Teredo Worm

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Read MORE about Teredo in our
scienceblog.com article. Please click here.

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Teredo bartschi at the very early stage of burrowing into a mangrove trunk in Batan (Aklan Province, Philippines)
To view the video, please click here.

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“Here at the Amazon River Basin we have some sea coast areas and teredo is considered a tasteful food for some people. They call teredo as “turu” and they eat turus in raw or baked mode.
So, when I came across Poseidon Sciences website about tamiloks I laughed and said, “Wow, how the people are so similar in this world.” It’s very curious and funny, to think in how so distant people can think equal about shipworms, eating them”.

—-From: Mr. Francisco Tarcisio Moraes, Forest Engineer, Manaus, Amazonas, Brasil .

Wood damage from Teredo worms in the marine environment

Shipworms, also called by mariners as the ‘termites of the sea’ belong to the genus called Teredo, the most notorious of which is Teredo navalis, originally native to the Caribbean Sea. It is actually a clam that tunnels through wood submerged in the sea. Though the Teredo serves an ecological value in degrading timber that falls to the ocean, it has also caused considerable damage to wooden boats even since man first ventured out to sea. Shipworms have been a bane to ancient mariners till the advent of copper clad ships by the 18th century and modern toxic coatings.

These boring clams weakened the unprotected wooden hulls of ships to the point that they break apart in the open sea without any warning. The Greeks and the Phoenicians certainly knew about them since 3,000 BC, lathering the hulls of their ships with wax and tar to keep them away. The Romans used combinations of lead, tar and pitch to cover their boat.

Unbeknownst to Columbus, his first voyage to the Caribbean Sea in 1492 exposed his ships to the world’s most Teredo-infested waters, likely due to the higher salinity of the Caribbean. The ships that arrived later brought back Teredo navalis to Europe, where they can be found even as far away as the North Sea, having adapted to the cold environments. Unknown number of ships had been lost at sea just because of Teredo worms. These same worms caused the collapse of the wooden supports used for the dikes of Holland in 1731 causing flooding, 250 years after the first voyage of Columbus. Only the timely replacement of the outer surfaces of the dike with stones prevented more catastrophes. Over the last few hundred years, all of the oceans have been colonized by Teredo worms.

The behavior of the shipworm inspired Marc Brunel, a French engineer, to devise a method, which he patented in 1818, to tunnel under the Thames River in England, the first of its kind ever built under a river bed. His technique called the “tunneling shield” made use of his observations while working on a shipyard on how the valves with fine ridges were used by the Teredo to drill through the wood, while protecting itself from being crushed. The Teredo also secretes a calcium-rich framework that coated the inside surface of the tube, keeping it stable and crush proof.

In modern times, we have yet to escape the wrath of the Teredo. Wharves, piers, jetties and piling started collapsing in San Francisco Bay between 1919 and 1921, resulting in almost 20 billion dollars worth of damage in today’s money, all because of Teredo. The mouth of the Hudson River of New Jersey and New York was once considered a ‘dead’ waterway, devoid of fish life because of the overwhelming industrial pollution since the 1930’s. Ship captains used to sail their boats through NY harbor just to kill off shipworms and barnacles. That’s how polluted it was. In 1972, the US Federal Clean Water Act limited discharge into the rivers and proactively revitalized the waterways. By the 1990’s fish had returned. And so did the Teredo, with a vengeance. During this period also saw the voluntary ban by the lumber industry on the use of creosote and CCA (chromated copper arsenate) to prevent further leaching of the toxic chromium and arsenic to the environment. These wood preservatives prevented fungi from rotting the wood away and also quite good at killing off the shipworms as well. The environmentally sound actions had unintended consequences—piers and piling that no longer used preservatives started collapsing, hollowed through by Teredo worms.

Economic value? So far, there is no known commercial value for Teredo other than in some Pacific Islands where they are a delicacy. Teredo worms make a special Philippine delicacy called tamilok, appreciated by natives of Palawan Island and Aklan Province of Panay Island, where extensive mangrove forests serve as home for the clams. It is prepared raw as a ceviche or kinilaw in the local language, with vinegar, chili peppers and onions. It is a delicacy that is certainly not for the timid.

Biology of Teredo

Considering the economic importance of preventing Teredo infestation, it is surprising how little known about the life cycle of this clam. This website is a work in progress and we welcome suggestions and additions to update the information. Some of the biological information comes from our ongoing observations at our marine test site in Panay Island, where mangrove forests serve as home of Teredo bartschi Clapp, 1923.

In general, the sex in the wild is 1 Teredo male per 1,500 females. After fertilizing the eggs by the male Teredo, the developing embryos are protected inside the mother until they develop into larvae competent to colonize other locations outside the home tunnel.

Then,the little Teredos settle in the same wood or nearby timber. Then it starts burrowing through the wood as it grows, parallel to the grain, only turning to avoid any knot on the wood or if there is any obstruction. By the time it reaches adulthood, it is already at least a foot long and half inch thick. If you think this is big for a worm, its Sumatran cousin, the Giant Teredo, grows to six feet long, but lives in the muddy bottom of the sea rather than inside wood. Unlike other typical clams, the shell covers only a tiny portion of the Teredo and used more like a drill bit to burrow a circular hole through the wood. The tube-like home is capped at the opening of the burrow with a secreted calcareous cover, with protruding siphons that allow the animal to breathe, feed on plankton and excrete wastes. It appears that the Teredo lives out its life within its tunnel home, continuing to extend the length of its burrow. Actual life span of the Teredo in the wild is not known.

The cellulose that makes up the wood is not sufficiently nutritious as food and the shipworm cannot normally digest it. It overcomes this limitation through a symbiotic relationship with bacteria, Teredinibacter turnerae, in its gills that secrete enzymes, called cellulases and nitrogenases, breaking down the cellulose and fixing nitrogen to build amino acids. Cellulases are the same enzymes, derived from fungi, used to create your stonewashed denim jeans by breaking down the cellulose on the outer surface of the cloth. Now, it is also a major ingredient in most laundry detergents to improve cleaning efficiency. The potential of Teredo-derived cellulases is in its future use in biofuels because it is likely more efficient than fungal cellulases in converting paper-mill cellulose waste into ethanol or methanol

Poseidon Teredo Test Station

Although Teredo is present all over the world, developing biocontrol measures through new biocidal approaches takes much longer in temperate countries due to seasonal effects. For this reason a new test site has been established along the coast in the island of Panay where Poseidon already has a station for subsea immersion. The Teredo site is located north of the island in the town of Batan in Aklan province (see map).

The Poseidon Teredo Test Station is located within the mangrove forest heavily populated with Teredo. Sizes of the Teredo vary depending on the size of the branch or tree trunk they are tunneling through. Seawater flushes the mangroves with 4 foot tides, exposing the trunks for a few hours each day, allowing easy access to the exposure site during low tides.

Initial observations on trunks brought to the laboratory for examination generated some interesting insights into the biology of the Teredo worm.

• The calcareous wall of the tunnel remained soft when wet and easily damaged. However, when carefully removed without damage, the ‘tube’ hardens, retaining the shape of the tunnel.

• The color of the Teredo is milky white when the wood is opened to expose the clam. However, once exposed to air and light, the clam changes in color in less than one minute to a bluish tinge.

Ongoing investigations are focused on basic and applied research on Teredo. These include:

• Determining the minimum period of marine exposure to observe settlement and tunneling.
• Determining its preference for different wood types
• Understanding the seasonal and diurnal fluctuations that may affect Teredo settlement behavior
• Determining optimal size of test stakes for wood protection studies
• Developing convenient means of estimating Teredo size using correlation between tunnel depth and diameter of opening

This is an exciting exploration which helps in the long term plans of developing nontoxic options to prevent Teredo damage to wood structures of economic value. Anyone interested in collaboration on basic Teredo biology or in applied research, please contact Jonathan R. Matias at the following email: jrmatias@poseidonsciences.com

Please click HERE to read an article about teredo.

Here are some additional information on the biology of Teredo. From: Lancelot Alexander Borradaile, Frank Armitage Potts. The Invertebrata: A Manual for the Use of Students

Teredo (Figure 430.) is the most specialized of the boring lamellibranchs. While most lamellibranchs burrow in mud, others tend to work in consolidated sediments such as Pholas in chalk and sandstone, and Saxicava in the hardest limestone. Teredo and Xylophaga bore in wood. The latter makes shallow pits, but Teredo, working with extraordinary speed, excavates long cylindrical tunnels (sometimes as much as foot in a month or two). The wood is reduced to sawdust by the rotatory action of the two shell valves, in which the adductor muscles fibres maintain a rhythmical contraction. The sawdust is swallowed by the animal and is largely retained in a relatively enormous caecum of the stomach but a great deal of the material passes into the cavity of the digestive gland is there ingested by the epithelial cells. There is no doubt that Teredo has developed enzymes which are almost unique in the Animal Kingdom, which digest cellulose and hemicellulose. The structure of the animal is remarkable for the extraordinary long siphons and mantle cavity; while the mantle oftens lays down a calcareous lining to the tube and always a pair of calcareous valves, the pallets, which close the mouth of the tube when the siphons are retracted. The foot is very much reduced. A constant current into and out of the mantle cavity is maintained by ciliary action, and the ctenidia, though so greatly modified and elongated, constitute a collector mechanism; but it does not seem that diatoms obtained in this way form any part of the normal food of the creature, which exists almost entirely on the carbohydrates furnished by wood which also contains small quantities of proteins.

Please read more here.