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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

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Abstract

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. longevity 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 skeletons .4)
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
longevity
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
skeletons .4)
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.
Results
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
Spirobranchus giganteus.
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.
Discussion
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
ma maxima.
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
ure, Japan.
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... In case of post mortem coral encrustation on a dead serpulid one would expect to see flattened tubes base which characterizes all encrusting serpulids (see Jäger 1983). However, there is no function and therefore no need for flattened tube base in serpulids growing within coral substrate such as Spirobranchus giganteus and S. cor niuculatus (Nishi & Nishihira 1996, 1999 or sponge substrate such as Hydroides spongicola (Bastida-Zavala & ten Hove 2002). The orientation of one serpulid is strongly tilted within the coral and very similar to the life position of Spirobranchus corniuculatus in the skeleton of Porites lutea at coral reefs in Okinawa (Nishi & Nishihira 1996;Nishi & Nishihira 1999). ...
... However, there is no function and therefore no need for flattened tube base in serpulids growing within coral substrate such as Spirobranchus giganteus and S. cor niuculatus (Nishi & Nishihira 1996, 1999 or sponge substrate such as Hydroides spongicola (Bastida-Zavala & ten Hove 2002). The orientation of one serpulid is strongly tilted within the coral and very similar to the life position of Spirobranchus corniuculatus in the skeleton of Porites lutea at coral reefs in Okinawa (Nishi & Nishihira 1996;Nishi & Nishihira 1999). Modern Spirobranchus corniculatus (as S. giganteus) is living in coral colonies of Porites in coral reefs at Okinawa and it is among the longest-lived annelids, some exceeding 20 years of age (Nishi & Nishihira 1996). ...
... The orientation of one serpulid is strongly tilted within the coral and very similar to the life position of Spirobranchus corniuculatus in the skeleton of Porites lutea at coral reefs in Okinawa (Nishi & Nishihira 1996;Nishi & Nishihira 1999). Modern Spirobranchus corniculatus (as S. giganteus) is living in coral colonies of Porites in coral reefs at Okinawa and it is among the longest-lived annelids, some exceeding 20 years of age (Nishi & Nishihira 1996). Thus, it is likely that large serpulids in Messinian corals may also have had long lasting relationship with their host. ...
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The Serpulidae are a large family of sedentary polychaetes, characterized by a calcareous habitation tube, which they cannot leave. The calcium carbonate tube is in the form of both aragonite and calcite, in fairly constant ratio for each taxon. Tubes are cemented firmly to any hard substrate (in only few species tubes are free). Although in the majority of the species the tubes encrust the substrate for all their length, the distal part may eventually detach and grow erectly. Certain species in dense populations build tubes vertical to the substrate in clumps and cement the tubes to each other. This gives serpulids the capability of forming reef-life structures when densely settling. Despite the relative smallness of the individual tubes (rarely longer than 15 cm and wider than 1 cm), such reef-like structures may cover tens of m², with a layer more than 1 m thick. Serpulid reefs can be divided roughly into seven groups, according to the building modality and the type of habitat they occupy: (i) pseudocolonies; (ii) littoral belts; (iii) subtidal to deep-water reefs; (iv) reefs in coastal lakes and harbours; (v) brackish water reefs; (vi) tapestries in freshwater caves; (vii) biostalactites inside marine caves. The role of serpulid reefs in the ecosystems they inhabit is multifarious and may be distinguished in functions (biomass and production, benthic pelagic coupling, resistance and resilience, reproductive and survivorship strategies, trophodynamics, bioconstruction, living space and refuge, nursery, sediment formation and retention, food for other species, carbonate deposition and storage) and services (water clearance, reef associated fishery, cultural benefits). On the other hand, many serpulids are important constituents of biological fouling, and their calcareous masses damage submerged artefacts, causing huge economic costs. Positive and negative roles of serpulid reefs need to be compared with common metrics; the overall balance, however, is still to be assessed.
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Eight neuroactive molecules were examined for their larval metamorphosis-inducing activities in three species of serpulid polychaetes, Hydroides ezoensis, Pomatoleios kraussii, and Ficopomatus enigmaticus. L-3,4-dihydroxyphenylalanine (L-DOPA) and D-DOPA induced larval metamorphosis in all species, while dopamine did not. Epinephrine and norepinephrine also induced larval metamorphosis in H. ezoensis and P. kraussii. Approximately 58-67% of H. ezoensis larvae metamorphosed when exposed to L-DOPA at concentrations of 3 x 10⁻⁶-1 x 10⁻⁵M, while D-DOPA induced 43-44% metamorphosis at 2 x 10⁻⁵-3 x 10⁻⁵M. Dose-dependent induction by L-DOPA and low activity of the enantiomer suggest the possibility of receptor mediation in metamorphosis induction by L-DOPA. Because of the delayed reaction and the absence of tube formation, L-DOPA is thought to act not on epithelial chemo receptors but to affect other pathways of metamorphosis. Competence for metamorphosis in H. ezoensis by L-DOPA fluctuated with larval age and two peaks were observed on the 5-6th and 9-1lth days after fertilization. © 1995, The Japanese Society of Fisheries Science. All rights reserved.
Article
Larvae were reared in the laboratory between 28o and 30oC. Settlement was achieved after 11-12 days. Larvae swim and feed actively, and are positively phototactic during the planktonic stage. Prior to settlement, the larval worms pass through a distinct searching phase. Larvae would only settle and construct tubes if provided with fragments of living Porites coral. In these cases settlement was rapid and always on the non-living edge of the coral. Juvenile worms are incorporated within the expanding coral skeleton. -from Author
Article
X-radiographs were made of vertical slices through the centers of 47 hermatypic coral colonies collected at Eniwetok Atoll, Marshall Islands. The image thus obtained are useful for the study of colony geometry, development, and response to damage.Comparison of radioactive inclusions of known age with previously reported cyclic skeletal density variations normal to the axis of growth confirms the annual nature of the density banding. Growth rates based on density bands and radioactivity inclusions are calculated for all 47 specimens, and measurements of the individual ‘growth bands’ are presented for 25 of them.Bulk densities measured by X-ray transmission ranged from 1.0 to 2.2 g/cm3, with an average range of 1.3–1.6 g/cm3. Intra-specimen skeletal densities typically vary by 10–30%; the period of high density skeletal deposition appears to coincide with the season of higher rainfall and warmer surface water at Eniwetok. Pigment residues left by boring algae are more commonly found in low density portions of the skeletons, but this distribution is believed to result from rather than cause the variations in the density of the deposited aragonite.Linear growth rates for the same specimen vary by factors of two or more from year to year, but the 25 specimens studied did not show a common pattern in the linear growth rate. Other than showing some general trends in growth as a function of species and depth, linear growth rates do not appear to be a particularly informative parameter.The density and growth rate variations are important factors in the measurement of coral growth and metabolism, and to the study of environmental controls of coral growth.
Article
X-radiographs were made of slices cut from the growth axes of two 0.4–0.5 m diameter colonies of Parites lobata, and of a slice cut from a 720 mm long core drilled from the growth axis of a large colony of P. solida. X-radiographs of the core-slice of P. solida were made with the slice tilted lengthways at several different angles. The annual density banding patterns for the two colonies of P. lobata revealed that one grew exceptionally quickly (≈ 19 mm · yr−1) while the other grew more slowly than is usual ( ≈ 8 mm · yr −1). The fast-growing colony maintained a smooth outer surface while the slower-growing colony displayed the more usual bumpy outer surface throughout most of its growth. X-radiographs of the smooth-surfaced fast-growing colony of P. lobata showed a series of alternating dense bands ≈ 1 mm wide and less dense bands up to 3 mm wide. Similar fine bands have been previously reported as lunar banding within the familiar annual density banding pattern in massive corals of one dense band and one less dense band. An annual pattern appeared to be present as groupings of the fine dense bands. The fine bands were clearly displayed because the colony grew unusually quickly, and because it maintained a relatively smooth outer surface. As a result, the fine bands were aligned, through the thickness of the skeletal slice, with the X-ray beam that displayed them. Fine bands were not so apparent in X-radiographs of the bumpy-surfaced colony because they were seldom aligned with the X-ray beam. The annual banding pattern in Porites, and in many, if not all, massive corals, appears to be composed of such fine bands. The fine bands may not necessarily represent lunar periodicity. The thickness of slices removed from colonies for X-radiography, together with the alignment and curvature of fine bands within the slices, tends to merge or overlap the X-ray image of individual fine bands and, as a result, emphasizes seasonal patterns in their width, frequency and, perhaps, density. The fundamental nature of the fine banding pattern was demonstrated by X-radiographs of the core-slice of P. solida taken at different angles. At certain angles, the fine bands were displayed in regions where, at other angles, only the familiar annual density pattern had been seen. Fine bands appear to be generated at the outer growth surface of colonies and may represent a direct and immediate response to environmental factors.
Article
This study, on the seven-spined morphotype of Spirobranchus polycerus, a serpulid polychaete commensal with the hydrozoan coral Millepora complanata Lamarck examines live worm abundance, net recruitment and the probability of mortality, on single blades of coral at four Barbados fringing reefs, Heron Bay (HB), Greensleeves (G), Sandridge (S) and Six Men's Bay (SMB). Variation in the number of worms blade-1 over the part 5 to 12 yr, is explained largely by variation in mortality at HB, and largely by variation in recruitment at SMB. At G and S the relative importance of these two factors appears to have shifted with time. A smaller number of worms blade-1 at SMB than at HB, G or S, may be a consequence of a recruitment limited to the past 1 to 4 yr, which, in turn, may partly explain the interdependence of effects of reef and blade size class on recruitment and mortality. The relationship between level of recruitment and blade base perimeter suggests that the availability of recruits has been consistently high at HB over the past 5 to 12 yr and has increased at G and S in the past 1 to 4 yr. The situation is consistent with a worm population gradually extending northward, dependent on a pool of larvae to the south and limited by a tendency to lose larvae in the north west drift. Because of periodic destruction of tall coral blades in heavy seas, mortality in the seven-spined S. polycerus is, in part, a result of the commensal relationship between the polychaete and the coral. Selection for simultaneous hermaphroditism may be a response to the short life-span of the seven-spined form of S. polycerus and the isolation of breeding individuals resulting from the natural destruction and discontinuous distribution of the host coral.