Predation Upon Subtidal Tonicella lineata of
Mussel Point, California (Mollusca: Polyplacophora)
Stuart R. Seiff
ABSTRAC.
There appears to be relatively little predation
upon subtidal Tonicella lineata at Mussel Point,
California, and there is significant discrimination
against feeding on them in the laboratory. A chemical
repellent, or some kind of tactile inhibitor of predation
are deemed possible explanations. The mechanism of the
protection against predation is not known, but appears
to be associated with the dorsal surface of living
animals.
11175
page 1
Predation Upon Subtidal Tonicella lineata of
Mussel Point, California (Mollusca: Polyplacophora)
Stuart R. Seiff
Hopkins Marine Station of Stanford University
Pacific Grove, California 93950
Running Title: Predation Upon Tonicella lineata
Please send all correspondence and proofs to:
Predation Upon Tonicella lineata
Stuart R. Seiff
INTRODUCTION
In the kelp beds off Mussel Point, Pacific Grove,
California, the chiton Tonicella lineata (Wood, 1815)
is abundant on subtidal Lithophyllum encrusted rocks.
While colors and patterns make them inconspicuous on
a background of coralline algae, they appear vulnerable
to predation by nonvisual predators such as starfish.
Mauzey et al. (1968) state that, on occasion, the
sea stars Dermasterias imbricata (Grube, 1857),
Evasterias troschellii (Stimpson, 1862), and Orthasterias
koehleri (deLoriol,1897) eat subtidal individuals of
Tonicella in the Pacific Northwest. No published
information is available on predation of subtidal
Tonicella in Californian waters. I herein report on
laboratory experiments and subtidal observations
pertaining to the discrimination of nonvisual predators
against Tonicella and the possible reasons for the lack
of predation.
Predation üpon Tonicella lineata
Stuart R. Seiff
METHODS AND RESULTS
Tonicella seem quite vulnerable to predation by non-
visual predators while situated on the Lithophyllum
covered rocks in the Mussel Point kelp bed. However,
their abundance implies that they are not heavily preyed
upon.
A 24 hour subtidal observation period was under-
taken to observe, in a natural setting, the activities of
subtidal Tonicella and associated fauna. The area
selected was a coralline encrusted rock in the Mussel
Point kelp bed measuring 1.2 x.6 x.25 meters. There
were 16 Tonicella present at the site, along with 2
Pisaster brevispinus (Stimpson, 1857), 1 P. giganteus
(Stimpson, 1857), 5 Patiria miniata (Brandt, 1835), and
1 Mitra idae (Melvill, 1893), Observations were made
every four hours. During this time no Tonicella were
consumed, though starfish were observed on top of the
Predation Upon Tonicella lineata
Stuart R. Seiff
Theré u thos pe appavenrt predarin op Tonicelts
Itthusappearsthatsubtidal
chitons at various times.
onaarenotmassivelypre by the species
just mentioned.
In order to further investigate the lack of predation,
several laboratory experiments were performed. During the
course of study, a total of 92 Tonicella were exposed to
48 starfish in test aquaria. This resulted in 4,300
starfish hours of exposure during which time only
3 apparently healthy Tonicella were eaten. These were
all consumed by Pisaster brevispinus.
Strongylocentrotus purpuratus (Stimpson, 1857) ate
a Tonicella when the tank temperature rose above 14°0 as
a result of a running seawater system' malfunction. The
phenomenon of temperature affecting predation on Tonicella
is discussed by Barnes (1972, pp 17-18).
However, none of the following potential predators
consumed Tonicella in aquaria during at least 48 hours
exposure: the seastars Pisaster giganteus, Orthasterias
Predation Upon Tonicella lineata
5
Stuart R. Seiff
koehleri, and Leptasterias spp., and the carnivorous
gastropods Mitra idae and Conus californicus (Hinds, 1844).
During the various tests, starfish were often observed with
Tonicella beneath them. Thus, lack of contact between the
starfish and chitons was not a factor in the low predation
levels.
In more specific studies, 15 subtidal Tonicella, 15
Nuttallina californica (Reeve, 1847), and 15 Cyanoplax spp.,
all between 1.9 and 3.0 cm. in length, were allowed to
cm
attach to the bottom of a 43 x 27 x 25Aaquarium. The
potential nonvisual predators Pisaster ochraceus
(Brandt, 1835), P. giganteus, P. brevispinus, Patiria
miniata, and Orthasterias koehleri were introduced. The
seawater temperature was 14°0. The results, (Table 1),
after 3 days' exposure, show that no Tonicella were
eaten while the other chitons were. This differential
predation was significant using the chi square test (p(.01).
Predation Upon Tonicella lineata
Stuart R. Seiff
In order to be certain that the Tonicella in the
previous experiment were of the proper size for con¬
sumption by the starfish, 15 Tonicella, ranging in
size from 3.1 to 1.2 cm., were placed in another
aquarium with the same individual predators for 3 days.
None were eaten. These results indicate that starfish
preferentially consumed other chitons, and did not
eat Tonicella even when they were the only available
food source and a wide size range existed.
A series of laboratory experiments was conducted
to examine several possible reasons for this lack of
predation. All of the experiments were conducted either
in 43 x 27 x 25 cm. aquaria or 33x28 x13 cm. plastic
trays filled with running seawater at 14t1°0. The
number and size of Tonicella varied with the individual
experiment, as did the species, size and nuiber of the
predators.
Predation Upon Tonicella lineata
Stuart R. Seiff
1. To determine whether contact between a starfish
and a Tonicella would produce a repellent in the form
of a pH change, the valves and feet of 5 Tonicella, not
exposed to starfish, were tested with pH paper. The
paper was placed on the wet back and foot of each chiton
and readings of 7.57.1 were obtained. After contact with
the starfish, Orthasterias koehleri, the pH readings of
both the valves and feet remained 7.5f.1. Thus, no
indication was found that an altered pH was the means by
which Tonicella avoid predation.
2. The presence of a chemical repellent within
Tonicella was tested for by use of a suspension of whole
ver hou-
Tonicella. ,Ywo live Tonicella (approximately 1.25-2 cm.)
everyheur
were ground upsusing a mortar and pestle.

The tissue and fluid were added to a tray containing
5 Cyanoplax spp. and the predators Pisaster brevispinus,
P. giganteus, P. ochraceus, and Orthasterias koehleri.
Predation Upon Tonicella lineata
Stuart R. Seiff
A control tray containing the same numbers of animals was
also set up, but no suspension of Tonicella was added.
In this experiment the running seawater was turned off
so as not to dilute the suspension. Fresh seawater was
added every hour with the new suspension. After 3 hours,
a Cyanoplax spp. was eaten by the Orthasterias koehleri
in the tray containing the Tonicella suspension. There
is thus no evidence for an active chemical repellent.
3. Cellulose sponge impregnated with suspension
of Cyanoplax spp. was attached to the backs of 5 Tonicella
in an attempt to determine if Cyanoplax possèss à chemical,
attractive to starfish, which Tonicella might lack. The
sponge was affixed using Devcon "Zip-Grip 10". The Tonicella
were placed in a tray with 1 Pisaster brevispinus, 1 P.
Ochraceus, and 1 Orthasterias koehleri. After 96 hours
of exposure, none of the Tonicella with the sponge were
eaten. It would thus seem that Cyanoplax does not have
Predation Upon Tonicella lineata
Stuart R. Seiff
a chemical attractant.
4. As chemical properties alone do not appear to account
for the low rate of predation on Tonicella, the function
of the valves was more closely investigated. Four Tonicella
were inverted and affixed to glass slides using Devcon "Zip-
(oevee corp., Danvers Mass.)
Grip 10". They were placed in a tray with 1 Orthasterias
koehleri, 1 Pisaster brevispinus, and 1 P. ochraceus.
Within 3 days, 2 Tonicella were consumed, 1 by P. brevispinus
and 1 by P. ochraceus. It thus appears that inverted
Tonicella are very susceptible to predation by sea stars.
5. When Tonicella are not inverted, the valves are
the first part of the chiton that a predator comes in
contact with. Microscopically, the valves of Tonicella
appear smooth and shiny, unlike most other chitons. To
test whether or not a starfish's fube feet could hold onto
the smooth valves of a Tonicella, one was placed under
a starfish. When removal of the chiton was attempted, the
tube feet held on. Therefore, the protection seems due
to a nonmechanical property of the valves,
Predation Upon Tonicella lineata
10
Stuart R. Seiff
6. In determining whether the texture of Tonicella
valves aloné is sufficient to repel starfish and other
predators, the valves of 5 Tonicella were epoxyed to the
backs of 5 Cyanoplax. These were placed in a tank with
5 normal Cyanoplax, i Pisaster brevispinus, 1 P. giganteus,
1 P. ochraceus, 1 Orthasterias koehleri, and 1 Patiria
miniata. Within 2 days, P. brevispinus had eaten 2
Cyanoplax with Tonicella valves, and Orthasterias koehleri
had eaten 2 with valves and 2 without. Thus, 4 of the 5
Cyanoplax with Tonicella valves were consumed. It appears
that for the Tonicella valves to be effective against
predation, the Tonicella must be alive.
DISCUSSION
Pisaster brevispinus appears to be the dominant
nonvisual, subtidal predator of Tonicella, and its
rate of predation is low. According to Nakashima (1974),
only .25% of the diet of P. brevispinus in the Mussel
Predation Upon Tonicella lineata
11
Stuart R. Seiff
Point kelp bed is composed of Tonicella.
In the Pacific Northwest, Dermasterias, Evasterias,
and Orthasterias consume small amounts of Tonicella
(Mauzey et al., 1968). Additionally, Pisaster
ochraceus primarily eats chitons, including Tonicella,
during the winter when the starfish mass together in
groups and become rather sessile. The grazing movements
of the chitons bring them into contact with the starfish
(Mauzey, 1966). The diet of Leptasterias hexactis (Stimpson,1862)
has been reported to be composed of 45% Tonicella in
intertidal areas where there is little else to eat
(Mauzey et al., 1968). In contrast, local Tonicella
were not consummed by these starfish when in aquaria,
yet these starfish did consume other chitons.
The concept of 2 species, one intertidal and one
subtidal, has been advanced by Barnes (1972). Perhaps
a taxonomic distinction between the Tonicella collected
from Mussel Point and those studied by Mauzey in the
12
Predation Upon Tonicella lineata
Stuart R. Seiff
Pacific Northwest could account for the difference in the
predation.
Explanations for the low predation on the Mussel Point
Tonicella, which appear to be easy prey, may include
difficulties encountered by starfish when removing
Tonicella from various substrates, lack of a chemical
attractant, possession of a chemical repellent, or
some form of a tactile inhibitor of predation. Cryptic
coloration, however, is not a possibility here as starfish
are not visual predators.
That both inverted Tonicella and Cyanoplax with
Tonicella plates attached to their backs were eaten
suggests that Tonicella's protection is dependent on
its being alive and upright. Thus, a living dorsal
surface may be the site of protection. Whatever the
protection, it is not 100% effective as indicated by
the 4 apparently healthy Tonicella that were eaten.
Predation Upon Tonicella lineata
13
Stuart R. Seiff
SUMMARY
Starfish predation on Tonicella lineata in the
Pacific Northwest has been reported as common. However,
subtidal Tonicella from Mussel Point, Pacific Grove, California,
are rarely consumed in aquaria by starfish which will
consume other species of chiton. A chemical repellent,
or some kind of tactile inhibitor of predation are
deemed possible explanations. The mechanism of the
protection of the local population from predation is not
known but appears to be associated with the dorsal surface
of living animals.
ACKNOWLEDGMEN
I thank Dr. Robin D. Burnett for his assistance and
patience throughout the entire investigation, Dr. Isabella
A. Abbott for her help in the identification of the various
species of algae encountered, Mr. Charles H. Baxter for
his aid in animal species identification, Dr. John Pearse
for his assistance in obtaining information on local Asteroid
predation, and Dr. Donald P. Abbott for his helpful suggestions
throughout my work
Predation Upon Tonicella lineata
Stuart R. Seiff
LITERATURE CITED
Barnes, James Ray
1972. Ecology and reproductive biology of Tonicella
lineata (Wood, 1815) (Mollusca-Polyplacophora).
Ph.D. dissertation, Dept. of Zoology, Oregon State
University. 161 pp.; 47 figs.
(June 1972)
Mauzey, Karl Perry
1966. Feeding behavior and reproductive cycles in
Pisaster ochraceus. Biol.
Bull. 131 (1):
127-144; 7 figs.
Mauzey, Karl Perry, Charles Birkeland, and Paul K. Dayton
1968. Feeding behavior of Asteroids and escape
responses of their prey in the Puget Sound region.
49 (4): 603-619; 4 figs.
Ecology

(27 March 1968)
Nakashima, Richard
1974. Asteroid predation in Monterey Bay. Unpublished
paper, Division of Natural Sciences, University of
California, Santa Cruz. 14p
14
Predation Upon Tonicella lineata
15
Stuart R. Seiff
Table Caption
Table 1: Species present during preference feeding test.
addrional
The remains of 2, Nuttallina were foundon the
bottom of the aquar
ium; the identity of the
predator was unknown.
Predation Upon Tonicella lineata
Stuart R. Seiff
Table 1
Species
No.
saster ochraceus
Pisasterg
ganteus
Pisaster brevispinus
Patiria miniata
Orthasterias koehler
Unobserved
Species (No.) preyed on
Nuttallina (3), Cyanoplax (6)
Cyanoplax (1)
Nuttallina (1), Cyanoplax (1)
Nuttallina (2)