15

ADDITIONAL INFORMATION, IF ANY, CONCERNING AUTHORS, ADDRESS, TITLE, OR CITATION DATA
PLEASE TYPE ABSTRACT DOUBLE SPACED BELOW
Acmaea limatula moves only when splashed or submerged, whether
this period comes during the day or night. Movement commences shortly after
wetting, rises to a high level as the tide comes in, drops during periods of
high tide, and increases again as the tide receeds. At night rising tides pro-
duce upward movement, but during the day the animals move downward on both
rising and falling tides, particuarly during the latter. Some homing occurs,
particularly on horizontal sufaces.
Acmaea limatula spends most of its time on the red encrusting algae
Hildenbrandia and Peyssonelia when these are available. The main foods of
the limpet are microscopic algae and the encrusting red and coraline algae
Hildenbrandia, Peyssonelia, Lithothamnion and Lithophyllum. Non-encrusting
forms are not eaten unless they are short, growing close to the rock surface.
Dietary studies suggest that in habitats where both A. limatula and A. pelta
occur, there is little competition for food.
EATON, CHARLES M. (Hopkins Marine Station, Pacifio Grove,
Calif., USA.) The activity and food of the file limpet, Aomaea
limatula (Mollusca: Gastropoda: Prosobranchia). The Veliger.
PLEASE DO NOT TYPE BELOW THIS LINE
THE ACTIVITY AND FOOD OF THE FILE LIMPET, ACMAEA LIMATULA
(Mollusoa: Gastropoda: Prosobranchia)
Charles MoKendree Eaton
Hopkins Marine Station of Stanford University,
Pacific Grove, California
INTRODUCTION
Acmaea limatula Carpenter, 1864, has been studied from the stand-
point of taxonomy, distribution, and habitat (Test,11946), response
of the heartrate to changes in temperature (Segal, 1962), osmotic behavior
(Segal and Dehnel, 1962) and reproduotion and growth (Seapy, 1966).
Published accounts of other aspects of its biology, however, are lacking.
It has been the purpose of the present study to investigate the activity
pattern and feeding habits of this species.
GENERAL ACTIVITY IN RELATION TO PHASE OF TIDE
To determine the general activity pattern of A. limatula, field
observations on a population of thirteen limpets were carried out over a
period of forty-five hours from May 2 to May 4, 1966. The population was
looated at Mussel Point, Pacific Grove, California, on a flat, vertical
granite face which was totally exposed and covered by water twice a day.
Coordinates were drawn on the surface of the rock with a lacquer paint,
and the animals were marked with colored paints to distinguish each
individual. The position and orientation of each animal were then observed
andd recorded at intervals of 1.5 hours. At the end of the 45-hour
observation period, a series of positions for each animal had been determined,
fostnste
C. M. Eaton
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the distance between successive positions representing the net,
minimum displacement between observation periods. Figure 4 a,b,c
shows displacement tracks for three individuals. In order to
observe the movements of the limpets during periods of high tide
and rough water, it was necessary to wear a wet suit with two
weight belts and to use underwater writing material (x-ray film
with the emulsion removed and the surface roughened with sand-
paper proved very satisfactory for pencil notes).
As can be seen from Figure 1, individuals of Acmaea limatula
move actively only during periods when they are either splashed
by water or submerged. The time of day or night at which the
period of wetting occurs does not appear to influence the amount
of activity. The movement during periods of complete exposure
(0130 to 0600, May 3) approaches zero. During each period of
rising tide a large amount of activity was observed, but the
animals do not begin moving immediately upon being splashed, and
some remain inactive for a time after they are first submerged
(0600 to 0730, May 3; 1730 to 1900, May 3; and 0730 to 0900, May 4).
Following the incoming tide, the activity characteristically
drops during periods of high water, to be followed again by a
sharp increase as the tide is falling. These periods of high tide
are often accompanied by great surge, and many of the animals
stop moving altogether, clamping down on the surface of the rock.
Although the movement again increases as the tide receeds, it is
interesting to note that in all cases, except for the period
00
between 2230 to 0000, May 2, the activity does not reach the level
observed during incoming tides.
180
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C. M. Eaton
VERTICAL MOVEMENT IN RELATION TO PHASE OF TIDE AND TIME OF DAY
The vertical displacement of the population of thirteen
limpets with reference to tide and time of day is shown in
Figure 2. It is clear that during periods of nocturnal rising
tides, Acamaea limatula shows a definite upward displacement,
but, during the daytime hours (0730 to 1350, May 3; and 0900
to 1500, May 4), the displacement is characteristically in a
downward direction, whether the tide is rising or falling.
This correlates nicely with the studies on light sensitivity
in various Acmaea species made by Ross (1966); A. limatula was
the only species studied showing a strong negative response to
light. It should also bennoted that the tendency to move down¬
ward during the daytime, in terms of either the number of
individuals moving or the total displacement, is proportionally
reateraduring the receedinggtides than on the incoming tides.
Again, although nocturnal receeding tides tend to produce ran¬
dom movement (five individuals moved up, four down in each case)
the displacement upward is proportionally less than that for the
rising nighttime tidesl
Rogers (1966), in his study of Acmaea scutum, found that
this species conforms to the more typical vertical displacement
pattern shown by many intertidal invertebrates (Wieser, 1952;
Glynn, 1965, Figure 30 and pp. 53-55). A. scutum moves up with
rising tides, and down with falling tides, no matter whether the
period of submersion comes during the day or night, though
upward movement during the day is less than that at night.
G
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Cm M. Eaton
wa:
A series of experiments w done in the laboratory in
order to substantiate Acmaea limatula's partial non-conformity
to the general rule for the vertical movements of transient
intertidal invertebrates. In all four experiments eight indi¬
viduals were subjected to simulated rising tides for periods of
1.5 hours; only the amount of light was varied. In each case,
fresh organismsewere collected from the field at low tide,
except for the first daylight experiment in which the same
individuals were used as in the preceeding darkroom experiment.
The specimens were placed in a line in the middle of a rough¬
ened sixteen-inch piece of marble, four facing upward, four
downward. After the activity of the animals had ceased, the marble
slab was placed in aquarium with the water level coming two
inches below the line of limpets. The water was then adjusted
so as to rise two inches every fifteen minutes and comressed air
vabbled
was  into the water to create simulated waves and splash.
Thennatenwasthen adjustedseastenise twerthehes-uver
fitbeenminutesand senpsessedainuns sunzintethe-watente
araatesinutatodmaoean The first two experiments
were run in the darkroom, the last two outside in the early
afternoon sunlight.
These experiments (Figure 3) confirmed A. limatula's
general tendency to move downward during daylight incoming tides
and upward during nighttime incoming tides. It should be men¬
tioned here that the graphs denoting distance of vertical dis¬
placement for the experiments run in the daylight are not entire¬
ly accurate, for in both experiments two individuals moved off
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C. M. Eaton
the piece of marble onto the bottom of the agquarium during the
first half hour. Their vertical downward movement was then listed
as a minus eight inches in both experiments, even though the
downward displacement might have been considerably greater had
the marble slab been longer.
HOMING TENDENCY
V
Homing, as used in this paper, is the consistent returning
to the same exactlocation with thessame orientation. Figures
4a and 4b illustrate the non-homing behavior shown by twelve
of the thirteen limpets in the population followed in the field.
These typical displacement tracks show that the animals spent
each consecutive exposed period in a new location.
Only one individual in the population homed consistently
for the entire forty-five hour period (Figure 4c). Interestingly
enough, the homing limpet not only returned to its home site as
the tide went out, but also during periods of high tide accom¬
ted n
panied by surge. This type of behavior was also observed in
homing Acmaea limatula observed in other locations. They would
leave their home sites as the tide wastrising, return when the
tide was highiand then either remain at home or leave again as
the tide was falling. This behavior helps to emphasize the
characteristic drop in activity during periods of high tide as
shown in Figure 1.
Although only one of thirteen animals in the population
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whose activity was closely followed, homed consistently for a
period of four low tides, the percentage of homing animals may be
higher for the total population. In another field observation
made on Mussel point, nine of fifteen Acmaea limatula homed
consistently for a 48-hour period. These limpets were located
on a horizontal rater than a vertical surface, and although the
numberg of animals observed is small, the findings suggest that
homing may be more prevalent among populations of A. limatula
which must cope with desiccation accompanied by direct
sunlight.
DISTRIBUTION IN RELATION TO ALGAE
The algae present seem to play a significant role in the
distribution of Acmaea limatula. A good example of this can be
cited from the population whose movements are shown in Figure 1.
The surface of the vertical face on which the thirteen limpets
were located was occupied mainly by diatoms and microscopic
green and blue-green algae on the left-hand upper side of the
rock, and by encrusting red algae, mainly Hildenbrandia and
some Peyssonelia, on the lower right-hand side. These two
regions occupied approximately equal areas, and both areas
bore occasional small clumps of Endocladia or Gigartina. Though
Hildenbrandia and Peyssonelia dominated only about half of the
rock surface (Figure 5), the thirteen limpets observed spent a
combined total of 500 hours in this lower right-hand region.
C
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C. M. Eaton
During the 45-hour observation period, only two limpets ventured
into the region bearing mainly green and blue-green algae and
diatoms, where they spent a total of 85 hours.
Although individual Acmaea limatula can be found in widely
differing regions within the intertidal of Mussel Point, the
larger populations (up to 37/square yard) are invariably located
in regions where Hildenbrandia or Peyssonelia or both are
abundant. In order to demonstrate this relationship between
limpets and algae, a 3.4 square foot rock surface was chosen con¬
taining fourteen A. limatula, a fairly abundant crop of the
red-encrusting alga Hildenbrandia, and a wide variety of other
algal growths. A clear plastic sheet was placed over the region
and the areas occupied by the various algae were outlined with wax
marking pencils. The locations of the fourteen A. limatula were
noted. The drawing was traced onto a large piece of graph paper,
and the different regions were cut out and weighed. By compar¬
weights
ing these to the weight of one square inch of graph paper,
it was possible to get a fairly accurate dtermination of the areas
ptesent
occupied by the various algae. Figure 6 shows what
qualifative
more a observations confirm, that, at least during low
tide, A. limatula is often found in direct association with the
red encrusting algae. This, of course, is only an instantaneous
glance at the distribution of A. limatula, but it seems per¬
tenent when viewed in conjunction with Figure 5 and the gut
content analyses below.
limatula
Although on Mussel Point large populations of Acmaea
were found only on the red encrusting algae, Hildenbrandia and
Peyss
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C. M. Eaton
Peyssonelia, this may not necessarily apply to other regions
along the Pacific Coast. It was noted, for example, that on
Point Lobos, just south of Carmel, California, fairly large
populations of A. limatula seemed to thrive on low horizontal
expanses of sandstone covered primarily with microscopic and
tock surfaces
and encrusting coralline algae. Extensive low, horizontal ewper
are not found on Mussel Point, but as can be seen from the
gut analyses below, A. limatula does eat microscopic algal films
theg ar
and encrusting coraline algae when available.
RELATIONSHIP OF FOOD AVAILABLE TO FOOD EATEN
To correlate the availability of various algae with the
foods actually eaten by Acmaea limatulay a series of gut anal¬
yses were performed on animals from differing areas. Eight
regions were chosen which showed either differences in the algal
species present, or in the relative abundance of the species.
Five limpets were collected from each region after making a
rough assessment of the relative amounts of different algae
available to the animals. The stomach contents of these 40
animals were observed microscopically and with the Rind help of
Doctor Isabella Abbott, the algal fragments present were ident¬
ified and an estimate of the relative abundance of different
species was made.
Figure 7a-h and Table 1 indicate that the main source of
food for A. limatula consists of the microscopic algae and of
the encrusting forms, Hildenbrandia, Peyssonelia, Lithophyllum,
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and Lithothamnion. Strangely enough, A. limatula seems to
ignore the encrusting red alga Petrocelis (Figure 7g) even
though it grows in relative abundance within the intertidal
region inhabited by this limpet.
The non-encrusting algae are rarely ingested except for
tiny individuals of larger species, or species which form a short
fuzz growing close to the rock surface (Table 1, III, Figure 7b,e,f,h)
In such cases the thalli found were very small and capable of
being swallowed whole. Only once was a fragment of a large,
non-encrusting algae (not an entire thallus) found within a
stomach, although many such algae were available to;the indi¬
viduals analyzed. The item foundingested was a section of a
large brown alga which could not be found in the surrounding
area.
Figure 7h provides an excellant example of Acmaea limatula's
tendency to avoid the larger non-encrusting algae as food
sources. Although this limpet eats the encrusting coraline
algae Lithophyllum and Lithothamnion, the non-encrusting formline
Corallina was completely ignored here, even though it dominated
the region.
FOOD NICHE SPECIALIZATION IN ACMAEA LIMATULA AND
ACMAEA PELTA
Acmaea limatula and the very eurytopic limpet Acmaea pelta
may often be found occupying the same general areas and hab¬
itats in the intermediate and low intertidal zones on Mussel
Point. In order to substantiate the presence of overlapping
sater
species distribution jo
populations, Craig and the author mapped oseie
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C. M. Eaton
three transects, each three feet wide,extending from the low to
the high intertidal zones. Populations of the two species
overlap broadly, and several places were discovered where both
A. limatula and A. pelta were abundant see also Craig, 1966).
With such an overlap in distribution on the part of two spac
species in the same genus, one might expect considerable comp¬
etition, especially for food since both species are herbivores
and scrapers. Interestingly enough, little competition for food
actually exists. The two species live side by side,
A. pelta eating the larger, non-encrusting algal forms (Craig,1966)
and A. limatula ingesting primarily the encrusting red and
coraline algae.
SUMMARY
1. Individuals of Acmaea limatula move actively only during
periods when they are either splashed by water or submerged.
The time of day or night at which the period of wetting occurs
does not appear to influence the amount of activity.
Animals do not begin moving immediately upon being splashed,
and some remain inactive for a time after they are first
submerged. Activity reaches a high level as the tide is
rising, characteristically drops during periods of high tide,
and shows some increase again as the tide recedés.
3. With rising tides at night, a definite upward movement occurs.
During the daytime hours, the displacement is characteristically
-11- C.M. Eaton
in a downward direction during both rising and falling tides.
during
The tendency to move downwardAthe daytime is proportionally
greater during the receding tides than on the incoming tides.
Only one of the thirteen limpets in the population studied in
detail homed consistently for the entire 45-hour pbservation
period. However, on a large horizontal rock, nine of fifteen
homed consistently for a 48-hour observation period.
Where the red encrusting algae Hildenbrandia and Peyssonelia are
present, Acmaea limatula spends most of its time on these.
The main foods of A. limatula are microscopic algae and the
and coraline
encrusting redAalgae Hildenbrandia, Peyssonelia, Lithophyllum,
and Lithothamnion. The encrusting red alga Petrocelis is
ignored, even though it is relatively abundant in the region
inhabited by the limpet. Non-encrusting forms are not eaten
unless they are very short, growing close to the rock surface.
Although A. limatula and Acmaea pelta may often be founoccu-
pying the same general areas and habitats in the intermediate,
and low intertidal zones of Mussel Point, there is little
interspecific competition for food. A. pelta eats the larger
non-encrusting algae while A. limatula ingests primarily the
encrusting red and coraline algae.
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C. M. Eaton
ACKNOWLEDGMENTS
I would like to express my sincere thanks to the faculty
and staff of Hopkins Marine Station, especially to Drs. Donald
P. Abbott and Isabella A. Abbott for their advice and enoourage-
ment. This work was made possible by Grant G 1806 from the
Undergraduate Research Participation Program of the National
Science Foundation.
13
C. M. Eaton
LITERATURE CITED
Craig, Peter C.
1966. The activity pattern and food habits of the limpet
Acmaea pelta. The Veliger
Glynn, Peter W.
1965. Community composition, structure, and interrelationships
in marine intertidal Endocladia muricata-Balanus glandula
association in Monterey Bay, California. Beaufortia 12 (148):1-198
Rogers, Don A.
1966. The effects of light and tide on movements of the limpet,
Acmaea scutum (Gastropoda: Prosobranchia). The Veliger
Ross, Thomas L.
1966. The light response in the limpet Acmaea limatula (Mollusca:
Prosobranchia). The Veliger
Seapy, Roger R.
1966. Reproduction and growth of the file limpet, Acmaea limatula
Carpenter, 1864. The Veliger 8 (4) :300-310
Segal, Earl
1962. Initial response of the heart-rate of a gastropod,
Acmaea limatula, to abrupt changes in temperature. Nature
195 (4842) :674-675
14
C. M. Eaton
LITERATURE CITED (cont.)
Segal, Earl and Paul A. Dehnel
1962. Osmotic behavior in an intertidal limpet, Acmaea limatula.
Biol. Bull. 122(3): 417-430.
Test, Avery Ransome (Grant)
1946. Speciation in limpets of the genus Acmaea. Contrib. Lab.
Vert. Biol., Univ. Michigan, No. 31:1-24.
Wieser, W.
1952. Investigations of the microfauna inhabiting seaweeds on
rocky coasts. J. Mar. Biol. Assn. U.K., 31:35-44.
1. Permanent address:
15.
FOOTNOTES
C. M. Eaton
16
C. M. Eaton
Table 1
Frequency of occurrence of Algae found in gut of Acmaea limatula
NUMBER OF ANIMALS
TYPE OF ALGA
WITH ALGA IN GUT
I. Microscopic Algae
(small greens, blue-greens
40
and diatoms)
II. Encrusting Algae
1. Hildenbrandia occidentalis
2. Peyssonelia pacifica
15
3. Lithophyllum sp.
4. Lithothamnion sp.
10
5. Ralfsia pacifica
III. Low, Turf-forming Algae
(up to 3mm. high,
1. Gelidium coulteri
2. Clodophora trichotoma
3. Leathesia difformis
IV. Other Algae
1. Centroceras clavulatum
2. Colpomenia peregrina
3. Rhodoglossum affine
4. fragment of a large brown alga
14
C
17
C. M. Eaton
TABLE CAPTIONS
Table 1.
Frequenoy of occurrence of algae found in the gut of
Aomaea limatula.
C. M. Eaton
18
FIGURE CAPTIONS
Figure 1
Movement of Acmaea limatula in relation to phases of the tide,
May 2-4, 1966. Time of day is shown at the top. Distance
moyed represents average net displacement for 13 limpets.
Since the limpets occupied different vertical positions on
the rock, the number exposed, awash, and submerged at each
observation time is indicated. HHW- higher high water; LHW-
lower high water.
Figure 2
Vertical movement of Acmaea limatula on a vertical rock face
at selected phases of tide and time of day, May 2-4, 1966.
Only the vertical components of movement are represented.
Each vertical bar shows total net displacement upward or
downward for 13 individuals over a three-hour period when
conditions on the rock surface changed from total exposure
to total submersion on a rising tide, or from total submersion
to total exposure on a falling tide. Numbers above and be¬
low each vertical bar show numbers of animals whose net dis¬
placement during the period was upward and downward, re-
spectively; numbers on the zero line indicate numbers of
animals remaining stationary, or showing only horizontal
movement.
19
C. M. Eaton
FIGURE CAPTIONS (cont.)
Figure 3
Vertical movement in the laboratory under simulated conditions
of incoming tides.
Figure 4
Typical displacement tracks for 3 individuals of Acmaea limatula.
Observations were made at intervals of 1.5 hours over a period
of 45 hours, May 2-4, 1966. Limpets did not always move between
successive observation periods even when submerged or awash.
Figure 5
Distribution of thirteen Acmaea limatula in relation to algae
available, for a period of 45 hours, May 2-4, 1966.
Figure 6
Distribution of fourteen Acmaea limatulå at low tide in relation
to algae available within a 3.4 square foot area, mid-May, 1966.
Figure 7
Relationship of food available to food eaten in eight different
areas on Mussel Point, May, 1966. The lines at the ends of the
upper vertical bars show the range of variation encountered in
the five limpets examined in each region.
AVAGE DIST.
MOvÉD PER
INDIVIDUAL
(INCHES)
NO. OF
ANIMALS
EXPOSED, AWASH
OR SUBMERGED
MAY 2
MAY
MAY 4
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