Teredo triangularis

Invasion History

First Galapagos Record: 2015

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General Invasion History:

The shipworm Teredo triangularis was described by Edmondson in 1942, from Maui, Hawaii, and was considered a native oceanic species (Carlton and Eldredge 2009). It is widely distributed in the Indo-West Pacific, including the Indian Ocean, the Philippines, Saipan, and Japan (Turner 1966; Nair 1984; Betcher et al. 2012; Museum of Comparative Zoology 2021). It is considered in introduced in the Galapagos Islands, and the Pacific coast of Colombia (N. Treneman, personal communication cited by Carlton et al. 2019). 

Invasion History in the Galapagos:

Teredo triangularis was found to be common in driftwood around Santa Cruz Island in 2005–2016 (Teredo triangularis, Carlton et al. 2019, S1). Hull fouling is the likely vector for the spread of shipworms by wooden ships and boats.

Invasion history elsewhere in the world:

Aside from the Indo-West Pacific, Teredo triangularis is considered introduced in the Galapagos Islands, and the Pacific coast of Colombia (N. Treneman, personal communication cited by Carlton et al. 2019). 

Description

Teredo triangularis belongs to the family Teredinidae (shipworms) which are highly modified mollusks, hardly recognizable as bivalves, and adapted for boring into wood. The shell is reduced to two small, ridged valves which cover the head, and are used for grinding and tearing wood fibers. The body is naked and elongated and ends with two siphons, protected by elaborate calcareous structures called pallets (Turner 1966).

The shell of T. navalis, like those of other species, has three subglobular lobes. The smallest of these is the auricle, which is semicircular and subtriangular. The pallets have a short stalk, but the blade of the pallet does not sheath the stalk. The distal margin of the inner face is concave and lined with dark periostracum (Turner 1971). Note that this account is based on the description of T. navalis and the key to Turner (1971), which only describes the species' pallets.

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Taxonomy

Ecology

General:

Shipworms dig long burrows in submerged wood in marine environments. They burrow by rocking and abrading the wood fibers. The mantle covers most of the length of their body and secretes a calcareous lining along the interior of the burrow. They normally have their anterior end with head and shells inside the burrow, and their siphons protruding outwards. The pallets plug the burrow when the siphons are retracted (Barnes 1983). Teredo triangularis is known from fixed wood structures, and driftwood (Nair and Dharmaraj 1983; Nair 1984; Carlton et al. 2019). 

Food:

Wood; Phytoplankton

Consumers:

Protozoan parasites

Competitors:

Trophic Status:

Herbivore

Herb

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Habitats

General Habitat	Coarse Woody Debris	None
General Habitat	Marinas & Docks	None
General Habitat	Vessel Hull	None
General Habitat	Mangroves	None
Salinity Range	Polyhaline	18-30 PSU
Salinity Range	Euhaline	30-40 PSU
Tidal Range	Subtidal	None
Vertical Habitat	Epibenthic	None

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Life History

Shipworms are protandrous hermaphrodites, beginning life as male and transforming to female, but they have no capacity for self-fertilization. Males release sperm into the water column, which fertilizes eggs for the female. The fertilized eggs are then brooded in the gills. Larvae are retained in the gills to the veliger stage (Hoagland 1986a; Richards et al. 1984). Some species release veligers at an early stage with a long planktotrophic period, while others are released at a later stage, with a brief planktonic period (Turner and Johnson 1971). The larvae settle in the pediveliger stage, and then rapidly metamorphose and begin boring into wood within 4 days. They quickly develop a calcified shell, pallets, and burrow lining (Turner and Johnson 1971). Shipworms may obtain some or most of their nutrition from plankton, but some comes from wood, which consists largely of cellulose (Paalvast and van der Velde 2013). Symbiotic bacteria fix nitrogen, essential for protein synthesis (Turner and Johnson 1971; Barnes 1983). 

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Tolerances and Life History Parameters

Broad Temperature Range	None	Subtropical-Tropical
Broad Salinity Range	None	Polhaline-Euhaline

General Impacts

Economic Impacts: Shipworms as a group damage wooden structures and vessel hulls. However, specific impacts of T. triangularis are unknown.

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References

Betcher, Meghan A. and 7 authors (2012) Microbial distribution and abundance in the digestive system of five shipworm species (Bivalvia: Teredinidae), PLOS ONE 7(9): e45309
https://doi.org/10.1371/journal.pone.0045309

Barnes, Robert D. (1983) Invertebrate Zoology, Saunders, Philadelphia. Pp. 883

Carlton, James T.; Eldredge, Lucius (2009) Marine bioinvasions of Hawaii: The introduced and cryptogenic marine and estuarine animals and plants of the Hawaiian archipelago., Bishop Museum Bulletin in Cultural and Environmental Studies 4: 1-202

Carlton, James T.; Keith, Inti; Ruiz, Gregory M. (2019) Assessing marine bioinvasions in the Galápagos Islands: implications for conservation biology and marine protected areas, Aquatic Invasions 14(1): 1-20

Harvard Museum of Comparative Zoology 2008-2021 Museum of Comparative Zoology Collections database- Malacology Collection. <missing URL>



Hoagland, K, Elaine (1986b) Genetic variation in seven wood-boring teredinid and pholadid bivalves with different patterns of life history and dispersal, Malacologia 27(2): 323-339

Hoagland, K. Elaine (1983) Life history characteristics and physiological tolerances of Teredo bartschi, a shipworm introduced into two temperate zone nuclear power plant effluents., In: Sengupta, N. S., and Lee S. S.(Eds.) Third International Waste Heat Conference.. , Miami Beach, FL. Pp. 609-622

Nair, N. Balakrishnan (1984) The problem of marine timber destroying organisms along the Indian coast, Proceedings of the Indian Academy of Sciences 93(3): 203-223

Nair, N. Balakrishnan; Dharmaraj, K. (1983) Marine wood-boring mollusks of the Lakshadweep Archipelago, Indian Journal of Marine Science 12: 96-00

Paalvast, Peter; van der Velde, Gerard (2013) What is the main food source of the shipworm Teredo navalis? A stable isotope approach, Journal of Sea Research 80: 58-60

Richards, Beatrice R.; Hillman, Robert E.; Maciolek, Nancy J. (1984) Shipworms, In: Kennish, Michael J.; Lutz, Richard A.(Eds.) Lecture Notes on Coastal and Estuarine Studies - Ecology of Barnegat Bay, New Jersey. , New York. Pp. 201-225

Turner, R. D.; Johnson, A. C. (1971) Marine Borers, Fungi, and Fouling Organisms of Wood, Organisation for Economic Co-operation and Development, Paris. Pp. 259-301

Turner, Ruth D. (1966) A survey and illustrated catalogue of the Teredinidae (Mollusca: Bivalvia), The Museum of Comparative Zoology, Harvard University, Cambridge. Pp. <missing location>

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