16
9.
ADDITIONAL INFORMATION, IF ANY, CONCERNING AUTHORS, ADDRESS, TITLE, OR CITATION DATA
Jobe, dlon H.
A ST
PLEASE TYPE ABSTRACT DOUBLE SPACED BELOW
JOBE, ALAN H. (Hopkins Marine Sta,, Stanford Univ., Pacific Grove,
Calif., USA). A study of morphological variation in the limpet Acmaea
pelta (Mollusca: Gastropoda: Prosobranchia). The Veliger
Populations of Acmaea pelta (Eschscholtz, 1833) on the
Monterey Peninsula, California exibit variation in shell shape and
color. Field studies showed possible correlations of these
variables with algal association, substrate, and exposure. Shell
shape seems to be dependent upon substrate and exposure. Shell
color may be related to diet, but preliminary investigations of
gut carbohydrases failed to reveal any distinctive guantitative
acwes
differences in the amylase, fucoidinase and alginase, found in
the A. pelta forms assayed.
PLEASE DO NOT TYPE BELOW THIS LINE
A Study of Morphological Variation in the Limpet Aomaea pelta
(Mollusca: Gastropoda: Prosobranchia)
by
Alan Jobe
Hopkins Marine Station of Stanford University, Pacific Grove, Calif.
93950 %
Acmaea pelta (Eschscholtz, 1833) is a low intertidal
species of limpet that is widely distributed on the American
west coast. A great variation in shell appearance has been
noted-Light,, especially when comparing large and
small specimens. Preliminary observations indicated a possible
correlation between habitat and morphology, which led to a
study of the distribution of A. pelta with respect to substrate
and algal association. These field studies, reported below.
indicated definite relationships between morphologic types
and habitat, leading to a study of digestive enzyme potential.
Field Studies
Field observations were done at Mussel Point, Pescadero
Point, and Cypress Point on the Monterey Peninsula,
California. Three morphologic forms of A. pelta were
observed, differing in color, shape, and length-to-height
ratios of the shell. These different forms of A. pelta
were positively identified as being variations of the
species using standard radula length and teeth determinations,
as well as the classification by jaw shape proposed
by Walker (1966). These various morphologic forms are described
below in terms of color, shell shape, and length-to-height
K (Se fesnste
95
Alan Jobe
ratios as measured with a vernier caliper.
Norohologic Formsien
Brown form: The typical large brown A. pelta is
rized by a convex slope from the high peaked shell
charate
apex to the periphery and is often infected with the fungus
1+oral
common to shells of diberg animals of the Pacific Coast
(Boner, 1936). These brown-colored specimens are generally
over 30 mmn in length, and have a length to height ratio of
2.3 as seen in Table 1. Illustrations of the brown shells
are in Fig. 1, Group A.
tia): Two separate populations of the
Black form (Pely
small black A. pelta were observed, on the mussel beds and
on and under Pelvåtia fastigata. Those found associated with
Pelwötia (Fig. 1, Group c) had a straight to concave slope
from the apex to edge and a characteristically cleaner shell
chan any other A. pelta form. The shell shape was flatter
than the brown 4. pelta, and had a uniform lengöh-to-height
ratio for the entire size range encountered. This flat
shell often had a rather hooked apex and a more wavy
peripheral edge than the black form seen in the mussel
beds (see below).
Black form (Mussel beds): A. pelta was found on the
mussel bed areas, generally on the mussels, Nytilus
tella
forianus, and on the goosenecked barnacles,
cali
These were generally black with length-to-heigh
polymerus.
16
Alan Jobe
ratios which varied with size, as seen in Table 1. No
specimens over 20 mm were found in the beds. The profile
of the members of this form (Fig. 1, Group D) approaches
that of the large brown A. pelta. The shells of this form
are not as clean and as shiny as those found under Pelvétia,
and the shell periphery is smooth.
Green form: The third group of A. pelta, intermediate
in size between the black A. pelta on Pelvétia and the
large brown A. pelta form, are shown in Fig. 1, Group B.
This group shows a great variation in shell shape and often
displays the growth ring type of change in the exterior shell.
Most specimens are greenish-black in color. Some, however.
are almost white and others are ribbed or checkered.
Kabitat.
A survey of the intertidal zone of the Monterey Peningila
revealed fifferences in the density of the k. pelta populationge.
Mussel Point and Pescadero Point had rich populations while
Point Pinos was sparcely populated. The reason for this
uneven distribution was not investigated.
Brown form: This form of A. pelta occupies a high inshore
intertidal position from  to above 16 feet. The brown
Alen Jobo
orgrnisms wore found predominatoly on more barren rocks and
wore oxposod to more sun and orid conditions then tho other
typos. Thoy woro gonerally found on vortical rathor then
orizontel faces. The broun limpots wore found in an
apparontly rendom association with onerusting algae and
amrä.
oth, hieh elvei
ähgel films as woll as m
e
Tastigat
Tine, and other algao. Occasionally
Rhodoglos
Tu L

ono was found on bare rock close to sand with no macroscopio
algoo ovidont.
a o
Polv
tia): At low tido 253 of this form
Ltoe
Polvitia. An obvious scar
was on tho holdfast or stipo of un
was fond undor those limpots, indiesting that this algaomay
bo a peimary food sourco. Tho romaining 753 were attachod
to tse rock substratum under the Po
vêtin. Tho Pol
2512
bods providod moisture and shelter from the sun. In moro
oxposod proas as Pescadoro Point, whero Polvêtia is not
found in large beds, the black A. Selta wore less numerous

and randonly distributed. Noro again thoy wero to bo found
in locations offering sholtoe and moisture.
(7
lack forn
90.
s): A. Mlth in tho mussel beds
be

woro sot associated with conspicuous algao. This form could
be found oxpocod to the sun at low tido, as opposed to tho

Po
i form which was novor found oxposod to dioct

sunlicht. Tho mussol beds providod a damp, sholterod onvåron
mont that is subjectod to splash oxcomt at very low tide.
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Alan Jobo
Geoon forn
Tho middle sizod groen A. pelta had a

Polviti
habitat virtually idontieal to tho black e
form.
Wiguro 2 shows tho porcent distribution of thoso difforent
ol
t pos of A. n as relatod to position and habitst in the
intortidal.
Laboratory Studios
"ho d intortidal distribution, alone with Graig's (1786)
obsorvations on fooding habits suggested that,since
tho differont forms woro ecting different algse, possibly
thero was ad
foronce in digestive enzymes in tho A. po
forms. The digestivo enzyme potentinl of the different
forms of A. pelta was assayod by moasuroment of roducing
sucar rolonsed from purified polysaccharides (Wolson, 10h4).
Tho polysaccharides studied woro fucoidin, laminarin, and
alginic acid from broun alcal sourcos, agar and K-carrageenin
Trom rod algao,and starch. Sinco somo of those carbohydrates
contain sulfated groups, particularly fucoidin, sodiu
hydroxide was substitutod for barium hydroxide (Wolson, 104)
to avoid possiblo precipitation of tho sulfatod sucar
fragmonts produced by onzymatic hydrolysis. A 10% exbract
of tho ontire digestive system including osophagus, buccal
selivary glands, and hind gut was propared from animals of
tho black and broum morphologie forms. Tho tissues woro chilled
on ico and homogenizod in ice cold homogenizing medium.
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Alen Jobo
Wach 1 ml of tissuo was homogonized in a modiu containing
o aa
us stroptomein solution (5 m/l) to inhibit
onctorial grouth, ! ml of a saturated solution of ovomucoid
isolated by tho mothod of Frodricg and Doutsch (1949), and
7 ml of buffor (0.21 Tris buffer at pü 7.2 and 0.2 acotste
buffor at oH 3.5). Ovomucoid was usod as a tryosin inhibitor
bocause of probloms oncountorod with protoinasos in tho
onzyme extract, ouho ovomcoid inerensod activity approximatoly
two-fold. Ono half ml of onaymo oxtract, one half ml of a
O.53 solution of purifiod polyseccharide ond one and ono half
for was incubatod at 2090 for ono hour. Tho amount
or bu
of polyseccharido in a ono nl aliquot was eqnivalent to
appromimatoly 200 micrograms of roducing aucar on complote
hydrolysis. Tho colorimetrie doterminations woro mado with
a Riott-Sumorson photo-oloctrie colorimeter uaing a green
rülter, and values were corrocted for roducine sugar prosent
in onzymo and substrato controls. Tho corroctod values are
exprossod in torms of mierograms of glucose por hour per ml
aliquet of rosction modium, and aro oquivalent to 0.02 ml of
gut iquo.
Rosults
Markod amylaso activity, paeticularly at pR S.5,was
domonstratod in oxtracts from larco broum A. pouma and the
11.
2og
Alan Jobe
black form found on Pelvétia. Table 2 gives the quantitative
results. Higher act
ivity was obsorved in extracts i
from the
brown animals. Low levels of fucoidinase and alginase were
consistently demonstrable at pH 7.2. No enzymatic hydrolysis
of K-carrageenin, laminarin, or agar was observed at either
pH.
Disoussion
The field work demonstrated a differonce in shell shape

of the A. pelta found in dillerent habitats in the intertidal.
t appears that shell growth and the resulting shell shape is
robably a response to the substrate upon which the animal
ves. The high peaked convex shell of the black variet
ound in the mussel beds may be an adaption to attachment
to a substrate such as is presented in the mussel beds where
large flat surfaces are at a minimum. The flatter A. pelta
under Pelvétia have an excess of flat but rough rock surface
to grow and move on. The wavy shell periphery is an indication
of an adaption to this environment. This seems to be a
reaction to the substrate similar to but not as extreme as
that of the limpet A. scabra whose shell grows to conform
to irregularities of the home site (Hewatt, 1910). A.
pelta
havatentallyp
is ertian high, almost center peaked limpet. This
is true when exposed and of reasonable size, as in the brow
26
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Alan Jobo
form and the larger soocimons from tho mussol bods. Sinco
no large spocimons woro found in the mussel bods and small
ones woro abundant, mortality may inerease with ago, tho
larger limots being unable to survivo on this aubstrato.
Substrato and exposure therofore appoar to be large factors
in dotermining sholl morphology.
po
Tho reason for tho different colors soon in A.

is not cloar, but a possible correlation with diffowout
algal food is plausible. Tho reported experiments do not
ate that digestivo potential is tho critical
sm toindi
Tactor. Thoy also shou that alginic acid and fucoidin could
be utilized only slouly in comparasen to utilization of
tarch. Althouch extracts prepared from broun forms
displayed more activity tham thoso obtainod from blach ones,
this di foronce may bo simply rolated to tho onso of
ng ereptor purity of tho extrachs
dissecting and tho rosul
proparod from the larcer broun limpots.
thouch not rolated to digestivo potential, the
difforonces in color of poak and poriphoral portions of
shells suggests  possible changes in diet
denge tge lite of tie amal.
on te omporimonts will bo roquirod
to oxploro this rolationship.
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Alan Jobo
Surmary
Populations of Aemaoa da (Nachscholtz, 1033) oxhibit
ot
variation in sholl shapo and color. Fiold studies showed
correlations of these variables with algal
association, substrate, and oxpesuro. Shell shapo sooms to
bo dopondont upon substrate and oxposure. Sholl color
bo rolatod to diot, but proliminary invostimations of
carbohydrases failod to revoal any distinctivo quantit
att
foronces in the amylaso, fucoidina:
nd a
t
in tho A. polt forms assayed.
20
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c
Alan Jobo
Ackouledgemonts
This work was mado possiblo by Grant G/006 from the
Undorgraduate Rosearch Participation Program of tho Wational
Scionco Foundation.
Thanks to Dr, J. Thillips, my advisor, who isolated and
jurified tho polysascharides agar, K-caragoonin, lamina
fucoidin, and alcinic aeid for tho digestive enzym
e
Thacks to Miss Cathy Walker who holpe

ification to tho A.
positivo idon
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Alan Jobe
LITERATURE CITED
Bonar, Lee
1936. An unusual ascomycete in the shells of marine animals.
Univ. Calif. Publ. Botany 19: 187-194.
Craig, Peter C.
1968. The activity pattern and food habits of the limpet
Acmaea pelta (Mollusca: Gastropoda: Prosobranchia). The
Veliger
Fredricg, E., and H. F. Deutsch
1949. Studies on ovomucoid. Jour. Biol. Chem. 181: 499-510.
Hewatt, Willis G.
1940. Observations on the homing limpet, Acmaea scabra Gould.
Amer. Midland Naturalist 24: 205-208.
Nelson, N.
1944. A photometric adaptation of the Somogyi method for the
determination of glucose. J. Biol. Chem. 153: 375-380.
Walker, Catherine G.
1968. Studies on the jaw, digestive system, and coelomic deri-
vatives in representatives of the genus Acmaea (Mollusca: Gas-
tropoda: Prosobranchia). The Veliger
208
1. Permanent address:
Footnotes
12
Alan Jobe
206
0
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Alan Jobe
Table Legenda
Table 1: Length to height ratios of the different forms of A. pelta
as related to position in the intertidal.
Table 2: Enzyme activity expressed in micrograms of reduced sugar per
0.02 ml of gut tissue. Any value less than 2 micro¬
ams is
considered inconclusive.
C
Alan Jobe
Figure Legends
Figure 1: A photograph that illustrates the different varieties of
A. palta encountered on the Monterey Peninsula. Group A is the
brown form, Group B is the green form, Group C is the black form

(Eelvitia), and Group D is the black form (mussel beds).
Sigure 2: Percent distribution of the three morphologic types of
A. palta (each type z 1005) as related to position and habitat in
the intertidal. Black A. palta (231 animals) show in solid bars,
brown (123 animals) in open bars, and green (168 animals) in cross
hatched bars.
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Form of Anirul
Brown A. pelta
Black Apalta
Plack A. pelta
Black 4. pelta
Black A. polta
Black A. pelta
Table 1
Sizo
Location
Nich intertidal
30 m

Under Peltia
15 m

Under Pelvtia
15 ma
Wussel beds
15 m
10 to 15 mm Mussel beds
Mussel beds
10 r
Nubor
Checkod
22
12
23
Langth to
Moicht ratio
2.3
2.86
2.93
2.53
2.89
3.21
Klan oto
20
Standard
Deviaticn
O.246
0.270
0.263
O.295
0.272
C
Polysaccharide
Sbarch
Agar
K-carrageenln
Laminarin
Fucoidin
Alginic Acid
Table 2
Plack A. pelta
(Pelvitia)
7
pll 5.5 p 7.2
52ug 2ug
1ug
3ug
13
2g
Bromm A. polta
pl 5.5 pI 7.2
112 ug 50 ug
iug
513
5ug

tan Jote
216
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C
B
A
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