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PLEASE TYPE ABSTRACT DOUBLE SPACED BELÖW
WHITE, T. JEFFERY (Hopkins Marine Sta., Pacific Grove, Calif.,
USA.) Metabolic activity and glycogen stores of two distinct popula-
tions of Acmaea scabra (Mollusca: Gastropoda: Prosobranchia). The
Veliger
Populations of the limpet Acmaea scabra found high in the intertidal
remain immotile and do not feed for long periods of time, while lower pop-
ulations move and feed more frequently. Studies were carried out to deter-
mine whether any nutritional or metabolic adaptations enable these high pop-
ulations to sustain themselves over these prolonged periods between feeding.
Comparisons were made of glycogen conte and respiratory rate between two
populations; one at plus two feet in the intertidal, the other at plus six feet.
It was demonstrated that the higher populations have greater glycogen stores
and lower respiratory rates than the lower populations. The differences
could revresent an adaptation to survive for long periods between feeding.
aaaaa-
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Metabolic Activity and Glycogen Stores of Two
Distinct Populations of Acmaea scabre
(Mollusca: Gastropoda: Prosobranchia)
by
T. Jeffery White
Hopkins Marine Station of Stanford University
Paific Grove, California
Frotste.
43
1. Jelfery white
2
TRODUC
ION
Of the several species of Acmaea found in the intertidal of Mon-
terey County, A. scabra (Gould 1846) occupies the highest zone on the
rocks (Hewatt 1935). It ranges between the tide levels of plus two
and plus six feet. Hewattihasyobserved, and my own observations have
confirmed, that these limpets make excursions in search of food only
when submerged or amidst heavy wave action. Lower populations move
more often, and more regularly, than do populations located at higher
tide levels. For example, individuals of the higher populations have
been observed to remain immotile for periods up to three days.
In April and May, 1966, studies were carried out at the Hopkins
Marine Station of Stanford University, Pacific Grove, California, to
determine what physiological factors enable these populations to sustain
themselves over prolonged periods between feeding. Two parameters were
investigated; oxygen consumption and glycogen stores. These parameters
were chosen in conjunction with the hypothesis that a decrease in meta-
bolic activity and larger stores of glycogen may allow the animals to
survive under conditions that preclude frequent feeding.
MTTHODS
All specimens were collected off Mussel Point, Pacific Grove,
California. Individuals were taken from two different parts of the
intertidal; below plus two feet and above plus six feet. Within twen¬
ty minutes after collection, individual animals were placed in a sep¬
arate water-filled jar and their oxygen consumption measured for a three
hour period by the Winkler method (Welsh & Smith,1949, pg.146). The
water temperature remained constant at 11 C. In order to minimize
T. Jeffery White
and Lonsumgtön
oxygen evolutionby algae on the shells, the shells were scraped and the
animals kept in the dark. After the respiratory measurement was comple-
ted, each animal was removed from its shell, blotted and weighed. These
same individuals were then used to determine the amount of glycogen
present in the entire body. The whole animal was homogenized in 2mls.
of 10% trichloroacetic acid. After centrifugation, the glycogen was
precipitated from the trichloroacetic acid supernatant by the addition
of an equal volume of 95% ethanol. The precipitate was dissolved in
Amls. of water and the carbohydrate content determined using the phe¬
nol-sulfuric acid method of Dubois (1956).
RTS
LTS AND DI
JSSION
The results of measurements of oxygen consumption are represented
in Table 1 and glycogen content in shown in Table 2.
The findings show a difference in metabolic activity and glyco¬
gen stores in animals from the two intertidal locations. The results
show that the higher forms have higher glycogen stores and lower meta¬
bolic activity than the animals from the lower intertidal area. Thes
combination ofthscould be the critical factor permitting maintenance
of the animal between feedings. Measurements of glycogen in the higher
group also shows a somewhat greater range, as is reflected in the higher
standard deviation. A greater degree of variation in glycogen content
would be anticipated if life between feedings is dependent upon the use
of glycogen stores. The higher mean glycogen content in the limpets
from higher portions of the intertidal also suggests an increased
storage potential in these animals.
The glycogen and respiratory data also permit calculation of the
470
1. Jeffery White
minimum time these higher populations could survive between feedings,
if glycogen were the sole respiratory substrate. Assuming six moles
of oxygen consumed per mole of glucose utilized, this could permit
submerged maintenance for sixty hours. The lower population of Acmaea
scabra, with its higher respiratory activity and lower glycogen store,
could only maintain itself for seventeen hours. Since Baldwin (1966)
has found that the aerial respiration rate in A. scabra is several times
less than the submerged rate, the above values are certainly minimal
for aerially-breathing limpets.
Lower metabolic activity and higher glycogen content are not the
only characteristics of high populations that suggest adaptations for
survival in the higher portions of the intertidal. Nawatt (1940) has
observed that the shells of Acmaea scabra from higher intertidal areas
are higher and thicker, while the shells of this species living in low,
moist areas are thinner and flattened. In addition, the study of Jessee
(1966) indicates that A. scabra of the higher intertidal shows a greater
tendency to home than A. scabra found in the low intertidal. Animals
with a strong homing tendency present a greater irregularity of shell
shape that is complementary to the home site. The resulting better fit
of animal to substratum may decrease susceptibility to desiccation.
A third adaptation of the higher forms, shown by the study of Hardin
(1966), demonstrates that higher populations of A. scabra can withstand
greater temperatures than populations lower in the intertidal.
44
Jeffery White
CTTR
SUMMARY
1. Metabolic activity and glycogen content of pop-
from the higher and lower por-
ulations of Acmaea scabr
tions of the intertidal wer
re determined.
2. Animals from plus six feet showed lower metabolic
activity and larger glycogen stores than animals from plus
two feet.
3. The possible survival value of this difference
is discussed.
142
T. Jeffery White
44

ACKNOWLEDGEMI
NTS
This work was made possible by grant GY8Oo from the
Undergraduate Research Participation Program of the National
Science Foundation. I am also happy to acknowledge the
guidance of Dr. John Phillips.
C
T. Jeffery White
TTDT
REFERENCES CITED
Baldwin, Simeon
1966. Manometric measurements of respiratory activity in Acm
sa digitalis
and Acmaea scabra. The Veliger
Dubois, M.
1956. Colorimetric method for the determination of sugar and related
substances. Anal. Chem. 28:350
Hardin, Dane
1966. A comparative study og lethal temperatures  the limpets Acmaea
scabra and Acmaea digitalis. The Veliger..
Hewatt, W. G.
1935. Scological succession in the Mytilusc
ornianus habitat as
observed in Monterey Bay, California. Ecol. 16:211-251
Hewatt,
W. C.
1910. Observations on the homing limpet Acmaea
abra Gould.
Amer. Midl. Nat. 24:205-8
1er5 7
Jessee, William F.
1966. Wcological and mechanistic studies of homing behavior in the
limpet, Acmaea scabra. The Veliger
Smith, Ralph I. & Welsh, John H.
e, 41 F175
1949. Laboratory Exercises in Invertebrate Physiology., Minneapolis
Burgess Co.) 179pgsllfigs.
444
FOOTNOTES
* Permanent address:
a
S
445
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1. eiery White
AUf

PIGURT LAGENDS
Table 1 Glycogen stores from high and low populations (these figures correspe
to the same animalsas the first 21 figures in Table 2)
Table 2 Metabolic activity of high and low populations
44
O
C
—
en e.
Asal 1267
Ascab
—
190
100
360
160
700
8/0
110
300
630
115
600
660
1110
610
690
24
10
00
2-10113
2-1513
K-211.9
-522.15
SD=111.9
.-8.8625
S.E.=5.233
S. =10.29
XdSEd=29.8
7o

Table 1
1. Jellery White
44
O
Oygey Gsagte asj oslon ldg frs

AT1.
A. scabra +67.
cbra
115
230
191
100
292
165
30.
12
200
160
156
118
315
124
202
150
200
20
318
16
180
206
550
130
110
108
135
02
180
116
2 =939
521
X =2
-195.12
4:78
S.D.:
S.D.=81.0
20.11
S. E. =2.
S.E.=3.67
S.S. Sfr - 1.15
xese.-20.01
P =6.001
Table 2
1. Jellery Whi
44