Vol. 6; Supplement
Page 17
THE VELIGER
Chemoreception by Tegula funebralis
(Mollusca : Gastropoda)
WILLIAM ROMNEY BURKE
Hopkins Marine Station of Stanford University,
Pacific Grove, California
(3 Text figures)
OBSERVATIONS IN THE FIELD and in the laboratory
to one stimulation by the detached tube foot; moderate
showed that escape responses are elicited in Tegula fune¬
— noticeable avoidance after being stimulated once - but
bralis (A. ADAMS, 1854) by the immediate presence of
without the rapidity or the sharpness in turning of a
starfish. Since contact with the starfish is not essential
strong response; slight = several stimulations necessary
to effect the response, I proposed to determine the location
to elicit a reaction as noticeable as a moderate response).
of possible chemoreceptive sites.
3) A homogenate of starfish tube feet (4 g wet weight
of tube feet to 8 cc of sea water) was made. The super-
MATERIALS AND METHODS
natant resulting after centrifugation was diluted to several
Species used in the tests were Tegula funebralis and
different concentrations. For tests 1 ml supernatant was
Pisaster ochraceus (BRANDT, 1835). All test animals were
added to 200 cc sea water in a small dish. The number
taken from the intertidal region at China Point. Hopkins
of snails out of the water after a specified time was
Marine Station, Pacific Grove, California.
scored. Since the potency of individual extracts of tube
The Tegula funebralis were anesthetized in an isotonic
fect varied, a new control group was required for each
solution of Mg Clz. Twenty animals were kept as controls
preparation.
following anesthesia; from some of the remaining animals
RESULTS AND DISCUSSION
various structures were removed (head tentacles, epi¬
podial structures, epipodial fringe, osphradium) and
The results are shown in the form of bar graphs in Figures
others had either the bottom or the side of the foot
1 to 3.
scraped. The operated animals were then observed in
The results in Figure 1 demonstrate that scraping of
order to determine any deviation from the behavior of
much of the epithelial layer of the side or bottom of the
the control snails.
foot does not impair sensitivity to chemical stimulation
Pisaster ochraceus was selected from among the various
by starfish secretions. This same modification of the snail
species of starfish because of its abundance and its highly
does not remove its ability to be stimulated by contact
effective stimulation of Tegula funebralis (YARNALL,
with tube fect as is indicated in Figure 2. Also, while
1964).
it is not indicated in the figures, excising of the border
Three types of tests were performed.
of the sides and bottom of the foot does not cause
1) Snails were arranged around the sides in the bottom
noticeable change in the chemoreceptive ability of the
of a plastic bucket to which a Pisaster ochraceus was
snail.
then added. The sea water level was maintained at 6 cm
Normal snails exhibit escape responses when any side
(approximately 4½ liters). The number of snails out of
of the foot is stimulated by a detached tube foot. These
the water after a specified time was scored.
responses are specific only for detached tube feet; human
2) Detached starfish tube feet were touched against
hands, bare probes, and probes with detached Tegula
Tegula funebralis which had been placed on a water
funebralis feet will not elicit any escape response.
table over which ran a continuous supply of sea water.
The necessity for touch as a stimulus for these sites
Responses observed were those described by FEDER
may be demonstrated by placing the left or right side
(1956). They were classified as strong, moderate, and
of a snail without epipodial structures against a starfish
slight (strong = immediate and marked escape reaction
arm. Such a modified snail will become excited and
Vol. 6; Supplement
Page 18
THE VELIGER
show faster random motion. Detached tube feet held near
receptive properties on physical contact. Their reactions
the surface of the side of the foot do not cause a reaction.
to tube feet are specific, although not as marked as those
The head tentacles appear to be primarily tactile re
of the head tentacles.
ceptors. Normal responses are elicited after their extir-
The epipodial structures also appear to function as
stimulus localizers. Epipodialectomized animals, when
pation (Figures 1 to 3). But chemoreception on physica
contact is assuredly another of the tentacles’ properties.
stimulated on the side of the foot by tube feet, do not
for responses of the tentacles to detached tube feet are
veer away from the tube feet in as directed a manner
definite and specific.
as control animals. They usually turn at an angle of
The main function of the head tentacles is apparently
45° or less to the opposite side from which they were
to help localize the source of stimulation, so that in this
stimulated
case the snail might be better able to steer away from the
The osphradium, a bipectinate structure located at the
base of the mantle and in close association with the
starfish. When stimulated by detached tube feet, animals
ctenidium, is in this herbivorous species quite small and
difficult to remove. Because of the severity of the operation
Controls
for removal of the osphradium, a group of special control
6 min. (20 snails)
animals was prepared. These control animals were sub¬
Bottom of foot scraped
jected to all steps in the operation, including cracking
6 min. (10 snails)
of the shell, except that their osphradia were left intact.
Two groups of test animals, those partially osphradiec
Side of foot scraped
tomized and without part of their shell and a group that
6 min. (10 snails)
was totally osphradiectomized and with shell pieces
fitted back together, were used. In the partially osphra-
No epipodial fringe
6 min. (20 snails)
diectomized animals the osphradial nerve was cut distal
to the left parietal ganglion, and that portion of the
No epipodial structures
osphradium growing along the edge of the ctenidium on
6 min. (20 snails)
No head tentacles
Controls
6 min. (20 snails)
(20 snails)
Controls for partial
No epipodial structures
osphradiectomy - 8 min. (6 snails)
20 snails)

Partial osphradiectomy
Side of foot scraped
8 min. (7 snails)
(20 snails)
Controls for total
No head tentacles
osphradiectomy  12 min. (5 snails)
(20 snails)
Total osphradiectomy
Controls for partial
2 min. (5 snails)
osphradiectomy
(1l snails)
25 50 75 100%
Partial osphradiectomy
Figure 1:
(Il snails)
Escape of Tegula funebralis from Pisaster ochraceus
Controls for total
Abcissae represent percent of snails out of water.
osphradiectomy
5 snais)
deprived of tentacles did not give responses oriented as
Total osphradiectomy
much away from the tube foot as the control animals
did, i. e., the operated animals usually turned less than
(5 snails)
90°, as opposed to the controls.
25
50 75 100%
Likewise, the chief function of the epipodial structures
seems to be that of tactile receptors. Their extirpatior
Figure 2: Response of Tegula funebralis to tube feet of
makes little difference in Tegula funebralis’s reactions to
Pisaster ochraceus. In each group the top line represents
tube feet or tube feet extract (Figures 1 to 3). Also, like
strong response, the middle line moderate response, and
the head tentacles, epipodial structures do have chemo¬
the bottom line slight response (see text),
Vol. 6; Supplement
Tube foot
extrac
Controls
5 min. (8 snails)
No head tentacles
5 min. (8 snails)
Controls
5 min. (8 snails)
No epipodial
structures - Smin. (8 snails)
Controls
10 min. (4 snails)
Partial
osphradiectomy Omin. (6 snais)
Controls
5 min. (5 snails)
Total
osphradiectomy - 15 min. (5 snails)
2550
100%
Figure 3: Detection of Pisaster ochraceus extract by
Tegula funcbralis. (Extract contained 1.04 X 10“ parts
by wet weight of tube fect.) Abscissae represent percent
of snails out of the extract.
the ventral side was removed. The mass of the osphradium,
located under the ganglion, could not be reached by
this technique, which resulted in partially osphradiec¬
tomized animals. Total osphradiectomy involved removal
of the remaining osphradial mass.
There is no appreciable difference in the bchavior of
the partially osphradiectomized animals and their con¬
trols (Figures 1 to 3). Obviously, most of the osphradium,
or at least the yellow mass in close connection with the
parictal ganglion, must be removed before olfactory
properties are eliminated.
Ösphradiectomized animals show no more movement
of the tentacles or general excitement in the presence
of tube foot extract or in a bucket with a starfish than
they do in ordinary sea water. These animals do withdraw
their head tentacles slightly from detached tube feet, but
the reactions are not at all as strong as those given by
any of the other test animals. Äfter 15 minutes of exposure
to starfish one osphradiectomized animal crawled out of
the water, but it returned 30 seconds later.
Those sites found to be chemoreceptive in a gustatory
sense, that is requiring physical contact, are the sides of
the foot, the head tentacles, and the epipodial structures.
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THE VELIGER
The osphradium functions as an olfactory sense organ,
being chemoreceptive without physical contact.
The chemorcceptive sitcs of Tegula funebralis are ex¬
tremely sensitive. While not indicated by figures a straight-
line correspondence between the concentration of Pisaster
ochraceus tube foot extract (expressed logarithmically
and the probability of eliciting an escape response in T
funebralis could be demonstrated. The 50% threshold
effect lies about midway between the 1/64 and the 1/32
dilutions of an extract 33% by wet weight of tube feet,
1 ml of which is added to 200 cc sea water; i. e., T.
funcbralis will escape 50% of the time within 5 minutes
from a solution that is 2.6 to 5.2 X 10“ parts by wet
weight of tube fect. Decreasing the dilution results in
gradually increasing activity by the test animals.
The movement resulting from the presence of the
starfish or of its secretion appears to be random. Tegula
funcbralis have been observed to run into a starfish up
to four times before finally climbing out of the bucket.
The snail appears to test the concentration of starfish
secretion and orients and moves randomly. It eventually
reaches an area of lower concentration of the chemical
stimulus. However, in the immediate proximity of a
starfish contained in a bucket in a small volume of water
(about 4½ liters) therc is not likely to be much of a
concentration gradient, and the only available arca of
lower concentration is out of water.
Tegula funebralis can and do often adapt themselves to
the presence of Pisaster ochraceus (see FEDER, 1956).
This adaptation is not duc to breakdown of the tube foot
substance, but rather fatigue of the chemoreceptive sites.
Snails added to a pan from which they were prevented
from escaping by a wire screen and in which a starfish
has immediately beforchand resided show marked activity
for about 15 minutes, after which time they become
quicscent. New T funcbralis then added also show in-
creased activity for about 15 minutes, while the "fatigue
of the original snails is still manifested. Neither the sub¬
sequent reintroduction of the starfish nor the removal
of the wire screen caused any of the twenty "fatigued
animals to move out of the bucket within 15 minutes.
SUMMARY
Tegula funcbralis has both gustatory and olfactory sense
sites. The side of the foot, the head tentacles, and the
cpipodial structures serve as contact chemoreceptive sites.
Extirpation or scraping of these structures does not alter
the overall sensitivity to Pisaster ochraceus. Scraping the
bottom of the foot, cutting of the border between the
side and the bottom of the foot, removal of the epipodial
fringe (on the left side of the foot), removal of up to
Vol. 6; Supplement
Page 20
THE VELIGER
half of the ctenidium do not noticeably alter chemore¬
result in appreciable change of chemoreceptive abilities
ception. The osphradium functions as an olfactory organ
of T. funebralis.
and is capable of detecting the presence of an extract
containing 2.6 X 10“ parts by wet weight of tube feet
LITERATURE CITED
from Pisaster ochraceus. The osphradium, when stimu¬
FEDER, H.
lated, seems to cause the animals to be more sensitive
to stimulations of the head tentacles and epipodial struc-
1956. Natural history of Pisaster ochraceus. Doctoral diss.,
Stanford Univ.
tures. Removal of part of the osphradium does not
Identification and Location of Carbohydrases in the
Intestinal Tract of Tegula funebralis
(Mollusca : Gastropoda)
WARREN R. BERRIE
AND
MITCHEL W. DEVEREAUX
Hopkins Marine Station of Stanford University,
Pacific Grove, California
(6 Tables)
parts: buccal cavity, salivary glands, esophagus, stomach
SINCE Tegula funebralis (A. ADAMS, 1854) is an herbi¬
and digestive gland (since it was impossible to separate
vorous marine animal, it is quite evident that it must
have an efficient and well developed carbohydrate diges-
the stomach from the digestive gland), digestive gland
tive mechanism. Although this subject has been explored
(portions freed from the stomach), spiral caecum, thin
hindgut, and thick hindgut.
to some degree already (GALLI, 1956), there still seemed
The purpose of the first experiment was to determine
much to be investigated. We limited our efforts to the
the site of enzyme production. The gut segments were
study of five carbohydrates present in the environment
excised from snails fresh from the field. These tissues
of the animal: starch, laminarin, alginate, fucoidin, and
were refrigerated so as to retard any loss of enzyme
cellobiose. Using these materials we hoped to localize the
activity due to denaturation or autolysis. Pools of tissue
points of enzyme production within the alimentary canal
from five animals were washed, weighed, and extracted
and sites of carbohydrate digestion. The extent to which
in a tissue grinder equipped with a Teflon pestle (Van
intracellular and extracellular digestion is involved in the
Waters and Rogers Inc., Catalogue no. 48652) with either
foregut and hindgut was also studied.
a citrate-phosphate buffer, pH 5.8, or a phosphate buffer,
The substrates were: starch (Baker and Adamson,
pH 7.4. These buffers were chosen since they approximate
reagent grade), alginate (Kelco Co., commercial grade)
the extremes of hydrogen ion concentration occurring in
cellobiose (Pfanstiehl Chemical Co., C. P grade). Lamin¬
the digestive tract. Enzyme activity was determined by
arin and fucoidin were isolated from Fucus by the
method of BLACK, DEWAR, & WOODWARD (1951 - 1952).
incubating an appropriate aliquot of tissue extract with
one of the substrates and assaying for reducing sugar by
The alimentary canal was divided into eight anatomical