E
Behavioral Interactions Between Copepods and Six
Species of Sea Anemones Found in the Monterey Bay Region
Mark R. Colville
Hopkins Marine Station of Stanford University
Pacific Grove, California
Running Title:
Behavioral Interactions Between Copepods and Sea Anemones
Send all proofs and correspondence to:
Behavioral Interactions Between Copepods and Sea Anemones.
Abstract
The behavioral interactions between copepods (species?) and
six species of anemones (Tealia lofotensis, Tealia crassicornis,
Tealia coriacea, Anthopleura elegantissima, Anthopleura xantho-
grammica, and Epiactus prolifera) were examined. Lab and field
studies over a six week period showed that the copepods feed on
anemone mucus and are dependant on the anemone for survival.
Mature copepods were found to inhabit anemone species specifically.
It was also found that copepods showed species specific zonation
on the anemone; occupying areas where their color matched that
the anemone. Adult copepods failed to visually or chemically
cue
to anemones.
Introduction
Copepods were observed to be ectocommensal with six species
of anemones; Tealia lofotensis, Tealia crassicornis, Tealia cori-
acea, Anthopleura elegantissima, Anthopleura xanthogrammica, and
Epiactus prolifera. (Hand, 11956). Observations of copepods in the
field and in the lab raised several questions concerning anemone-
copepod behavioral relationships.
What are the advantages that may accrue to the host and
1)
symbiont from this relationship?
2) Are copepods protected against nematocyst discharge
from anemones of a species other than their host; and are
they protected from other anemones of the same species as
their host?
shavioral Interactions Between Copepods and Sea Anemones
Are there particular zones of the anemone that the copepods
inhabit species specifically?
4) Do the copepods display any host recognition through
chemical or visual cues?
Each question was approached in a series of experiments.
The results of all these experiments will be discussed together
in an attempt to present a broad overview of the behavioral rela-
tionship.
Methods and Materials
All animals were collected in the Monterey bay area during
the month of May, 1975. The locations of the collection sites
are shown in figure 1. Anemones were removed from the substrate
with a scraper, and sealed in seperate jars to prevent the escape
of copepods during transport back to the lab. All anemones were
kept in acquaria in the lab, with a constant flow of fresh seawater.
Only
anemones that were attached, expanded and sensitive to stimuli
were used in lab experiments.
Field Observations
able 2 lists the different types and locations of anemones
collected with copepods. Copepods generally were more abundant
on subtidal anemones, and were never found on anemones above
mean lower low water mark.
Table 2 also describes the types of copepods found on the
different anemones.
The species of the copepods are not known,
but are designated as distinct by size and color. Table 2 shows
the percentage of anemones with copepods at the different locations.
Behavioral Interactions Between Copepods and Sea Anemones
The average number of copepods observed on inhabited anemones is also
shoun.
Lab Observations
All copepods observed appeared to be cyclopoids (Brady, 1880).
The copepods appeared fully developed and no larvae were observed during
the course of the six week experiment. The copepods are poor swimmers
with legs adapted mainly for crawling on the surface of the anemone.
As copepods crawl over the surface of the anemone, the tentacles move
slightly in response to the tactile stimulus, but no feeding response
is evoked. The large 2mm copepods are capable of rapid movement, but
move infrequently; remaining stationary for up to 2 hours. The 1 mm
copepods are characterized by rapid movements over the entire anemone
surface, rarely remaining stationary for more than a minute.
Experiments:
Advantages to Host and Copepod
To determine if the copepods eat anemone tissue or mucus, excised
tentacles were stained in methylene blue for 40 minutes until both
the tentacle and surrounding mucys were dark blue. A white copepod
placed on the stained preparation in fresh seawater for 24 hours.
was
At the end of the 24 hour period, the copepod's gut had turned a pale
blue, indicating stained material had been injested. Squash preparations
copepods revealed no signs of nematocysts in the copepods.
To defermine if copepods are dependent upon the anemones for sur¬
vival, six copepods were kept isolated from anemones in fresh seawater.
All six copepods died within 10 days. Two of the six died within three
days. Dead copepods were never observed on anemones or in tanks con¬
taining commensal anemones. Other data indicate dead copepods are not
eaten by the host.
Behavioral Interactions between Copepods and Sea Anemones
Lab and field observations were conducted in an attempt to determine
if the anemones benefited or were harmed by the presence of copepods.
tab observations were made for capture and injesting of copepods by
anemones, and dead copepods were fed to anemones to see if they would
pe eaten. Visual comparisons were made in the field between anemones
with and anemones without copepods.
There were no observed differences in appearance between commensal
and noncommensal anemones. Anemones were never observed to capture
their copepods, or copepods that had died and were fed to the anemone.
Copepods that had been crushed were quickly captured and injested.
Feeding experiments were conducted to determine if the anemone's
feeding behavior was modified by the presence of copepods, and to ob-
serve copepod behavior during anemone feeding. It was found that the
presence of copepods did not hinder the anemone's ability to capture
other prey the size of copepods. Tigriopus were instantly captured
and injested by the anemones. When anemones feed of large prey, copepods
are observed to move away from the area where the prey is captured.
At no time were copepods seen on the captured food, or going into or
out of the coelenteron. Copepods that had been coated with limpet
juices were captured and injested by the anemone.
2) Extent of Copepod Immunity
Copepods found on the same anemone species appeared to be species
specific. Several transfers of copepods among anemones of the same
species as the host and among anemones of different species were conducted.
It was found that copepods from all six different species of
anemones were able to be transferred to other anemones of the
Behavioral Interactions Between Copepods and Sea Anemones
same species without harm to the copepods. Anemones from the same
or different areas did not react to intraspecific transfers of
copepods, even if they were previously noncommensal. Anemones
did react to interspecific transfers of copepods, with the excep-
tion of copepod transfers made between Anthopleura elegantissima
and Anthropleura xanthogrammica. In all other transfers, the anemone
elicited a vigorous feeding response toward the copepod, and the cope-
pod displayed escape behavior.
Species Specific Zonation
Preliminary field observation of Tedia lofotensis and T. crassi-
cornis indicated that copepod species were located where their color
matched that of the aneomone. Seven T. lofotensis were collected
and observed in the lab for a period of three weeks. The anemones
were divided into five zones (actinopharynx, oral disc, tentacle base,
tentacles, and column) and copepods of each type were counted and
their locations recorded. Because T. crassicornis did poorly in
the lab, zonation studies were done in the field. Twenty T. crassicornis
were observed on two separate dives. Because of inaccuracy in counting
copepods while diving, the anemones were divided into only three zones
(oral disc, tentacles, and column).
The results are summarized in Tables 3 and 4. They show that
T. lofotensis, the red copepods are found primarily on the tentacles,
were they are the same color as the anemone. White copepods show a
preference for the tentacle base area and the tentacles, but show no
preference between the two areas, which are of different colors.
In the lab, seven red copepods were placed on the oral disc of a
lofotensis, which is a brownish-green in color. Within 30 minutes
five had moved to the tentacles, which are red, and two had moved onto
Behavioral Interactions Between Copepods
and Sea Anemones
the pharynx, which is also red. The copepods maintained these
positions for two hours, when the experiment was terminated.
4) Cueing Towards the Anemone
In the field it was noted that often an anemone with few or
copepods could be found less than three feet away from an
anemone with over 50 copepods. This observation led me to ques¬
tion the method by which copepods spread to new anemones, and how
they come to inhabit anemones only of a particular species.
Four T. lofotensis were placed in seperate tanks that were
entirely white so any movements of copepods off the anemones could
be easily observed. Copepods were then placed in the tank at
distances from one to seven centimeters away. The time taken for
copepods to move to the anemones was recorded.
When placed in the tanks, copepods appeared to swim in a random
manner, or else to merely settle to the bottom of the tank.
there appeared to be no orienting behavior unless the copepod was
brought within .5 cm. of the anemone or actually touched to the
anemone. If brought this close, the copepod would quickly move
to the anemone.
In another experiment, a commensal T. lofotensis was placed
cm. away from a. noncomménsal. Observations were made daily
for
three weeks to determine if any copepods had moved to the
copepodless anemone.
It was found that copepods never spread to the uninhabited
anemone, nor were copepods ever observed swimming off of the
comménsal anemone.
Behavioral Interactions Between Copepods and Sea Anemor
Discussi
Copepods appear to be commensal on the anemones. Experiments finding
that copepods injest anemone mucus, and die when isolated suggest
that the copepods could be dependent upon the anemone mucus for sur¬
vival. The anemones, on the other hand, do not appear to benefit nor
be harmed in any way by the presence of copepods. Being unable to
capture and eat these copepods, the only benefit the anemone might
derive from the relationship would be a removal or cleaning of mucus.
It appears that copepods do not directly eat the food an anemone captures.
Copepods do not travel into the coelenteron, and if they become coated
with the fluids of a captured prey, they may be stung and captured
by the anemone.
The behavior of the anemone is not appreciably modified by the
presence of copepods. Although sensitive to the tactile stimulus of
the copepod, the anemone appears unable to discharge nematocysts, and
does not display the vigorous movements characteristic of a feeding
response. The anemone is not, however, unable to capture all animals
the size of copepods; quickly siezing and injecting animals of similar
or even smaller size.
These copepods show both species specific habitation and immunit,
except when associated with the genus Anthopleura, where the same
copepods are immune to both species. It seems interesting that the
two species of Anthopleura seem more alike in terms of copepod immunity
than
the three species of Tealia. The copepods found on A.elegantissima
and A. xanthogrammica were indistinguishable from each other and were
immune on either Anthopleura species. The three Tealia species, however,
Behavioral Relationships Between Copepods and Sea Anemones
were highly specific to seperate types of copepods. Comparisons of
mucus from the different anemones could shed further light on this
problem. It was also interesting to note that copepods were immune
to all anemones of the same species, even when collected from widely
different areas. (Carton, 1963. Bouligand, 1966)
t was discovered that interspecific transfers of copepods elicit
dual recognition of foreignness by both the anemone and the copepod.
An anemone, when touched by a foreign copepod, immediately exhibits
a vigorous feeding response, yet nematocysts do not discharge. The
anemone somehow 'recognizes" the copepod as prey, yet the cue causing
nematocyst discharge is lacking. The copepod also exhibits a swimming
avoidance behavior away from the anemone. This swimming behavior was
never seen by copepods on their host anemone. Experiments using ex¬
cised anemone tentacles show that copepods will cling tenaceously to
tentacles of their host, yet will remain indifferent towards tentacles
of a different anemone species. It appears then, that the copepod's
avoidance behavior is a response to the anemone's sudden movements,
and not avoidance of the anemone tissue itself.
Copepods living on Tealia lofotensis and Tealia crassicornis showed
a preference for zones in which their color matched that of the anemone.
jecause white copopods inhabiting T. lofotensis are not camouflaged
anywhere on the anemone, one would not expect these copepods to prefer
any particular zone. Table 3 shows that the white copepods show an
equal preference for either the tentacle bases or the tentacles of the
of the anemone, which are brown-green and red respectively.
This color blending of copepods to anemones was shown in the other
anemones as well. Copepods on all six species of anemone were generally
found to be the same color as the anemone. Copepods with blue egg
sacs were found on blue Epiactus prolifera, light green copepods were
Sehavioral Interactions Between Copepods and Sea Anemones
found on subtidal A. elegantissima, and white copepods were found at
the white bases of T. coriacea tentacles. The manner in which the
copepods assumed the color of the anemone was not determined. No larvae
were observed in lab, so their color is not known. It was shoun,
however, that the copepods cannot change color within one week. Red
copepods that were either isolated or placed on white tentacles never
showed a color change. Copepod predation was never observed in the field
but certain fish and crustacea are often in close association with
anemones. This color matching might afford the copepods some prote
tion against these predators. (Ross, 1974)
It is intriguing that none of the copepods worked with display
visual or chemical cueing towards an anemone at a distance greater
than .5 cm. This would indicate that the spread of copepods to new
anemones is accomplished during another stage in the copepod's life
cycle. (Dudley, 1966). It would be interesting to know the method
in which the copepod larvae seek out specific species of anemones.
Sehavioral Interactions Between
Copepods and Sea Anemones
Acknowledgements
wish to thank Chuck Baxter for his helpful
criticism during
the writing of this paper and a special thanks to all the
were so quick to offer help when it was needed.
Behavioral Relationships Between Copepods and Sea Anemones
Literature Cited
Recherches Recentes sur les Associes aux
Bouligand, Y. 1966.
Anthozoaire. p.267-306. In Rees, W. J. (ed.) The Cnidaria
and their Evolution. Proc. Symp. Zool. Soc. Lond. 16.
Academic Press, N.Y.
Brady, George Stewardson. 1880.
A Monograph of the Free and
Semi-parasitic Copepods of the British Islands. Roy. Soc.
London.
Carton, Y. 1963. Etude de la Specificite Parasitaire chez 1.
Actinae (copepoda cyclopoida). C. R. Sebd. Seanc. Acad.
Sci. Paris. P. 256.
Dudley, P. 1. 1966. Developement and Systematics of Some Pacific
Marine Symbiotic Copepods. The Biology of the Notodelphy-
idae. Univ. Wash. Publ. Biol. 21: vt. 288p.
Hand, Cadet H. 1956. The Sea Anemones of Central California.
Wasserman Journal of Biology, v.12. no.3. v.13 no. 1-2.
Ross, D. M. 1974. Behavior Patterns in Associations with Other
Animals. p.281-312. In Muscatine and Lenhoff (eds.).
Coelenterate Biology: Reviews and New Perspective.
Academic Press, N. Y.
c
ure Legend
1) A map of the Monterey bay region, showing the five collection
sites.
3)
4)
Table Legend
Table showing zonation behavior of red and white copopods on
lealia lofotensis. When the anemones were fully expanded
no copepods were observed on the column. No counts were made
when the anemones were closed.
Zonation behavior of copepods on Tealia crassicornis. Only
anemones that were fully expanded were counted.
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Copepod I
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Location
pharynx
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entacl
base
tentacle
colum
tota.
pharynx
oral
disc
tentacle
base
tentacles
column
total
Observe
Cope
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Location
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and
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tentacles
column
total
No.
Observed
294
of Total
81.2