Taxonomic name: Watersipora subtorquata (d'Orbigny, 1952)
Organism type: bryozoan
Watersipora subtorquata (d’Orbigny, 1852) is a loosely encrusting bryozoan. It is tolerant to copper based anitfouling coatings and is infamous for fouling ships hulls and facilitating the fouling and spread of other marine invasives. Watersipora subtorquata is considered cosmopolitan and widely invasive among cool temperate water ports. Preventative measures are the only practical means of control at this time.
Watersipora subtorquata colonies are bright orange to red with variable amounts of black and may be flat or foliose, developing in to a lobed mass up to 25cm in height. Individual zooids are composed of soft polypide tissue and a rigid rectangular or coffin-shaped zooecium. The zooecium are 0.3-0.7 mm wide and 0.75-1.5 mm in height radiating from the founding zooid. Its inner and older parts of the colony turn dark or black, while the outer growing edges are usually orange or red. Zooids have a u-shaped crown of 19-24 ciliated, orange translucent tentacles, called a lophohpore, which is extended through its aperture to feed. W. Subtorquata lacks spines, avicularia, and ovicells common to many bryozoans. An identifiable characteristic is its black, sinusoid aperture, having a convex proximal border (Cohen 2005).
Watersipora arcuata, Watersipora edmondsoni, Watersipora new sp., Watersipora subovoidea
estuarine habitats, marine habitats
Watersipora subtorquata is most common to lower intertidal and shallow subtidal areas. It is known to inhabit salinities of 25-49 parts per thousand, temperatures of 12-28°C, and depths to the tens of meters. It grows on a wide range of substrates including rocks, shells, debris, docks, kelp, ship hulls, pilings, pontoons, and other bryozoans. Since they are an early successional species, they are especially efficient at colonizing artificial structures as they are they are new surfaces (Keough and Ross 1999; Cohen, 2005; Glasby et al. 2007).
Watersipora subtorquata is an abundant fouling organism. It is tolerant to copper based antifouling biocides so it facilitates the spread of other invasives by providing a non-toxic surface for other fouling species to settle. This trait is known from observation to occur in multiple species in the genus, including Watersipora arcuata (formerly, like W. subtorquata, referred to as W. cucullata) (Wisely 1958, Allen 1959)
A study in which a ship's hull was coated with three antifouling paints resulted in 64% of its surface covered with W. subtorquata within 16 weeks and 22 other species occurring exclusively on top of W. subtorquata colonies (Floerl et al. 2004).
In addition to its facultative interaction of spreading other non-indigenous species, W. subtorquata has its own competitive interactions with native bryozoans and community structures. It is the most common intertidal bryozoan in many areas of introduction. W. subtorquata along with Bugula neritina is considered the most common introduced species in harbors and estuaries in the context of hull fouling. In fact, its resistance to antifouling toxins that can collect in ports may give it an advantage over native biota. W. subtorquata has also demonstrated the ability to lie dormant in overly toxic conditions and recover as conditions improve. In Australia it is declared a medium priority pest (Floerl et al. 2004; Hayes et al. 2005; Mackie et al. 2006; Piola and Johnston, 2006).
Watersipora subtorquata has a convoluted taxonomy and history. Subsequently, its native range is presently unknown. Previously, bryozoans with the described physical attributes and sinusoid aperture of "W. subtorquata" were referred to with several names that ended up converging on an unclear "Watersipora subtorquata" complex (Gordon 1989). Recent DNA testing and sampling has defined W. subtorquata and differentiated it as a separate species from closely related W. subovoidea (=cucullata), W. edmondsoni, and a new, unnamed, Watersipora species (Mackie et al. 2006). All of which have at one time been included in the "W. subtorquata" complex. Comments in the distribution section denote details on which populations been sampled, tested, and concluded to be W. subtorquata. Further sampling and testing will be required to define the actual range of W. subtorquata and other Watersipora spp.
W. subtorquata is still thought to be a cosmopolitan species and the northwest Pacific is thought to be its most likely origin.
W. subtorquata may have been previously referred to or recorded as many different names including: Cellepora subtorquata, Escharina torquata, Watersipora subovoidea, Dakaria subovoidea, Cellepora ovoidea, Watersipora cucullata, Lepralia cucullata, Watersipora atrofusca, Lepralia atrofusca, Schizoporella atrofusca, Watersipora aterrima, and Watersipora edmondsoni. Watersipora subtorquata is also very similar to Watersipora arcuata, which is reliably differentiated by its aperture upon examination by light microscope (Banta 1969). While virtually morphologically cryptic species appear to be present (Geller et al. 2006), efforts have been made to reconcile the use of morphometrics and colony color in the field with genetic definition of lineages, which to date has been carried out using the mitochondrial gene COI (Ryland et al. in prep.).
Native range: uncertain (please see notes)
Known introduced range: United States, Australia, New Zealand, United Kingdom.
Preventative measures: Preventative measures are the only current practical means controlling Watersipora subtorquata populations. Alternative methods of antifouling are necessary to prevent W. subtorquata and other antifouling resistant species from spreading and facilitating the spread of others via vessel hulls. The problem of ballast water fouling is being addressed by programs such as the GloBallast Water Management Programme but solutions to prevent hull fouling are much needed. Hull fouling prevention strategies combined with analysis of maritime activity is very much necessary to stop the spread of marine invasives. Physical removal or chemical treatment of nonindigenous aquatic Watersipora subtorquata is not yet a cost effective option. Since its populations are usually fairly widespread, local population controls are deemed ineffective. (Biosecurity New Zealand, 2005; Hayes et al. 2005; GloBallast, undated).
It is a suspension feeder which feeds on microscopic plankton and organic material, which it sweeps in to its mouth with its ciliated tentacles (lophophore) (Cohen, 2005).
Watersipora subtorquata is hermaphroditic, sexual self-fertilizing bryozoan which broods its larvae inside its zooecia. Its free swimming, crimson lecithotrophic larvae lack a mouth and digestive tract. They must settle to a substrate within a day of release, usually only after a few hours, where they metamorphose into a zooid. This primary zooid then replicates asexually, budding into a colony.
Watersipora subtorquata lecithotrophic larvae are brooded inside zooecia and released upon maturation. They only spend a few hours to one day in this free swimming state as they lack the necessary mouth and digestive tract to sustain themselves. They settle to a substrate and metamorphose into a primary zooid. This zooid buds in to a colony capable of hermaphroditic, sexual reproduction of new larvae.
Reviewed by: Dr. Josh Mackie, Invertebrate Zoology and Molecular Ecology Lab. Moss Landing Marine Laboratories. California USA
Principal sources: Cohen, A. N. 2005. Watersipora subtorquata (d'Orbigny, 1952). Guide to exotic species of San Francisco Bay. San Francisco Estuary Institute, Oakland, CA,.
Geller, J, Mackie, J., Schroeder, G., and Gerhinger, D. 2008. Distribution of highly invasove bryozoans belonging to a cryprtic species complex in the genus Watersipora determined by DNA sequences. Final Report to California Department of Fish and Game, Moss Landing Marine Laboratories, Moss Landing, CA.
Mackie, J.A., Keough, M.J., and Christidis, L. 2006. Invasion patterns inferred from cytochrome oxidase I sequences in three bryozoans, Bulga neritina, Watersipora subtorquata, and Watersipora arcuata. Marine Biology. Vol. 149: 285-295.
Boyd, M.J. 2002. Appendix B: Non-indigenous marine species of Humbolbt Bay, California, A report to the California Department of Fish and Game. A Survey of non-indigenous species in the coastal and estuarine wawters of California. CA Department of Fish and Game.
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Thursday, 22 May 2008