Vol. 6; Supplement
Page 46
THE VELIGER
The Light Responses of Tegula funebralis
(Mollusca: Gastropoda)
DOROTHEA F. KOSIN
Hopkins Marine Station of Stanford University,
Pacific Grove, California
(7 Text figures)
night exposure shows great migration downwards during
THE BEHAVIOR OF Tegula funebralis (A. ADAMS, 1854)
full daylight; the snails gather in the shadiest parts under
on the shore is complex. The snails are found clustered
algæ, behind rocks, on the shady side of the aquarium.
in cracks and crevices of rocks on both sunny and foggy
In darkness (with only a dim ruby light for occasional
days when the tide is low. Their movements in tidepools
observation), the snails all remained at water level all
are inconsistent; sometimes all snails are gathered on the
the time. Snails kept at a constant low light intensity
shady side, at others they are scattered throughout the
(about 70 foot candles) tended to stay at the top, though
pool. They are subjected to the action of waves and cur-
somewhat less than those in complete darkness.
rents, as well as tidal exposure and submersion, at dif¬
ferent light conditions over the tidal cycle. To establish
irise
the role of each factor (such as light) would be difficult
in nature, but in the laboratory most of the other factors
—
can be controlled and light varied.
constont dorkness
20
METHODS
constant light

Tegula funebralis were tested for reactions to light in sev¬
—.—.—
eral manners: (1) Three aquaria, as much alike in con¬
tents as possible (rocks, shell fragments, algæe, number of
snails) were set up under different light conditions and
the snail movements noted. (2) Groups of snails were
subjected to different intensities and spectral regions of
visible light, and their reactions observed and timed. (3)
Individuals were allowed to move in directional light.
310
(4) Eyes and other appendages were removed and the
5
response of such operated snails compared with the nor-
doy-night
mal. Such operations were not generally harmful: all
operated animals survived for at least two weeks and no
infections were obvious. (Before operation, the snails
were anesthetized by slow addition of an equal volume of
isotonic MgCl- solution to sea water in which a number
of snails were lying upside down. A temperature of 30° C
also served to keep the snails extended out of their shells.)
RESULT
12 PM
12M
I2PM
May
May 2
May 3
(1) The experiments with 3 aquaria in different light con-
ditions indicate that Tegula funebralis avoid light. Fig.
Figure 1: Distribution of 20 Tegula funebralis in each of three
shows the number of snails at or near the surface of the
similar aquaria under different light conditions: normal day and
night; constant illumination at 70 foot candles; and darkness.
water (all others being on or near the bottom). The day
Vol. 6; Supplement
Page 47
THE VELIGER
In constant conditions the distribution of Tegula funeb¬
ralis remains constant. When light conditions are alter-
20-
nated between light and dark the distribution alternates
50 Foot-candles
correspondingly up and down. (Fig. 2) The alternating

light was presented out of phase with the day-night cycle
and was conducted with snails which had been in the
20 FC.
dark for two weeks. The response to the change of light
conditions starts immediately, and the new distribution is
reached within approximately one hour.
5 Foot-candles
(2) Another method for measuring the light response

was exposing groups of snails to beams of different inten¬
Note: The following abbreviations are used where appro-
priate in all figures in this article.
a shell aperture
ht head tentacle
k kidney
an anus
cm columellar muscle
me mantle cavity
et ctenidium
op operculum
os osphradium
e eye
darkness
foot
rectum
s shell
g gonad
o
spiral caecum
h heart
st stomach
Time (minutes)
Figure 3: Rate of movement of snails out of a beam of light at three
light
—dark-
light
—dork-
light
dork-
different intensities (5, 20, 50 f.c.). The rate in darkness is compared.
20
sities of light, and observing their rate of exit from the
lighted area. As soon as the snails were placed in a circle
of light, they began turning and pushing each other
around in their attempt to move out of the light. They
move to the darkest areas available, and rest only when
they reach a crack or maximum darkness. The same
number of snails left in the same area, but without light,
disperse much more slowly. (Fig. 3). Snails previously
adapted to different light intensities were also tested in
this manner (Fig. 4). Those previously exposed to full
sunlight (6000 F.C.) scarcely responded at all
(3) Both operated and normal snails give a "shadow re-
action," which is best observed if the snail is lying on its
back, with foot partly extended. (If it is not extended far
enough, it will withdraw into the shell when shadowed.
If it is extended too far, the snail turns over and will not
react at all. When the snail is attached to a surface by its
foot, shading causes it to pull back its head, and to remain
in that position for some time,— e. g. up to 5 minutes).
—

But when it is upside down, its normal reaction to a
2M 12PM 12M 12PM 12M 12PM
shadow is a slight contraction and pulling back of the
foot, followed by a short period of quiet, and then a relax-
Figure 2: Effect of alternating light (70 foot candles) and darkness
ation or extension of part or all of the foot. There is great
on 20 snails that had previously been in darkness for two weeks.
The cycle is opposite to that of actual day and night.
variation in the amount of contraction, even in the same
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Vol. 6; Supplement
THE VELIGER
The same procedure was followed at different spectral
regions isolated by glass filters; the intensities were ad-
5 Foot-candles
20 Foot-candles
justed to give about equal reading on a G. E. light
meter, which approximates the human eye over much of
1
the visible range. No significant difference in the duration
of the response was noted to shading of either red, yellow,
blue or green light (Fig. 6). However, in the far red
5.
light from a photographic ruby lamp (10 watts at 1 foot)
no shadow response could be elicited.

A sudden illumination, even by bright light, does not

cause such a consistent and quick reaction; it is the dis¬
appearance of light which causes the withdrawal. Nor
does re-illumination visibly affect the total shadowing re¬
Time (minutes)
action. If a snail is left in darkness for over an hour, then
— darkness ----70 ft. candles ----6000 ft candles
put on its back, there may be a long contraction but this
cannot be repeated as well as the shadow reaction. During
Figure 4: Rate of movement of snails out of a beam of
the first minute or longer of such light exposure, the snail
light (5 and 20 foot candles), after previous adaptation to
may be very insensitive to shadows. The amount of time
darkness, 70 foot candles and full daylight (6000 f.c.)
snail. The duration also varies, but not necessarily with
Epithelium
1o mm

the visible degree of contraction. A snail may contract
deeply but shortly, or only slightly, but remain still for


some time. Fig. 5 indicates the duration of contractions
Opening of
caused by 19 successive shadowings of 3 different snails;
opfic cup
Conn
the average is 3 to 4 seconds. (The light was a microscope
Cornea
lamp about 30 cm above the snail, with some 7.5 cm of
sea water to absorb much of the infra red. The visible in-
tensity at the level of the snail was 20 F.C.)




S
Figure 7: Sagittal section of the eye lobe of

)
Tegula funebralis, about 25 microns thick.
necessary for this adaptation is dependent on the bright-
ness of the light, and the intensity of light to which the
snail had been exposed before the one hour dark period.
o
Only when the snail becomes adapted to the new intensity
Order of shadowing
will it react to shadows.
(4) In avoiding light, snails move to the closest dark area.
Figure 5: Duration of contraction reaction induced by 19
In this they are aided by their eyes. A light directly above
successive shadowings of three different snails (represented
the snail causes it to move straight out of the light beam in
any direction. If the left eye is removed the snail turns
by solid, broken and dotted lines). Average duration
in about half a circle to the left before moving straight
about 3.5 seconds (omitting the four failures, of zero
out of range of the light. Similarly a snail turns toward the
durations). Light, 20 foot candles.
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Vol. 6; Supplement
THE VELIGER
Hlongest
Fraverage
Eshortest

Green
Blue
White
Red
White
- Normal Animals
Eyeless
Figure 6: The effect of various spectral regions, and of white light, upon the shadowing response. The narrow
columns represent different animals (5 to 8 in different histogroms). Eyeless animals are shown in the last group.
Intensities approximately equal, by G.E. photo-cell.
right when its right eye is removed. When both eyes are
There was no difference in their reactions. Figure 2
removed the snail generally turns around irregularly be¬
shows the response of eyeless snails. Apparently the
fore leaving the lighted area.
shadow reaction is more the result of a general body sen¬
In light from one side a normal snail moves away from
sitivity, than of reception by a specific light sensitive organ.
the source with its head in its own shadow. The head turns
These experiments indicate that the eyes are used for
from side to side, and each time that an eye is illuminated
directional orientation in the light. It is the only function
the snail turns back to its shadow or turns its head to the
of the eye that I have been able to discover. The anatomy
other side. In the same light an eyeless snail moves
of the eye suggests this as well (Fig. 7). It is a simple.
irregularly, even directly toward the light. Apparently it
small ocellus containing a firm, clear substance which may
cannot distinguish direction without its eyes. A snail with-
correspond to a “lens". The small opening to the outside
out its right eye will turn, usually toward the right, until
might function like a pin-hole camera, to form an image
its left eye is in shadow and then move directly out of
at the retina. Around the edge of the opening is a ring
the path of the light. When the left eye is removed the
of unpigmented cells which might be a cornea. The re¬
snail turns, usually to the left, until its right eye is in
tina appears to be formed by a direct invagination of the
shadow before moving straight out of the beam of light.
epidermis, continuous through the clear corneal area
Normal snails, snails without eyes, without epipodial
The optic nerve branches proximal to the optic cup,
tentacles and lobes, without propodial tubercles, and with
sending fibers over its entire surface to connect with the
none of these organs were tested for a shadow reaction.
retina.
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Vol. 6; Supplement
THE VELIGER
The eyes of Tegula funebralis may represent a concen¬
SUMMARY
tration of the same sensitive tissue present on the general
body normally outside of the shell. The pigmentation of
Tegula funebralis is negatively phototactic. It becomes
the retina resembles that of the epidermis, which contains
adapted to bright light, and loses its sensitivity temporar¬
melanin. Attempts to isolate a photosensitive pigment
ily. It has a general body sensitivity shown by a shadow
from the eyes, according to the recipe for squid retinas
reaction. Its eyes, simple lens ocelli, seem responsible for
(BLISS, 1948) failed, probably because of the very small
directional orientation to light. Without eyes its orienta-
amount of tissue employed.
tion is irregular.
LITERATURE CITED
BLISS, A. F.
1948. The absorption products of visual purple of the squid
and its bleaching products. Journ. Biol. Chem. 176: 563 - 569
Observations on the Epipodium, Digestive Tract,
Coelomic Derivatives and Nervous System of the
Trochid Gastropod Tegula funebralis
JOHN A. MACDONALD
AND
C. BURKE MAINO
Hopkins Marine Station of Stanford University,
Pacific Grove, California
(15 Text figures)
to determine the extent of specific body cavities. Both
IN SPITE of the abundance of Tegula funebralis (A.
Mallory’s connective tissue stain and Harris' hematoxylin
ADAMS, 1854) in the California intertidal, no account of its
produced excellent results after fixation with Bouin’s fluid,
anatomy has yet appeared in the literature, although the
made with seawater. A silver impregnation (RowELL,
anatomy of other trochids has been described (Randles,
1963) worked well for isolated nerves, but also stained
1905; Fretter and Graham, 1962). To partially fill this
muscle and connective tissue heavily in sections of the
void, a brief account of certain external and internal fea¬
entire animal
tures of T. funebralis is herein presented
Epipodium: The epipodium of Tegula funebralis is com¬
The specimens of Tegula funebralis examined were col¬
posed of five elements: the neck lobes, anterior papillae,
lected at Mussel Point, Pacific Grove, California, during
April and May, 1963. The animals were dissected alive
epipodial tentacles, epipodial papillae, and epipodial
ridges (Figures 1 and 2). On both sides of the animal
after having been anesthetized with magnesium chloride
the anterior quarter of the epipodium is occupied by
both frozen and paraffin sections were cut in order to
the heavily ciliated neck lobe, which runs posteriorly
make more detailed observations. Injection of suspension
from near the base of the optic peduncle. The border of
of carborundum and carmine powders in sea water helped
Page 51
Vol. 6; Supplement
THE VELIGER
these neck lobes may be the removal of particles expelled
from the mantle cavity, though FRETTER & GRAHAM
DG
HG
(1962, p. 532) state that the neck lobes of British trochids
are rolled into half-siphons for channeling water in and
out of the mantle cavity. No evidence of this was seen in
ME
Tegula funebralis.
Beneath the overhang of each neck lobe are from one
CL
to ten anterior papillae, each with a central spot of ciliated
unpigmented epithelium (Fig. 3). They retract slightly
Bvgan
CM
when touched; this reaction and their structure suggest
—
that they may be sensory receptors.
HT
NL ET
PE
Figure 1: Entire animal, left side, shell removed
QUE
G gonad
C ctenidium
CT
HG hypobranchial gland
CL cephalic lappet
HT cephalic tentacle
CM columellar muscle

DG digestive gland
M mouth
ME mantle edge
E eye
NL neck lobe
ER epipodial ridge
OP operculum
ET epipodial tentacle
SC spiral caecum
Figure 3: Anterior papilla, diagrammatic
longitudinal section
the left neck lobe is fringed, the number and grouping
CUE ciliated unpigmented
CT connective tissue
of points being variable, whereas the edge of the right lobe
epithelium
PE pigmented epithelium
is smooth; on both lobes the cilia beat distally, especially
when the lobe is touched with a probe. The function of
Just posterior to the neck lobe is the first epipodial
tentacle, which on the left side bears an epipodial papilla
(Fig. 6) similar in appearance to an anterior papilla;
DG
- HG
the first epipodial tentacle on the right side does not bear
such a papilla. The other three tentacles on each side
bear papillae (Fig. 4). The epipodial tentacles are similar
in structure to the cephalic tentacles and are innervated
from the pedal cords; observations of the use of both
ME
cephalic and epipodial tentacles in the field and in aqua¬
- CL
CM

ER

HT

- ET
NL E
ER


Figure 2: Entire animal, right side, shell removed.

e
HT cephalic tentacle

CL cephalic lappet
LK left kidney
CM columellar muscle
M mouth
E eye
ME mantle edge
ER epipodial ridge
Figure 4: Epipodial tentacle, diagrammatic
NL neck lobe
ET epipodial tentacle
ET epipodial tentacle
EP epipodial papilla
OP operculum
G gonad
SP sensory papillae
ER epipodial ridge
HG hypobranchial gland
R rectum
Page 52
Vol. 6; Supplement
THE VELIGER
ria seem to indicate that they are tactile, and perhaps
olfactory, receptors. An active animal will be seen to draw
its tentacles repeatedly over the substrate as it advances.
Resting animals either “caress“ their shells with the ten-
tacles, or gently wave them. In the presence of predaceous
asteroids such as Pisaster ochraceus (BRANDT, 1835), T.
funebralis waves cephalic and epipodial tentacles vigor¬
ously while trying to escape; Mc GEE (unpubl.) has noted
a similar response in Tegula brunnea (PHILIPPI, 1848) ex-
OS-
posed to spawning males of their own species.
— HG
LORK
LM
-OLK
C
-PE
RR
LK
EBV
PC
MC
SC
V
DG
Figure 5: Epipodial tentacle, diagrammatic cross section

H haemocoel
MC column of transverse
LM longitudinal muscle
muscle and connective
band
tissue
N nerve
PE pigmented epithelium
Figure 7: Dorsal view of entire animal with mantle
cavity laid open; structures of coelomic origin
are indicated
C ctenidium
OLK left kidney opening
DG digestive gland
ORK right kidney opening
EBV efferent branchial
OS osphradium
PE¬
vein
PC pericardium
F foot
R rectum
G gonad
RK right kidney
HG hypobranchial gland
RS radular sac
LK left kidney
SC spiral caecum
The epithelium of the epipodial tentacles is heavily pig¬
mented; distally it forms papillae bearing non-motile sen¬

sory cilia. Similar cilia are found on the tentacles of other
prosobranchs (FRETTER & GRAHAM, 1962, p. 313) and on
the oral tentacles of the nudibranch Hermissenda (AGERS-
BORG, 1925). Passing down the length of the tentacle is
à large central nerve, longitudinal muscle bands, and an
Figure 6: Epipodial papilla, diagrammatic
extension of the hemocoel. The center of the tentacle is
longitudinal section
occupied by an irregular column of muscle and con¬
CT connective tissue
PE pigmented epithelium
nective tissue fibers (Fig. 5). The epipodial ridge is a
N nerve
UE unpigmented epithelium
long flap of tissue which begins just posterior to the first
Page 53
Vol. 6; Supplement
THE VELIGER
epipodial tentacle on either side and runs just dorsal to
the other three epipodial tentacles and continues to the


hindmost tip of the foot.
7

-BW
Digestive Tract: The anterior part of the digestive system
seen in Figure 8, shows the buccal cavity to be limited
— ME

ventrally by the subradular membrane, which extends
HARC

RA¬
posteriorly into the radular sac. Ventrally, the radular sac
is anchored by striated musculature to the posterior part
— SG
N
DSG


of the odontophore. The radula is fused to the subradular
membrane anteriorly, but is free posteriorly. The com¬
ARC

plex movements of the odontophore are controlled by
striated musculature acting on the four radular "carti¬
lages.
The disposition of the rest of the digestive system is
seen in outline in Figure 9. There are three main regions:
the foregut, composed of buccal cavity and esophagus;
the stomach and digestive gland, which comprise the mid¬
DG
RA
ES
ST-
C

—




Figure 9: Dorsal view of entire digestive system

ARC anterior radular carti- I intestine
lage
M mouth


BW cut edge of body wall
ME mantle edge
2
. . ..
DG digestive gland
RA radula

2
DSG duct of salivary gland SC spiral caecum
G gonad
SG salivary gland
R rectum
ST stomach
PRC
BC SRM
ARC
Figure 8: Buccal region, diagrammatic
PE
longitudinal section
Vgggvvote
ARC anterior radular carti-M mouth
NNNN000
lage
PRC posterior radular
BC buccal cavity
cartilage
ES esophagus
RA radula
Figure 10: Cross section through esophagus
J jaw
RS radular sac
SRM subradular membrane
gut region; and the hindgut, consisting of intestine and
rectum. Only one duct is shown leading to the digestive
gland from the stomach; there are also numerous fine
1
pores in the same area which appear to lead to the gland.


The areas of the posterior visceral hump occupied by
the digestive gland and gonad vary somewhat from spec-
ST
imen to specimen. In freshly killed specimens which were
not treated with magnesium chloride, peristaltic move¬
Figure 11: Cross section through spiral caecum
ments could be seen in the hindgut, but were not observed
in the foregut.
SC spiral caecum
ST stomach
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THE VELIGER
Vol. 6; Supplement

ER

-CA
H
ETA
ar
V
MA


EP¬
M
CC
PE-

Figure 12: Cross section through rectum

PN¬
er
CA cilia
CT connective tissue
RK
LK
M
Figure 14: Left side of foot, diagrammatic cross section
LRPI
CC cross connection bet¬
ET epipodial tentacle
ween pedal cords
H haemocoel
EBV
CT connective tissue
MA muscular area
ZRRp.
EN epipodial nerve
P pedal cord
EP epipodial papilla
PE pigmented epithelium
ER epipodial ridge
PN pedal nerve
I-
relatively large, and fluid may be caused to flow between
the left kidney and the pericardial space.
Nervous System: The nervous system of Tegula funebra¬
RK
lis (Figs. 14 & 15) is similar to that of other trochids
AO
(RANDLES, 1905, pp. 57-66, figs. 30-33). The right pleuro¬
parietal connective runs over the esophagus and splits
Figure 13: Diagrammatic dorsal view of pericardia
into two nerves, the first running to the branchial gan¬
glion, subjacent to the osphradium, and the second run¬
cavity showing coelomic derivatives
ning posteriorly between the ventral ctenidial membrane
A auricle
PC pericardium
and the perivisceral sinus, and crossing the esophagus
AO aorta
RK right kidney
and the loop of the hindgut to end in a pair of visceral
EBV efferent branchial
RRPP right renopericardial
ganglia above the right kidney. The left pleuro-visceral
vein
pore
connective crosses beneath the esophagus and runs poste¬
I intestine
LRPP left renopericardial
riorly to connect with the visceral ganglia. RANDLES
LK left kidney
pore
(1905) found a dialyneury between the left pallial nerve
Vventricle
and the right pleuro-parietal connective in Trochus; no
such connection was observed in Tegula funebralis,
Coelomic Derivatives: Structures of cœlomic origin are
shown in figure 13; these include the right and left kid¬
ACKNOWLEDGMENTS
neys, the pericardial cavity, and the gonad. The presence
We are indebted to the faculty, staff, and graduate stu¬
of both right and left renopericardial ducts is in accord
with the condition found in other trochids (RANDLES.
dents of the Hopkins Marine Station, especially to Mr.
1905) and in Haliotis (HARRISON, 1961). The duct to
Nick Holland and Mr. Welton Lee, for advice, technical
the right kidney is very small; whether it is functional or
assistance, and encouragement in the execution of this
work.
not is undetermined. The opening to the left kidney is
Vol. 6; Supplement
LN
CB
-LC
CG
APN
LPN
PRPN
CPL
RPP
BRG
LPV

EN¬
PN¬
Figure 15: Nervous system, diagrammatic dorsal view.
The large masses dorsal to the pedal ganglia represent the
pleural ganglia; the small hollow objects between the
pleural ganglia are the statocysts
APN anterior pedal nerve LN labial nerve
BG buccal ganglion
LPN left pallial nerve
BRG branchial ganglion
LPV left pleuro-visceral
CB cerebral commissure
connective
CC cross connection bet¬
ON optic nerve
ween pedal cords
P pedal cord
CG cerebral ganglion
PG pedal ganglion
CP cerebro-pedal connect- PN pedal nerve
RPN right pallial nerve
CPL cerebro-pleural con¬
RPP right pleuro-parietal
nective
connective
EN epipodial nerve
TN tentacle nerve
LC labial commissure
VG visceral ganglia
Page 55
THE VELIGER
LITERATURE CITED
AGERSBORG, H. P KJERSCHOW
1925. The sensory receptors and the structure of the oral
tentacles of the nudibranchiate mollusk Hermissenda crassi-
cornis (EsCHSCHOLTz, 1831). Acta Zool. 6: 167 - 182
FRETTER, VERA, & ALASTAIR GRAHAM
1962. British prosobranch molluscs; their functional anatomy
and ecology.
London, Ray. Soc.; xvi + 755 pp.; 317 figs.
HARRISON, F M.
1961. Some excretory processes in the abalone Haliotis ruf¬
escens. Journ. Exp. Biol. 39: 179-192
RANDLES, W. B.
1905. Some observations on the anatomy and affinities of the
Trochidae. Quart. Journ. micr. Sci. 48: 33 -78
ROWELL, C. H. F.
1963. A new technique for silvering invertebrate central ner¬
vous systems. Quart. Journ. micr. Sci. 104: 81 - 87