Teredo navalis

Taxon

Family /Order/ Class/ Phylum

Teredo navalis Linnaeus 1758

Teredinidae / Myoida / Bivalvia / Mollusca

COMMON NAMES (English only)
Common shipworm
Naval shipworm

SYNONYMS
Pholas teredo Mueller 1776
Teredo vulgaris Lamarck 1801
Teredo sellii van der Hoeven 1850
Sellius marina Jeffreys 1860
Teredo japonica Clessin 1893
Teredo beachi Bartsch 1921
Teredo beaufortana Bartsch 1922
Teredo novagliae Bartsch 1922
Teredo sinesis Roch 1929
Teredo pocilliformis Roch 1931
Teredo borealis Roch 1931.

SHORT DESCRIPTION
This mollusc has a wormlike, elongated body and two
small shells at the anterior body end acting as wood-boring organ. Larvae are planktotrophic and adults are herbivorous
suspension feeders. Individuals are found completely embedded in wood, which is digested with the help of
endosymbiotic bacteria. A tiny opening allows water ventilation with two retractable siphons. The tunnels are covered
with calcareous substances excreted by the species and may be closed with two calcareous plates.

BIOLOGY/ECOLOGY

Dispersal mechanisms

Larvae with water currents.

Reproduction

It is a protandric hermaphrodite. During metamorphosis male gametes develop after six weeks. They can also
self-fertilise. After reproduction it changes back to the male phase and another cycle is started. Fertilisation is
internal. Up to 5 million larvae are developed per cycle. The larval phase is 11–35 days, usually 28 days.

Known predators/herbivores

Planktonic larvae are consumed by filter feeders. Adults are only vulnerable to predators once the wood they
colonise collapses.

Resistant stages (seeds, spores etc.)

None.

HABITAT

Native (EUNIS code)

A3: Sublittoral rock and other hard substrata. Wood in the littoral zone.

Habitat occupied in invaded range (EUNIS code)

A3: Sublittoral rock and other hard substrata. The key habitats are permanently submerged wooden structures,
such as pilings and marina piers.

Habitat requirements

Inside the wood, in sealed tunnels, it survives low anoxic conditions for more than 5 weeks and also tolerates air
or freshwater exposure. In wood, ice cover is tolerated. It survives water temperatures up to 30 °C. Larvae

Close-up of Teredo navalis

Photo: Marco Faasse, www.cryptosula.net

tolerate salinities down to 9 PSU and adults even lower salinity levels. The maximum tolerable salinity is above
40 ppt.

DISTRIBUTION

Native Range

The native range is unclear – this is a truly cryptogenic species.

Known Introduced Range

In Europe the species was first recorded in 1731, destroying wooden dyke gates in the Netherlands. Today it is
found along the British Channel and North Sea coasts. The easternmost border of shipworm settlement in the
Baltic is the Island of Rügen, Germany.

Trend

Stable.

MAP (European distribution)

Legend

Known in country

Known in CGRS square

Known in sea

INTRODUCTION PATHWAY
Adults naturally spread with floating wooden objects (e.g. drift wood, wooden ship hulls). Larvae are pelagic for
approximately two weeks and are dispersed by water currents. Teredenid larvae were found in ballast water samples
indicating the likeliness of this dispersal vector.

IMPACT

Ecosystem Impact

Unknown.

Health and Social Impact

Unknown.

Economic Impact

It was first recorded in Europe in 1731 when it destroyed wooden dyke gates in the Netherlands causing a
terrible flood. Recently caused damages along the German coast in the western Baltic were estimated to cost
approximately 25 - 50 Mil Euros.

MANAGEMENT

Prevention

Unknown.

Mechanical

Canadian logging companies used explosives near to floating timber to kill the shipworms with the shock waves.
Alternatively wooden pilings may be covered with Polyethylene or Polyvinyl or replaced by metal, concrete or
solid plastic structures. Wood replacement with tropical hard-wood is also effective.

Chemical

Any wooden structure in the sea has to be protected from marine borers. The earliest strategies to reduce the
shipworm impact were extended ship hull exposure to air or fresh water. Chemical treatment, i.e. poisonous hull
paintings or copper plating, were used by early seafarers. European medieval seafarers used tar, which had to be
renewed annually. Today, chemical impregnation is probably the most effective shipworm deterrent. However,
unwanted toxic side effects may occur.

Biological

Unknown.

REFERENCES

Hoppe K (2002) Teredo navalis – the cryptogenic shipworm. In Leppäkoski E, Gollasch S, Olenin S (eds) Invasive

Aquatic Species of Europe: Distribution, Impacts and Management. KLUWER Academic Publishers, Dordrecht,
The Netherlands, pp 116-119

Sellius G (1733) Historia naturalis teredinis seu xylophagi marini tubulo conchoidis speciatim Belgici. Trajecti ad

Rehenum, [xxxiv], 356

Sordyl H, Bönsch R, Gercken J, Gosselck F, Kreuzberg M, Schulze H (1998) Dispersal and reproduction of the

shipworm Teredo navalis L. in coastal waters of Mecklenburg-Western Pomerania. Deutsche
Gewässerkundliche Mitteilungen 42:142-149

OTHER REFERENCES

Calloway BC, Turner RD (1988) Brooding in the Teredinidae (Mollusca: Bivalvia). In: Thompson M-F, Sarojiani R,

Nagabhushanam R (eds) Marine Biodeterioration: Advanced Techniques Applicable to the Indian Ocean, AA
Balkema, Rotterdam. pp 215-226

Gollasch S (1996) Untersuchungen des Arteintrages durch den internationalen Schiffsverkehr unter besonderer

Berücksichtigung nichtheimischer Arten. Diss., Univ. Hamburg. Verlag Dr. Kovac, Hamburg, p 314

Grave BH (1928) Natural history of shipworm, Teredo navalis, at Woods Hole, Massachusetts. Biological Bulletin

(Woods Hole) 55:260-282

Hayward PJ, Ryland JS (1996) Handbook of the Marine Fauna of North-West Europe. Oxford University

Press, Oxford

Kristensen ES (1979) Observations on growth and life cycle of the shipworm Teredo navalis L. (Bivalvia;

Mollusca) in the Isefjord, Denmark. Ophelia 18:235-242

Lane CE (1959) Some aspects of the general biology of Teredo. In: Ray DL (ed) Marine Boring and Fouling

Organisms. University of Washington Press, Seattle, pp 137-144

Nair NB, Sraswathy M (1971) The biology of wood-boring teredinid molluscs. Advances in Marine Biology 9:335-

509

Norman E (1977) The geographical distribution and the growth of the wood-boring molluscs Teredo navalis L.,

Psiloteredo megotara (Hanley) and Xylophaga dorsalis (Turton) on the Swedish west coast. Ophelia 16(2):233-
250

Quayle DB (1992) Marine wood borers in British Columbia. Canadian Special Publication of Fisheries and Aquatic

Sciences, pp 55

Schütz L (1961) Distribution and dispersal of the borer Teredo navalis L. and its entering of the Kiel Canal near

Kiel. Kieler Meeresforschung 17:228-236

Turner RD (1971) Australian shipworms. Australian Natural History 17(4):139-145

Weis JS, Weis P (1996) The effects of using wood treated with chromated copper arsenate in shallow-water

environments: a review. Estuaries 19:306-310

Author: Stephan Gollasch

Date Last modified: October 30

th

, 2006