana is a fat, globose littorine, This species does not penetrate upper (and with rounded columella, and strong spiral fresher) parts of estuary (Coos Bay). The ridges on its whorls. It can be white to salinity tolerance ranges from 22–24 (Brusca black, but is often a yellowish brown and Brusca 1978). (Keep and Longstreth 1935). A smaller Temperature: Occurs over a wide range. variety was formerly called L. rudis. This A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/19870 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Tidal Level: Individuals are not found more penis in L. plena exhibits a bifurcation that than a few feet above high tide line but are occurs further from the tip resulting in a long found at higher levels in salt marshes (Kozloff and often-coiled projection (see supplemental 1974b). Littorina spp. are ”just above the images on our website). The pallial oviduct in reach of the waves, along the shores of the females is also distinctive but requires entire bay" (San Francisco, California, removal of the shell to be seen. Packard 1918). Larva: Associates: Juvenile: Abundance: Individuals are relatively Longevity: The lifespan of the congener, L. common in rocky areas (Brusca and Brusca scutulata, is estimated to be at least 7 years 1978). Littornia plena and L. scutulata are (Behrens 1974). The longevity of L. plena is probably the most common littorine in bays, not known. as well, at least in more open coastal Growth Rate: habitats. Food: Herbivorous. Littorines rasp microscopic (e.g., Endocladia, unicellular Life-History Information green and blue green algae, diatoms), and Reproduction: Dioecious (separate sexes) macroscopic algae (e.g., Cladophora, with internal fertilization. Most copulation Pelvetia, Rhodoglossum) from rocks occurs in spring and summer, en masse, with (Castenholz 1961; Dahl 1964). a spawning season of April to early October. Predators: Crabs, fish, birds, and predatory Sexual maturity occurs when shells are ~2–3 gastropods. mm in height (by 1 year of age) and they Behavior: Individuals live in a “home produce negatively-buoyant pelagic egg territory”, i.e., they stay in a small area near a cases, the morphology of which can be a certain pool and "emerge by night, and reliable species indicator (Fig.