Schizoporella japonica (orange ripple bryozoan)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Latitude/Altitude Ranges
- Water Tolerances
- Pathway Causes
- Pathway Vectors
- Impact Summary
- Economic Impact
- Environmental Impact
- Risk and Impact Factors
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Links to Websites
- Principal Source
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Schizoporella japonica Ortmann, 1890
Preferred Common Name
- orange ripple bryozoan
Other Scientific Names
- Schizoporella unicornis Johnston in Wood, 1844
- Schizoporella unicornis var. japonica Ortmann, 1890
Summary of InvasivenessTop of page
The incrusting bryozoan Schizoporella japonica was originally described from Japan. In the middle of the 20th century, S. japonica was introduced to the Pacific coast of North America, where it is now well established. In 2010, the species was recorded for the first time in European waters in North Wales and in 2011 in the Orkney Islands and other localities in northern Scotland. These introductions seem most likely to have occurred through an ocean-going vessel or to have been transported with oysters. The bryozoan species colonizes freely available substratum, including artificial underwater structures and vessel hulls, with colonies rapidly becoming extensive and sometimes dominating fouling assemblages. The species has high competitive ability and shows high abundance and dominance in harbours. Long term confusion of S. japonica with other Schizoporella species has generated uncertainty regarding the extent of native and introduced ranges of the group, indicating that S. japonica may be much more widely distributed than what has been suggested until now.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Bryozoa
- Class: Gymnolaemata
- Order: Cheilostomatida
- Family: Schizoporellidae
- Genus: Schizoporella
- Species: Schizoporella japonica
Notes on Taxonomy and NomenclatureTop of page
More than 50 recent bryozoan species have been placed in the genus Schizoporella, including nine European species (Zabala and Maluquer, 1988; Hayward and Ryland, 1999; Tompsett et al., 2009; Bock, 2015; WoRMS, 2015). These species are spread throughout the world’s oceans, being present in all climatic zones, from polar to tropical regions (Marcus, 1940; Hayward and Ryland, 1995), and inhabiting virtually all kinds of substrata. The species S. japonica by Ortmann (1890) was originally described as S. unicornis var. japonica using specimens collected by Dr. L. Döderlein, in 1880-1881, from Sagami Bay, Honshu, Japan. Its holotype is stored in Strasbourg Museum (Ryland et al., 2014). Over the years there has been extensive confusion between this and other Schizoporella species, commonly S. errata, S. unicornis and S. pseudoerrata (Ryland et al., 2014). S. unicornis var. japonica has recently been elevated to species status as S. japonica by Dick et al. (2005).
DescriptionTop of page
Detailed descriptions of S. japonica can be found in Ortmann (1890) and Grischenko et al. (2007) for Japan, in Dick et al. (2005) for the Pacific coast of America and in Ryland et al. (2014) for Northern Europe. Bryozoan morphology varies according to environmental conditions and geographic area where species are collected (Ryland et al., 2014).
S. japonica forms an encrusting heavily calcified colony consisting, at first, of more or less circular flat sheets, which later may become bi-layered, occasionally with foliose lobes free from substrate or overgrowing other colony. Colonies spread over rocks, shells and other substrata, rapidly becoming extensive, pale whitish-pink to vivid orange-red or deep red in colour. Individual animals within a colony are called zooids. Zooids represent a living polypide inside a non-living case called zooecium. The walls of bryozoan zooecia are strengthened with a variety of substances depending on the species, normally calcium carbonate, chitin or a mixture of both. Morphology of zooecia is important for identification of the species. S. japonica zooids are generally rectangular, rounded distally, arranged in columns radiating from the centre, quite variable in size, usually 0.48-0.90 mm long. Each polypide is connected to its nearest neighbours by a strand of living tissue called protoplasm. Each zooecium has a hole at the top, called an orifice, through which the polypide can extend its ring of tentacles, or lophophore, when it is feeding. The orifice can be sealed by an operculum and occasionally by perforated calcification. The orifice of S. japonica is broader than long, semi-circular on the distal side. There is often a small umbo (knob) below the orifice. Avicularia may be distinguished near the orifice and have protective function. On a given zooid, oral avicularia may be absent, single or paired. Morphology of avicularia is important for species distinction; for detailed morphology of S. japonica avicularia see Dick et al. (2005). The zooecium contains a compensation sac (ascus) in its interior, immediately beneath the calcified front. This sac acts as a reservoir and allows internal volume changes (necessary because the zooecium is otherwise rigid) and opens to the exterior via a notch (sinus vanna) in the proximal rim of the orifice. S. japonica, together with S. errata, S. pseudoerrata and S. unicornis, has broadly and shallowly U-shaped sinus, wider than deep. Zooids can specialise morphologically, being responsible for specific tasks. Autozooids are specialised in feeding or collecting food, with slightly to moderately convex, evenly perforated, frontal walls. Vertical walls have uniporous or multiporous septula (Hayward and Ryland, 1999). In all colonies, a large percentage of zooids are autozooids, and some colonies consist entirely of autozooids, some of which also engage in reproduction. Feeding polypides of S. japonica (the internal living movable parts) have a lophophore of ciliated tentacles (about 19 tentacles in specimens from Friday Harbor, USA), which generate a water current that traps small particles of food and diverts them to the digestive tract. The digestive tract consists of a pharynx, a stomach and a U-shaped gut that terminates in an anus. The nervous system is composed of a single bilobed ganglion at the base of the lophophore near the pharynx. Ovicells are zooids specialized in reproductive activities. They act as brood chambers, producing eggs and holding them safe until they are ready to hatch. They look like a helmet, or hood, on the anterior end of some zooids. In S. japonica, ovicells are raised, conspicuous, resting on the frontal wall of the succeeding zooid, globose, 0.28-0.40 mm long by 0.28-0.40 mm wide, with scattered small pores over the entire surface and heavy ribs converging from the margin towards the midline.
DistributionTop of page
As differences between Schizoporella species can be subtle (Tompsett et al., 2009), certain species had been assumed to have cosmopolitan ranges. However, it is now recognized that, in many instances, this is probably not the case (Dick et al., 2005; Ryland et al., 2014). For example, S. unicornis has been repeatedly reported from the Pacific coast of North America; however, these records likely refer to S. japonica. It is also possible that many records from the Northeast Pacific are based on the misidentification of S. japonica, S. pseudoerrata and S. errata (Dick et al., 2005; Ryland et al., 2014). Similarly, records of S. unicornis from Australia (Ross and McCain, 1976; Vail and Wass, 1981; Tzioumis, 1994) should be considered with caution. These may instead represent populations of S. japonica introduced on oyster seed that were transplanted from Japan to Australia in the mid-1900s (Dick et al., 2005).
The first case of S. japonica invasion in European waters was recorded in a marina at Holyhead, North Wales, in July 2010. From May 2011, the species was found abundantly in the Orkney Islands and, subsequently, at other localities in northern Scotland (Ryland et al., 2014). The authors have no evidence to suggest whether Japan or North America was the source for this invasion. S. japonica is now widespread in the UK and has also been recorded in Ireland and Norway (see review in Loxton et al., 2017).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.Last updated: 10 Jan 2020
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|China||Present||Liu et al. (2001)||As S. unicornis|
|Japan||Present||Native||Mawatari and Mawatari (1980)||As S. unicornis|
|-Hokkaido||Present||Native||Kubota and Mawatari (1985); Grischenko et al. (2007); Ryland et al. (2014)|
|-Honshu||Present||Native||Okada (1929)||As S. unicornis; Mutsu Bay|
|Ireland||Present||Introduced||Invasive||Loxton et al. (2017)|
|Norway||Present||Introduced||Loxton et al. (2017)|
|Russia||Present||CABI (Undated a)||Present based on regional distribution|
|-Russian Far East||Present||CABI (Undated)||Near Vladivostok; Original citation: Gris?henko and Zvyagintsev (2012)|
|United Kingdom||Present||Introduced||Invasive||Ryland et al. (2014); Loxton et al. (2017)|
|Canada||Present||Introduced||CABI (Undated a)||Present based on regional distribution|
|-British Columbia||Present||Introduced||Powell (1970)||As S. unicornis; from San Juan Islands, Vancouver Island, and Pendrell Sound|
|United States||Present||Introduced||CABI (Undated a)||Present based on regional distribution|
|-Alaska||Present, Widespread||Introduced||2003||Dick et al. (2005)||Higgins Point, East Tongass Narrows, Ketchikan|
|-California||Present||Introduced||Powell (1970); Ryland et al. (2014)|
|-Washington||Present||Introduced||Invasive||Ross and McCain (1976); Thorpe and Ryland (1987)|
|Australia||Present||CABI Data Mining (Undated); Ross and McCain (1976); Vail and Wass (1981); Tzioumis (1994)|
|Atlantic - Northeast||Present||Introduced||Invasive||Ryland et al. (2014); Loxton et al. (2017)|
|Pacific - Eastern Central||Present||Introduced||Osburn (1952); Powell (1970); Ryland et al. (2014)|
|Pacific - Northeast||Present||Introduced||Ross and McCain (1976); Thorpe and Ryland (1987); Dick et al. (2005)|
|Pacific - Northwest||Present||Native||Ortmann (1890); Ryland et al. (2014); CABI (Undated);|
History of Introduction and SpreadTop of page
Osburn (1952) was the first to report S. unicornis in California, finding it common in bays where oysters from the Atlantic coast had been introduced. However, Osburn’s records are now known to have been based on a mixture of S. japonica, S. errata and S. pseudoerrata (Powell, 1970; Soule et al., 1995). Powell (1970) also reported a Schizoporella species (identified as S. unicornis, but likely S. japonica) to be present in Newport Bay, Los Angeles, as long ago as 1938. The same author refers to additional material from Newport collected in 1943, from Morro Bay, California, collected in 1968, from several stations in the San Juan Islands and from Canada (Strait of Georgia,, Vancouver Island and as far north as Pendrell Sound). This range was extended to further localities in Washington State and later in San Francisco Bay in 1977 (Ross and McCain, 1976; Ryland et al., 2014). From 1998, the species has been found in Alaska, in the areas of Ketchikan, Sitka, and Valdez and Tatilek, Prince William Sound (Hines and Ruiz, 2000; Dick et al., 2005; Ruiz et al., 2006). All these authors argue that the species has been introduced from Japan in the early to mid-1930s, along with the Pacific oyster Crassostrea gigas, rather than from the Atlantic.
Risk of IntroductionTop of page
It is likely that S. japonica will continue to spread in European waters (Ryland et al., 2014). Furthermore, because some records of S. unicornis in Australia may actually correspond to S. japonica (Dick et al., 2005), a possibility of invasion in that region is feasible.
HabitatTop of page
In the native range (Akkeshi Bay, Japan), the species has been reported from rocks (approximately 87% of the samples) and shells on the sublittoral (Grischenko et al., 2007; Grisсhenko and Zvyagintsev, 2012).
In the invaded range (North Wales, UK), the species has been found just below the waterline on floating structures, such as plastic fenders, mooring buoys, or the vertical walls of pontoons (Ryland et al., 2014). Most authors suggest that S. japonica is a typical fouling species. However, at East Tongass Narrows (Alaska, USA), Dick et al. (2005) reported colonies of S. japonica covering square metres of exposed benchrock and occupying large portions of the undersides of boulders. Similarly, Powell (1970) reported collecting ‘‘massive colonies’’ of this species (which he reported as S. unicornis) intertidally on the underside of boulders and on dead eroded oyster shells.
Habitat ListTop of page
|Intertidal zone||Principal habitat||Harmful (pest or invasive)|
|Intertidal zone||Principal habitat||Natural|
Biology and EcologyTop of page
New bryozoan colonies are usually started by individuals resulting from sexual reproduction. All known bryozoans are hermaphrodite. Brooding takes place in an ovicell. The developing egg appears to derive nutrition from its parent zooid because, if removed, the egg dies. Eventually the ciliated larva escapes and, after its planktonic existence, the larva settles onto a substrate and develops into the first animal stage, which is called ancestrula. Ancestrula of S. japonica (size 350-400 x ~300 μm) have D-shaped orifices and eight marginal spines (Ryland et al., 2014). After a short period of growth, the bryozoan begins to reproduce asexually (by budding), forming a circular colony.
Physiology and Phenology
According to Ryland et al. (2014), S. japonica is a cold-water species, which breeding season in Britain extends through the winter. According to their observations, embryos of S. japonica from UK waters (Holyhead, Wales) are reddish, apparently increasing in size during development; half-sized embryos are present even in midwinter (February). In the Strait of Georgia (Canada), the breeding season of S. japonica occurs all year round, with the species showing higher level of fecundity than other local bryozoans (Powell, 1970).
Population Size and Density
In North Wales, colony dimensions range from less than 1 cm up to 20 cm (Ryland et al., 2014).
Bryozoans are filter-feeding animals. Feeding polypides capture food particles from the water through a "crown" of hollow tentacles called lophophore. Food particles are trapped by mucus and conveyed towards the mouth, which lies in the centre of the base of the lophophore. Detritus and plankton are digested in the U-shaped gut running from the mouth, in the centre of the lophophore, down into the animal's interior and then back to the anus.
In its natural range (Akkeshi Bay, Japan), S. japonica withstands water temperatures from -1.4 to 21°C and salinity ranging from 26 to 31 ppt (Grischenko et al., 2007). Powell et al. (1970) noted that S. japonica (recorded as S. unicornis) occurred in hyposaline waters, in salinities down to 15 ppt.
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Water TolerancesTop of page
|Parameter||Minimum Value||Maximum Value||Typical Value||Status||Life Stage||Notes|
|Salinity (part per thousand)||15 to 31 ppt tolerated|
|Water temperature (ºC temperature)||-1.4 to 21°C tolerated|
Pathway CausesTop of page
Pathway VectorsTop of page
Impact SummaryTop of page
Economic ImpactTop of page
The species is able to colonize most freely available substrata, including artificial underwater structures and vessel hulls, sometimes dominating fouling assemblages (Tzioumis, 1994). This fouling can be a nuisance to shipping and ports, and has the potential to become a problem to industrial components, cooling vents, etc., as is the case for other bryozoans.
When associated with oysters, the species does not seem to harm commercial aquaculture, as colonies prefer to live on dead eroded shells, rather than on living oysters (Powell, 1970). However, when they do, this reduces bivalve commercial value. S. japonica can also become a significant fouler of bivalve aquaculture gear.
Environmental ImpactTop of page
Impact on Biodiversity
S. japonica is a significant competitor for space and resources, known to inhibit growth of adjacent species.
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Abundant in its native range
- Highly adaptable to different environments
- Is a habitat generalist
- Capable of securing and ingesting a wide range of food
- Has high reproductive potential
- Reproduces asexually
- Infrastructure damage
- Negatively impacts aquaculture/fisheries
- Competition (unspecified)
- Rapid growth
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect as a commodity contaminant
- Difficult to identify/detect in the field
- Difficult/costly to control
Detection and InspectionTop of page
According to Ryland et al. (2014), the species can be photographed in situ, and collected by scraping and lifting with a knife. For the study of skeleton components, specimens can be treated with diluted hypochlorite bleach for 24-48 h in order to remove non-calcified tissue, and then cleaned by ultrasound via optical (transmitted light) and scanning electron (SEM) microscopy. Protocols for preparation of Schizoporella material for SEM can be found in Tompsett et al. (2009).
Similarities to Other Species/ConditionsTop of page
The genus Schizoporella can be identified by its sinuate primary orifice, single or paired adventitious avicularia lateral to the orifice, frontal shield with areolae and pseudopores and prominent ovicells. However, differences between species of the genus can be subtle and very few of them have been described by modern standards (Tompsett et al., 2009), which has caused confusion about the geographic ranges of S. japonica and other Schizoporella species worldwide. The main characters traditionally used for species separation in this genus are size, budding pattern and layering of the colony, shape of the orifice and sinus, appearance of the porous frontal wall, and morphology of the ovicell, especially ribbing and distribution of pores. Full comparisons between S. japonica and S. unicornis in Europe and between S. japonica, S. errata and S. pseudoerrata in North American localities have been performed by Ryland et al. (2014). Additional comparisons of S. unicornis and S. errata based on scanning electron microscopy analysis may be found in Tompsett et al. (2009). Generally, S. japonica zooids have a much greater length:width ratio than other species. Density of frontal pseudopores also provides a useful discriminatory character.
Knowledge of the geographical range and habitat of the Schizoporella species being studied is often useful for species distinction. S. unicornis can only be confused with S. japonica in the Atlantic coasts of Western Europe, including the British Isles, but not in the Pacific coast of North America, where it has repeatedly been reported in error (Hayward and Ryland, 1999; Ryland et al., 2014). In Europe, the habitat of these two species may differ: S. japonica is so far only known from harbours and marinas, and is a typical fouling species, whereas S. unicornis occurs in non-fouling conditions, on stones, rocks, shells and kelp holdfasts (Ryland et al., 2014). S. errata may be confused with S. japonica on the Pacific coast of America. However, because the former is rather a warm-water species, it is likely to be common south of San Francisco, while the opposite is true for S. japonica (Dick et al., 2005). Although the latter has spread northwards through Canada to southern Alaska, it may extend southwards beyond San Francisco to Morro Bay and (historically, at least) to the Los Angeles area, where confusion between the two species may still occur.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
No specific prevention methods have been developed for S. japonica. However, general methods of invasive species control and prevention are well known. An European surveillance network and appropriate monitoring strategy are recommended, with the aim to assess risks, impacts and invasiveness of the alien species, as well as the efficiency of its eradication and control measures (Nehring and Klingenstein, 2005). Regulatory international measures against invasions in European Seas are discussed in Gollasch (2006) and risk assessment, methods of preventive treatment and control, and management solutions for ballast water, which can be applied to this species, are discussed elsewhere (Haugom et al., 2002; Taylor et al., 2002; David and Gollash, 2015). Bishop and Hutchings (2011) have evaluated the usefulness of port surveys focused on pest identification for exotic species management.
Gaps in Knowledge/Research NeedsTop of page
The misidentification of Schizoporella species in several ecological studies highlights the need for molecular characterisation of cryptic species complexes. More studies on the ecology of Schizoporella species are needed, which has so far been poorly investigated.
ReferencesTop of page
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Dick MH, Grischenko AV, Mawatari FS, 2005. Intertidal Bryozoa (Cheilostomata) of Ketchikan, Alaska. In: Journal of Natural History, 39 3687-3784.
Grischenko AV, Dick MH, Mawatari SF, 2007. Diversity and taxonomy of intertidal Bryozoa (Cheilostomata) at Akkeshi Bay, Hokkaido, Japan. In: Journal of Natural History, 41 1047-1161.
Kubota K, Mawatari S, 1985. A systematic study of bryozoans from Oshoro Bay, Hokkaido. 2. Ascophora. In: Environmental Science, Hokkaido, 8 195-208.
Liu X, Yin X, Ma J, 2001. Biology of marine-fouling bryozoans in the coastal waters of China., Beijing, China: Science Press. 860 pp.
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Mawatari S, Mawatari SF, 1980. Studies on Japanese Anascan Bryozoa 5: Division Malacostege (3). In: Bulletin of the Liberal Arts and Science Course, School of Medicine of Nihon University, 8 21-114.
Okada Y, 1929. Report of the biological survey of Mutsu Bay. 12. Cheilostomatous Bryozoa of Mutsu Bay. In: Scientific Reports of the Tohoku Imperial University, 4 (4) 11-35.
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Principal SourceTop of page
Draft datasheet under review
ContributorsTop of page
15/05/15 Original text by:
Ekaterina Shalaeva, Consultant, UK
Distribution MapsTop of page
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