Taxonomic name: Bugula neritina (Linnaeus, 1758)
Synonyms: Anamarchis neritina, Sertularia neritina
Common names: brown bryozoan (English), bryozoan (English), common bugula (English)
Organism type: bryozoan
Bugula neritina (brown bryozoan) is an erect, bushy bryozoan. It is an abundant fouling organism that colonises any freely available substratum, including artificial underwater structures and vessel hulls.
Bugula neritina forms flexible bushy colonies, branching biserial, to about 10cm high and is purplish-brown in colour. Zooids white and globular, with the outer corner pointed (Bishop Museum 2002, in Gordon and Mawatari, 1992). Zooids are large and measure an average of 0.97 X 0.28mm. B. neritina differs from other species in this genus in that it possesses no avicularia and no spines. The lophophore measures an average of 0.764mm in diameter and bears 23 tentacles (SMSFP 2001). Embryos brooded in ovicells are dark brown in colour and measure approximately 0.25mm in diameter (SMSFP 2001 in Winston 1982).
Bugula spp., Bugula stolonifera, Bugula turrita
Bugula neritina colonies are typically found in harbours and embayments, intertidal to 5m, attached to any available hard substrate (Bishop Museum 2002). Larvae colonise a variety of artificial substrata including hulls (Mackie et al. 2006). Studies have shown B. neritina larvae prefer to attach to rougher surfaces and prefer to attach to organic material. For example, in nature they frequently affix themselves to algae and to established bryozoan colonies (Lynch 1947). B. neritina is found in euhaline and polyhaline regions (water salinity around 30-18‰) (Winston 1977).
In North America B. neritina occurs on rocky reefs and seagrass leaves (Hayes et al. 2005).
Bryozoans are one of the main organisms to encrust and foul ships, piers, buoys and other man-made marine surfaces and structures (VMNH 2005). B. neritina populations may tolerate high levels of pollution (including copper) which increases its potential to be a fouling pest. A tolerance to toxicants could provide a competitive advantage in polluted areas (Piola and Johnston 2006). Verification of the chemical tolerances of invasive and non-invasive lineages of B. neritina, and other fouling organisms in general, is needed to test this hypothesis (Josh Mackie., pers.comm., 2007).
Bugula neritina colonies are the source of a novel chemical compound (bryostatin) which has been shown to be effective against leukaemia and a number of other kinds of cancer. A newly described species of bacterium, which is symbiotic to B. neritina cryptic species 'type D', appears to be the source of bryostatins (Davidson and Haygood, 1999; Davidson et al. 2001).
Nudibranchs have been recorded as consumers of Bugula neritina (NIMPIS 2002). Southern California studies have shown a high mortality rate for bryozoans during red tides (algal blooms). Bryozoans are preyed upon by grazing organisms such as sea urchins and fish. They are also subject to competition and overgrowth from sponges, algae, and tunicates (PWSRCAC 2004).
Bryozoans provide habitat for many species of juvenile fish and their invertebrate prey such as polychaete worms, amphipods and copepods (SMSFP 2001 in Winston 1995). Bryozoans are also found in association with other species that act as support structures: mangrove roots, oyster beds, mussels, etc. (SMSFP 2001).
The feeding activities of bryozoans and other filter feeding animals strain out excess food and debris particles to help keep the water clean (VMNH 2005). Bryozoan colonies located in 1m2 of seagrass bed could potentially filter and recirculate an average of 48,000 gallons of seawater per day (SMSFP 2001 in Winston 1995).
Bugula neritina a common fouling organism worldwide, is reported from all seas except sub Arctic and sub Antarctic regions (Bishop Museum 2002). The cosmopolitan distribution of the species appears to be due to shipping introductions (Mackie et al. 2006). Furthermore, genetically divergent but morphologically unrecognised (=’cryptic’) species of B. neritina have been identified in the United States.
Native range: Bugula neritina was widespread before surveys commenced in most areas (Keough and Ross, 1999). One mitochondrial haplotype (based on sequences of the mitochondrial gene COI) is globally widespread, occurring on coastlines in Australia, Curacao, USA and Hawaii, and the UK, indicating a widespread introduction (Mackie, Keough and Christidis, 2006). The native locale of this lineage is unknown from molecular studies. Three cryptic species referred to as B. neritina are known to occur in the USA; these are referred to as Type S and Type D (occurring in California) (Davidson and Haygood, 1999); and a third divergent 'cryptic species' lineage has been identified in the northern part of the taxonomic range in the eastern USA (McGovern and Hellberg, 2003).
Introduction pathways to new locations
Aquaculture: Bugula neritina attaches to oyster shells and be transferred along with oyster shippings (Cohen 2005).
Ship ballast water: Bugula neritina can be transported via tiny colonies attached to the sides of ballast tanks or on floating material inside the ballast tanks (Cohen 2005).
Ship/boat hull fouling: Ship/boat hull fouling is a common means of movement of Bugula neritina colonies and a likely source of ongoing introductions.
Local dispersal methods
Agriculture (local): Bugula neritina attaches to oyster shells and be transferred along with oyster shippings (Cohen 2005).
Natural dispersal (local):
Preventative measures: A two year study was undertaken for the Department of Environment and Heritage (Australia) by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) to identify and rank introduced marine species found within Australian waters, and those not found within Australian waters. All of the non-native potential target species identified in this report are ranked as high, medium and low priority, based on their invasion potential and impact potential. Bugula neritina is identified as one of ten potential domestic target species most likely to be spread to uninfected bioregions by shipping. B. neritina is also identified as one of ten most damaging potential domestic target species, based on overall impact potential (economic and environmental). A hazard ranking of potential domestic target species based on invasion potential from infected to uninfected bioregions identifies B. neritina as a 'medium priority species' - these species have a reasonably high impact/or invasion potential.
For more details, please see Hayes et al. 2005.
The rankings determined in Hayes et al. 2005 will be used by the National Introduced Marine Pest Coordinating Group in Australia to assist in the development of national control plans which could include options for control, eradication and/or long term management.
It has been suggested that ballast water control measures be implemented to control the spread of B. nertina via the oyster aquaculture industry (PWSRCAC 2004).
Chemical: Copper-based treatments have been used to control many pest species. The attachment of B. neritina larvae to copper, mercury and control paint was investigated by Wisely (1962) who found that the numbers attaching to the control paint strips was seven times greater than the numbers attaching to copper, and twenty times greater than the numbers attaching to mercury (NIMPIS 2001). Introduction of B. neritina by
copper-painted vessels may be aided by a potential tolerance to toxicants (Piola and Johnston 2006).
The bryozoan is a suspension feeder. It has a retractable U-shaped crown of tentacles (lophophore) which bear cilia that create a current, bringing microscopic plankton and organic particles toward the animal. Particles are then guided into the mouth by action of the tentacles and cilia (Bishop Museum 2002).
Each bryozoan colony begins from a single, sexually produced, primary zooid. This zooid undergoes asexual budding to produce a group of daughter cells, which themselves form buds, and so on. Most bryozoans are hermaphroditic, each zooid capable of producing sperm and eggs. Sperm is released into the coelom and the fertilised eggs are retained and brooded for a time before being released (Bishop Museum 2002).
Bryozoans have swimming, lecithotrophic larvae that attach and metamorphose within 1 or 2 days following release from the colony. Larvae are initially photopositive but soon become photonegative/Geopositive, settling usually within a few hours of release (Lynch, 1947). Larvae may have gregarious settlement (Keough, 1984). Bugula larvae generally settle throughout the year except during midwinter (Sutherland and Karlson 1977). Field studies in Australia and North America show considerable variation in life history in B. neritina from different habitats, apparently due to genetic or early environmental effects (Keough, 1989; NEMESIS 2006). B. neritina's life history may include an annual period of dormancy, in which colonies recede to a regenerative holdfast (Dyrynda and Ryland 1982). This senescence occurs at differing times of year and appears dependent upon water temperature, with populations in cool-temperate areas receding during winter and populations in warm areas receding over summer months (Keough and Chernoff, 1987).
Reviewed by: Dr. Josh Mackie, Invertebrate Zoology and Molecular Ecology Lab. Moss Landing Marine Laboratories. California USA
Compiled by: IUCN/SSC Invasive Species Specialist Group (ISSG) with support from La Fondation d'entreprise Total
Last Modified: Thursday, 8 May 2008