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Shipworm

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Shipworm
This dried specimen ofTeredo navalis,and the calcareous tunnel that originally surrounded it and curled into a circle during preservation, were extracted from the wood of a ship. The two valves of the shell are the white structures at the anterior end; they are used to dig the tunnel in the wood.
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Superorder: Imparidentia
Order: Myida
Superfamily: Pholadoidea
Family: Teredinidae
Rafinesque,1815
Genera

See text

Theshipworms,also calledTeredo wormsor simplyTeredo(fromAncient Greekτερηδών(terēdṓn)'wood-worm', viaLatinterēdō), aremarinebivalvemolluscsin the familyTeredinidae,a group of saltwaterclamswith long, soft, naked bodies. They are notorious for boring into (and commonly eventually destroying) wood that is immersed inseawater,including such structures as woodenpiers,docks,and ships; they drill passages by means of a pair of very small shells ( "valves") borne at one end, with which they rasp their way through. They are sometimes called" termites of the sea ".[1]Carl Linnaeusassigned thecommon nameTeredoto the best-known genus of shipworms in the 10th edition of histaxonomicmagnum opus,Systema Naturæ(1758).

Characteristics

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Teredo navalisfromPopular Science Monthly,September 1878

Removed from its burrow, the fully grown teredo ranges from several centimeters to about a meter in length, depending on the species. An average adult shipworm measures 4 to 6 inches (10 to 15 cm) in length and less than one-quarter inch (6.4 mm) in diameter, but some species grow to considerable size.[2]The body is cylindrical, slender, naked, and superficiallyvermiform(worm-shaped). In spite of their slender, worm-like forms, shipworms possess the characteristicmorphologyofbivalves.Thectinidialie mainly within the branchialsiphon,through which the animal pumps the water that passes over thegills.

The two siphons are very long and protrude from theposteriorend of the animal. Where they leave the end of the main part of the body, the siphons pass between a pair of calcareous plates called pallets. If the animal is alarmed, it withdraws the siphons and the pallets protectively block the opening of the tunnel.

The pallets are not to be confused with the two valves of the main shell, which are at theanteriorend of the animal. Because they are the organs that the animal applies to boring its tunnel, they generally are located at the tunnel's end. They are borne on the slightly thickened, muscular anterior end of the cylindrical body and they are roughly triangular in shape and markedly concave on their interior surfaces. The outer surfaces are convex and in most species are deeply sculpted into sharp grinding surfaces with which the animals bore their way through the wood or similar medium in which they live and feed. The valves of shipworms are separated and the aperture of themantlelies between them. The small "foot" (corresponding to the foot of a clam) can protrude through the aperture.

When shipworms bore into submerged wood, bacterial symbionts embedded within a sub-organ called the typhlosole in the shipworm gut, aid in the digestion of the wood particles ingested[3]TheAlteromonasorAlteromonas-sub-group of bacteria identified as the symbiont species in the typhlosole, are known to digest lignin, and wood material in general. The tough molecular layers of lignin surround the cellulose elementary fibrils in the wood particles, and the lignin must be digested initially to allow access by other enzymes into the cellulose for digestion.[4]Another bacterial species (Teredinibacter turnerae), in the gills secrete a variety of cellulose-digesting enzymes which may be secreted into the shipworm gut via a special organ called the gland of Deshayes. These secretions aid the shipworm's own carbohydrate-active enzymes (CAZymes) in digesting the wood particles in combination with the enzymes and potentially other metabolites secreted by the symbiont bacterial in the typhlosole[5][6]

The excavated burrow is usually lined with acalcareoustube. The valves of theshellofshipwormsare small separate parts located at the anterior end of the worm, used for excavating the burrow. The protective role of the shells is lost because the animal spends all its life surrounded by wood.[7]

Teredo navalisdevelops from eggs tometamorphosinglarvaein about five weeks. They spend half of this time in the mother's gill chamber before being discharged as free-swimming larvae into the sea. Their sexes alternate, young arehermaphroditeswhile adults can be either male or female. Typically, organisms are male at first and female subsequently. A second male to female phase may occur, however shipworms rarely live long enough to complete the second phase. They have a lifespan of 1 to 3 years.[8]

Anatomy

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Disposition of the main organs in a shipworm. GDA: anterior digestive gland; GDV: ventral digestive gland, with its orifices in the stomach. Orifices uri. et gen., urinary and gential orifices. The left ventricle is sectioned near its base. The nerve ganglion is in blue. The distance between pallets and foot spans several time the animal's diameter.

Shipworm anatomy reveals the typical organs of a bivalve mollusk, although with dimensional or positional peculiarities due to the thinness and length of the occupied space. Furthermore, some structures find no equivalent in other bivalve groups.

  • Gills are divided in two halves, the anterior one of small size, the posterior one much more developed. They are linked by the alimentary tract running on the side of the visceral mass.
  • The heart-kidney system is tilted, bringing the kidneys in a dorsal position relative to the heart, whose atria find themselves behind the ventricle. Furthermore, the anterior and posterior aorta become respectively posterior and anterior.
  • The anus opens at the end of a long anal tube.
  • The digestive gland is divided into several parts, with separate orifices in the stomach.
  • A vastcaecumis linked to the stomach.
  • The digestive tube bears a very peculiar structure, the gland of Deshayes, probably homologous to salivary glands,[9]which link to the oesophagus and stretch to the dorsal side of the posterior part of the gills.
  • The orifice of the gallery bears pallets with their own musculature.
  • The siphon retractor muscles are inserted on the calcareous covering of the gallery, and not on the shell's valves which are much further out.
  • The anterior and posterior anterior muscles have an antagonistic action.

Normally, the shipworm's body fills the entire length of the gallery, but the anterior region can retract itself slightly with respect to the latter's extremity. Without the gills, the viscera only cover one-fourth of the total length and only their anterior part is partially covered by the shell.[10][11]

Taxonomy

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Shipworms are marine animals in the phylumMollusca,orderBivalvia,familyTeredinidae.They were included in the now obsolete orderEulamellibranchiata,[12]in which many documents still place them.

Ruth TurnerofHarvard Universitywas the leading 20th century expert on the Teredinidae; she published a detailed monograph on the family, the 1966 volumeA Survey and Illustrated Catalogue of the Teredinidaepublished by theMuseum of Comparative Zoology.More recently, theendosymbiontsthat are found in the gills have been subject to study thebioconversionof cellulose for fuel energy research.[13]

Shipworm species comprise severalgenera,of whichTeredois the most commonly mentioned. The best known species isTeredo navalis.Historically,Teredoconcentrations in theCaribbean Seahave been substantially higher than in most other salt water bodies.

Genera within the family Teridinidae include:[14]

Species

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TheTeredogenushas approximately 20speciesthat live in wooden materials such as logs, pilings, ship, and practically any other submerged wooden construction from temperate totropicaloceanzones. The species is thought to be native to theAtlantic Oceanand was once known as the Atlantic shipworm, although its exact origin is unknown.[15]The longest marine bivalve,Kuphus polythalamia,was found from a lagoon nearMindanaoisland in the southeastern part of thePhilippines,which belongs to the same group of mussels and clams. The existence of huge mollusks was established for centuries and studied by the scientists, based on the shells they left behind that were the size ofbaseball bats(length 1.5 meters (5 ft.), diameter 6 cm (2.3 in.)).[16][17]Thebivalveis a rare creature that spends its life inside anelephant tusk-like hard shell made ofcalcium carbonate.It has a protective cap over its head which it reabsorbs to burrow into the mud for food. The case of the shipworm is not just the home of the black slimy worm. Instead, it acts as the primary source of nourishment in a non-traditional way.K. polythalamiasifts mud and sediment with its gills. Most shipworms are relatively smaller and feed on rotten wood. This shipworm instead relies on a beneficialsymbiotic bacterialiving in its gills. The bacteria use thehydrogen sulfidefor energy to produceorganic compoundsthat in turn feed the shipworms, similar to the process ofphotosynthesisused bygreen plantsto convert thecarbon dioxidein the air into simplecarbon compounds.Scientists found thatK. polythalamiacooperates with different bacteria than other shipworms, which could be the reason why it evolved from consuming rotten wood to living on hydrogen sulfide in the mud. The internal organs of the shipworm have shrunk from lack of use over the course of its evolution[citation needed]The scientists are planning to study the microbes found in the single gill ofK. polythalamiato find a new possible antimicrobial substance[citation needed]

Habitat

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Teredo navalisare a cosmopolitan species that can be found both in theAtlanticandPacificoceans.[7]Since they occupy woodenflotsamand naturaldriftwoodsuch as dead tree trunks, they are spread as the wood is carried by currents. They also travel inside the wooden-hulled vessels that help increase their spread worldwide.[18]However, the origin ofT. navalisremains uncertain due to the widespread usage ofshipsinglobal tradeand the resulting spreading of shipworms.[19]

During the free-livinglarvastage, the species colonizes new habitats and spreads. Larvae are extremely sensitive to the presence of wood and will take advantage of any opportunity to attach to and penetrate wooden structures. In theBaltic Sea,free-floating piles carved by shipworms can be observed floating hundreds of kilometers away from the original wooden structures. The limiting element for propagation issalinity,which must be greater than 8% for successful reproduction. Reproduction occurs during warmsummermonths, and the larvaemature for productionin just eight weeks. Each year, severalgenerationscan be produced. Consequently,freshwateris deadly to theseinvertebrates.[7]Their ideal temperature range is 15 to 25 degree C and therefore T. navalis can be found in temperate and tropical zones.[19]

The shipworm lives in waters withoceanic salinity.Accordingly, it is rare in thebrackishBaltic Sea, where woodenshipwrecksare preserved for much longer than in the oceans.[20]

The range of various species has changed over time based on human activity. Many waters in developed countries that had been plagued by shipworms were cleared of them bypollutionfrom theIndustrial Revolutionand the modern era; as environmental regulation led to cleaner waters, shipworms have returned.[21]Climate changehas also changed the range of species; some once found only in warmer and more salty waters like theCaribbeanhave established habitats in theMediterranean.[21]

Cultural impact

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Shipworms greatly damage wooden hulls and marinepiling,and have been the subject of much study to find methods to avoid their attacks.[21]Copper sheathingwas used on wooden ships in the latter 18th century and afterwards, as a method of preventing damage by "teredo worms". The first historically documented use of copper sheathing was experiments held by the British Royal Navy withHMSAlarm,which was coppered in 1761 and thoroughly inspected after a two-year cruise. In a letter from the Navy Board to the Admiralty dated 31 August 1763 it was written "that so long as copper plates can be kept upon the bottom, the planks will be thereby entirely secured from the effects of the worm."

In theNetherlandsthe shipworm caused a crisis in the 18th century by attacking the timber that faced thesea dike.[citation needed]After that the dikes had to be faced with stones. In 2009,Teredocaused several minor collapses along theHudson Riverwaterfront inHoboken, New Jersey,due to damage to underwater pilings.[22]

Teredolitesboringsin a modern wharf piling. The US one cent coin in the lower left of this image is 19 mm across.

In the early 19th century,engineerMarc Brunelobserved that the shipworm's valves simultaneously enabled it to tunnel through wood and protected it from being crushed by the swelling timber. With that idea, he designed the firsttunnelling shield,a modular iron tunnelling framework which enabled workers to tunnel through the unstable riverbed beneath the Thames. TheThames Tunnelwas the first successful large tunnel built under a navigable river.[21][23]

Henry David Thoreau's poem "Though All the Fates" pays homage to "New England's worm" which, in the poem, infests the hull of "[t]he vessel, though her masts be firm". In time, no matter what the ship carries or where she sails, the shipworm "her hulk shall bore, / [a]nd sink her in the Indian seas".[24]The hull of the ship wrecked by a whale, inspiringMoby Dick,had been weakened by shipworms.[21]In the NorseSaga of Erik the Red,Bjarni Herjólfsson,said to be the first European to discover the Americas,[25]had his ship drift into the Irish Sea where it was eaten up by shipworms. He allowed half the crew to escape in a smaller boat covered in seal tar, while he stayed behind to drown with his men.

Cuisine

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Shipworm astamilok

Today shipworms are primarily eaten in parts ofSoutheast Asia.InPalawanandAklanin thePhilippines,the shipworm is calledtamilokand is eaten as a delicacy. It is prepared askinilaw—that is, raw (cleaned) butmarinatedwith vinegar orlime juice,choppedchili peppersand onions, a process very similar to shrimpceviche.Similarly,T. navaliscan be found inside the dead and rotten trunk ofmangrovesinWest Papua, Indonesia.To the locals, theKamoro[26][bare URL]tribe, it is referred to astambeloand is considered as a delicacy in daily meals. It can be eaten fresh and raw (cleaned) or cooked (cleaned and boiled) as well and usually marinated with lime juice and chili peppers. SinceT. navalisare related toclams,mussels,andoysters,[27]the taste of the flesh has been compared to a wide variety of foods, frommilktooysters.[28]Similarly, the delicacy is harvested, sold, and eaten from those taken by local natives in the mangrove forests ofWest Papuaand some part ofBorneo Island,Indonesia,and the central coastal peninsular regions of Thailand nearKo Phra Thong.

T. navalisgrow faster than any other bivalve because it does not require much energy to create its small shell. They can grow to be about 30 cm (12 in) long in just six months.Musselsandoysters,on the other hand, with their much bigger shells, can take up to two years to reach harvestablesize.[27]

See also

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References

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  1. ^Garcia, Sierra (2021-12-24)."How" Termites of the Sea "Have Shaped Maritime Technology".JSTOR Daily.Retrieved2022-05-01.
  2. ^Castagna, Michael."Shipworms and Other Marine Borers"(PDF).National Oceanic and Atmospheric Administration.United States Department of the Interior Fish and Wildlife Service Bureau of Commercial Fisheries.Retrieved30 November2023.
  3. ^Goodell, B., J. Chambers, D. V. Ward, C. Murphy, E. Black, L. B. Kikuti Mancilio, G. Perez- Gonzalez, J. R. Shipway. 2024. First report of microbial symbionts in the digestive system of shipworms; wood boring mollusks. International Biodeterioration & Biodegradation. 192 (105816).ISSN 0964-8305.https://doi.org/10.1016/j.ibiod.2024.105816
  4. ^Goodell, B., Nielsen, G. (2023). Wood Biodeterioration. In: Niemz, P., Teischinger, A., Sandberg, D. (eds) Springer Handbook of Wood Science and Technology. Springer Handbooks. Springer, Cham.https://doi.org/10.1007/978-3-030-81315-4_4
  5. ^Goodell, Barry; Chambers, James; Ward, Doyle V.; Murphy, Cecelia; Black, Eileen; Mancilio, Lucca Bonjy Kikuti; Perez- Gonzalez, Gabriel; Shipway, J. Reuben (2024)."First report of microbial symbionts in the digestive system of shipworms; wood boring mollusks".International Biodeterioration & Biodegradation.192:105816.doi:10.1016/j.ibiod.2024.105816.
  6. ^Distel, D. L.; Morrill, W.; MacLaren-Toussaint, N.; Franks, D.; Waterbury, J. (2002)."Teredinibacter turnerae gen. nov., sp. nov., a dinitrogen-fi xing, cellulolytic, endosymbiotic gamma-proteobacterium isolated from the gills of wood-boring molluscs (Bivalvia: Teredinidae)".International Journal of Systematic and Evolutionary Microbiology.52(6): 2261–2269.doi:10.1099/00207713-52-6-2261.hdl:1912/110.ISSN1466-5026.PMID12508896.Archived fromthe originalon 2008-09-07.Retrieved2010-09-23.
  7. ^abcDidžiulis, Viktoras."Invasive Alien Species Fact Sheet – Teredo navalis"(PDF).Nobanis.Retrieved30 November2023.
  8. ^"Teredo navalis".Marine Invasions Research at the Smithsonian Environmental Research Center.Retrieved30 November2023.
  9. ^Morton, B. (1978). "Feeding and digestion in shipworms".Oceanography and Marine Biology – an Annual Review(16): 107–144.
  10. ^Sigerfoos, C. P. (1907). "Natural history, organization, and late development of the Teredindæ, or ship-worms".Bulletin of the Bureau of Fisheries.27:191–231. Bureau of Fisheries Document No. 639.
  11. ^Turner, Ruth (1966).A survey and illustrated catalogue of the Teredinae (Mollusca: Bivalvia).Cambridge, Massachusetts: The Museum of Comparative Zoology, Harvard University. pp. 8–45.OCLC767789449.
  12. ^Ponder, Winston F.; Lindberg, David R., eds. (2008).Phylogeny and Evolution of the Mollusca.University of California Press.ISBN978-0-520-25092-5.
  13. ^Yang, JC; Madupu, R; Durkin, AS; Ekborg, NA; Pedamallu, CS; Hostetler, JB; Radune, D; Toms, BS; Henrissat, B; Coutinho, PM; Schwarz, S; Field, L; Trindade-Silva, AE; Soares, CA; Elshahawi, S; Hanora, A; Schmidt, EW; Haygood, MG; Posfai, J; Benner, J; Madinger, C; Nove, J; Anton, B; Chaudhary, K; Foster, J; Holman, A; Kumar, S; Lessard, PA; Luyten, YA; Slatko, B; Wood, N; Wu, B; Teplitski, M; Mougous, JD; Ward, N; Eisen, JA; Badger, JH; Distel, DL (Jul 1, 2009)."The complete genome of Teredinibacter turnerae T7901: an intracellular endosymbiont of marine wood-boring bivalves (shipworms)".PLOS ONE.4(7): e6085.Bibcode:2009PLoSO...4.6085Y.doi:10.1371/journal.pone.0006085.PMC2699552.PMID19568419.
  14. ^Bouchet, P. (2015)."Teredinidae Rafinesque, 1815".WoRMS.World Register of Marine Species.Retrieved2015-02-14.
  15. ^Didžiulis, Viktoras."NOBANIS - Invasive Alien Species Fact Sheet - Teredo navalis"(PDF).Retrieved30 November2023.
  16. ^"This Is a Giant Shipworm. You May Wish It Had Stayed In Its Tube. - T…".The New York Times.2020-11-15. Archived fromthe originalon 2020-11-15.
  17. ^[1]Live example seen on 19 April 2017 on the BBC's website.
  18. ^Castagna, Michael."Shipworms and Other Marine Borers"(PDF).National Oceanic and Atmospheric Administration.United States Department of the Interior Fish and Wildlife Service Bureau of Commercial Fisheries.Retrieved30 November2023.
  19. ^abHo, Maggie."Teredo navalis".Marine Invasions Research at the Smithsonian Environmental Research Center.Retrieved30 November2023.
  20. ^"Historic shipwrecks could be preserved in the Antarctic".ScienceNordic.Archived fromthe originalon 2017-02-28.Retrieved2017-02-28.
  21. ^abcdeGilman, Sarah (December 5, 2016)."How a Ship-Sinking Clam Conquered the Ocean".Smithsonian.
  22. ^"Pier-eating monsters: Termites of the sea causing piers to collapse".Hudson Reporter.Retrieved2009-09-29.
  23. ^"Thames Tunnel Construction".Brunel Museum. Archived fromthe originalon 2008-06-14.Retrieved2008-08-31.
  24. ^Thoreau, Henry D.,"Though All the Fates".
  25. ^"The Saga of Erik the Red".Icelandic Saga Database.Retrieved2017-07-04.
  26. ^"Renaissance of Kamoro Culture | Stichting Papua Erfgoed".papuaerfgoed.org.
  27. ^abcoxworth, Ben (20 November 2023)."Wood-eating shipworms may soon be farmed for shipworm-eating humans".New Atlas.Retrieved30 November2023.
  28. ^Ortiz, Jodelen O. (May 2, 2007)."Tamilok A Palawan: Delicacy".Archived fromthe originalon April 17, 2009.Retrieved2009-04-30.

Further reading

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[edit]
Look upshipwormin Wiktionary, the free dictionary.
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