Hydroides elegans is a small tube-forming serpulid polychaete worm
commonly found in hard-bottom coastal and estuarine fouling communities. The
species is present in the IRL and elsewhere in Florida but is an introduced
species not native to the United States.
Adult H. elegans have 65-80 body segments and an opercular crown with
14-17 spines, each with 2-4 lateral processes and a medial row of short
serrations. The opercular crown also has a small central spine. The
calcareous tubes produced by H. elegans are white and sinuous,
sub-trapezoidal in cross-section and possessing 2 longitudinal ridges and many
transverse wrinkles (Imajima 1976, NIMPIS 2002).
Potentially Misidentified Species
Kaplan (1999) estiamates 10-15 Hydroides species occur in the South
Atlantic and Caribbean. Individual species distributions are uncertain and
identification to species level is difficult and requires examination of the
details of the setae and opercular crown. NIMPIS (2002) indicates that the
collar setae are a key feature for differentiation and notes that in H.
elegans the collar setae are bayonet-shaped and have a denticulate
(toothed) subapical zone.
HABITAT AND DISTRIBUTION
Hydroides elegans is subtidal to low intertidal fouling organism that
utilizes a variety of natural and artificial hard substrates including oyster
and rock reefs, wood, concrete pilings, aquaculture cages, intake pipes, and
vessel hulls. It is now widely distributed in the topics and subtropics, particularly in harbor fouling
communities. The introduced range of the species includes coastal areas on
both sides of the Atlantic (NIMPIS 2002). The species was established in parts
of the southern Caribbean as early as the mid 1950s, and it was confirmed
present in Florida in 1971 (Carlton and Ruckelshaus 1997).
Occurrence on IRL collection blocks
in locations ranging from Cape Canaveral to south Hutchinson Island suggests that
Hydroides elegans is established and widespread in the Lagoon, although the
relatively stenohaline character of the early life history stages (see below)
may limit population distribution.
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
Imajima (1976) reports a maximum body length of 20 mm and a maximum tube length
of up to 80 mm. The maximum width at the thorax is 1.5 mm.
H.A. ten Hove, annelid expert from the Zoological Museum of the University of
Amsterdam, has cited Hydroides elegans as probably the most widespread
harbor-fouling serpulid worm of the worldwide tropics and subtropics (BioNet Annelid Archives).
Bagaveeva and Zvyagintsev (1999) report that H. elegans biomass may
reach several kg/m² by late summer in the northwestern Sea of Japan where it is
also believed to be an introduced species.
Reproduction in Hydroides elegans is sexual and the the sexes are separate
(NIMPIS 2002), although some sources (e.g., CSIRO 2001) report the species as
hermaphroditic. Gametes are released to the environment and fertilization is
external (Nishi 1992). Qiu and Qian (1998) report that most reproductive
individuals had tube lengths of 12 mm or more and average fecundity ranged
between 1100-9050 oocytes per female.
Reproductive seasonality varies by location and has been reported as occurring
from late summer to early winter in both hemispheres with some populations in
milder climates capable of year-round reproduction (Miura and Kajihara 1984,
Udhayakumar and Karande 1996, Lewis and Smith 1991). Qiu and Qian (1998)
suggest salinities above 25 ppt and temperatures above 20°C are requisite
conditions for reproduction.
A planktonic larval period persists for less than a week before
settlement-stage Hydroides elegans individuals recruit into hard benthic
habitats (NIMPIS 2002).
The global distribution of Hydroides elegans encompasses a temperature range of
approximately 13-30°C (Qiu and Qian 1998, Kocak and Kucuksezgin 2000, NIMPIS
Kocak and Kucuksezgin (2000) report that Hydroides elegans in the Aegean Sea
occur at salinities as high as 42ppt. Experimental work by Mak et al. (1980)
revealed mass mortality after 45 hours at a salinity 0f 15 ppt and Qiu and Qian
(1998) indicate that young animals died within 8 days of settlement at 20ppt.
They suggested that low seasonal salinity could be an important limiting factor
to the species. The reported relative intolerance of low salinity conditions,
especially in young individuals, may similarly be an important factor limiting
the occurrence and distribution of H. elegans in the IRL.
H. elegans is relatively tolerant of hypoxic conditions. Udhayakumar and
Karande (1996) report survival at oxygen concentrations of 1.55 mg/L in
Bombay, India and Kocak and Kucuksezgin (2000) report survival at 1 mg/L in the
Hydroides elegans is a suspension feeder. Adult animals filter phytoplankton
and suspended organics from the water column and Udhayakumar and Karande (1996)
indicate that diatoms were an important dietary component in the animals they
studied. Larvae also feed on water column phytoplankton. Laboratory-cultured
H. elegans larvae have been reared on Dunaliella and
Isochrysis (NIMPIS 2002).
The requirement of Hydroides elegans for suitable hard substratum leads to
association with various organisms that provide these substrates such as the
eastern oyster Crassostrea virginica.
Carlton and Ruckelshaus (1997) and NIMPIS (2002) suggest Australasia and the
Indian Ocean as possible centers of origin for the species. The centers of
origin for cosmopolitan species are difficult to determine with certainty, but
substantial evidence suggests Australia as a likely historical source for Hydroides elegans. ten Hove has presented much of the evidence (ten Hove 1974, BioNet Annelid Archives) and it is summarized here.
The species was first described from Sydney Harbor by Haswell (1883), although
by 1888 it had also been found in the Italian Mediterranean (Zibrowius 1991).
The local distributions of the species in these two areas were very different,
however, with Mediterranean populations restricted to harbor and lagoonal
communities while historic Australian populations occurred as part of natural
coastal communities at a depths of around 20 m (Allen (1953). Moran and Grant
(1984) suggest that the more recent rise to prominence of H. elegans in
Australian harbor fouling communities is the result of increased pollution
loads in the harbors. The natural occurrence of a number of Hydroides
congeners in Australia adds weight to the argument implicating this part of the
world as the original source of H. elegans.
Ship hull fouling is widely suggested as the most important transport vector in
the spread of H. elegans, with accidental transport in shipments of
harvested wild or cultured bivalves noted as a secondary source of introduction
The first report establishing the presence of H. elegans in Florida
dates to 1971 (Zibrowius 1971, Carlton and Ruckelshaus 1997). ten Hove notes
his discovery of H. elegans in Curaçao at the same time. He also
notes, however, that reexamination of earlier Curaçao collections (from a
Venezuelan ship hull and from floating buoys) from as far back as the mid-1950s
reveals the presence and probable establishmentof H. elegans at that
time in Curaçao.
Potential to Compete With Natives
Hydroides elegans competes with co-occurring fouling community species for
space, food, and possibly other resources. For example, NIMPIS (2002) reports
that competition by H. elegans for food and oxygen has been implicated
in up to 60% mortality for cultured oysters in Japan. The native North
American congener H. dianthus has been similarly implicated in the
mortality of juvenile oysters from smothering.
Additionally, tube-forming species like H. elegans are considered to be
"ecosystem engineers" capable of modifying the habitats in which they occur.
Architectural habitat modification due to the presence of calcareous tubes
would be expected to affect community structure at localized scales.
Possible Economic Consequences of Invasion
Direct economic impacts of these tube-dwelling biofoulers include the cost of cleaning ship
hulls, aquaculture gear, and other submerged structures. Other costs include
decreased operational efficiency of fouled vessels due to drag and of water
intake pipes due to clogging (MIMPIS 2002).
The economic impact of Hydroides elegans in the IRL is undetermined.
Bagaveeva E.V., and A.Y. Zvyagintsev. 1999. The introduction of polychaetes
Hydroides elegans Haswell, Polydora limicola Annenkova,
Pseudopotamilla ocelata Moore into the north-western part of the Sea of
Japan. Abstract. Paper presented at the First National Conference on Marine
Bioinvasions January 24-27, 1999, Massachusetts Institute of Technology,
Carlton J.T. and M.H. Ruckelshaus. 1997. Nonindigenous marine invertebrates and
algae. Pp 187-201 in: Simberloff D., Schmitz D.C., and T.C. Brown (eds).
Strangers in Paradise. Island Press, Washington DC. 467 p.
CSIRO 2001. Hydroides sanctaecrucis Marine Pest Information Sheet.
Centre for Research om Introduced Marine Pests (CRIMP) Infosheet 15.
Imajima M. 1976. Serpulinae (Annelida:Polychaeta) from Japan. I. The genus
Hydroides. Bulletin National Science Museum, Series A (Zoology)
Kaplan E.H. 1999. A Field Guide to Southeastern and Caribbean Seashores: Cape
Hattaras to the Gulf Coast, Florida, and the Caribbean. Peterson Field Guide
Series. Houghton Mifflin Company, NY. 425 p.
Kocak F., and F. Kucuksezgin. 2000. Sessile fouling organisms and environmental
parameters in the marinas of the Turkish Aegean coast. Indian Journal of Marine
NIMPIS. 2002. Hydroides elegans species summary. CSIRO National
Introduced Marine Pest Information System (Hewitt C.L., Martin R.B., Sliwa C.,
McEnnulty, F.R., Murphy, N.E., Jones T. and S. Cooper Eds). Available online.
Qiu J. and P. Qian. 1998. Combined effects of salinity and temperature on
juvenile survival, growth and maturation in the polychaete Hydroides
elegans. Marine Ecology Progress Series 168:127-134.
ten Hove H.A. 1974. Notes on Hydroides elegans (Haswell 1883) and
Mercierella enigmatica Fauvel 1923, alien serpulid polychaetes
introduced into the Netherlands. Bulletin Zoologisch Museum Universiteit van
Zibrowius H. 1971 Les especies Mediterraneenes du genre Hydroides
(Polychaeta, Serpulidae) remarques sur le pretendu polymorphisme de
Hydroides uncinata. Tethys 2:691-746.
Zibrowius H. 1991. Ongoing modification of the Mediterranean marine fauna and
flora by the establishment of exotic species. Mesogee 51:83-107.