Phylum: Mollusca Lottia digitalis (=Acmaea) Class: Gastropoda, Prosbranchia Order: Archeogastropoda, Patellacea A fingered limpet (Rathke, 1833) Family: Lottidae

Description Size—about 25 mm (one inch); largest 30 mm (figure 4). Other genera of Acrriaeldae (Haven 1971); average under 15 mm; this besides Lottia, above, cannot be keyed by specimen 20 mm (Ricketts and Calvin 1971). shell alone: differences in radula are Color—greenish gray to dull brown; large important as well (Keen 1971). General ways solitary animals sometimes more brilliantly of distinguishing them by shell include the marked (Ricketts and Calvin 1971); ribs following: usually not lighter than spaces between them Acmaea sp. have a nearly central apex, (Carlton and Roth 1975); always a solid the shell is white to pink-rayed, and the radula brown spot 'owl-shaped' inside shell on the is adapted for browsing on coralline algae. apex (fig 3); a horseshoe-shaped muscle scar They are chiefly sublittoral. (The name open at the anterior end (fig. 3) (Keen 1971). Acmaea once en-compassed those limpets Shell Shape—oval, caplike, fairly high now called Lottia and Notoacmea. These elevation (but not all as high as this have now been divided: Lottia sp. have uncini specimen, fig. 2); apex above or even (marginal teeth) on the radula; they have fine overhanging anterior margin, forming hook. to heavy radial ribs and an apex anterior to Strong rough ribs on posterior slope, forming the center as well as a convex posterior moderately scalloped edge (fig 1), may be slope. Notoacmea lack the uncini on the absent on anterior slope. Posterior convex, margin of the radula; they are not heavily anterior concave (fig 2). ribbed, the apex can be subcentral to quite Body—no dark spots on head or sides of anterior.) Notoacrnea persona, a nocturnal foot: species characteristic; a pair of uncini limpet preferring shade and caves as a (flap-like structures) on basal plate of radula habitat, has an anterior apex directed (inside mouth), a remnant of marginal teeth anteriorly, and a straight anterior slope; the (Keen 1971): genus Lottia. This characteristic posterior slope is convex. The surface has observable only by a drying and staining lab fine regular striae, not strong ribs. N. persona preparation (not figured). can be large (53 mm) and is found above Lottia in the tidal zone (Fritchman 1961). It is Possible Misidentifications chiefly an inhabitant of the open coast, but There may be as many as 16 species of has been found in quiet waters in Puget rocky intertidal limpets on our coast; few are Sound (Kozloff 1974b). as adaptable as L. digitalis in tolerating Notoacmea scutum is a thick shelled, different habitats, especially in estuaries. (L. rather flat limpet with a subcentral apex, a digitalis and L. pelta are the only limpets that coarse sculpture of flat ridges (actual radial penetrate very far into Coos Bay's estuary). lines). It is occasionally found in bays (Puget Lottia pelta, sometimes estuarine, has Sound) (Kozloff 1974b). heavy ribs like L. digitalis, but lacks the Two other species of Lottia have heavy concave anterior slope of the latter (its ribbing, and could be confused with L. anterior slope is convex). Its apex is digitalis; they also inhabit similar territory, at subcentral, not near the anterior margin; its least on the outer coast. The chief inhabitant ribs are usually equally developed on all of the high splash zone is the rough limpet L. slopes, and it is smoother than L. digitalis. It scabra, with strongly projecting ribs, a can have a pattern of radial bands or of white strongly scalloped margin, low profile, and checks. It occurs at lower tidal levels than both posterior and anterior slope being does L. digitalis. convex. It has distinctive black spots on its The above limpets of the family head and on the sides of its foot. It prefers Acmaeidae differ from the Patellidae in having gently sloping or horizontal surfaces. Its range only a single ctenidium (feather-shaped gill) is generally too far south for Oregon. Digitized 2010 – Last Updated 1979 – E-mail corrections to [email protected] L. strigatella, formerly C. paradigitalis, was Balanus. In California: L. scabra, L. gigantea once thought to be a 'hybrid' of L. digitalis and (at lower limit) (Haven 1971). L. pelta (Carlton and Roth 1975). It is the closest species to L. digitalis, but is smoother, Quantitative Information has fine radial lines, but no ribs; a convex Weight— posterior, slightly concave anterior slope, and Abundance—most common upper intertidal is only to 20 mm in length. Its apex is often limpet in Oregon (Frank 1965c); within its eroded. The interior is glossy, bluish white range, common from Monterey north (Ricketts with brown stains, and with the outside and Calvin 1971). Tends to aggregate (Millard pattern showing through (Keen 1971). The 1968). animal is completely white. This species is found with L. digitalis at Coos Head, just Life History Information inside the bay entrance, under marine Reproduction—separate sexes; eggs and conditions (Frank 1965a). sperm shed into sea; length of planktonic life unknown (Haven 1971). Spawning winter Ecological Information and spring; peak recruitment: spring Range—Unalaska Island south to Guadalupe (Fritchman 1961). Island, Baja California. Growth Rate—very consistent (Frank 1965c), Local Distribution—outer coast; bays: Coos fastest fall and winter, stopped in summer; Bay-Coos Head, lower South Slough. growth decreased by crowding. Habitat—prefers steep slopes in upper Longevity—occasionally 6 years (Frank (splash) zone (Haven 1971); pilings (in bays); 1965a). tolerates 'variable and hazardous' conditions Food—encrusting microalgae: blue greens, (Frank 1965c); mud, swirling sand, debris, diatoms (Frank 1965c). industrial pollution, sewage, strong wave Predators—sea stars, oyster catchers; action. In lower levels (zone 2 in Ricketts and shorebirds, Pachygrapus (Morris et al 1980). Calvin 1971) lives among barnacles, algae on Behavior—does not 'home' precisely like L. flat surfaces. This specimen on a log. Avoids scabra, but has a home range (Haven 1971). dessication but tolerates and requires aerial Has a seasonal vertical migration: higher in conditions (Haven 1971). Found on 'virtually winter (with higher waves). Secretes mucus all hard substrates' (Haven 1971). sheet between itself and substrate to aid in Salinity—tolerates a wide range, from slowing dessication and because it doesn't fit concentrated sea water to fresh water precisely into the rock. Can accumulate large (Wolcott 1973). concentrations of lead (ie. animals under Temperature—a cold water species; Golden Gate Bridge) (Morris et al 1980). tolerates high temperatures less well than does L. scabra (Wolcott 1973). Found more Bibliography commonly in winter than summer (central 1. CARLTON, J. T., and B. ROTH. 1975. California) (Haven 1971). Phylum Mollusca: Shelled Gastropods, Tidal Level—oldest and largest animals are p. 467-514. In: Light's manual; found highest; found from higher high tides up intertidal invertebrates of the central into splash zone (zone 1 in Ricketts and California coast. S. F. Light, R. I. Calvin 1971); adapted to dessication better Smith, and J. T. Carlton (eds.). than most limpets, and is never found University of California Press, permanently submerged: lower limit: zone 2, Berkeley. at about mean high water (Frank 1965c; Keen 2. FRANK, P. W. 1965a. Growth of three 1971). species of Acmaea. Veliger. 7:201- Associates—in flat areas of zone 2: algae, 202. barnacles, amphipods Orchestoidea, 3. ——. 1965c. The biodemography of Orchestia; gribble Limnoria, littorine snails, an intertidal snail population. Ecology. insects (springtails). On vertical rock surfaces, 46:831-844. Coos Head: L. paradigitalis (strigatella), 4. FRITCHMAN, H. K. 1961. A study of Balanus glandula, Littorina scutulata, L. pelta the reproductive cycles in the (at lower limit) (Frank 1965c). On pilings: California Acmaeidae (Gastropoda). The Veliger. 3:57-63, 95-101. Digitized 2010 – Last Updated 1979 – E-mail corrections to [email protected] 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 Puget Sound, the Strait of Georgia, and the San Juan Archipelago. University of Washington Press, Seattle & London. 8. MILLARD, C. P. 1968. The clustering behavior of Acmaea digitalis. The Veliger. 11 Supplement:45-51. 9. MORRIS, R. H., D. P. ABBOTT, and E. C. HADERLIE. 1980. Intertidal invertebrates of California. Stanford University Press, Stanford, California. 10. RICKETTS, E. F., and J. CALVIN. 1971. Between Pacific tides. Stanford University Press, Stanford, California. 11. WOLCOTT, T. G. 1973. Physiology, ecology, and interzonation in limpets (Acmaea), a critical look at 'limiting factors'. Biological Bulletin. 145:389- 422.

Digitized 2010 – Last Updated 1979 – E-mail corrections to [email protected]

Digitized 2010 – Last Updated 1979 – E-mail corrections to [email protected]