Population Studies on Dodecaceria
Kauhanen 2
INTRODUCTION
One of the cirratulid polychaetes found in Monterey Bay,
Dodecaceria fewkesi, is a significant reef builder. It is
known to exist in thick mats of coralline algae and also in
massive limestone tube networks (Hartman, 1944) both inter-
tidally and subtidally. These two forms differ greatly in
appearance when viewed in the field. Variation in tube open-
ing, as noted by Berkeley (1932; 1954) is present, along with
differing amounts of tube protrusion. Moore (1909), Berkeley
(1932; 1952; 1954), and Hartman (1944) described the general
morphology of Dodecaceria yet little is known of the ability
of these polychaetes to withstand environmental stresses.
Investigation of tolerances of Dodecaceria fewkesi from various
habitats to salinity, decreased oxygen tension, and tempera¬
ture were carried out at Hopkins Marine Station, Pacific
Grove, California, during April and May 1976. The purpose
of these experiments was to examine the variation in stress
tolerances of spatially separated populations as an indication
of reproductive isolation. Results of these experiments and
a discussion of certain morphological variations among dis-
tinct Dodecaceria populations are presented here.
MATERIALS & METHODS
Parts of the colonies were removed using a hammer and
chisel while on SCUBA. These clumps were kept in the labora¬
tory submerged in running seawater at 12°0. Prior to any of
Population Studies on Dodecaceria
Kauhanen 3
the stress experiments, each group remained under identical
temperature, light, salinity, oxygen tension, and feeding con-
ditions for a period of three weeks.
Animals were collected from the following locations:
Intertidal; east of the Monterey Boat Works at the 0.O to
-1.0 foot tidal height on granite rock surrounded
by a slow sloping sand beach of protected surf
exposure.
in calm water on Wharf #2 pilings in Monterey,
Wharf;
at a depth of 5 to 15 feet.
Hopkins Reef in 65 to 80 feet of water on granite
Deep Reef;
outcroppings protruding upward from the sandy
bottom. Surge and strong currents are infrequent.
rocky edge of the Carmel Canyon in 20 to 40 feet
Monastery;
of water. The dive spot was on the north end of
San Jose Creek Beach where surge is often great.
foot of Macrocystis bed growing from a depth of
Pinnacles;
75 to 90 feet on granite outcroppings rising out
of the sand. It is located midway between Lone
Cypress and Cypress Point on the 17 Mile Drive
and a half mile out from shore. Surge conditions
are often strong here also.
Portions of the colonies were cracked with a chisel and
worms were removed for experimentation. By placing the worm
tubes in a MgCl, solution isotonic with seawater for about
one hour prior to cracking, a higher percentage of uninjured
Kauhanen 4
Population Studies on Dodecaceria
worms was obtained. Only uninjured subjects were used for
experiments. All observations were made with a dissecting
microscope.
For the osmotic stress experiments, Instant Ocean (Aqua¬
rium Systems, Inc.) was added to 12°0 distilled water. These
solutions were glass-fiber filtered and salinity was checked
with a refractometer. Ten ml of 14% solution, approximating
50% normal seawater concentration, was added to twelve 25 ml
shell vials. This was repeated for the 45%0 solution or
roughly 150% seawater. Eight vials were run with a single
worm per vial and four vials with three worms per vial. All
vials were kept in a 12°0 water bath and the experimental sub¬
jects were checked for mortality. If no movement occurred
when the animals were disturbed with a probe, viewed at 20X
magnification with a dissecting microscope, they were presumed
to be dead.
Oxygen was depleted from seawater by bubbling N, through
a large jug of cold seawater for 25 minutes. Twenty ml were
then carefully siphoned into 25 ml shell vials, a worm added,
and a 5 mm layer of mineral oil poured over the surface. This
method for the exclusion of oxygen has been shown to be effec¬
tive (Bahr, 1974). The oxygen content of the depleted sea¬
water was found to be 0.3 ml/liter by the Winkler test modi-
fied by Carritt and Carpenter (1966). Inspection for mortal-
ity was done through the tube without disrupting the surface.
Heat stress was accomplished by placing twelve 25 ml
Population Studies on Dodecaceria
Kauhanen 5
shell vials for each of the five populations in a 29°0 constant
temperature oven. Each vial contained one worm and 20 ml of
seawater. Examinations for mortality were made periodically
using a dissecting microscope.
Some worms were gently folded in half to simulate their
natural position inside their tubes and carefully placed in
2.5 mm internal diameter glass tubes about 2 cm in length with
one end melted shut. These were kept in running seawater.
RESULTS
Collection sites for Dodecaceria yielded different morphs
of the worm. Body length, number of segments, and number of
branchial tentacles raanged from 42.1 mm, 160 segments, and 7
pairsof tentacles for the Deep Reef morph to 13.8 mm, 85 seg-
ments, and 3 pair of tentacles for the Pinnacle variety. Values
for segment number and tentacle number of all worms examined
form a continuum between these extremes. Table 1 shows these
variations and variations in the colony morphology. Two major
colony types occurred, those in 1 to 2 cm thick coralline algal
mats found where surge was prevalent (Fig. 1 & 2) and those
growing in massive clusters 6 to 30 cm thick. The massive
type can be further divided into those building cement-like
boulders such as the Intertidal morph (Fig. 3) and those of
a more individual, less densely packed tube form, found on the
Deep Reef and Wharf (Fig. 4 & 5, respectively). The tube
openings of Intertidal, Deep Reef, and Wharf Dodecaceria, all
Population Studies on Dodecaceria
Kauhanen 6
have tube protrusions, whereas the coralline type is flush
with the colony surface. Tube orifices are solitary in the
coralline and Wharf areas, but fused to contain two or three
worms in the Deep Reef and Intertidal colonies. The general
form of the worms was consistent with the descriptions of D.
fewkesi by Fewkes (1889, Sabella pacifica) and Berkeley (1952,
D. pacifica).
The results of osmotic stress experiments are contained
in Figures 6 and 7. Intertidal and Wharf individuals survived
considerably longer at 14% than did the Deep Reef or Pinnacle
polychaetes. The Intertidal, Deep Reef, and Wharf worms with¬
stood 45%0 salinity longer than Monastery or Pinnacle subjects.
The experiment was terminated after eight days so as to limit
the effect of accumulated waste products, 0, depletion, or
other extraneous factors influencing mortality. When worms
were exposed to either 25% seawater or distilled water, im-
mediate release of a yellow-green pigment was observed and
death resulted. In 175% and 200% seawater, color was again
released with subsequent death, but it was darker green to
black in hue.
Oxygen depletion experiments resulted in no mortality
within three days to Dodecaceria from any of the collection
areas. After eight days, 5 of the 6 initial worms from each
location were still alive (see Table 2). All of the Dodeca¬
eria from the Pinnacles were active until the experiment was
terminated after eight days. No major differences in tolerance
Population Studies on Dodecaceria
Kauhanen 7
were noticed among groups.
Preliminary temperature stress experiments showed that
Dodecaceria kept at 31°0 could survive more than six hours
although the worms did release their gametes. Figure 8 shows
survival time at 29°0. The Wharf and Intertidal groups not
only survived significantly longer, by a 2 X 2 independence
test (G-statistic), but were the most active when introduced
to this stress. (p£.00)
Tube building was observed in D. fewkesi placed in glass
tubes. After ten days, the inside of the glass was definitely
hazed by a white chalky substance and beginning signs of tube
extending were evident. After 25 days, the majority of the
worms in glass tubes had added up to 2.5 cm of this substance
to their now curving tubes (Fig. 9). This whitish substance
reacted in the same manner as the CacO, tube masses found in
nature when treated with 5% HCl. It was similar in appearance
except it lacked the sand grains found in the natural matrices.
DISCUSSION
One explanation for the variation in colony morphology
is the effect of habitat. It is possible that strong surge
could keep tube protrusion reduced, slowing vertical growth
of the colonies at Monastery and Pinnacles. In areas of less
surge, such as the Wharf and Deep Reef, tubes may not be kept
cropped, allowing detritus and sand to collect in between the
tubes and become cemented into the matrix. Intertidal tube
Population Studies on Dodecaceria
Kauhanen 8
projections are not obvious unless the tube openings are pro¬
tected from wave shock. It appears possible that a transplanted
larva from any colony might forma tube, influenced by the
environment, which resembled the local colonies of that area.
This I was unable to verify since the worms were slow to recon¬
struct tubes, and larvae were not available. However, Inter-
tidal forms in glass tubes made tube extensions indistinguish-
able from those of the Deep Reef. In this case, the habitat
seemed to control the architecture of the colony. Glass tube
colony transplants among all five areas could yield conclusive
results as to the question of environment or genetic control
of colony morphology.
Individual body variation seems to coincide with size:
the more segments, the greater the length, and the more branchial
tentacles present. If all groups are considered one popula¬
tion, a continuum in characteristics is evident with the ex-
ception of length. Perhaps scouring by surge in areas of
coralline algae dwarfs the worms realized length by limiting
colony thickness. All the worm variations noted can be easily
influenced by environmental conditions and thus cannot be used
in evidence for or against the existence of a single or multi¬
ple species.
Osmotic stress does not seem to be an environmental
problem for D. fewkesi since in the lab they tolerated salinity
concentrations beyond extremes to which they are exposed in
the field. Intertidal Dodecaceria are exposed to greater
Population Studies on Dodecaceria
Kauhanen 9
environmental fluctuation so one would expect them to exhibit
greater tolerance to stressful conditions than subtidal worms.
In the field, exposure to air is limited to a few hours daily
by their location at the zero tidal level. This limits the
extent of potential osmotic stress resulting from exposure,
local fresh water input, and evaporative water loss. The
Wharf population of Dodecaceria also inhabits a fluctuating
and potentially hostile environment and may consequently ex¬
hibit greater salinity tolerance than other subtidal forms.
Even when removed from their tubes, all worms are quite able
to withstand a large range of salinity. It is assumed that
in the field, this ability is enhanced by the colony morphology
Reduced oxygen tension had little effect on Dodecaceria
over several days. This could be adaptive if the worms should
become buried by shifting sand. It is interesting that no
noticeable differences resulted among populations.
D. fewkesi can tolerate a wider range of temperatures
than it might encounter naturally. They are never exposed
long enough that temperatures could reach their lethal level.
The worms from the Wharf and Intertidal, areas which underge
the greatest temperature fluctuations, withstood exposure to
29°0 the longest and remained the most active of the worms
examined under these conditions. It is not clear wether
long-term acclimitization or inherent population differences
account for the variation in high temperature tolerance.
Population Studies on Dodecaceria
Kauhanen 10
SUMMARY
1. The Dodecaceria collected at five various habitats varied
in appearance yet none of these variations indicate cer¬
tain genetic isolation over environmental effects.
2. Habitat may play the significant role in colonial morph-
ology, with surge possibly being a key factor.
3. No individual morphological evidence was found to support
a single or multiple species as within colony variation
is adequate to form a continuum of values if all popula¬
tions are treated as one.
4.
Tube extending is identical between Intertidal and Deep
Reef populations in the lab.
All populations tested were well adapted to handle any
naturally occurring osmotic stress.
6. Dodecaceria can live for more than eight days in reduced
O, tension of 0.3ml/liter.
7. Temperature must be extreme to be lethal as even at 31°0
a time interval of over six hours was needed to cause death
to the worms.
ACKNOWLEDGEMENTS
My earnest appreciation goes to Jim Watanabe as my ad¬
visor, photographer, and mentor through this project. Also
my thanks go to Larry Harding and Chuck Baxter for their time
and concern in editing.
e
Population Studies on Dodecaceria
Kauhanen 11
LITERATURE CITED
Bahr, L. M. 1974. Energetic aspects of the intertidal oyster
reef community at Sapelo Island, Georgia. Ecology 57(1).
121-131.
Berkeley, E. & C. 1932. On a collection of littoral Poly-
chaeta from the west coast of Vancouver Island. Contrib
to Canadian Biol. & Fisheries, NSZ (f21):311-318.
Berkeley, E. & C. 1952. Canada Pac. Fauna. Fish. Res. Bd. of
Canada 9b(2):33-34.
Berkeley, E. & C. 1954. Notes on the life history of the
Polychaeta Dodecaceria fewkesi. Journal Fish. Res. Bd.
of Canada 11(3):326-334.
Carritt, D. E. & J. H. Carpenter. 1966. Comparison and eval-
uation of currently employed modifications of the Winkler
Method for determining dissolved 0, in sea water. A NASCO
Report, Journal Marine Research 24(3):286-318.
Fewkes. 1889. New invertebrata from the coast of California,
Bull. Essex Instit. 21:99-146.
Hartman, Olga. 1944. Polychaeteus Annelids from California.
Allan Hancock Pacific Exped. 10:239-310.
Moore, J. P. 1909. Polychaeteus Annelids from Monterey Bay
and San Diego. Proc. Acd. Nat. Sci., Philadelphia 61:235.
294.
Population Studies on Dodecaceria
Kauhanen 12
Figure Captions
Figure 1. Pinnacle Dodecaceria, shown as they occur with
coralline algae. The scale is in cm. Note the
flushness of the colony.
Figure 2. Monastery Dodecaceria in coralline algae.
Figure 3. Intertidal Dodecaceria from the zero tidal level.
Figure 4. Deep Reef Dodecaceria with tube protrusions ap-
parent. Note fused tubes by the 11 cm mark.
Figure 5.
Wharf Dodecaceria with widely varying topography
to the colony.
Figure 6.
Dodecaceria tolerance to osmotic stress at 11%a
Note that even the first to die are considerably
tolerant.
Figure 7.
Osmotic stress at 45%.. Many of the subjects were
alive at the end of 8 days. It is interesting to
note that Deep Reef worms survived 45%much more
successfully in relation to the other populations
than it did in 14%.
Mortality plot at 29°0 for Dodecaceria. Note the
Figure 8.
Intertidal LD50 at this temperature is greater
than 48 hours. Temperatures of this duration and
degree are not found in the field.
Artificial tubes with CacO, extentions inhabited
Figure 9.
by Dodecaceria. Note size and bending of tube.
Population Studies on Doded
Kauhanen 13
TABLE CAPTIONS
Table 1.
Morphological characteristics of Dodecaceria fewkesi
which vary in the field between populations. Length
is given in mm one standard error. The sample
size is given in parenthesis. Branchial tentacular
stubs refer to stump-like tentacles less than imm
in length. Variztion on segment number was roughly
t 10%. Sex is for the population sampled only, not
for all populations in the area of collection.
Table 2
Time of death under reduced 0, tension; 0, is O.3m1/1.
It appears Dodecaceria can tolerate anerobic condi¬
tions.
Population Studies on Dodecaceria
FIGURE 1
FIGURE 2
Kauhanen 14
opulation Studies on Dodecaceria
Kauhanen 15
FIGURE 3

LNTTU75
Soet O Att vou.
Population Studies on Dodecacer:
FIGURE 4
FIGURE 5
Kauhanen 16
Population Studies on Dodecaceria
FIG URE 6
—+.

26

4

—
O

48 72
24
OURS
W
6
Kauhanen 17
120
Population Studies on Dodecaceri
Kauhanen 18
NO. SURVIVING
c.

O
S
0

N
82
Population Studies on Dodecaceria
Kauhanen 19
FIGURE 8

12
10
14

2 8
YG
O
WV

4
Z
10 20
30 40 50
HOURS
Population Studies on Dodecaceria
FIGURE 9
Kauhanen 20
Populati
TABLE 1
LENGTH
(mm)
NUMBER
BRANCHIAL
TENTACLES
S NUMBER
SEGMENTS
SEX
TUBE
OPENING
(worm / hole)
TUBE MASS
THICKNESS
INTERTIDAL
175t.63
(13)
3 p
1.0-3.5mm
2pr stubs
110
volcano-like
2mm
(2)
reef-like
15-30
WHARF
29.641.18
(14)
4-6p
Cmm
4 6 stubs
not always in pr.
135
tube projection
8mm
(1)
6
DEEP REEF MONASTERY PINNACLES
42112.0
13.61.51
13.84.54
(5)
(22)
(9)
5-7p
4 p
3-4p
1-7mm
2mm
2mm
5 7 pr stubs
1pr stubs
160
85
90
O
tlush with
tlush with
tube projection
Amm
coralline
coralline
algae
algae
(23)
encrusts
encrusts
10
Population Studies on Dodecaceria
TABLE 2
02
NTERTIDAL
WHARE
DEEP REEF
MONASTERY
PINNACLES
O
Kauhanen 22
DAYS
4
5
6
8
O
0