Editing Shipworm (section)

== Characteristics ==
[[File:PSM V13 D568 Teredo navalis.jpg|thumb|''Teredo navalis'' from ''[[Popular 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 {{convert|4|to|6|in|cm|0|order=flip}} in length and less than {{convert|1/4|in|mm|0|order=flip|abbr=on}} in diameter, but some species grow to considerable size.<ref>{{cite web |last1=Castagna |first1=Michael |title=Shipworms and Other Marine Borers |url=https://spo.nmfs.noaa.gov/sites/default/files/legacy-pdfs/leaflet505.pdf |website=National Oceanic and Atmospheric Administration |publisher=United States Department of the Interior Fish and Wildlife Service Bureau of Commercial Fisheries |access-date=30 November 2023 |ref=Fisheries Leaflet 505}}</ref>

The body is cylindrical, slender, naked, and superficially [[Wiktionary:vermiform|vermiform]] (worm-shaped). In spite of their slender, worm-like forms, shipworms possess the characteristic [[Morphology (biology)|morphology]] of [[bivalve]]s. The [[Ctenidium (mollusc)|ctinidia]] lie mainly within the branchial [[Siphon (mollusc)|siphon]], through which the animal pumps the water that passes over the [[gill]]s. The two siphons are very long and protrude from the [[Anatomical terms of location|posterior]] end 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 the [[Anatomical terms of location|anterior]] end 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 the [[Mantle (mollusc)|mantle]] lies 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,<ref name="Goodell2024TyphSymbIBB">{{cite journal|author=Goodell, B.|author2= J. Chambers|author3= D. V. Ward|author4= C. Murphy|author5= E. Black|author6= L. B. Kikuti Mancilio|author7= G. Perez- Gonzalez|author8= J. R. Shipway|year=2024|title=First report of microbial symbionts in the digestive system of shipworms; wood boring mollusks|journal=International Biodeterioration & Biodegradation|volume=192|issn=0964-8305|doi=10.1016/j.ibiod.2024.105816|bibcode= 2024IBiBi.19205816G|doi-access= free}}</ref> The ''Alteromonas'' or ''Alteromonas''-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.<ref>{{cite book|author=Goodell, B.|author2= Nielsen, G. |year=2023|chapter=Wood Biodeterioration|editor=Niemz, P.|editor2= Teischinger, A.|editor3= Sandberg, D. |title=Springer Handbook of Wood Science and Technology|series=Springer Handbooks|pages= 139–177 |publisher=Springer, Cham. |doi=10.1007/978-3-030-81315-4_4|isbn= 978-3-030-81314-7 }}</ref> 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.<ref name="Goodell2024TyphSymbIBB"/><ref name="Distel">{{cite journal |last1=Distel |first1=D. L. |last2=Morrill |first2=W. |last3=MacLaren-Toussaint |first3=N. |last4=Franks |first4=D. |last5=Waterbury |first5=J. |year=2002 |title=''Teredinibacter turnerae'' gen. nov., sp. nov., a dinitrogen-fixing, cellulolytic, endosymbiotic gamma-proteobacterium isolated from the gills of wood-boring molluscs (Bivalvia: Teredinidae) |url=http://ijs.sgmjournals.org/cgi/content/abstract/52/6/2261 |url-status=dead |journal=International Journal of Systematic and Evolutionary Microbiology |volume=52 |issue=6 |pages=2261–2269 |doi=10.1099/00207713-52-6-2261 |pmid=12508896 |issn=1466-5026 |archive-url=https://web.archive.org/web/20080907142514/http://ijs.sgmjournals.org/cgi/content/abstract/52/6/2261 |archive-date=2008-09-07 |access-date=2010-09-23 |hdl-access=free |hdl=1912/110}}</ref>

The excavated burrow is usually lined with a [[calcareous]] tube. The valves of the [[Exoskeleton|shell]] of [[shipworms]] are 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.<ref name="Nobanis" />

''[[Teredo navalis]]'' develops from eggs to [[metamorphosing]] [[larvae]] in 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 are [[hermaphrodites]] while 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.<ref>{{cite web |title=''Teredo navalis'' |url=https://animaldiversity.org/accounts/Teredo_navalis/#D8BFE597-9172-4025-8269-617B480D59B7 |website=Marine Invasions Research at the Smithsonian Environmental Research Center |access-date=30 November 2023}}</ref>