P. Demopulos
Diet, Activity and Feeding
in Tonicella lineata
INTRODUCTION
Tonicella lineata (Wood, 1815) is a common and
distinctive chiton of the Pacific coast. In western
North America it extends from the Aleutian Islands to
San Diego, California and is also relatively abundant
in Northern Japan (Burghardt and Burghardt, 1969).
In the area of Monterey Bay, California, it ranges from
intertidal pools to 65m depth (Smith and Gordon, 1948.
p. 205). Such a wide distribution in latitude and depth
implies exposure to a varied spectrum of physital and
biological factors. However, the microhabitat in which
Tonicella lineata and other species of Tonicella are found
is surprisingly narrow, for this genus appears to require
the presence of coralline algae, either crustose or
erect, as a substratum (Barnes, 1972, and Yakovleva, 1952).
The larvae of Tonicella lineata settle only if
presented with a coralline algal substratum (Barnes, 1972).
Also, this species displays a disruptive dorsal coloration
which blends well with the surface of coralline algae.
offering an excellent defense against visual predation.
In view of this seeming dependence on coralline
algae, it has been proposed (Barnes, 1972), but not
supported with quantitative data, that corallines are
used by Tonicella as food. The present report concerns
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P. Demopulos
Diet, Activity and Feeding
Page 3
in Tonicella lineata
the diet of Tonicella lineata and the possible existence
of activity and feeding patterns. A distinction between
intertidal and subtidal populations is also discussed.
DIET INVESTIGATION
Materials and Methods
Specimens were collectéd at Mussel Point, Pacific
Grove, California, from three relatively distinct habitats:
a high intertidal tidepool (at approximately the +4 ft tidal
level); a low intertidal region characterized by an
abundance of Phyllospadix scouleri Hooker; and subtidal rocks
at depths of 6 to 10m within the canopy of Macrocystis
pyrifera (Linnegus) C.A.Agardh. A list of coralline and
other algae found in each habitat is provided in Table 1.
Identifications were verified by Dr. Isabella Abbottesta Un
Coralline algae predominate in each region.
A total of 25 Tonicella lineata (6 tidepool, il inter-
tidal and 8 subtidal) were collected at varying times
throughout the day-night and tidal cycles. Specimens
were preserved immediately in a solution of 10% buffered
formaldehyde in sea water.
The contentgof the entire digestive tract, from
stomach to anus, of each animal was subjected to micro-
scopic examination, and a visual estimate was made of the
P. Demopulos
Diet, Activity and Feeding
in Tonicella lineata
various constituents of biologic and inanimate origin.
Along withgut content determinations, the relative
fullness of the anterior digestive tract was recorded
for all specimens. Three catégories were employed.
These are: "full" (greater than 70% of the digestive
tract filled with ingested material), "moderate fullness"
(30-70% filled); and "empty" (less than 30% of the digestive
tract containing ingested matter).
Results
The percentages of the identifiable gut content con-
stituents in animals from each habitat are presented in
Figs. 1-3. Coralline algae always represented the major
food ingested. It was not possible to distinguish between
species of coralline algae on the basis of fragments in
the gut for the rasping of the radula removes cell layers
and not whole regions of the algal thallus, hindering
identification.
The category, "Detritus and Substrate", was
predominantly minerah material, Some efthiswas
almost certainly Caco, from corallines (chalky white grains
dissolving with production of gas on treatment with 1% HCI).
Other material in this category appeared to be decomposed
plant or animal tissue, but no clear cell structure was
observed. In any event, the percentage of coralline algae
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P. Demopulos
Diet, Activity and Feeding
in Tonicella lineata
ingested is probably even higher than indicated graphically.
for a substantial part of the "Detritus and Substrate"
category very likely represents coralline algal
structural material.
Figure 6 illustrates the relations between "fullness"
of the anterior digestive tract and time of day. Subtidal
specimens were fuller at night. No consistent variation
in the "fullness" of intertidal animals with time of day
was observed.
ACTIVITY
Materials and Methods
Activity patterns were investigated in the field
on subtidal and intertidal populations over a 24-hour
period. In the subtidal survey, two separate rock faces
with algal distributions conforming to that listed in
Table i and bearing a combined total of 11 Tonicella lineata,
were chosen. Positions of all animals were recorded at
4-hour intervals, using a 50cm x 50cm quadrat frame.
Intertidally, the tidepool habitat described previously
was chosen for study. Specimens were marked with numbered
witte
squares of waterproof paper aattached to the valves using
an acrylic glue (Tm "Zip-Grip 10", Devcon Corp., Danvers,
Mass.). Fifteen specimens were observed hourly, tide
permitting, throughout a 24-hour period. Ten of these were
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P. Demopulos
Diet, Activity and Feeding
in Tonicella lineata
marked and placed in the tidepool site one week before
study; five were returned to this site one day before study,
Results
Movements of the subtidal and intertidal populations
are given in Figs. 4 and 5 respectively. All estimates
are minimal for only net displacement in a straight line
was measured. For the intertidal animals, movement from
1900-2300 hrs was determined by dividing the total movement d
during the four-hour period by 4 and plotting-it in 4 hourly
increments. Further observatins were not possible because
of rough surge.
During the 24-hour surveys of activity, 3 of the 11
subtidal individuals exhibited homing, returning before
sunrise to the positions and orientations noted at the
initiation of the watch. Intertidally, 3 of the 15 marked
chitons homed with the approach of low tide at the end of
the complete 25-hour tidal cycle.
TAXONOMY
Consistent differences in size and coloration are
found between intertidal and subtidal populations of
Tonicella lineata. Barnes (1972) voiced the suspicion
that a taxanomic differentiation between subtidal and inter-
tidal communities exists in Oregon and Washington, and
kaattt
relatir
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Diet, Activity and Feeding
P. Demopulos
in Tonicella lineata
indicated that further work was in progress relating to
this question.
Sex, length and width measurements, valve and girdle
coloration, and numbers of anterior and posterior valve
notches were recorded for 36 specimens (6 subtidal and 30
intertidal, including tidepool). Aant difference
Godens 151
(p(0.2) in the total number of valve notches was found.
Intertidal animals consistently exhibited a greater sum
of anterior andeposterior notches.
Subtidal specimens are typically smaller (i to 2 cm
in length) with purple lines on the girdle, and lavender
and pink hues closely matching th coralline substrate.
Intertidal individuals have darker valve and mantle
coloration and yellow lines on the girdle, ranging 2 to
4 cm in length.
DISCUSSION
Coralline algae clearly comprise the majority of
material ingested by Tonicella lineata; the narrowness
of microhabitat exhibited in the field is reflected in the
limited number of algal genera and species ingested
(see Figs. 1-3 and Table 1). It is nonetheless surprising
that no red algae other than coralline algae were ingested
by subtidal specimens, for reds such as Rhodymenia spp.
were available. The absence of green algae in the guts
of subtidal animals and brown algae in Uhteptidal digestive
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P. Demopulos
Diet, Activity and Feeding
Page 8
in Tonicella lineata
etd  a
tracts, corresponds to the scarcity of greens subtidally
and browns intertidally in the sites studie. Brown algae
were also scarce subtidally, and absent from the gut contents
of subtidal animals.
Diatoms averaged about 10% of the gut contents in
all habitats studied. Microscopic observation reveals fewer
intact, more "digested" diatoms in the posterior portions
of the gut. As diatoms are common epiphytes on coralline
algae, they may be passively ingested with the corallines
and subsequently utilized as a food source.
Coralline algae, due to the considerable calcium
carbonate content, would appear to providé a poor source
of nutrition per bulk weight. However, they are abundant
and grazing competition is probably low.
The findings that activity in Tonicella lineata
e
conforms to a phéteporiodie cycle subtidally and a tidal
cycle intertidally are noteworthy. Nocturnal activity
subtidally would be advantageous in avoiding predators with
vision. Although such predators have not been demonstrated
for this chiton, the close visual conformity that T. lineata
displays with its coralline substrate strongly suggests
such a possibility. Likewise, decreased activity with
low tide may be advantageous in the intertidal, for
heightened activity in an aerial environment would result
in respiratory inefficiency (B. Robbins, 1974) and increased
exposure to destication.
P. Demopulos
Diet, Activity and Feeding
Page 9
in Tonicella lineata
The correspondence of relative "fullness" of the
anterior digestive tract in subtidal specimens with the
observed cyclic activity patterns suggests,asexpected
that increased activity is associated with increased feeding.
Intertidally, the gut "fullness" data does not support a
similar conclusion.
Subtidal individuals of T. lineata were generally
smaller and differently colored than those from the inter-
tidal; they had fewer valve notches, and a somewhat
different activity pattern. Whether these represent tax-
onomic, ecological, or age differences in the two
populations is unclear. Experiments in which members of
the two populations are transplanted and juxtaposed might
be helpful in clarifying this question.
P. Demopulos
Diet, Activity and Feeding
in Tonicella lineata
SUMMARY
1. Tonicella lineata characteristically occurs
on a coralline algal substratum.
2. Coralline algae comprise an average of more
than 50% of its diet.
3. Subtidally, Tonicella lineata exhibits
increased activity nocturnally. Intertidally,
heightened activity conicides with periods of
high water.
4. Indications of homing behavior were observed in
some intertidal and subtidal individuals.
5. Intertidal and subtidal populations of Tonicella
lineata differ in body size, color, activity pattern,
and number of valve notches.
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P. Demopulos
Diet, Activity and Feeding
in Tonicella lineata
ACKNOWLEDGEMENT
I wish to thank Ms. F. Fulton, Mr. C. Harrold,
Mr. J. Konigsberg, Ms. R. Nishi; Dr. J. Phillips,
Mr. S. Seiff, Mr. J. Watanabe, and particularly Dr.
Isabella Abbott for their help.
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P. Demopulos
Diet, Activity and Feeding
in Tonicella lineata
LITERATURE CITED
Barnes, James Ray
1972. Ecology and reproductive biology of Tonicella
lineata (Wood, 1815). Ph.D. Dissertation. Dept. of
Zoology, Oregon State University. 161 pp.; 47 figs.
(June 1972)
Burghardt, Glenn E. and Laura E. Burghardt
1969. A collector's guide to West Coast chitons.
45 pp.; 4 plts. San Francisco, Calif. (San
Francisco Aquarium Society, Inc.)
Robbins, Bruce A.
1974. Aerial and aquatic respiration in the chitons
Nuttallina californica and Tonicella lineata.
The Veliger
Smith, Allyn G. and Mackenzie Gordon Jr.
1948. The marine mollusks and brachiopods of Monterey
Bay, California, and vicinity. Proc. Calif. Acad.
Sci. 26 (8): 147-245; 4 figs.; 2 plts.
(15 December 1948)
Yakovleva, A.M.
1952. Shell-bearing mollusks (Loricata) of the seas
of the USSR. Zool. Inst. Acad. Sci. USSR, No. 45;
viii + 127 pp.: 53 figs.; 11 plts.
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P. Demopulos
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Diet, Activity and Feeding
Page 13
in Tonicella lineata
FIGURE CAPTIONS
Gut contents of six Tonicella lineata from
tidepool habitat. Bars indicate menæ range.
Berlofaltme wis har mlise Man.
Gut contents of 11 Tonicella lineata from low
intertidal habitat.
Bars indicate mean-and range.
Her Le win bar mcente mean
Gut contents of 8 T. lineata in subtidal habitat.
Bars indite ane.  e a
INTÉ MA
Activity of 11 T. lineata in subtidal habitat
over one 24-hour period.
Activity of 15 T. lineata in intertidal habitat
over one 24-hour period.
Relative "fullness" of the anterior digestive
tract of subtidal specimens vs. time of day.
Diagonal lines indicate "full" digestive tracts,
stippling "moderate fullness", and unmarked bars
represent "empty" specimens. (Explanation of
categories on p.4)
P. Demopulos
Diet, Activity and Feeding
in Tonicella lineata
TABLE CAPTION
Cerenege ot t l
oen
Table 1: Predominant algae and their eitritats in
the three habitats studied.
Page 14
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