title for limpet section of the Odyssey
   
  Foods, feeding, & growth
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  Foods & growth of different species
  This section contains information on foods and growth of different species, organised alphabetically.  Information on the role of the radula in feeding can be found in another section RADULA STRUCTURE & FUNCTION.
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Diodora aspera

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Research study 1
 

photographs of juvenile keyhole limpets Diodora aspera from Pernet 1997 Veliger 40: 77photograph of a keyhole limpet Diodora aspera
The hole in a keyhole limpet Diodora aspera begins to form at the edge of the shell at 3-4mo of age.  In time, it closes off by virtue of the shell growing around it.  Eventually, at 1.5yr of age, the rudiments of the larval shell disappear leaving the hole at the top of the shell.


graph of length of keyhole limpets Diodora aspera in relation to ageStudies on rates of growth in keyhole limpets show that an individual of 5cm shell length is about 10yr old, while a 6cm animal may be up to 20yr old (see graph).  Pernet 1997 Veliger 40: 77.

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Lottia asmi

 
Research study 1
 

photograph of limpet Lottia asmi from Linda Schroeder, Pacific Northwest Shell Club, Seattle, WA
Lottia asmi
inhabits the shells of black turban-snails Chlorostoma funebralis and feeds on diatoms growing there.  In Bodega Bay, California limpets occupy about 8% of all Tegula individuals.  A single limpet will add about 5% extra mass for the turban snail to carry and also affects its host’s balance.  These parasitic costs are lessened because a limpet regularly changes  hosts, perhaps in response to feeding needs.  Fritchman 1962 Veliger 4: 41; Evans 1992 Mar Behav Physiol 19: 241. Photos courtesy Linda Schroeder, Pacific Northwest Shell Club, Seattle, Washington PNWSC.

 
Research study 2
 

graph comparing occupation of limpets Lottia asmi on living black turban shells Chlorostoma funebralis versus empty C. funebralis shellsphotograph of black turban snail Chlorostoma funebralis with limpet on its shellOn beaches around the Hopkins Marine Station, Pacific Grove, California most black turban-shells Chlorostoma funebralis host limpets Lottia asmi.   The limpets transfer from host to host, and appear to graze on algal coatings growing on the shells of the host.  Preference of the limpets is for living shells and they tend to avoid empty shells or ones occupied by hermit crabs (see graph).  Eikenberg & Wickizer 1964 Veliger 6 (Suppl.): 66.

NOTE  the authors remove the live snail by pulling it out, and then plug the aperture with both plasticine and plaster of Paris.  In retrospect, the authors think that this may not have been a good choice because of possible leaching of chemicals that could have been aversive to L. asmi.  In other experiments, they use wax, which may have been more suitable

 

Black turban snail Chlorostoma funebralis
with limpet of unknown identity 0.3X

 

 

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Lottia digitalis

 
Research study 1
 

photograph of limpet Lottia digitalis
Ribbed limpets Lottia digitalis in Port Renfrew, British Columbia subsist mainly on encrusting diatoms that grow in their high-level habitat.  Breen 1972 Veliger 15: 133.

 
Research study 2
 

graph of amounts of filamentous green algae in enclosures containing zero, one, or two limpets Lottia digitalishistogram showing growth of limpet Lottia digitalis in enclosures containing one or two limpetsStudies on Lottia digitalis on high intertidal1 rocky shores in Tatoosh Island, Washington show that light has indirect effects on food availability, growth, and abundance. In this area, winter light per day is only about 15% as much as summer light. As expected, algal growth is high in unshaded (open) experimental enclosures2 with zero- or one-limpet densities, but is significantly lower in equivalent shaded enclosures or in treatments with 2-limpet densities (see histograms on Left).

Growth of L. digitalis parallels these effects, being high in unshaded, single-limpet enclosures, but significantly less in enclosures with 2-limpet densities, shaded, or both (see histograms above Right). The effects of light on algal growth also indirectly affect abundance of littorines Littorina sitkana3, because decreased algae means less food and protection. Additional evidence, not shown here, indicates that limpets compete with littorines for food.  The author suggests that because both herbivorous species grow and reproduce mostly during winter, the interplay of light and herbivory during this season have the potential for long-term effects on community dynamics.  Harley 2002 Limnol Oceanogr 47: 1217.

NOTE1  this area, above the barnacle Balanus glandula zone, is host to several winter-growing foliose algae: Porphyra, Urospora, Bangia, and Enteromorpha

NOTE2 enclosures are copper rings 2.5cm tall and 15cm diameter.  These restrict movement of limpets, but not littorines.  Some enclosures are shaded with vexar cloth suspended 6cm above the rock surface, reducing incident light by about 60%.  The author discusses possible shade-artifacts (e.g., effects on water flow, temperature, and desiccation) from the experimental treatments and this should be “must” reading for anyone planning experiments using enclosures of any type

NOTE3 other littorines present are L. subrotundata and L. plena, but the effects on abundance of these species are not so apparent as for L. sitkana

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Lottia gigantea

 
Research study 1
 

Feeding excursions of owl limpets Lottia gigantea in steep cliff areas around Monterey Bay, California are generally limited to periods of high tide, or to periods of low tide at night when the substratum is wet.  Movements cease during periods of high wave-shock.  Small Lottia giganteathat stray into neighbouring owl-limpet territories during feeding excursions are easily driven off by the territory occupant.  However, on their own territories, especially if near their home scars, these small individuals react with aggressive territorial responses. Wright 1978 Ann Report Western Soc Malacol 11: 7.

NOTE  the author enterprisingly observes the study population by being lowered by block and tackle from the cliff-top in a bosun’s chair

 
Research study 2
 

photograph of owl limpet Lottia gigantea bearing "drag enhancers" from Mike Judge, Manhatten College, NYAs limpets forage for food, do drag1 effects from waves and currents affect their efficacy in feeding? This is examined in a study at Hopkins Marine Station, Pacific Grove, California on owl limpets Lottia gigantea.  To mimic the drag effects of higher current flow, vertical metal plates2 , or “drag enhancers”, of different sizes are glued onto the shells of limpets. The plate sizes are designed to increase drag by 3, 6, 10.5, and 14 times relative to that on an unaltered limpet. The researcher uses a telescope at a secure shore base, away from the incoming tide, to monitor how far the treatment and control (no attached plates) limpets move from the time of low tide when they are stationary, to the end of their feeding bouts or until dark (minimum of 8h).  graph showing speed of locomotion of owl limpets Lottia gigantea in relation to relative drag increaseExperiments are conducted over several days in summer.  Apparently, during these particular days the limpets are never completely immersed, so observations are able to be made throughout the tidal cycle. 

graph of time spent moving by owl limpets Lottia gigantea in relation to relative drag increaseResults show that although a limpet’s speed is not significantly affected by increased drag (see graph above Right), it grazes less substratum because it spends significantly less time moving (see graph lower Right). The study requires accepting that the increase in drag caused by the glued plates is a fair simulation of natural shell drag from increased water flow, and that no other “unanticipated” effects3 on behaviour exist.  If this premise is accepted, the author's conclusion that a grazer’s potential impact on community structure could therefore be lessened in more wave-exposed or high current-flow areas is also accepted.  Judge 1988 Functional Ecol 2: 363. Photo courtesy Mike Judge, Manhatten College, Riverdale, New York.

NOTE1  fluid moving past an object has 2 drag components: frictional and pressure.  As frictional drag (skin drag) is so much smaller than pressure drag for these plates, only the latter is included in the study

NOTE2  as shown in the photograph above, 2 small copper plates are attached to each limpet in situ, one perpendicular to the long axis of the limpet and one parallel.  The plates are equal in size on a given individual, but different sizes of plates are used on different limpets to mimic different magnitudes of drag

NOTE3  one such effect could come from the different masses of the drag enhancers, as this is not controlled for. This may have been one contribution to the high variability in the data, reflected by low coefficients of determination (r2 in the above regression plots)

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Lottia insessa

 
Research study 1
 

drawing of kelp plant Egregia laevigata showing partsIn areas around Santa Barbara the limpet Lottia insessa lives on and eats only feather-boa kelps Egregia menziesii and E. laevigata.  The limpets graze off the epidermal and cortical layers of the plants, producing scars and sometimes holes through the stalks and its branches or rachises.  Studies on the relationship show that while grazing by the limpets does not significantly affect Egregia laevigata’s growth or development of reproductive sporophylls, it can cause severe damage, resulting in loss of parts or even in total loss of the plant.  In one count of 203 plants washed ashore, for example, 74 (36%) of the losses could be attributed to photograph of limpets feeding on the stalk of a sea palm Postelsia palmaeformissevere limpet damage and the remainder to failure of attachment to the substratum.  Interestingly, the more limpets a plant hosts, the more scars it gets, and the weaker it becomes – yet, these damaged portions attract even more settlement of limpets.  Apparently, the scars are ready-made protective habitats for the limpet recruits and growth is faster in them. 

The relationship of the limpet with its host plant, however, is not all one-way in favour of the limpet.  Apparently, losses caused by limpet-grazing act like pruning does in terrestrial plants, encouraging side branches to develop and generally keeping the plant smaller. This aids in survival of the plant by reducing its size and susceptibility to wave impact in storms.  Such losses are doubly beneficial for the plant because the weakened bits are usually ones heavily infested with limpets, and their loss is beneficial to the plant.  In preferentially occupying, eating, and often destroying Egregia plants that are mostly post-reproductive and/or damaged, the limpet is behaving like a “prudent predator”.  Black 1976 Ecology 57: 265.

 

Several limpets feeding on surface tissues of a sea palm
Postelsia palmaeformis.
  The upper 3 individuals appear to be
Lottia insessa
, while the lowermost individual is Lottia pelta 0.5X

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Lottia limatula

 
Research study 1
 

photograph of limpet Lottia limatula from Center for Marine Biodiversity & Conservation, Scripps Institution of Oceanography, UC San Diego Lottia limatula on the shores of Pacific Grove, California generally forage only when wetted by the tides. The species eats mainly microscopic algae and encrusting red algae. While foraging, individuals move up and down with the tides about 1m vertical distance.  Time of day appears not to be important in these movements. However, while the limpets move up at night when the tide is rising, in the day they tend to move down when the tide is rising.  Individuals tend to clamp down in strong surge.  The author reports no strong evidence of homing (only 1 of 13 individuals monitored shows evidence of homing).  In areas of overlap with Lottia pelta (see Research Study 2 in the section to follow), there is some evidence of food-resource partitioning in that pelta seems to prefer larger, non-encrusting algae, while limatula, as mentioned, prefers encrusting red algae.  Eaton 1968 Veliger 11 (Suppl): 5. Photo courtesy Center for Marine Biodiversity & Conservation, Scripps Institution of Oceanography, UC San Diego.

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Lottia pelta

 
Research study 1
 

photograph of limpets Lottia peltaphotograph of limpet Lottia digitalisGrowth estimates for 2 sympatric species of limpets Lottia pelta and L. digitalis on the coast of Oregon indicate faster rates in the former species, no discernible sex differences in either species, and maximum age of about 6yr in the latter species (see graph for growth on lower Right).  Frank 1964 Veliger 7: 201.

NOTE  rates are extrapolated from 1yr of growth of marked individuals (668 L. digitalis and 16 L. pelta).  However, the author urges caution in interpreting the data because of the high variability inherent in it

NOTE  a third species, paradigitalis, is included in the study but not dealt with here

 
Research study 2
 

schematic showing amounts of various algae eaten by limpets Lottia pelta in relation to availability of the algae in the habita of Pacific Grove, CALottia pelta around the Hopkins Marine Station, Pacific Grove, California move upwards a few centimeters when awash on an incoming tide, and downwards a few centimeters when awash on an outgoing tide.  Examination of dissected gut contents from individuals in the high-level Endocladia region show, firstly, a variety of algae being consumed and, secondly, a preference for certain red-algal species out of proportion to their occurrence in the habitat, including Endocladia.  Microscopic forms, including diatoms, filamentous green algae, and some blue-green algae are highly preferred.  Craig 1968 Veliger 11(Suppl): 13.

NOTE  the Endocladia region is approximately 1-2m above MLLW.  The author presents feeding data for 3 other lower zones, showing other kinds of dietary preferences and avoidances but these results are not included here.  Diet components are estimated by eye to roughly 10% levels. 

NOTE  several of the genera listed in the data have undergone name changes since 1968, so anyone interested is advised to consult and up-to-date identification guide to west-coast algae

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Lottia persona

 
Research study 1
 

drawing and photograph of limpet Lottia persona showing lines purported to be annual growth ringsgraph showing growth of limpets Lottia persona in OregonA study on limpets Lottia persona in Oregon reveals that their shells have growth rings that can be used in aging.  The rings are annual and are formed in winter.  Each major line seems to be comprised of several secondary lines (see drawing). If these are arranged into a frequency histogram of shell lengths for each ring number as shown in the accompanying graph, a fair representation of growth over time is obtained.  Age, then, is the ring number plus part of a year, the latter representing the time from settlement to the first winter.  From these data a large L. persona is 5-6yr old.  Kenny 1968 Veliger 11: 336. Photograph courtesy Linda Schroeder, Pacific Northwest Shell Club, Seattle, Washington PNWSC.

NOTE there is no doubt that the lines are growth lines, but for many populations their clustering on the shell is not so clearly defined. Many factors lead to deposition of a line on a limpet shell, including high summer temperature, salinity shock, and desiccation. The discovery of a clear relationship between age and growth rings in this Oregon population is striking, however, and the subject should repay further investigation

 
Research study 2
 

graph showing relationship between size and predicted age in limpets Lottia persona in AlaskaA study on reproductive cycles of several species of limpets in Port Valdez, Alaska includes information on growth of Lottia persona.  Although it is difficult to estimate the age of a limpet from size-frequency groupings because of highly variable size range found in any particular age class, extensive sampling at 4 sites yields the estimate shown here.  Seasonal seawater temperatures in this area range from 1.5-13oC.  From these data, maximum age in this locale is about 12yr.  The authors note that there is no obvious relationship of shell size or estimated age of L. persona to tidal height.  Blanchard & Feder 2000 Veliger 43: 289.

NOTE the authors choose to present their data linearly, but expectation based on other growth curves would be as shown in light blue (compare with the data shown graphically in Research Study 1 above)

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Lottia scabra

 
Research study 1
 

photograph of limpet Lottia scabra in its home scar
Dissections of guts of Lottia scabra in the Monterey Bay region of California disclose diatoms, pieces of encrusting and mat-forming algae, and small pieces of granite scraped from rock surfaces.  Hewatt 1940 Amer Midl Nat 24: 205; for information on shell microstructure of L. scabra see Gilman 2007 Veliger 48: 235.

 

 

 

 

Lottia scabra in its home scar 2X

 
Research study 2
 

As limpets crawl about they leave behind a mucous trail.  The mucus is important for adhesion and for coupling the force of foot-muscle contractions to the substratum for locomotion.  However, it is costly to produce and may account for over 20% of a limpet’s daily energy budget - much of it expended table showing amount of microalgae adhering to mucus of limpets Lottia scabra, Lottia gigantea, and Lottia digitalisduring locomotion.  It may not all be lost, though, as studies on limpets at the Bodega Marine Laboratory, California show that the mucus acts as an adhesive trap for, and stimulates growth of, microalgae that the limpets may later consume.  The effect is most evident for homing limpets, such as Lottia scabra and L. gigantea, that maintain home scars or territories, respectively, and tend to move along their own paths as they forage about.  Interestingly, the effect is much less for Lottia digitalis, a species that does not occupy home scars and that has a less well-defined home range.  Field tests of the phenomenon, using filters on which limpets have crawled, and then attached to the shore for 1d, show greater adhesion of microalgae to Lottia gigantea and L. scabra mucus than to L. digitalis mucus or to non-mucous controls (see table of data).  The study is interesting, but further research needs to be done to determine if homing limpets actually consume more of their own mucus than non-homing limpets consume theirs, and if defrayment of energy costs to the limpets is actually significant.  Connor & Quinn 1984 Science 225: 843; Connor 1986 Biol Bull 171: 548.

NOTE the authors coin a nice word provendering to describe the process (derived from the M.E. and O.F. word provendre, referring to dry food for livestock)

NOTE the data presented here are only for adhesion during short-term field exposures and some of the means do not show significant differences.  However, other laboratory data on adhesion and longer-term growth of microalgae, corroborate the data shown here

 
Research study 3
 

map of study locations As part of a general interest in the impact of impending global increase in temperature, researchers conduct experiments on feeding and growth of limpets Lottia scabra at 2 locations on the Californian coast: Bodega Bay and Pacific Grove.  Both locations are similar in terms of rocky substrata, biota, wave exposure, and tidal patterns, but differ in spring/summer air temperatures: 16-21oC at Bodega Bay and 20-24oC at Pacific Grove.  Limpet-enclosures and -exclosures are used to assess feeding and growth of limpets in different temperature treatments (shaded or unshaded treatments using canopies) at each location over a 4-mo period from Mar-Jun.  A main part of the research hypothesis to be tested is that increased thermal stress will reduce growth and increase mortality of L. scabra.  Results show temperature-related changes in microalgal food supply but, surprisingly, no direct or indirect effects of temperature manipulation on growth or mortality of L. scabra.  Thus, temperature changes do not alter the importance of herbivory at either site. The authors conclude that an increase in temperature, as from climate change, may affect producers and consumers differently and that effects at one trophic level may not transfer to other trophic levels.  Morelissen & Harley 2007 J Exp Mar Biol Ecol 348: 162.

NOTE  digital photographs are used to estimate algal abundances and grazing activity, and also limpet movements, recruitment, and mortality

NOTE  differences in rock temperatures in shade/no shade treatments are 6oC at Bodega Bay and 3oC at Pacific Grove

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Lottia scutum

 
Research study 1
 

photograph of Lottia scutum showing minor shell damageGrowth in limpets also includes shell repair from damage.  Such damage includes, most commonly, chipping of the shell margin, crushed apices, fungus erosion (ascomycetes: Didymella conchae), cracks, and erosion from attached barnacles.  Extent of damage may relate to a species’ position on the shore.  For example, assessment of damage to several limpet species in Monterey Bay, California discloses virtually no damage to high level-inhabiting Lottia digitalis (only 3 of several hundred show significant damage), but considerable damage to low level-inhabiting L. scutum (60 damaged out of 60 examined = 100%) and L. limatula (32 out of 32 = 100%).  The lower zones of the shore are subject to greater wave action and thus to more impact damage, and also to greater numbers of shell-damaging predators, such as crabs.  Laboratory studies by the author using experimentally damaged individuals further show that repair is more rapid in low-dwelling species, such as L. scutum and L. limatula, than in high-dwelling species such as L. digitalis and L. scabra.  Shell repair is done by laying down layers of nacreous material on the inside shell surface.  Bulkley 1968 Veliger (Suppl) 11: 64.

NOTE  the author’s description of how this is done is not very clear, but it appears that slots are drilled from the shell edge to varying distances towards the apex, but not as far as the mantle-attachment line on the inside of the shell

 

Lottia scutum showing minor shell damage 2X

 
Research study 2
 

photograph of limpets Lottia scutum in a small tidepoolSeveral sympatric species of limpets and littorines in the San Juan Islands area of Washington feed on a common food resource of diatoms.  With over 130 species of diatoms to choose from, one would think that food competition would not be an important element in the lives of these grazers.  Surprisingly, however, studies in which limpets Lottia scutum, L. pelta, and L. strigatella, and the winkle Littorina scutulata are allowed to feed on natural microflora growing on clay pipes show that all 4 grazers selectively remove just 3 diatom species.  The 3 preferred diatom species are characterised by having moderate-sized cells in long chains that form a loosely anchored overstory within the diatom mat.  Their consumption by the snails is facilitated by the chain morphology (“the whole chain may be pulled into the mouth like spaghetti”) and uppermost location in the mat.  Although the 4 gastropods appear to be using the same resource in about the same way, food competition is unlikely because of differences in zonation and microhabitat selection of the different species.  Among the limpets, for example, L. digitalis lives in the high intertidal zone, L. pelta in the middle region, and L. scutum slightly lower and in tidepools.  The winkle Littorina scutulata overlaps in distribution with the first 2 species of limpets but, because of its small size, has access to cracks and fissures that the other grazers cannot enter.  Nicotri 1977 Ecology 58: 1020.

NOTE  the clay (drainage) pipes are conditioned in the sea for one month, implanted in a mudflat (to prevent the snails from crawling away), then “inoculated” with the 4 grazers (one species per pipe), and left for 1mo

 
Research study 3
 

photograph of a limpet Lottia scutum in its feeding patchschematic showing amount of cover of algae relative to number of feeding occurrences by limpets Lottia scutumPlate limpets Lottia scutum  inhabit mid-tidal regions and feed on various encrusting algae and on diatom scums.  On shores around the Hopkins Marine Station, Pacific Grove, California they consume primarily the encrusting red algae Petrocelis middendorffii and Hildenbrandia occidentalis.  Interestingly, studies in this area show that L. scutum maintains a steady mixed diet of 60% Petrocelis and 40% Hildenbrandia - a proportioning that is constant over a wide range of availability of the 2 algal foods.  Note in the above diagram that feeding of L. scutum on open rock surfaces (diatoms?) and on Hildenbrandia is more or less in proportion to the surface cover of the algae, while feeding on Petrocelis is disproportionately greater than its surface cover.  

The second set of data shows food preferences of Lottia on 2 other boulder areas differing in relative amounts of algal foods.  Note the tendency in the lower data array for the limpets to favour different foods. The author proposes that such an admixture may avoid excessive cusp wear on the radula associated with, for example, eating the tough-textured Hildenbrandia.  Close-up photography and underwater listening devices enable feeding methodologies of individual limpets to be studied.  These observations show that feeding usually causes negligible damage to the encrusting algae except if a plant is visited repeatedly. In such cases, visible wounding may occur.  Replenishment of algal patches exposed by feeding is usually by vegetative growth and not by new settlement of spores.  Such mixed-diet feeding is advantageous over even moderate ranges of abundances of the various foods, and allows switching to any especially common food if one of the components of the mixed diet becomes too rare to rely on.  The author discusses the results in relation to past feeding models presented in the scientific literature.  Kitting 1980 Ecol Monogr 50: 527.

NOTE  this is an old name for the soft, black, encrusting sporophyte stage of Mastocarpus papillata (papillatus).  The gametophytic stage is the familiar warty, purplish-black upright plant living in mid- to high-intertidal regions

 
Research study 4
 


Growth
of Lottia scutum on shorelines in Sonoma County, California is faster in late-spring to early summer than in winter for all size classes. In this area the principal food is macroalgae.  Average life span is about 2yr. Phillips1981 Mar Biol 64: 95.

NOTE  measurements are for periods of 4-6wk, but are converted by the author to an equivalent “standard” month of 30d

 
 

Tectura depicta

 
Research study 1
 

Limpets Tectura depicta inhabit blades of eelgrass Zostera marina where they graze on their host’s epidermis (see photograph).  The authors of a study at Moss Landing Marine Laboratories, California on the effects its grazing has on Zostera refer to this limpet as a “commensal” but, as their results show considerable negative post-grazing effects on the plant’s photosynthetic abilities, its relationship with the plant is hardly photograph of limpet Tectura depicta grazing on an eelgrass blade, courtesy Lovell & Libby Langstrotha benign one.  Moreover, following Tectura’s unexpected recruitment in 1993 into a 30ha subtidal eelgrass meadow in Monterey Bay, California, density of Zostera declines 3-fold and more than half of the meadow converts to bare sand.  Within 6mo of the limpets’ appearance,  plant sizes are reduced by 50% and internal sugar reserves have declined more than 4-fold.  Most Zostera mortality occurs in the winter when internal energy reserves are at a minimum.  Since its arrival, T. depicta has apparently become greatly reduced in numbers, perhaps a result of its own destruction of eelgrass substratum and food source, and even in 2001 the eelgrass meadow has not recovered.  Zimmerman et al. 2001 Mar Ecol Progr Ser 218: 127. Photograph courtesy Lovell & Libby Langstroth, California Academy of Sciences.

NOTE  sometimes placed in the genus Lottia

NOTE  prior to this event, the species was known only from a handful of preserved specimens and fossil shells collected from near San Pedro, California, some 600km to the south.  The invading type is of an unusual oval shape


LimpetTectura depicta grazing on the surface of a Zostera
blade. Dark green colour indicates ungrazed epidermis 7X

 
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