Eco Bites
Ficopomatus enigmaticus - the estuarine tube worm
The estuarine tube worm (or Australian tube worm) has become a major nuisance in the lower Diep River estuary, particularly in the area around the wooden bridge and the Woodbridge Island Road bridge. Native to Australia, Ficopomatus enigmaticus has probably been most often introduced to new regions as fouling on ship and boat hulls, though some of its transport may have occurred as larvae in ballast water, or in some cases as fouling on transported oyster shells. In South Africa it was first noticed in the Cape Town area in 1951, and now occurs mostly in estuaries in the Cape Peninsula and along the south coast.
Read more about the biology of Ficopomatus enigmaticus.
Ficopomatus enigmaticus builds and lives in white, calcareous tubes that are about 2 mm in diameter and a couple of centimeters long. The tubes are somewhat flared at their open ends, and have conspicuous, collar-like rings or flanges spaced irregularly along their lengths. Older tubes are typically stained a gold-brown or dark brown along much of their length, with the areas around the flanges and the flared ends usually remaining white.
To feed, Ficopomatus enigmaticus extrudes a crown of 12-20 gray, green or brown branching gill plumes out of the open end of the tube. Cilia on the plumes move currents of water upward through them, oxygenating the blood within. Other cilia capture small food particles and pass them down to the mouth at the base of the plumes. When disturbed, the worm pulls the plumes quickly back into its tube and closes it with a funnel-shaped stopper, called the operculum, at the end of one modified gill plume. The top of the operculum bears numerous, small, black spines. The worm is usually about 2 cm long, including the operculum.
Ficopomatus enigmaticus grows in the low intertidal to shallow subtidal range on rocks, concrete, wood, shells and other hard surfaces, including pilings and the sides of floating docks, buoys and boat hulls. It can occur as single, separate tubes, or as tangled, agglomerate masses that form incrustations up to 10 cm or more thick.
It can survive in ocean salinities, but grows and reproduces only in lower salinities of about 10-30 ppt, and temperatures above 18° C. To spawn, eggs and sperm are released into the water where fertilization occurs. The larvae develop in the plankton, and after 20-25 days settle on and attach to an appropriate hard surface.
In colder areas the tube worm colonises water heated by power plant discharges and can cause problems when the growths block the discharges or intake pipes. In the Netherlands it clogs and interferes with the operation of locks. However, it has been suggested that large populations of Ficopomatus enigmaticus may remove suspended particulate matter, reduce excess nutrient loads and improve oxygen levels in boat basins or enclosed waters with poor water quality. Serious studies have not been done on the ecological effects, but there are suggestions that it competes for available food resources with other filter feeders if the colonies become extensive.
Control of Ficopomatus enigmaticus is fairly easy as large colonies can be removed mechanically or manually. However, with mobile larvae and a rapid growth rate, colonisation occurs quite quickly and continued control is required to keep areas clear of this tube worm.
Compiled by Niel van Wyk with information sourced from the website: http://www.exoticsguide.org/species_pages/f_enigmaticus.html May 2011.