ADDITIONAL INFORMATION, IF ANY, CONCERNING AUTHORS, ADDRESS, TITLE, OR CITATION DATA
PLEASE TYPE ABSTRACT DOUBLE SPACED BELOW
JESSEE, WILLIAM F. (Hopkins Marine Sta. of Stanford Univ., Pacific
Grove, Calif., USA). Studies of homing behavior in the limpet
Aomaea scabra (Gould, 1846). The Veliger
Homing behavior of A. scabra (Mollusca: Gastropoda: Prosobranchia)
from rocky shores was studied in field and laboratory. Populations
residing 7.1 and 2.4 feet above mean lower low water showed no sig-
nificant differences in höming ability. All size classes above
5-6 mm. in shell length showed equal homing abilities; smaller ani-
mals often did not exhibit homing. Scrubbing the substratum with a
fiber brush, or treatment with 32% NaoH had no significant effect on
homing tendency. Chiseling of the rock surface caused a drop in inci-
dence of homing. This suggests that homing behavior is mediated throug
perception of the topography of the substratum, and is not a chemo-
tactic response. Removal of the cephalic tentacles reduced the ten-
dency to home, while removal of the eyes did not.--Author.
PLEASE DO NOT TVPE BELON THAS LINE
2
C
Studies of Homing Behavior in the Limpet
Acmaea scabra (Gould, 1846)
by
William F. Jessee
Hopkins Marine Station of Stanford University, Pacific Grove,
Calif. 93950
0
ove
a
Tho tendeney of membors of the species Aemasa
abra (Gould, 1845) to re
repeatedly to a spocifie
location on their rock zubstratum, i.c. homing, has
been reported from time to timo, iu-tho-litemo
seh
Ouof tho first stud on the Pacific species
of Acmaea, by Wells (1917), gives the impression that
homing is a highly individual trait, even among mombers

orithe single species A. scabra. However, the tendency
to home was apparontly not studied in moro than a few
esentatives of each spocios, and tho frequency of
20
ag behavior was not ovaluated.
To attem
ts at such an evaluation were subsequently
reported (Howatt, 1940; Villee and Groody, 1940).
Hewatt's study of thirty-ono A.
scabra on granite rocks
reveoled homing behavior in all thirty-one individ-
uals. On the other hand, Villeesand Groody comcluded
from their study of 86 members of this species on a
sandstomo substratum, that there was no ovidence for
homing behavior. This latter study, however, was roe
stricted to observations made principally as low tide,
a time when there is little or no activity in tho lim-
pot population. All animals that had not beem observed
away from their homosite during the period of study
ro ignored.
In a more recent quantitative study by Brant (1950),
A seabre
298 marked  wero observed over a period of 34
days. Homing behavior was reported in 58.79 of this
test population. Proliminary observations by tho am
726
O
C
*

Sil ese
0
.
author collirmod thoso findings.
The principal object of this study was to inves-
tigato tho mochaniam involved in homing bchavicr. In
addition two othor aspocts of heming which have rocoived
little investigation aro included in this study. Toso
aro tho homing behavior of animals from high and low
elevations in tho intortidal, and the bohavior of
different size classes of limpots.
t
m
METHODS AND RESOLTS
Who obsorvations and oxperiments doscribed below
wero made at Pescadoro Point on tho Monteroy Peninsula,
California during Apzil and May, 1966.
Tho first series of experiments performed was
dosigned to detoct any difforences in the homing abile
ity of high and low populations, and in that of large
and amall animals. Ono hundred individuals of intormodiato
size, betwoen 10 and 15 mm. in length, wero measurod,
und tho animal and its homesite marked with red nail
polich. Fifty of those amimals woro on a homizental
granito surface with a median olevation of 62.4 ft..
e
—
this population will be roferred to as the
Wiow" group. Tho other:
fey amimals, hereafter called
the "high" population, were on a gently sloping rock
with a modian olovation of 97.1 ft. After waiting throo
days to insure that the position marked was indoed
the animal's homo, a procoduro that was followed in
all subsequent oxperiments, 30 in each group wero dise
-3
William F. Jessee
placed randomly 3 - 4 cm. from their homesites. The other
twenty in each area served as controls. The animals were
observed after 24 hours, and as shown in Table 1, no signi¬
ficant difference was seen in the homing ability of the
high and low groups.
A similar experiment was then carried out in an area
of intermediate elevation, +3.9 ft., to compare the homing
behavior of large animals, greater than 15 mm. in length,
with that of small ones between 6 and 10 mm. long. Here,
too, no significant differences were observed, as can be
seen from Table 2. However, a less complete study suggested
that animals smaller than 6 mm. usually do not home.
Experiments in the laboratory, utilizing glass plates
over which limpets had been allowed to move, revealed no
residual mucus in the form of trails as determined by the
India ink test of Peters (1964). Nonetheless, field exper¬
iments were performed to investigate the possibility that
mucus or some other chemical substance on the surface of
the rock was the agent active in governing homing behavior.
In the first type of experiment, a stiff fiber brush
was used to scrub a 14" strip around the homesites of 20
previously marked animals. The areas surrounding 15 other
animals, which served as controls, were left unscrubbed.
All animals were then displaced 4-5 cm. from their homes
-4-
William F. Jessee
to a position outside this strip. Their locations after 24
hours were noted, and are presented in Table 3. A variation
of this experiment was also carried out in which the home
itself was included in the area scrubbed. This was to
eliminate any possible attractant on the home, as well as
"trails" leading to the home. As shown in Table 3, neither
of these treatments completely destroyed the ability to
home.
A second group of experiments was performed to remove
chemical substances. All animals in a one foot square area
were removed and the rock painted with a solution of 32%
NaoH. The surface was then rinsed repeatedly with copious
quantities of seawater until the pH of the wash water was
near neutrality. The animals were then replaced within
4 cm. of their homes. Five animals outside the treated
area were also displaced a similar distance and utilized
as controls. At the end of the customary 24 hour waiting
period, 8 of the 10 animals in the experimental group had
returned to their homes.
Having established that the removal of chemical sub¬
stances on the rock had no noticeable effect on the homing
ability, experiments were begun in which the topography of
the rock surface surrounding the home was altered. A
geologist's pick and a chisel were used to create a strip
-5
William F. Jessee
1" wide around the homes of 25 animals. The topography of
the rock in this strip was totally changed. The animals
were then replaced 4 cm. from their homes, and outside the
chiseled area. Fifteen other animals were similarly dis¬
placed, but the topography of their surroundings was left
unaltered. This latter group served as a control. Within
24 hours only four of the 25 experimental animals had homed.
Seventeen of the 25 were not in their homes, the remaining
four having disappeared.
Some additional evidence suggesting the involvement
of topography in the homing mechanism was an experiment
performed with a small group of animals at China Point.
Seven animals were marked and displaced the customary 4-5
cm. from their homesites. A hammer and chisel were then
used to create a strip about 1" wide between the animal
and its home. As the tide came in, the animals were ob¬
served to move to the edge of the chiseled area, then
travel along the edge of this area until they reached its
end. At this point they resumed their travel toward the
homesite, six of the seven returning by the next low tide.
This reaction to territory made unfamiliar by alteration
suggests that recognition of some element of topography may
be involved in the homing mechanism.
C
-6-
William F. Jessee
DISCUSSION
If populations at the high and low levels are studied
using animals of comparable size, there is no significant
difference in the homing ability of the two groups. Nor is
there any significant difference in the homing ability of
animals of different sizes at the same intertidal level.
These observations confirm earlier ones by Haven (1966).
However, it was also observed that animals of less than 5-6
mm. in length usually do not home. Such animals are found
mainly in the lower intertidal. The inclusion of these
extremely small animals in earlier studies of homing behavior
may account for some of the discrepancies in the findings
of this study as compared to these earlier works.
The results of the experiments designed to elucidate
the mechanism of homing suggest that it is related to the
perception of the topography of the rock surface in the
vicinity of the limpet's homesite. The fact that the ani¬
mals would not cross an area of unfamiliar topography, but
went directly home upon reaching familiar territory points
to a "memory" of the convolutions of the rock surface. It
is, however, possible that some other factor in the environ¬
ment which was not investigated is responsible, at least in
part, for homing. Light or its polarization pattern, for
16
-7-
William F. Jessee
instance, could be such a factor. The probability that the
mechanism is indeed involved with topography is in good
agreement with the tentative results reported by Galbraith
(1965) on the mechanism of homing in Acmaea digitalis
Eschscholtz 1833 and Lottia gigantea Sowerby 1843.
The high percentage of animals which homed after
treatment of the rock with sodium hydroxide argues against
the possible use of some chemical agent as a homing quide,
as the concentrated alkalai would be expected to dissolve
to or denature any substances deposited by the limpets,
While other external factors, such as polarized light or
water currents, have not been ruled out, it is doubted that
the animal possesses the sensory equipment to utilize
such
highly variable sources for orientation. Work should,
however, be carried out to examine these possibilities.
The implications of a homing mechanism based on a knowledge
of topography, in an animal such as the limpet, demands
additional investigation.
8
ede
O
C
WWia k. Zessea
18
ADDENDUMy
were
Two additional series of experiments haveesatl
ater
completed in an effort to determine what portion of
the sensory apparatus is involved in homing behavior.
The first experiments, designed to determine the role
of the cephalic tentacles in homing, ereperformed at
Pebble Beach, San Mateo County, California in January and
February, 1967. In these experiments sixty animals were
marked in the customary manner and left for three days to
insure that the position marked was the home spot. Then a
small typewritten number was affixed to the shell of each
animal, and the same number placed adjacent to its home
using Duco cement. The animals were then brought into the
laboratory, where all were anesthetized in a solution of
magnesium chloride isotonic with seawater. Both cephalic
tentacles were then excised from forty animals, distal to
the eyespots. The remaining animals were uninjured and were
utilized as controls. All animals were then placed in a
salt water aquarium for a period of four to five days to
allow recuperation of the operated animals.
The animals were then returned to the beach during a
period of low tide, and placod within three to four centimeters
of their own homesites. The locations of the animals at the
end of 24 hours, or two high tides, were observed and are
summarized in table 4. Of those animals which could be
located at the end of the 22 hour period, 293 of the experi-
mental group had homed, as compared to 75% of the controls.
O


Dilliau k Besree
1
The second series of experiments was performed at
Moss Beach, San Mateo County, during April and May, 1967.
and was designed to determine whether or not the eyespots
are utilized in homing. Sixty animals were marked and in-
dividually numbered as before. After the usual waiting
period the limpets were brought into the laboratory, where
all were anesthetized with the magnesium chloride solution.
A dissecting needle which had been heated to redness was
then employed to cauterize both eyespots on forty of the
animals, the remainder being utilized as controls. After a four
to sixday period of recovery in the aquarium all the animals
were returned to the field and replaced within three to
four centimeters of their homes as before. The positions of
these animals were observed at the end of 24 hours, and are
also summarized in table h.
The eyespot is apparently not utilized in homing. Exam-
ination of the four experimental animals which failed to
home indicated that in these, substantial damage had been
done to the cephalic tentacles. In those animals in which
no damage was observed, there was 100% homing.
The loss of the cephalic tontacles appears to have a
statistically significant effect on homing. This observation
is, however, open to question. It is a distinct possibility
that the decrease in the instance of homing was a result
of trauma or other factors. The fact that some 29% of the
experimental group returned to their homes despite the loss
of the tentacles seems to substantiate this possibility;
the presence of alternative systems which may be utilized
WWlian K. Sesgea
in homing is another possible explanation. hsephalie
tenteeles ere in feet invelree in heningthieweuld
anpete ferther imple that homing pehavior-isbasee-enthe
mereepttorofthetopogrephyofthesubstrate.
O
O
C
Willau k. Jessee
16
SUMMARY
1. Homing behavior of Acmaea scabra was studied in the
field with respect to the intertidal height of the popula-
tion, the size of the individuals, and the mechanism involved
in homing movements.
2. No significant difference was found in the homing
ability of populations in the high intertidal region as
compared to those at lower levels.
3. The size of the animals was found to be unimportant
in determining their ability to home, except that extremely
small animals, less than 5 to 6 mm. in length, were usually
found to be non-homing.
4. The possibility that chemical substances on the rock
surface are the agents of homing behavior appears highly
unlikely.
5. Although a few other environmental factors were not
coerimentally eliminated, the evidence presented indicates
that the topography of the rock surface is utilized in
homing by A scabr:
6. (From addendum) Excision of the cephalic tentacles

anificantly reduced the tendency to home, while destruction
si
of both eyespots had practically no effect on the incidence
of homing.
O
C
0
Dillian f Jegse
17
1
ACKNOWLEDCEMENTS
The author wishes to express his thanks to Drs.
J. H. Phillips and D. P. Abbott, and to Mr. Stoner L.
Haven for their advice and assistance; the advice and
keen interest of the late Prof. V. C. Twitty was also
deeply appreciated, Thanks are extended to the Monterey
Foundation and Del Monte Properties, Inc. for permission
to work in the Pescadero Point area, This work was made
possible by Grant GY-806 from the Undergraduate Research
Participation Program of the National Science Foundation,
and by a grant from the Arizona Academy of Science.
C
Bieagges
12
18
--mr

LITIERAIURE CITED
Brant, Daniel - 1950 - "A Quantitative Study of the
Homing Behavior of the Limpet Acmaea scabr.
published work in the Department of Zoology,
University of California, Berkeley, California.
Galbraith, Robert T. - 1965 - "Homing Behavior in the
Limpets Acmaea digitalis and Lo
gigantea"
Amer. Midl. Nat. 74
(1): 245 - 246.
Haven, Stoner L. - 1966 - Personal communication.
Hewatt, Willis G. - 1940 - "Observations on the Homing
Limpet, Acmaea scabra Gould" Amer. Midl. Nat.
24 (1): 205 - 208.
Peters, Ronald S. - 1964 - "Function of the Cephalic
Tentacles in Littorina planaxis Phillipi
(Gastropoda: Prosobranchiata)" The Veliger.7.
(2): 143 - 148.
Villee, C.A. and T.C. Groody - 1940 - "The Behavior of
Limpets with Reference to their Homing Instinct"
Amer. Midl. Nat. 24 (1): 190 - 204.

Wells, Morris M. - 1917 - "The Behavior of Limpets
with Particular Reference to the Homing
Instinct" Journ. Anim. Behav. 7, (6): 387 - 395.
O
Williaen f. Tessen
1
Table 1. Homing behavior of A scabra populations at
high and low intertidal locations. Observations
made 24 hours after displacement of experimental
animals.
Table 2. Homing behavior of large, greater than 15 mm.
in length, and small, 6 - 10 mm. in length,
individuals of A. scabra. Observations made
24 hours after displacement of experimental
animals.
Table 3. Homing behavior of A. scabra following scrubbing
of home and/or surroundings. Observations made
21 hours after displacement of experimental and
control groups.
scabra following excision
Table 2.
Homing behavior of A.
of both cephalic tentacles or bilateral de-
struction of the eyespots. Observations made
24 hours after replacement of experimental and
control groups.
C
Low Animals
Displaced
—
Low Control
Animals
igh Animals
Displaced
—
High Control
Animals
—
5a1
30
20
30
able
25
19
27
20
Not

SlVan ee
Missing

2
O
O
(6

Tor
e
30 Animals
Displacod
—
Largo Control
Animals
Small Animals
Displaced
—
-
Small Control
Animals
Toi
20
15
40
50
able 2
Hom
19
15
36
No
Hom

SM
Mis:

0
O

Sürroundings
scrubbed
No sezabbing
—
Home and
surroundin
serubbed
No serubbing
al
20

10
30
20
able
rr..
n
10
—
10
23
16
Not!
O

See
Miss
O
ka  -
Cephalic
Tentacles
Eised
—
Controls
—
Eyospots
Destroyed

Controls
—
Total
10

20
10
20
able
Home
9
12
28
11

—
Liliau 6. Yesses
10.
Home Mis
ing
22
—