Fisheries Science 62(3), 400-403 (1996)
Age-estimation of the Christmas Tree Worm Spirobranchus giganteus
(Polychaeta, Serpulidae) Living Buried in the Coral Skeleton
from the Coral-growth Band of the Host Coral
Eijiroh Nishi*1 and Moritaka Nishihira*2
*1Natural History Museum and Institute , Chiba, Aoba
955-2, Chuo, Chiba 260, Japan
*2Biological Institute , Graduate School of Science, Tohoku University,
Aoba, Sendai 980-77, Japan
(Received September 25, 1995)
The tubicolous polychaete, Spirobranchus giganteus lives buried in coral skeletons. Its age and lon
gevity were estimated indirectly from the annual coral-growth rings of the host coral counted on soft X
rays radiographs. Since the polychaete tube grows 0.2 to 1 mm per year in orifice diameter, some had
lived more than 10 years, and a few had lived more than 40 years. The application of soft X-rays for age
determination of coral associated polychaete is useful for determining the correct age.
Key words: tubicolous polychaete, Spirobranchus giganteus, coral-growth ring, age and
Polychaetous annelids are used as fish bait and are an im
portant component of fouling organisms. Serpulid poly
chaete is representive of the latter, and are well studied in
fisheries (e.g., Okamoto et al.1)). Spirobranchus giganteus
appears in intertidal to subtidal zones as a typical species
of coral reef polychaetes.
There is little accurate data on the longevity of poly
chaete worms,2,3) mainly because of the difficulty in
monitoring them in the field, especially for long-living
large species. Among such species, Spirobranchus gigan
teus is the most remarkable, mostly living buried in coral
We assumed it is possible to estimate the age of S. gigan
teus by counting the annual growth bands in the coral
skeleton overlaying polychaete tubes. Soft X-radiographs
of slabs cut along the growth axis of many massive corals
displayed alternating dark and light bands which outline
the former positions of the outer surface of the colony.5)
These dark and light bands represent variations in the
density at which the skeleton was deposited. A pair of
bands-high density and low density (i.e., light plus dark
bands)-represents one year's growth.5-8) The annual nature
of the banding pattern has since been confirmed for a varie
ty of massive corals from different parts of the world using
various dating techniques.5-8)
Spirobranchus giganteus and S. polyceros have been
found in many coral species, and the age of the latter spe
cies was roughly estimated from the coral-growth data.9)
Spirobranchus giganteus grows on coral surfaces covered
by living tissues, and its tube is always covered by coral
skeleton. Thus, the orifice of the serpulid tube is always
present on the surface of living coral.
Spirobranchus giganteus occurs on Porites spp. in
Okinawa.10) We collected some massive Porites with poly
chaetes and estimated their annual growth.
Materials and Methods
Ten coral colonies of Porites lutea with 11 polychaete
worms were collected at Zampa Cape, central Okinawa Is
land, from June through September 1993, and in Novem
ber and December 1994. Coral skeletons were dried after
rinsing with synthetic detergent. Coral skeletons were
sliced into 2 to 5 mm thick slices at the area including the
polychaete tube, then radiographed under soft X-rays
(Softex, MB3, Hitachi). The exposure was 40 kVp, 3 mA,
for 4 to 5 minutes. The source to subject distance was 50
cm. The areas of interest of these soft X-radiographs are
shown in Fig. 1.
Coral-growth bands were usually formed at 0.2 to 1.0
cm intervals, with a white band usually 0.2 to 1.0 cm in
thickness and a black band 0.1 to 1.0 cm in thickness
(Figs. I and 2), and coral had probably grown 0.5 to 1.0
cm per year. The growth increment of the polychaete tube
was usually 0.2 to 1.0 mm per year in orifice diameter
(ranged from 0 to 1.2, average 0.6 mm, N=31), and the
growth rate varied greatly among individuals and between
years (Fig. 3).
Usually we prepared one or two slices per worm, with a
maximum of 10 per worm, and the slice included the
whole or only a part of the tube (Fig. 1). If the slice includ
ed the whole tube cut longitudinally as shown in Fig. 1(A
and B), the exact growth dates could be determined (Fig.
3). If the slice included two openings of the same tube as
shown in Fig. 1D, the growth rate between the two open
ings could be determined accurately (Fig. 3). Some slices,
however, contained only one opening clearly cut horizon
tally, so we could only compare the size of recent tube
Age Estimation of a Tropical Tube Worm 401
Fig. 1. Photos of slices and soft X-ray micrographs of coral skeletons
of Porites lutea and tubes of Spirobranchus giganteus; arrows show
one year representing annual growth.
A, photo of the slice of worm D showing a longitudinal section; B,
soft X-ray micrograph of the slice of worm D; C, close-up view of
the slice of worm D, showing the settlement site of the worm on the
coral skeleton and the beginning part of the tube buried in the coral
skeleton; D, soft X-ray micrograph of worm C, showing two open
ings of the same tube. a and b, opening of worm C; bb, beginning
part of the tube buried in the coral skeleton; s, settlement position of
the worm; t, tube of Spirobranchus.
Openings on the coral surface with the opening that ap
peared in the slice. (Figure 3 shows that the diameter of the
Fig. 2. Radiographs of coral skeletons of Pontes lutea and tubes of
Arrows show one year representing annual growth, bars with an
arrow show a pair of white and black bands, T and S show the tube
of serpulid and surface of the coral colony. Upper radiograph shows
colony F, lower shows colony E.
opening and the number of growth bands between the re
cent tube opening and the opening in the slice.)
Some examples of the growth of different individuals
over time are depicted in Fig. 3. Worm A grew slowly,
with the orifice diameter increasing about 2.5 mm from
1989 to 1994 (Fig. 3). On the contrary, worms C and D
grew rapidly, their orifice diameters increasing 4 mm over
5 years (Fig. 3). Worm B did not grow during 1985 and
1986 (Fig. 3). Worm E grew very slowly, and its age was es
timated at more than 40 years (Fig. 3, bottom graph, see
also Fig. 2, bottom radiograph).
On the slices of coral skeleton, it was in some cases possi
ble to trace the tube back to the settlement position of the
polychaete. On such slices, the recruitment site could be de
termined always on the dead parts of the coral skeleton.
Three worms formed a calcareous inner wall (tabulae) at
the middle portion of the tube (as in other serpulids, see
Lommerzheim11)), below which the posterior portion
could not be traced back because of damage to the tubes.
402 Nishi and Nishihira
Fig. 3. Growths in orifice diameter of Spirobranchus giganteus esti
mated from annual growth bands of coral skeletons
Bottom graph shows the growth of worm E which showed the
slowest and longest growth.
This study showed that Spirobranchus lived for more
than 10 years, and sometimes more than 40 years . The an
nual tube growth in orifice diameter was estimated at 0 .2
to 1.0 mm, so that a worm with an orifice diameter of
> 10 mm is probably at least 7 to 10 years old. Tube orifice di
ameters recorded in the field were mostly between 3 to 12
mm in Okinawa,12) with the maximum size being > 14
mm.") Therefore, some Spirobranchus live for 10 or more
years, and some live beyond that age.
It is very impressive that a worm, with a body length not
surpassing 10 cm, can live for more than 40 years. But the
congener associated with living corals has been reproted to
live a very long life; Spirobrachnus polycerus, smaller
(body length up to 5 cm) than S. giganteus, lives more than
10 years,9) and S, giganteus was estimated to live more
than 20 years in Australia. 14) The massive Porites has a lon
ger life span, reaching a diameter of more than 5 m (pers.
obs. by M. Nishihira), indicating a life of more than 100
years, because the annual growth rate of massive corals is
usually 5 to 15 mm.") The longer life span of host corals
seems to be related to the longer life of Spirobranchus .
The worm E, which has the maximum longevity, is prob
ably a rare case, and we can estimate the longevity of this
species to be usually 10 to 20 years, and rarely 30.
The growth rate of the worm represented by tube orifice
diameter varied greatly as shown in Fig. 3. It is likely that
the increase in tube diameter is affected by the available
food, and this parameter seems to depend on the habitat
or position of the colony. Dai and Yang16) studied
Spirobranchus at Taiwanese coral reefs, and concluded
that they are distributed in groups or randomly on the
coral colony. Such a distribution pattern is probably relat
ed to the growth pattern of the worms. The worm body
length and the tube orifice diameter are correlated,10) but
the tube orifice diameter seems unlikely to be the key
growth parameter for the worm.
The present study contained three basic assumptions: 1)
Spirobranchus cannot bore into the coral skeleton, 2) it
does not extend its tube beyond the surface of the coral
skeleton, and 3) a single worm occupies one tube, and does
not move to other tubes. The second assumption is proven
by the fact that the tube opening is always on the living sur
face of the coral. The observations of more than 100
worms revealed that their tubes were certainly present on
the coral surface (unpublished data). The first assumption
is valid, because Smith") studied the larval settlement of S.
giganteus and concluded that they settled on dead areas of
coral skeletons and extend their tubes directing into the liv
ing part of the coral. Thus we can conclude that Spirobran
chus does not bore into coral skeletons. When the worm
was pulled out from the tube, it could not secrete a new
tube, and the worm did not move to other tubes (pers.
obs., by E. Nishi). Therefore, the third assumption that
the worm does not exchange its tube, is also valid. Some
times, the juveniles appeared on the inner surface of a
dead empty tube, and the small worms were rarely found
in empty adult tubes (pers. obs. by E . Nishi). However,
the tubes of juvenile and immature worms are extremely
small, and are easily distinguished from adult tubes by the
naked eye. If the small worm lived in an empty adult tube,
the calcareous tube of the juvenile remained as a remnant,
so we did not include such tubes that contained 2 or more
worms in the present study.
As a conclusion, the present method is useful for es
timating the longevity of polychaete buried in living coral
skeletons, but the juveniles in adult empty tubes cannot be
studied by this method to determine the age and longevity
of worms. This method is also applicable to animals which
have a similar mode of coral utilization , such as Dendropo
Acknowledgments We wish to thank Dr . H. Yamashiro, Radioisotope
Institute, University of the Ryukyus, for his technical help in soft X-ray
usage, Dr. Harry A. ten Hove, for sending us some useful references, and
Dr. D. Barnes, Australian Oceanographic Institute , and anonymous re
viewers, for their useful comments on the manuscript . This work was
partly supported by a Grant-in-Aid for Scientific Research on Priority
Area (#204) "Dispersal Mechanisms ," and Priority area (#319), Project "S
ymbiotic Biosphere: An Ecological Complexity Promoting the Coexis
tence of Many Species" from the Ministry of Education , Science and Cu1t
1) K. Okamoto, A. Watanabe , H. Watanabe, and K. Sakata: Induc"
tion of larval metamorphosis in serpulid polychaetes by L-DOPA
and catecholamines . Fish. Sci., 61, 69-74 (1995).
2) S. V. Smith and E. C. Haderlie: Growth and longevity of some cal
careous fouling organisms, Monterey Bay , California. Par. Sct., 23
, 447-451 (1969).
3) B. H. Grave: Rate of growth , age at sexual maturity, and duration
of life of certain sessile organisms , at Woods Hole, Massachusetts.
Biol. Bull., 65, 375-386 (1933) .
4) H. A. ten Hove: Serpulinae (Polychaeta) from the Carribean: I, the
genus Spirobranchus. Stud. Fauna Curacao, 32, 1-57 (1970).
Age Estimation of a Tropical Tube Worm 403
5) D. W. Knutson, R. W. Buddemeier, and S. W. Smith: Coral
chronometers; seasonal growth band in reef corals. Science, 177,
6) R. W. Buddemeier, J. E. Maragos, and D. W. Knutson: Radio
graphic studies of reef coral exoskeletons; rates and patterns of
coral growth. J. Exp. Mar. Biol. Ecol., 14, 179-200 (1974).
7) D. J. Barnes: Growth in colonial scleractinians. Bull. Mar. Sci., 23,
8) J. M. Lough and D. J. Barnes: Intra-annual timing of density band
formation of Porites coral from the central Great Barrier Reef. J.
Exp. Mar. Biol. Ecol., 135, 35-57 (1990).
9) J. Marsden: Factors influencing the abundance of seven-spined mor
photype of Spirobranchus polycerus (Schmarda), (Serpulidae), on
uptight blades of hydrozoan coral, Millepora complanata. Mar.
Biol., 115, 123-132 (1993).
10) E. Nishi and T. Kikuchi: Preliminary notes on the ecology of
Spirobranchus giganteus at Okinawa. Pub. Amakusa Mar. Biol.
Lab., 12, 45-54 (1996).
11) A. Lommerzheim: Monographische bearbeitung der Serpulidae
(Polychaeta, sdentaria) aus dent Cenoman (Oberkreide) am Sudwes
trand des Munsterlander Bekkens. Decheniana (Bonn), 132, 110
12) E. Kinjo: Population ecology of Spirobranchus giganteus at
Kudaka Island, Okinawa. Unpublished B. thesis, Univ. Ryukyus,
Okinawa, 1992, p. 120 (in Japanese).
13) E. Nishi: Life of tropical serpulid worm remained in coral skeleton.
Iden 49, 72-74 (1995) (in Japanese).
14) R. Smith: Photoreceptors of serpulid polychaetes. P.h. D. thesis,
University of North Queensland, Townsville, 1985, p. 670.
15) D. J. Barnes and J. M. Lough: The nature of skeletal density band
ing in scleractinian corals: fine banding and seasonal patterns. J.
Exp. Mar. Biol. Ecol., 126, 119-134 (1989).
16) Cheng-Feng Dai and Hsiao-Pei Yang: Distribution of Spirobran
chus giganteus corniculatus (Hove) on the coral reefs of Southern
Taiwan. Zool. Stud., 34, 117-125 (1995).
17) R. Smith: Development and settling of Spirobranchus giganteus
(Polychaeta; Serpulidae). Proc. Ist Polychaete Conf., Sydney, pp.