Animal Diversity Web

Ge­o­graphic Range

The ori­gins of Teredo navalis are un­known. Ap­pro­pri­ately re­ferred to as naval ship­worms, T. navalis are mol­luscs that fre­quently dwell in the wood of ships. Due to the promi­nent use of ships in global trade and the con­se­quent dis­per­sal of the ship­worms, the ori­gins of T. navalis are un­cer­tain. Masses of naval ship­worms were first iden­ti­fied near the Nether­lands in the North Sea. They are com­mon to the Baltic Sea as well as the At­lantic and Pa­cific Oceans today. (Didz­i­ulis, 2007; Gol­lasch, et al., 2009)

• Biogeographic Regions
• nearctic
  • introduced
• palearctic
  • introduced
• oriental
  • introduced
• ethiopian
  • introduced
• neotropical
  • introduced
• australian
  • introduced
• atlantic ocean
  • introduced
• pacific ocean
  • introduced

Habi­tat

Naval ship­worms are ma­rine and es­tu­ar­ine or­gan­isms in­hab­it­ing var­i­ous sub­merged wooden sub­strates in­clud­ing float­ing wood, ships, or wharfs. Part of their lar­val stage is spent free-swim­ming in water. While they can tol­er­ate low saline lev­els (up to 5 ppt), they flour­ish at lev­els greater than 9 ppt. Their op­ti­mal tem­per­a­ture range is 15 to 25 de­grees Cel­sius and, as a re­sult, T. navalis can be found in tem­per­ate and trop­i­cal zones. (Didz­i­ulis, 2007; Tuente, et al., 2002)

• Habitat Regions
• temperate
• tropical
• saltwater or marine

• Aquatic Biomes
• pelagic
• benthic
• coastal
• brackish water

• Other Habitat Features
• estuarine

Phys­i­cal De­scrip­tion

While T. navalis looks like a brown worm on the out­side, it is ac­tu­ally a bi­valve. Its head is cov­ered with two white, tri-lobed shells used to bore into wood. The shells are up to 2 cm long and have con­cen­tric ridges. In­side the shell is a hook-like process called a sty­loid apoph­ysis. The foot is also at the an­te­rior end. At the pos­te­rior end are two siphons: in­cur­rent and ex­cur­rent. The for­mer is used for res­pi­ra­tion and feed­ing while the lat­ter is where waste and sperm or lar­vae exit. Pad­dle-like pal­lets act as a lid to cover the siphons when not in use. Naval ship­worms are about 20 cm in length but can range from 1.5 to 58 cm. They are 1 cm in di­am­e­ter. Cal­care­ous cov­er­ings are se­creted from their man­tles that coat the bur­rows they make. Male and fe­male adults can­not be dis­tin­guished ex­ter­nally. (NIMPIS, 2011; Didz­i­ulis, 2007; Grave, 1928)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes alike

• Range length

  1.5 to 58 cm

  0.59 to 22.83 in

• Average length

  20 cm

  7.87 in

De­vel­op­ment

Teredo navalis takes about five weeks to de­velop from eggs to meta­mor­phos­ing lar­vae. They spend half of this time in the mother’s gill cham­ber until they are re­leased into the water as free-swim­ming lar­vae. As the lar­vae de­velop, they tran­si­tion from being small and white to large and dark gray. Fer­til­ized eggs de­velop into cilia-cov­ered lar­vae, re­ferred to as tro­chophores. Over time, cilia are seen cov­er­ing only the velum in lar­vae, now called veligers. The velum serves as an organ par­tic­i­pat­ing in move­ment and feed­ing. A shell ap­pears about the same time in de­vel­op­ment as the velum and be­comes bi­valved after for­ma­tion. Older veligers are re­leased into the water. Dur­ing this free-swim­ming stage, the siphons, gills, and foot de­velop. Once ship­worms at­tach onto a wooden sub­strate, meta­mor­pho­sis is ob­served. (NIMPIS, 2011; Grave, 1928)

Sexes al­ter­nate in T. navalis. Young are her­maph­ro­dites while adults are ei­ther male or fe­male. Usu­ally, or­gan­isms are male first and then be­come fe­male later. A sec­ond male to fe­male phase may occur but ship­worms nor­mally do not live long enough for com­ple­tion of the sec­ond phase. (Coe, 1943)

• Development - Life Cycle
• metamorphosis

Re­pro­duc­tion

While no di­rect in­for­ma­tion was found on the mat­ing sys­tem of T. navalis, it can be in­ferred to be polyg­y­nan­drous. Males re­lease sperm into the water, which fe­males pick up via the in­cur­rent siphon. This oc­curs on mul­ti­ple oc­ca­sions, as fe­males spawn 3 to 4 times per sea­son. (NIMPIS, 2011)

• Mating System
• polygynandrous (promiscuous)

Re­pro­duc­tion typ­i­cally oc­curs in the sum­mer months when tem­per­a­tures reach 15 de­grees Cel­sius. Fe­males spawn 3 to 4 times per sea­son, each time re­leas­ing 1 to 5 mil­lion lar­vae. Teredo navalis em­bryos spend the first 2 to 3 weeks in the mother’s gill cham­ber. They are then re­leased into the water as free-swim­ming veligers. Re­leased lar­vae are 88 by 75 mi­crons with a depth of 55 to 57 mi­crons. They reach sex­ual ma­tu­rity 6 to 8 weeks after in­hab­it­ing wood. ("Teredo navalis", 2009; Culliney, 1975; Grave, 1928; "Teredo navalis", 2009; Culliney, 1975; Grave, 1928; NIMPIS, 2011)

As men­tioned pre­vi­ously, ship­worms al­ter­nate be­tween sexes dur­ing their life. When lar­vae ma­ture, half of their go­nads be­come sper­ma­to­cytes, the other half ovo­cytes. Usu­ally, sper­ma­to­cytes mul­ti­ply faster and are re­leased ear­lier. (Coe, 1943)

• Key Reproductive Features
• seasonal breeding
• simultaneous hermaphrodite
• sequential hermaphrodite
  • protandrous
• sexual
• fertilization
  • internal
• broadcast (group) spawning
• viviparous

• Breeding interval

  Shipworms spawn 3 to 4 times each season

• Breeding season

  Breeding season is usually in the summer

• Range number of offspring

  1,000,000 to 5,000,000

• Range gestation period

  2 to 3 weeks

• Range time to independence

  2 to 3 weeks

• Range age at sexual or reproductive maturity (female)

  6 to 8 weeks

• Range age at sexual or reproductive maturity (male)

  6 to 8 weeks

Fe­males carry off­spring in gill cham­bers dur­ing early de­vel­op­ment. When lar­vae reach the ad­vanced veliger stage, they are re­leased into the water. There is no ev­i­dence that moth­ers as­sist veligers in find­ing wooden sub­strates to in­habit. (Grave, 1928)

• Parental Investment
• female parental care
• pre-hatching/birth
  • protecting
    • female
• pre-weaning/fledging
  • protecting
    • female

Lifes­pan/Longevity

The lifes­pan of ship­worms is 1 to 3 years. (NIMPIS, 2011)

• Average lifespan
  Status: wild

  1-3 years

Be­hav­ior

Re­leased veligers are free-swim­ming. Upon at­tach­ment to a wooden sub­strate, veligers un­dergo meta­mor­pho­sis to be­come adult ship­worms. They bur­row into the wood and stay there for the du­ra­tion of their lives. Bur­row­ing oc­curs ei­ther up­ward or down­ward; there does not seem to be a pref­er­ence.

Neigh­bor­ing bur­rows never come into con­tact with each other. Naval ship­worms are able to some­how sense when they are close to an­other's bur­row and re­spond by dig­ging in a dif­fer­ent di­rec­tion or ceas­ing to grow. Sim­i­lar be­hav­ior is seen when T. navalis reach the end of the wooden sub­strate and are able to turn around to delve in par­al­lel to the orig­i­nal bur­row. (Grave, 1928)

• Key Behaviors
• motile
• sedentary

Com­mu­ni­ca­tion and Per­cep­tion

There is lim­ited in­for­ma­tion on how T. navalis com­mu­ni­cates.

Food Habits

Naval ship­worms pri­mar­ily feed on wood. They are able to do so be­cause of en­zymes pro­duced by the ni­tro­gen-fix­ing bac­te­ria within them. Teredo navalis use their shell to cut into the wood. The pieces are then trans­ported into the mouth via cilia. Or­gan­isms from the water may also be taken up for food via the in­halant siphon. Free-swim­ming veligers feed on plank­ton. (NIMPIS, 2011; Grave, 1928)

• Primary Diet
• herbivore
  • lignivore
• planktivore

• Plant Foods
• wood, bark, or stems
• phytoplankton

• Other Foods
• microbes

• Foraging Behavior
• filter-feeding

Pre­da­tion

The cal­cer­ous cov­er­ing they se­crete not only act as a lu­bri­cant but also de­ters preda­tors or poi­sons in the water. In re­sponse to these con­di­tions, thicker cal­care­ous ma­te­r­ial is se­creted at the an­te­rior end in ad­di­tion to the sides. Preda­tors in­clude bac­te­ria and par­a­sitic pro­to­zoa like Ar­chi­tophrya. Na­tive Aus­tralians and snails also eat naval ship­worms. (Grave, 1928)

• Known Predators

  • Bacteria
  • Parasitic Protozoa
  • Architophrya
  • Marine snails
  • Humans, Homo sapiens

Ecosys­tem Roles

Naval ship­worms break down sub­merged wooden sub­strates. The holes they cre­ate in the wood can be used by crus­taceans such as Idotea. Teredo navalis share a sym­bi­otic re­la­tion­ship with the ni­tro­gen-fix­ing bac­te­ria within them that help the ship­worms di­gest wood. Some pro­to­zoa are known to par­a­sitize this species. (NIMPIS, 2011)

• Ecosystem Impact
• creates habitat
• biodegradation

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

There are not any men­tioned ef­fects of T. navalis that are pos­i­tive to hu­mans. They do serve as food for Aus­tralian na­tives. (NIMPIS, 2011)

• Positive Impacts
• food

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Naval ship­worms have many neg­a­tive ef­fects due to their wood bor­ing ac­tiv­ity. They have been noted to cause dam­age in ships and dikes. Weak­en­ing of dike gates, com­bined with a heavy storm, re­sulted in flood­ing of the Nether­lands in 1731. Teredo navalis also eat away at piers and wharfs. In San Fran­cisco Bay, they can cause 200 mil­lion dol­lars worth of dam­age yearly. (NIMPIS, 2011; USDA, 2006)

Con­ser­va­tion Sta­tus

The con­ser­va­tion sta­tus of T. navalis has not been eval­u­ated.

• IUCN Red List

  Not Evaluated

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Other Com­ments

There are few ways to ef­fec­tively pre­vent de­struc­tion of wood by Teredo navalis. Other non-wooden ma­te­ri­als have been used to build ob­jects like ships or wharfs. Bio­cides are only tem­po­rary an­swers and are haz­ardous to hu­mans. Use of ge­o­t­ex­tiles to pro­tect an­tique ships serves as a phys­i­cal bar­rier to naval ship­worms. (NIMPIS, 2011)

Con­trib­u­tors

Mag­gie Ho (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Phil Myers (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor, Renee Mul­crone (ed­i­tor), Spe­cial Pro­jects.

Ref­er­ences

2009. "Teredo navalis" (On-line). Ac­cessed June 01, 2011 at http://​www.​itis.​gov/​servlet/​SingleRpt/​SingleRpt.

Bartsch, P. 1923. The sta­tus of Teredo beachi and Teredo navalis. Sci­ence, 57 (1485): 692.

Blum, H. 1928. On the phys­i­ol­ogy of the pal­let mech­a­nism of the ship­worm, Teredo navalis. Phys­i­o­log­i­cal Zo­ol­ogy, 1(3): 416-418.

Carl­ton, J. 1992. In­tro­duced ma­rine and es­tu­ar­ine mol­lusks of North Amer­ica: an end of the 20th cen­tury per­spec­tive. Jour­nal of Shell­fish Re­search, 11:2: 489-505.

Coe, W. 1943. De­vel­op­ment of the pri­mary go­nads and dif­fer­en­ti­a­tion of sex­u­al­ity in Teredo navalis and other pele­cy­pod mol­lusks. Bi­o­log­i­cal Bul­letin, 84: 178-186.

Culliney, J. 1975. Com­par­a­tive lar­val de­vel­op­ment of the ship­worms Bankia gouldi and Teredo navalis. Ma­rine Bi­ol­ogy, 29: 245-251.

Didz­i­ulis, V. 2007. "NOBA­NIS-in­va­sive alien species fact sheet, Teredo navalis" (On-line pdf). NOBA­NIS-Eu­ro­pean net­work on in­va­sive alien species. Ac­cessed June 01, 2011 at http://​www.​nobanis.​org/​files/​factsheets/​Teredo_​navalis.​pdf.

Gol­lasch, S., D. Hay­dar, D. Minchin, W. Wolff, K. Reise. 2009. In­tro­duced aquatic species of the North Sea coasts and ad­ja­cent brack­ish wa­ters. Pp. 507-528 in G Rilov, J Crooks, eds. Bi­o­log­i­cal In­va­sions in Ma­rine Ecosys­tems, Vol. 204. Ger­many: Springer.

Grave, B. 1928. Nat­ural his­tory of ship­worm, Teredo navalis, at Woods Hole, Mass­a­chu­setts. Bi­o­log­i­cal Bul­letin, 55 (4): 260-282.

Grave, B., J. Smith. 1936. Sex in­ver­sion in Teredo navalis and its re­la­tion to sex ra­tios. Bi­o­log­i­cal Bul­letin, 70 (2): 332-343.

Grave, B. 1942. The sex­ual cycle of the ship­worm, Teredo navalis. Bi­o­log­i­cal Bul­letin, 82 (3): 438-445.

Mann, R., S. Gal­lager. 1985. Growth, mor­phom­e­try and bio­chem­i­cal com­po­si­tion of the wood bor­ing mol­luscs Teredo navalis, Bankia gouldi, and No­toteredo knoxi (Bi­valvia: Tere­dinidae). Jour­nal of Ex­per­i­men­tal Ma­rine Bi­ol­ogy and Ecol­ogy, 85: 229-251.

Mann, R., S. Gal­lager. 1985. Phys­i­o­log­i­cal and bio­chem­i­cal en­er­get­ics of lar­vae of Teredo navalis and Bankia gouldi (Bi­valvia: Tere­dinidae). Jour­nal of Ex­per­i­men­tal Ma­rine Bi­ol­ogy and Ecol­ogy, 85: 211-228.

NIMPIS, 2011. "Teredo navalis, gen­eral in­for­ma­tion" (On-line). Na­tional In­tro­duced Ma­rine Pest In­for­ma­tion Sys­tem. Ac­cessed June 01, 2011 at http://​adl.​brs.​gov.​au/​marinepests/​index.​cfm?​fa=main.​spDetailsDB&​sp=6000016293.

Schel­tema, R., R. Tru­itt. 1956. The ship­worm Teredo navalis in Mary­land coastal wa­ters. Ecol­ogy, 37 (4): 841-843.

Tuente, U., D. Piepen­burg, M. Spindler. 2002. Oc­curence and set­tle­ment of the com­mon ship­worm Teredo navalis (Bi­valvia: Tere­dinidae) in Bre­mer­haven har­bours, north­ern Ger­many. Hel­goland Ma­rine Re­search, 56: 87-94.

USDA, 2006. "Sub­mod­ule 7: The Price We Pay -- Eco­nomic Im­pacts" (On-line). Na­tional In­va­sive Species In­for­ma­tion Cen­ter. Ac­cessed June 06, 2011 at http://​alic.​arid.​arizona.​edu/​invasive/​sub7/​p2.​shtml.