Andrus and Legard
Intertidal Chiton Habitats
page 10
avoidance of sunlight has been previously noted (Ricketts
and Calvin, 1968). This species was rare intertidally,
being more common subtidally.
STENOPLAX HEATHIANA
Stenoplax heathiana generally was found on the sides of
large, rather bare rocks resting on a sandy bottom; this is
in accord with observatinns by Johnson and Snook (1935)
and Ricketts and Calvin (1968). There seemed to be no size¬
habitat relationship. One reason these animals can occur
on a barren substrate is they eat large bits of drift algae
that lodge at the base of the rocks (MacGinitie and MacGinitie,
1968).
TONICELLA LINEATA
Barnes (1972) notes that the presence of encrusting
coralline algae is critical to the habitat of Tonicella lineata
in the area he studied. Our observations support thisd
T. lineata was rarely found without coralline algae and was
most abundant in coralline-dominated tidepools or subtidally
with corallines, both erecat forms and crustose about 2 mm
thick. It additionally was found next to Strongylocentrotus
purpuratus and among Anthopleura xanthogrammica. T. lineata
was rarely exposed to direct surf, occurring primarily below
the 0.0 ft tide level, though sometimes found at higher levels
in tidepools. Point Pinos was the only site where T. lineata
was found in crevices, in the open. Only one animal was
found at Stillwater Cove.
Andrus and Legard
Intertidal Chiton Habitats
page 11
JUVENILE CHITONS
The habitat of the majority of juvenile chitons was:
a) low in the intertidal ranging between the O and +3 foot
tidal levels; b) damp; c) shady or dark; d) protected from
wave shock by surrounding boulders, overhanging ledges, or
by being within crevices. This zone corresponded to that of
tunicates and sponges. Yet a young chiton was never found on
either, but rather on bare rock or rock encrusted with such
algae as Corallina gracilis forma densa Collins, and members
of the genera Lithothamnion, Lithophyllum, and Hildenbrandia.
SUMMARY
1. The habitats of 12 intertidal chitons from six sites on
the Monterey Peninsula in central California picked for
variability in surf exposure and substrate type, were
described in terms of physical factors and biological
associates. The chitons were Cryptochiton stelleri,
Cyanoplax hartwegii, Ischnochiton regularis, Katharina
tunicata, Mopalia ciliata, Mopalia hindsii, Mopalia lignosa
Mopalia muscosa, Nuttallina californica, Placiphorella velata,
Stenoplax heathiana, and Tonicella lineata.
2. The most important environmental parameters in determing
chiton habitats proved to be surf strength, light exposure,
substrate compositin, moisture and biological associates.
Andrus and Legard
Intertidal Chiton Habitats
page 2
INTRODUCTION
Chitons make up a conspicuous postion of the intertidal
fauna of the California coastline. Various species are
known to be characteristic of particular intertidal zones
(Ricketts and Calvin, etc.), yet little is known about their
specific habitats. Only two researchers have given this topic
more than cursory treatment in print; Barnawell, (1954)
for Mopalia spp. and Barnes (1972) for Tonicella lineata
(Wood, 1815).
We selected six areas of the Monterey Peninsula shore¬
line, differing in exposure and substrate, and examined the
speific habitats of the following chiton species: Cryptochiton
stelleri (Middendorff, 1846); Cyanoplax hartwegii (Carpenter,
1855); Ischnochiton regularis (Carpenter, 1855); Katharine
tunicata (Wood, 1815); Mopalia ciliata (Sowerby, 1840);
Mopalia hindsii (Reeve, 1847); Mopalia lignosa (Gould, 1846);
Mopalia muscosa (Gould, 1846); Nuttallina californica (Reeve,
1847); Placiphorella velata Carpenter in Dall, 1878; Stenoplax
heathiana (Berry, 1946); and Tonicella lineata. These habitats
are herein described. Also included is a description of the
habitat where juvenile chitons were most commonly found.
MATERIALS AND METHODS
From April 22 to May 9, 1974, each study site was surveyed
during the lower lowtides. Descriptions of plant and animal
page 3
Andrus and Legard Intertidal Chiton Habitats
associates of each species of chiton were recorded, along with
detailed chiton density maps (maps on file at Hopkins Marine
Station, Pacific Grove, California). Species were collected
and identified using Burghardt and Burghardt, 1969, the key
to chitons in Light, et.al., (1964); and a preliminary copy
of the chiton key appearing in Smith and Carlton (1975).
From May 10 to May 28, all six study sites were examined for
habitat parameters characteristic of the most abundant chiton
species. Relative surf and sun exposure, substrate conditions
and vertical distribution (as determined by algae distribution
- Doty, 1946) were noted. Sites were examined at high tide
as well as low water, to determine the surf strength.
STUDY SITES
Figure 1 shows the locations of the sites on the Monterey
Peninsula.
Yankee Point consists of large granite platforms split
by many deep channels. Isolated shallow tidepools and deep
pools, with sparse flora and abundant fauna, are exposed to
strong surf action.
Carmel Point consists of a broad belt of large granite
boulders bordered by a sandy beach, it experiences moderate
surf action. The boulders provide for few tidepools, and only
a few small, protected channels are present.
Stillwater Cove is protected by a natural off-shore
Andrus and Legard
Intertidal Chiton Habitats
page 4
breakwater of rocks. The study site substratum consists
mainly of horizontal tables of shale exposed at low tide.
at the north edge of a sandy beach.
The Cypress Point site resembles the site at Yankee
Point, but the slope of the terrain is steeper and a large
algae are more abundant.
Point Pinos marks the south entrance to the Monterey
Bay. Granite promotories and large, isolated rocks are
exposed to strong surf. These formations partially protect
the study area which was an area along the shoreline and was
composed of boulders separated by channels and pools.
Mussel Point is exposed at the south side of Monterey
Bay. The granite substrate often forms vertical surfaces
with distingt algal zonation.
The data collected during our study are presented in
table and figure form. Table 1 lists algal and animal
associates, surf strength, vertical range, and additional
comments useful in finding each species.
DESCRIPTION OF HABITATS CHARACTERISTIC OE SPECIES STUDIED
CRYPTOCHITON STELLERI
Cryptochiton stelleri was found next to and in very deer
tidepools and channels. They were not predominantly on huge
rocks on sandy beaches, contrary to the findings of MacGinitie
and MacGinitie (1968). We encountered individuals at the t1.O
Andrus and Legard
Intertidal Chiton Habitats
page 5
ft. tidal level, totally exposed to full sunlight. This
conflicts with reports that individulas are sensitive to light
and only remain out of water when it is foggy (Ricketts
and Calvin, 1968).
CYANOPLAX HARTWEGII
Cyanoplax hartwegii was found in two distinct habitats:
1) under Pelvetia fastigiata (J. G. Agardh) DeToni; and 2)
in small, wet crevices or depressions. Occasionally individuals
were found under Fucus distichus Linnaeus. Apparently,
constant moisture and protection from direct surf are major
characteristics of the C. hartwegii habitats. Less than 2%
of those studied were exposed to direct surf, perhaps becasue
they cannot maintain attachment when exposed to wave shock.
Macroalga cover was not always present, though crustose
coralline algae or Hildenbrandia occidentalis Setchell were
consistent companions at all locations except the wet shale
at Stillwater Cove. C. hartwegii's common occurance under
fronds of Pelvetia is described by Ricketts and Calvin (1968),
and we confirm this association. We found no avoidance of
direct sunlight, as long as sufficient moisture was present
(e.g., wet shale at Stillwater Cove), an observation in conflict
with one recorded by Ricketts and Calvin (1968).
ISCHNOCHITON REGULARIS
Ischnochiton regularis was found only on the bottom of
page 6
Andrus and Legard
Intertidal Chiton Habitats
smooth rocks, 15 cm to 30 cm in diameter, resting on a rocky
bottom. The only other organisms found on these rocks were
unidentified microscopic green and blue-green algae. Individuals
were usually found in groups of two or three per rock. All
seemed to avoid direct sunlight. No mention of I. regularis
habitat was found in the literature.
KATHARINA TUNICATA
Katharina tunicata was abundant in two distinct habitats:
1) in low numbers at the Iridaea flaccida (Setchell and Gardner)
Hollenberg and Abbott level of almost vertical granite surfaces,
a habitat found at almost all the study sites; and 2) in higher
numbers in shallow, exposed tidepools with crustose coralline
algae covering the bottom; this habitat occurred only at
Yankee and Cypress Points. In addition, small individuals
(less than 6 cm long) were found in depressions inhabited by
Strongylocentrotus purpuratus (Stimpson, 1857) and
Anthopleura xanthogrammica (Brandt, 1835). At Yankee Point
we observed a size gradient with larger animals further from
the surf. The largest were found in the protected channels on
the leeward walls. Our results agree with previous work
(MacGinitie and MacGinitie, 1968) in that individuals were
found along open, rocky coasts, not necessarily in direct
surf, but not in a habitat as well protected as Stillwater
Cove.
Andrus and Legard
Intertidal Chiton Habitats
page 7
MOPALIA CILIATA
Mopalia ciliata was the chiton least encountered, perhaps
because it was inconspicuous. Tucked in crevices among
Mytilus californianus Conrad, 1837, Tetraclita squamosa
rubescens Darwin, 1854, crustose coralline algae, Pelvetia
fastigiata and Endocladia muricata (Postels and Ruprecht)
J. G. Agardh, members of this species often had its girdle
buried in sand. Found mainly below the +2.5 ft tidal level
and noted subtidally at Mussel Point, this animal was exposed
to little or no surf.
MOPALIA HINDSII
We found Mopalia hindsii to be more exposed to air during
low tides than the other Mopalia species. Individuals were
usually in crevices nestled among associated algae, and often
covered with a thick algal growth on the valves.
MOPALIA LIGNOSA
Mopalia lignosa has the most specific habitat of the
chitons in this study. Individuals inhabited the undersides
of movable rocks resting on rocky bottom. Some animals were
found on the sides of rocks or in deep, smooth crevices and
occasionally at the bottom of high tidepools.
MOPALIA MUSCOSA
Mopalia muscosa was found predominantly in two habitats:
Andrus and Legard
Intertidal Chiton Habitats
page 8
1) in wet, protected, large crevices from the +1.5 ft to t3.0
ft. tidal levels; and 2) in high, protected tidepools up to
+5.0 ft tidal level. In addition, after individuals were found
under algae (Fucus distichus and Pelvetia fastigiata), and
under rocks. At Stillwater Cove, a high density also was
found on slight irregularities along flat, horizontal, very
wet shale. None were exposed to direct surf. More than 97%
of the individuals examined were in direct contact with moisture;
either touching a pool of water (in tidepools or crevices).
lying partially buried in moist sand, or sitting under wet
macroalgae. More than 90% of the individuals examined had
their anterior ends lower than their posterior ends and in
contact with moisture. Almost all individuals (with the
exception of those at Stillwater Cove) were found near either
Peyssonnelia meridionalis Hollenberg and Abbott or crustose
coralline algae.
NUTTALLINA CALIFORNIA
Nuttallina californica was found in three distinct
situations. Listed in order of highest to lowest density.
these were: 1) the bottom of bare rock depressions the size
of their bodies; 2) squeezed between the bases of Tetraclita
squamosa rubescens, Pollicipes polymerus, (Sowerby, 1833), and
Mytilus californianus; and 3) wedged in small crevices in high,
shallow tidepools. Rare individuals were found in large, shallow
depressions at the base of Pelvetia fastigiata and Postelsia
Andrus and Legard
Intertidal Chiton Habitats
page 9
palmaeformis Ruprecht. Surf strength at depression localities
varied widely from very strong at Yankee Point to moderately
weak at Stillwater Cove. Nuttallina californica was found
in areas both with and without macroalgae, though highest
densities were in the macroalgae-free depressions. Apparently.
a major habitat factor is the need for protection from the
direct shearing force of the surf. Only about 5% were not
firmly entrenched in a crevice, depression, or space where the
surf's force was depleted. MacGinitie and MacGinitie (1968)
say N. californica inherit and live in deep depressions in
rocks exposed at low tide, and feed on debris which collects
in these depressions. We found individuals on rocks exposed
to a wide range of surf strengths, but few such rocks were in
areas of weak surf. More than 98% of the animals were in
the presence of erect or crustoee coralline algae. None
were found on flat areas, unless sessile animals or high¬
profile algae were present. The largest individuals were found
in the high, shallow tidepools, but here the density was very
low.
PLACIPHORELLA VELATA
Placiphorella velata were found on the flat sides of
movable rocks and on the walls of deep tidepools, always below
the -1.0 ft tidal level. The individuals were always found in
shade and always with red crustose coralline algae. Their
Andrus and Legard
Intertidal Chiton Habitats
page 13
ACKNOWLEDGMENTS
The authors would like to thank the faculty and staff
of Hopkins Marine Station, in particular Robin Burnett and
Donald and Isabella Abbott. The description of juvenile
chiton habitats was done entirely by Rich Gomez for which we
thank him. Finally, special thanks to Chuck Baxter for
his invaluable help as an advisor.
Andrus and Legard
Intertidal Chiton Habitats
page 14
LITERATURE CITED
Barnawell, Earl Baker
1954. The biology of the genus Mopalia in San Francisco
Bay. M. A. Thesis. Dept. of Zoology, University
of California, Berkeley. 85 pp.; 9 figs.
Barnawell, Earl Baker
1960. Mopalia hindsii recurvans, subspec. nov. (Amphineura).
The Beliger 3(2): 37-40; plt. 6.
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.)
Doty.
Maxwell Stanford
1946.
Critical tide factors that are corcelated with
the vertical distribution of marine algae and other
organisms along the Pacific coast. Ecology 27(4):
315-328; 6 figs.
Johnson, Myrtle Elizabeth and Harry James Snook
1935. Seashore animals of the Pacific Coast. 659 pp.:
700 figs.; 11 plts. New York, N. Y. (The MacMillan Co.)
Andrus and Legard Intertidal chiton habitats
page 15
Light, Sol Felty
1964. Intertidal invertebrates of the central California
coast. Revised by Ralph I. Smith, Frank A. Pitelka,
Donald P. Abbott, and Frances M. Weesner. xiv + 446
pp.; 138 figs. Berkeley, Calif. (University of Calif.
Press).
MacGinitie, George Eber and Nettie MacGinitie
1968. Natural history of marine animals. xii + 523 pp.:
286 figs. New York, N.Y. (McGraw-Hill Book Co., Inc.)
Ricketts, Edward F. and Jack Calvin
1968. Between Pacific tides. 4th ed. Revised by Joel
W. Hedgpeth. xiv + 614 pp.; illus. Stanford, Calif.
(Stanford University Press).
Smith, Gilbert Morgan
1969. Marine algae of the Monterey Peninsula. 2nd ed. inc.
1966 Supplement by George J. Hollenber and Isabella A.
Abbott. ix + 752 pp.; illus. Stanford, Calif. (Stanford
University Press).
Smith, Ralph I. and James T. Carlton, eds.
1975. Light's Manual: Intertidal invertebrates of the
central California coast. Third edition. (University
of California Press), Berkeley, Los Angeles, London.
716 pp., 156 plates.
Stimson, John
1970. Territorial behavior of the owl limpet, Lottia
Gigantea. Ecology 51(1): 113-118; illus.
Andrus and Legard
Intertidal Chiton Habitats
TABLE LEGEND
Table 1
List of chiton species with corresponding
algal and animal associates, vertical
range, average spring surf strength, and
additional comments.
page 16
Andrus and Legard
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Andrus and Legard
Intertidal Chiton Habitats
FIGURE LEGEND
Figure
Map of Monterey Peninsula, California showing
the locations of the six study areas.
firas t legar
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