Phylum: Mollusca Lottia digitalis Class: Gastropoda, Patellogastropoda Order: A fingered limpet Family: Lottioidea, Lottiidae Description has heavy ribs like L. digitalis, but lacks the Size: about 25 mm (one inch); largest 30 concave anterior slope of the latter (its anteri- mm (Haven 1971); average under 15 mm; or slope is convex). Its apex is subcentral, not this specimen 20 mm (Ricketts and Calvin near the anterior margin; its ribs are usually 1971). equally developed on all slopes, and it is Color: greenish gray to dull brown; large smoother than L. digitalis. It can have a pat- solitary animals sometimes more brilliantly tern of radial bands or of white checks. It oc- marked (Ricketts and Calvin 1971); ribs usu- curs at lower tidal levels than does L. digitalis. ally not lighter than spaces between them The above limpets of the family Ac- (Carlton and Roth 1975); always a solid maeidae differ from the Patellidae in having brown spot 'owl-shaped' inside shell on the only a single ctenidium (feather-shaped gill) apex (fig 3); a horseshoe-shaped muscle (figure 4). Other genera of Acrriaeldae be- scar open at the anterior end (fig. 3) (Keen sides Lottia, above, cannot be keyed by shell 1971). alone: differences in radula are important as Shell: well (Keen 1971). General ways of distin- Shape: oval, caplike, fairly high ele- guishing them by shell include the following: vation (but not all as high as this specimen, Acmaea sp. have a nearly central fig. 2); apex above or even overhanging an- apex, the shell is white to pink-rayed, and the terior margin, forming hook. Strong rough radula is adapted for browsing on coralline ribs on posterior slope, forming moderately algae. They are chiefly sublittoral. (The name scalloped edge (fig 1), may be absent on Acmaea once en-compassed those limpets anterior slope. Posterior convex, anterior now called Lottia and Notoacmea. These concave (fig 2). have now been divided: Lottia sp. have uncini Body: no dark spots on head or sides of (marginal teeth) on the radula; they have fine foot: species characteristic; a pair of uncini to heavy radial ribs and an apex anterior to (flap-like structures) on basal plate of radula the center as well as a convex posterior (inside mouth), a remnant of marginal teeth slope. Notoacmea lack the uncini on the mar- (Keen 1971): genus Lottia. This characteris- gin of the radula; they are not heavily ribbed, tic observable only by a drying and staining the apex can be subcentral to quite anterior.) lab preparation (not figured). Notoacrnea persona, a nocturnal limpet pre- ferring shade and caves as a habitat, has an Possible Misidentifications anterior apex directed anteriorly, and a There may be as many as 16 species straight anterior slope; the posterior slope is of rocky intertidal limpets on our coast; few convex. The surface has fine regular striae, are as adaptable as L. digitalis in tolerating not strong ribs. N. persona can be large (53 different habitats, especially in estuaries. (L. mm) and is found above Lottia in the tidal digitalis and L. pelta are the only limpets that zone (Fritchman 1961). It is chiefly an inhabit- penetrate very far into Coos Bay's estuary). ant of the open coast, but has been found in Lottia pelta, sometimes estuarine, A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Unknown. 1983. Lottia digitalis. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to 140 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. quiet waters in Puget Sound (Kozloff in Ricketts and Calvin 1971) lives among bar- 1974b). nacles, algae on flat surfaces. This specimen Notoacmea scutum is a thick shelled, on a log. Avoids dessication but tolerates and rather flat limpet with a subcentral apex, a requires aerial conditions (Haven 1971). coarse sculpture of flat ridges (actual radial Found on 'virtually all hard substrates' (Haven lines). It is occasionally found in bays (Puget 1971). Sound) (Kozloff 1974b). Salinity: tolerates a wide range, from concen- Two other species of Lottia have trated sea water to fresh water (Wolcott heavy ribbing, and could be confused with L. 1973). digitalis; they also inhabit similar territory, at Temperature: a cold water species; tolerates least on the outer coast. The chief inhabitant high temperatures less well than does L. of the high splash zone is the rough limpet scabra (Wolcott 1973). Found more common- L. scabra, with strongly projecting ribs, a ly in winter than summer (central California) strongly scalloped margin, low profile, and (Haven 1971). both posterior and anterior slope being con- Tidal Level: oldest and largest animals are vex. It has distinctive black spots on its head found highest; found from higher high tides up and on the sides of its foot. It prefers gently into splash zone (zone 1 in Ricketts and Cal- sloping or horizontal surfaces. Its range is vin 1971); adapted to dessication better than generally too far south for Oregon. most limpets, and is never found permanently L. strigatella, formerly C. paradigitalis, submerged: lower limit: zone 2, at about was once thought to be a 'hybrid' of L. digi- mean high water (Frank 1965c; Keen 1971). talis and L. pelta (Carlton and Roth 1975). It Associates: in flat areas of zone 2: algae, is the closest species to L. digitalis, but is barnacles, amphipods Orchestoidea, Or- smoother, has fine radial lines, but no ribs; a chestia; gribble Limnoria, littorine snails, in- convex posterior, slightly concave anterior sects (springtails). On vertical rock surfaces, slope, and is only to 20 mm in length. Its Coos Head: L. paradigitalis (strigatella), apex is often eroded. The interior is glossy, Balanus glandula, Littorina scutulata, L. pelta bluish white with brown stains, and with the (at lower limit) (Frank 1965c). On pilings: outside pattern showing through (Keen Balanus. In California: L. scabra, L. gigantea 1971). The animal is completely white. This (at lower limit) (Haven 1971). species is found with L. digitalis at Coos Abundance: most common upper intertidal Head, just inside the bay entrance, under limpet in Oregon (Frank 1965c); within its marine conditions (Frank 1965a). range, common from Monterey north (Ricketts and Calvin 1971). Tends to aggregate (Millard Ecological Information 1968). Range: Unalaska Island south to Guadalupe Island, Baja California. Life-History Information Local Distribution: outer coast; bays: Coos Reproduction: separate sexes; eggs and Bay-Coos Head, lower South Slough. sperm shed into sea; length of planktonic life Habitat: prefers steep slopes in upper unknown (Haven 1971). Spawning winter and (splash) zone (Haven 1971); pilings (in spring; peak recruitment: spring (Fritchman bays); tolerates 'variable and hazardous' 1961). conditions (Frank 1965c); mud, swirling Larva: sand, debris, industrial pollution, sewage, Juvenile: strong wave action. In lower levels (zone 2 Longevity: occasionally 6 years (Frank A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] 1965a). Puget Sound, the Strait of Georgia, and Growth Rate: very consistent (Frank the San Juan Archipelago. University of 1965c), fastest fall and winter, stopped in Washington Press, Seattle & London. summer; growth decreased by crowding. 8. MILLARD, C. P. 1968. The clustering be- Food: encrusting microalgae: blue greens, havior of Acmaea digitalis. The Veliger. 11 diatoms (Frank 1965c). Supplement:45-51. Predators: sea stars, oyster catchers; 9. MORRIS, R. H., D. P. ABBOTT, and E. C. shorebirds, Pachygrapus (Morris et al 1980). HADERLIE. 1980. Intertidal invertebrates Behavior: does not 'home' precisely like L. of California. Stanford University Press, scabra, but has a home range (Haven Stanford, California. 1971). Has a seasonal vertical migration: 10. RICKETTS, E. F., and J. CALVIN. 1971. higher in winter (with higher waves). Se- Between Pacific tides. Stanford University cretes mucus sheet between itself and sub- Press, Stanford, California. strate to aid in slowing dessication and be- 11. WOLCOTT, T. G. 1973. Physiology, ecolo- cause it doesn't fit precisely into the rock. gy, and interzonation in limpets (Acmaea), Can accumulate large concentrations of lead a critical look at 'limiting factors'. Biological (ie. animals under Golden Gate Bridge) Bulletin. 145:389-422. (Morris et al 1980). Updated 1983 Bibliography 1. CARLTON, J. T., and B. ROTH. 1975. Phylum Mollusca: Shelled Gastropods, p. 467-514. In: Light's manual; intertidal in- vertebrates of the central California coast. S. F. Light, R. I. Smith, and J. T. Carlton (eds.). University of California Press, Berkeley. 2. FRANK, P. W. 1965a. Growth of three species of Acmaea. Veliger. 7:201-202. 3. ——. 1965c. The biodemography of an intertidal snail population. Ecology. 46:831-844. 4. FRITCHMAN, H. K. 1961. A study of the reproductive cycles in the California Ac- maeidae (Gastropoda). The Veliger. 3:57 -63, 95-101. 5. HAVEN, S. B. 1971. Niche differences in the intertidal limpets Acmaea scabra and Acmaea digitalis (Gastropoda) in central California. The Veliger. 13:231-248. 6. KEEN, A. M. 1971. Sea shells of tropical west America; marine mollusks from Baja California to Peru. Stanford University Press, Stanford. 7. KOZLOFF, E. N. 1974b. Seashore life of Unknown. 1983. Lottia digitalis. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to 140 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. .