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Introduction
The case of the two closely related holothuroids.
Cucumaria curata and Cucumaria pseudocurata is of special
ecological and evolutionary interest. In a recent survey
of intertidal invertebrates Brumbaugh (1980) made summary
statements of the literature that describe these two
species as having similar habitats: the surf swept rocks
of the middle to lower intertidal zones of Central California
rocky coastline. He also reports that C. pseudocurata
ranges from the Queen Charlotte Islands of British Columbia
to Monterey County, California while C. curata was only
known along one mile of coast from Yankee Point to Malpaso
Creek in Monterey County. The morphology and biological
aspects of C. pseudocurata have been described, however.
C. curata has had only taxonomic work published on it
(Cowles, 1907).
Not only are the two species alike in habitat, but
external morphological similarities complicate their study,
A set of field criteria have been established to help dis¬
tinguish between species (Brumbaugh, 1980). These criteria,
however, are of use only to one familiar with the cucumbers.
or when one has both species and a hand lens for close
comparison. Positive identification of the species must
be made by examination of body wall spicules, which are
obtained by dissecting away a small piece of the body wall
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and dissolving it in chlorine bleach. For further descrip¬
tion of C. curata see Cowles, 1907; for C. pseudocurata
see Deichmann, 1938b; for both see Rutherford, 1975 and
Brumbaugh, 1980.
No studies have investigated the very restricted
distribution of C. curata, nor its apparent coexistence
in what is described as the same habitat with C. pseudo-
curata, in areas of range overlap. This study was designed
to gain information on the specific habitat niches of the
two species. It is a general dictum of evolution and ecology
that two species cannot occupy the same ecological niche.
The further interesting questions of the restricted range
of C. curata (correctly Cypress Point to Malpaso Creek,
Monterey County) and the apparent sympatric speciation
still await study.
Methods
Three areas, all in Monterey County, were chosen for
the habitat study on the two holothuroids: Cypress Point,
Pescadero Point, and the Yankee Point to Malpaso Creek area.
Preliminary samplings made to discover adequate popu¬
lations of the two species, so that their specific habitat
niches could be characterized, indicated that C. curata
was generally found in more exposed situations than C.
pseudocurata. This information was used to design a strati-
fied sampling program for complex rocky shores, which examined
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horizontal belts moving from low, wave exposed levels.
up the reef to higher, more protected pools behind the exposed
faces. Horizontal swaths of approximately i m width
of equivalent conditions of exposure, slope, and visgosity,
were examined for Cucumaria, where they were often found
aggregated and in habitat niche characterization. A few
separate individuals were also found. These areas are
recognized as typical of Zones 3 and 4 in Ricketts and
Calvin (1968) belonging to "Open-Coast Rocky Shores.
Collections were made at negative tides when surf
was moderate. Specimens were collected with broad-tipped
forceps and placed in small numbered vials. Associated
physical and biological observations were recorded. In
the lab, they were placed in sea water, and allowed to relax,
Measurements of length were then taken, and a small piece
of the body wall was dissected for identification purposes
Earlier collections were also characterized for color and
tentacular morphology. Efforts were made in earlier collect¬
ing to take only individuals from groups to gain the most
variation across the belt of habitat. Later collecting
included taking one to three members from a group of specific
habitat (e.g. vertical faces of rocks in the lowest inter-
tidal region). It is doubtful that results were biased
by choice of individuals collected due to preconceptions
because of the difficulty of species identification in
the field. The lower and more exposed situations were prob¬
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ably under collected due to the presence of dangerous surf.
It probably also lead to overcollection of the larger,
more conspicuous individuals, despite every attempt to make
a thorough search. The wet suit was a great aid to the col¬
lector in these situations.
Results
Morphology and Color

Sixty-one cucumbers from the collection sites (Cypress
point, Pescadero Point, Yankee Point - Malpaso Creek)
that possessed ten equal tentacles proved to be C. curata.
Likewise, of twenty-seven cucumbers observed to have eight
larger tentacles with two smaller, ventrally located tentacles
all were C. pseudocurata.
Lengths of all cucumbers collected were measured and
plotted in Figure 1. The measurements taken were not
fully extended lengths, but were taken under uniform conditions.
The average length for C. curata (151 individuals) was 14.7 mm
as compared to 15.3 mm average length for C. pseudocurata
(126 individuals). The graph seems to show normal dis¬
tribution. Qualitatively, it might be added that C. curata
was the larger, heavier individual and C. pseudocurata
was usually thinner.
Qualitative features of the cucumbers proved to be
relatively constant through the study sites. The C. curata
examined, with few exceptions, were (observed under dissection
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scope with light) dark brown, sometimes lighter, with
vellowish tint on the dorsal side. Ventrally they were
white to yellowish at the sides, varying in the amount of
white. The C. pseudocurata examined proved to have a greater
variance in color. Dorsal side was normally chocolate brown
(black in sunlight) but ranged to gray, with some specimens
from Sonoma County white. Ventrally they ranged from tan
to white with pigment peppered throughout. The lighter
colored individuals came from shaded spots, such as under¬
neath Mytilus beds. No conspicuous differences were observed
in podia distribution or shape.
Niche Characterization
Results of collections at Cypress Point, Yankee Point -
Malpaso Creek area, and Pescadero Point (Figures 2-4)
will be presented in this order which represents a widening
gradient of wave exposure. Finally, a collection based on
vertical and horizontal surfaces at Yankee Point - Malpaso
Creek area and at Pescadero Point will be reported.
Cypress Point
The Cypress Point collection site consists of two
collection areas labelled in Figure 2, and is representative
of exposed outer coast, and Zone 3 to Zone 4 (Ricketts
and Calvin, 1968). In the schematic map, closely spaced
horizontal lines represent impinging wave action with the
direction of force perpendicular to the lines. The pools
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shown with slanted horozontal lines are typical pools from
which cucumberswere collected. The first heavy line repre¬
sents zero tide level and each heavy line "above" it is
roughly one meter in height. A lighter line connected to
a dark line represents about a half meter drop in height.
Collection totals are listed near the area where the
cucumbers were taken. In Area 1, the eleven C. curata
in the front zone were taken from: cracks in vertical
faces, small pools, and small coralline encrusted pockets,
The single C. pseudocurata was found in a dense aggregate
behind Mytilus. The second collection, eleven C. curata
to zero C. pseudocurata, was taken from the two nearest
pools. The cucumbers, it was noted, were always submerged,
but only to depths up to a foot. In Area 2, collections
were taken from inside the bowl, within the bowl, and
outside the bowl. The results were twenty-six C. curata
and zero C. pseudocurata.
Yankee Point - Malpaso Creek Area
These collections were made at a rocky outcropping.
several hundred yards north of Malpaso Creek, and just off
Yankee Point Drive. Figure 3 uses the same schematics as
previously described for Cypress Point. Waves directly hit
the front edge of the rock, and hit more or less at angles
down a channel to the left (south) in the figure. This
collection site shows clearly that a gradient of wave
action is at work here going from well protected, plat-
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formed pools ten meters or more from the surf to the ver¬
tically facing fronts near the low tide level.
Collections were made in relation to this gradient
of exposure. Beginning with the set of three pools most
distant from the surf, the collection made in this rela¬
tively shallow, flat pool (which sits just at the top
of Mytilus beds) shows that all twenty-four cucumbers
collected were C. pseudocurata. Similar results were ob¬
tained at the pool in the center, which was positioned with
nearly the same zoning pattern. The pool was at a distance
of ten meters from the surf, being protected from the
surf by a surge channel directly in front of it. Results
of a collection made from a variety of angles, walls, and
depths, but always within the pool, showed that there were
The cucum¬
twenty-seven C. pseudocurata to zero C. curata.
bers were situated in aggregates on encrusting corallines
at the bases of Corallina, and usually on flat surfaces.
Moving up the gradient, to more exposed areas at about
one to two meters from the surf, a collection area is defined
by boundry lines. This area is intermediate in wave action.
No cucumbers were ever found here on dry vertical faces,
but were always submerged, and often were wedged into the
encrusting coralline algae, at times in association with
Corallina. Collections totaled twenty-two cucumbers in
this area: nine were C. curata and thirteen were C. pseudo-
curata.
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The most exposed area,within one meter of the zero
tide line, cucumbers were found for the first time on ver¬
and
tical walls,,usually in a crack or well imbedded in en-
crusting coralline. Generally, Corallina and Caliarthron
also were in association. Cucumbers collected were as
follows: on vertical walls, out of pools, thirty-six were
C. curata and two were C. pseudocurata. In pools of this
area, ten were C. curata with one being C. pseudocurata.
Totals were fourty-six C. curata to only three C. pseudo¬
curata. The two C. pseudocurata found on vertical walls were
underneath Mytilus in tight aggregations.
Pescadero Point
Pescadero Point is the best example of a site with
differential wave action and varying degrees of desiccation.
The site consists of a wide front to the impinging waves,
with a small wash area breaking in to the right (Figure 4).
Located at the bottom of the figure, is a main pool about
20-25 meters from the leading edge of low tide. Moving from
the pool toward the surf, there is a gentle incline (con¬
sisting of a Mytilus bed) coming to a two foot ridge, which
begins a sloping rock face into the surf. Working to the
right, the pool narrows to a gentle, declining drain off
area and into another pooled area, which has wash feeding into
it.
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10
The main pool represents a fairly well protected.
stable area exposed to occasional splash from surf spilling
over the ridge (more specific characteristics may be found
in Brumbaugh, 1965). Collections in this pool ranging over
a variety of surface inclines within the pool, resulted in
all fo-rty cucumbers identified as C. pseudocurata. The
cucumbers were in close aggregations and often at the
base of Corallina and Caliarthron.
In the pool below the drain off area, to the right in
the figure, another collection was made. This pool effec¬
tively represents an area intermediate in wash; heavy
Corallina growth on encrusting coralline algae. Twenty-
seven C. curata versus six C. pseudocurata were collected
here. The cucumbers typically were imbedded into the en-
crusting algae on horizontal surfaces.
Another pool intermediate in exposure is located up
the gentle incline from the main pool, and just below the
ridge. Feeding it was a deep surge channel, that occasionally
brought waves splashing into it. It was located in the
middle of Mytilus beds. Collections made here varied from
horizontal surfaces within the pool to vertical faces both
within and above the pool. Collected were twelve C. curata
to nine C. pseudocurata. All of the cucumbers collected on
vertical surfaces above pool level proved to be C. curata.
Last of the zones at Pescadero Point is the front
incline, which has many vertical faces, pockets, and surge
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11
channels. This area is exposed to the brunt of the wave
action. It is characterized by a large Mytilus bed (also
Policipes) and a thick mat of Corallina and Caliarthron.
In the surge channels and pockets there are Strongylocentrotus
purpuratus, and at the lower edges there is the top layer of
the laminarians. Collections in this area (zone 4) ranged
from pocketed pools to vertical faces at zero tide level.
Of the twenty-eight cucumbers collected, twenty-seven were
C. curata, and one was C. pseudocurata, which was found in
a cluster under Mytilus. All of the cucumbers in this area
were well embedded in the encrusting coralline algae along
cracks on vertical faces or on horizontal surfaces. Close
association with Corallina was often noted.
One survey focused on one particular micro-habitat:
vertical walls of rocks outside of the pools, and not im¬
mersed in water. Collections were taken at both Pescadero
Point and Yankee Point - Malpaso Creek, and included both
lone and aggregate formations. The cucumbers were usually
along cracks, small pockets in encrusting corallines, and
under Mytilus. At Yankee Point - Malpaso, forty cucum¬
bers were collected: thirty-eight were C. curata, and two
were C. pseudocurata. Pescadero Point collections totaled
twenty-six: twenty-five were C. curata, and one was C.
pseudocurata. All three pseudocurata identified were lodged
behind Mytilus.
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12
Disoussion
Several trends may be established with regard to the
gradient of wave exposure and the distribution of C. curata
and C. pseudocurata in regions of range overlap. C. pseudo
curata dominates completely over C. curata in the protected
pools of the middle intertidal. This is supported by col¬
lections made in large, protected pools of both Pescadero
Point and Yankee Point - Malpaso Creek. These pools are
wide, shallow, and with flat bottoms. They are usually
ten meters or more horizontally from the surf at low tide,
and are raised in vertical relation to the surf. Biolog-
ical associates used for protection from wash are encrusting
coralline algae that lie in a flat sheet on the pool bottom,
and patches of Corallina and Caliarthron. Tetraclita and
Endocladia were often observed rimming the pools. All
ninety-one cucumbers collected within these pools were C.
pseudocurata.
In the lowest levels of the intertidal, where it is
most exposed, it is C. curata that dominates. This is
supported by collections made in front pools and vertical
rock faces at Cypress Point, Pescadero Point, and Yankee
Point - Malpaso Creek. This area is typlified by heavily
washed pools, surge channels, and rock faces. Biological
associates are again Corallina,Caliarthron, and encrusting
corallines. The encrusting corallines are most important
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13
to C. curata as a substrate. The encrusting corallines,
being a smooth, thick film, readily conforms to the sea
cucumber's body, providing a tight fit. Other associates
are Strongylocentrotus purpuratus, and occasional Haliotus
and Leptasterius. The area was usually situated at the
top of the laminarias, with scattered Iridea and Gigar
tina. Totals in these areas, not including Cypress Point,
are seventy-three C. curata and four C. pseudocurata.
Intermediate areas of exposure had mixed distributions
of the two species. The cucumbers were on both flat bottomed
pools, and above pool levels on vertical faces, but not
nearly in the numbers of the back and front respectively.
Total number of C. curata was forty-eight, and a total of
twenty-eight for C. pseudocurata.
The two interrelated factors in the niche differences
are wave action and dessication (lower limits of C. pseudo¬
curata outside of range overlap seem to be determined by
Pycnopodia helianthoides according to a study by Ruther-
ford,1973 ). In the protected areas, abscence of cucum¬
bers on vertical walls above pool level can be attributed
to problems of desiccation. In the exposed areas, at the
other end of the gradient, wave force seems to be a problem
for C. pseudocurata. Rutherford (1973 ) indicated in a
study on C. pseudocurata that surf was an important source
of mortality. One finds in unprotected areas that the
cucumbers are well wedged, in cracks, and under Mytilus.
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11
In addition, C. curata seems to be the most resistant to
desiccation, dominating on vertical rocks out of water.
Encrusting corallines are important in forming crusty
pockets around the cucumber, not only providing protection
against wave action, but also holding in water to prevent
desiccation. Corallina, Caliarthron, and Mytilus are im-
portant in this respect too. Many time cucumbers were
observed with the encrusting coralline algae grown over
almost the entire animal. This particular encrusting
feature was only observed in the unprotected pools.
Aggregations of both species were observed in both
protected and unprotected habitats. This is probably due
to brooding and direct development in both species. This
habit is claimed to deter desiccation (Rutherford,1973).
Differences were noted in the body wall of the two species.
C.curata has a thicker, tougher compared to C. pseudocurata.
C. curata also had the ability to contract and firm the
body wall to a greater extent than C. pseudocurata. Con
trolled experiments in desiccation and wave action toler-
ance may help define microhabitatual differences in the
two species.
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15
Summary
1. Three sites in Monterey County, California (Cypress
Point, Pescadero Point, and Yankee Point-Malpaso Creek,
were chosen to study microhabitatual differences in two
closely related holothuroids, Cucumaria curata and Cucu¬
maria pseudocurata.
2. Collections were taken along a gradient of exposure,
from protected pools receiving occasional, moderated
splash at low tides to the lowest levels of the inter-
tidal receiving heavy, constant splash, to determine dis¬
tribution of both species. C. curata dominated in the
exposed situations, whereas C. pseudocurata dominated
in the protected areas.
3. Two interrelated factorsin the niche differences are wave
action and desiccation, which were moderated by the cucum¬
bers' association with encrusting corallines, Corallina,
Caliarthron, and Mytilus, the behavior of clinging into
depressions, and the habit of aggregation.
Acknowledgements
I would like to express my appreciation to all those
involved who made the spring course both enjoyable and
successful. Thanks go to Janet Vogelzang for photographs,
and to Freya Sammer, for keeping a watchful eye on the evil
surf at 4 a.m. For typewriting assistance, I thank Kathy
Calhoun and Tina Peak. My deepest thanks go to Chuck Baxter
for timely advice and assistance.
References
Brumbaugh, J.H. 1965. The anatomy, diet, and tentacular
feeding mechanism of the dendrochirote holothurian
Cucumaria curata Cowles, 1907. Doctoral thesis, Bio-
Togical Sciences, Stanford University, Stanford, Calif.
119 pp.
Brumbaugh, J.H. 1980. Holothuroidea: The sea cucumbers
pp. 136-145, in R. Morris, D. Abbott, and E. Haderlie.
Intertidal Invertebrates of California, ist ed. Stanford
University Press, Stanford, Calif. 690pp.
Cowles, R.P. 1907. Cucumaria curata, sp. nov. Johns
Hoplins Univ. Circ. 195:1-2.
Deichmann, E. 1938b. New holothurians from the western
coast of North America and some remarks on the genus
Caudina. Proc. New England Zool. Club 16: 103-15.
Ricketts, E.F., and J. Calvin. 1968. Between Pacific
tides. Ath ed. Pevised by J.W. Hedgpeth. Stanford.
Calif.: Stanford University Press. 614 pp.
Rutherford, J.C. 1973. Reproduction, growth, and mortality
of the holothurian Cucumaria pseudocurata. Mar. Biol.
22: 167-76.
Rutherford, J.C. 1975. Class Holothuroidea, pp. 634-37,
in R.I. Smith and J.T. Carlton, eds., Light's manual:
Intertidal invertebrates of the central California
coast. 3rd ed. Berkeley and Los Angeles: University
of California Press. 716 pp.
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Figure Legends
Figure 1: Lengths Of Collected Individual Of Cucumaria
curata and Cucumaria pseudocurata
Figure 2: Cypress Point Collection Sites
Figure 3: Yankee Point - Malpaso Creek Collection Sites
gure 4: Pescadero Point Collection Sites
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