Arthurdendyus triangulatus (New Zealand flatworm)
Index
- Pictures
- Identity
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Description
- Distribution
- Distribution Table
- History of Introduction and Spread
- Introductions
- Risk of Introduction
- Habitat
- Habitat List
- Hosts/Species Affected
- List of Symptoms/Signs
- Biology and Ecology
- Climate
- Rainfall Regime
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Plant Trade
- Impact Summary
- Economic Impact
- Environmental Impact
- Threatened Species
- Social Impact
- Risk and Impact Factors
- Uses
- Diagnosis
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- References
- Links to Websites
- Organizations
- Contributors
- Distribution Maps
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Generate reportIdentity
Top of pagePreferred Scientific Name
- Arthurdendyus triangulatus (Dendy, 1894) Jones and Gerard (1999)
Preferred Common Name
- New Zealand flatworm
Other Scientific Names
- Artioposthia triangulata (Dendy, 1894)
- Geoplana triangulata Dendy, 1894
Local Common Names
- Denmark: Newzealandsk fladorm
- Faroe Islands: selendski flatmaðkurin
- Germany: Neuseelandplattwurm
- Iceland: Nýsjálenski flatorm
- Norway: New Zealandsk flatorm
- Sweden: Nyazeeländska plattmasken
Summary of Invasiveness
Top of pageA. triangulatus is a free-living terrestrial flatworm. Native to New Zealand, it was found outside its natural habitat in Belfast, Northern Ireland in 1963 (Ministry of Agriculture, Northern Ireland, 1963, 1964). The species is harmful because it is a predator of earthworms and a decline in earthworms could reduce soil fertility and earthworm-feeding wildlife. The flatworm is found in Ireland, Great Britain and the Faroe Islands. Although capable of active movement the flatworm has been spread mainly by the trade in containerised plants. Its tendency to shelter under debris on the soil surface and its sticky body, have facilitated inadvertent carriage on plant containers, agricultural equipment and soil. There have been several scientific reviews of the biology of A. triangulatus published (Blackshaw and Stewart, 1992; Cannon et al., 1999; Boag and Yeates, 2001). A. triangulatus is considered an indirect plant pest by the European and Mediterranean Plant Protection Organisation (EPPO) (IPPC-Secretariat, 2005).
Taxonomic Tree
Top of page- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Platyhelminthes
- Class: Turbellaria
- Order: Tricladida
- Family: Geoplanidae
- Genus: Arthurdendyus
- Species: Arthurdendyus triangulatus
Notes on Taxonomy and Nomenclature
Top of pageArthurdendyus triangulatus was originally described as Geoplana triangulata by Dendy (1894). Fyfe (1937) transferred it to the genus Artioposthia due to the presence of muscular gland organs (adenodactyli) in the genital atrium. Jones and Gerard (1999) subsequently erected the genus Arthurdendyus for planarians with elongate ovaries lateral to the male copulatory apparatus and a bell-shaped pharynx.
Description
Top of pageA. triangulatus is a large terrestrial flatworm measuring up to 10 mm wide and 200 mm in length when fully extended. However, the length is highly variable depending on the state of extension. The body is that of a flattened strap, narrowing towards the anterior. The colour is liver brown with a pale marginal fringe that extends from the underside. This fringe and the underside are beige and flecked with grey. The anterior head has a pink tinge with a row of minute black eye spots present on each side of the tip. The flatworm is covered in mucus and sticky to the touch. Non-specialist descriptions are given by Willis and Edwards (1977), Boag et al. (1994a) and Jones (2005). Egg capsules are shiny black and ovoid, typically measuring 4-8 mm in diameter.
Distribution
Top of pageA. triangulatus is widespread but relatively rare in its native range, which is restricted to the South Island in New Zealand. It has established itself in Ireland, Great Britain and the Faroe Islands but not so far in continental Europe. This is something of a puzzle as much of the horticultural plant trade to the British Isles and the Faroe Islands, the presumed method of transfer of these flatworms, passes through other countries, in particular the Netherlands. It was possibly introduced into Great Britain on plants collected by the Edinburgh Botanic Gardens since it was discovered there in 1965 (Boag et al., 1998b). Analyses of genetic variation in A. triangulatus using PCR-RFLP, suggests multiple introductions of A. triangulatus into the UK (Dynes et al., 2001). This contention is supported by the presence of several other non-indigenous flatworms in the UK and Ireland, e.g. Australoplana sanguinea, Kontikia andersoni and A. albidus. Therefore, the fact that this species has not established on continental Europe may be due to other factors such as climate. However, it would seem likely that at least some areas of continental Europe may be at risk from invasion by this species (Boag et al., 1995a).
Distribution Table
Top of pageThe 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 2020Continent/Country/Region | Distribution | Last Reported | Origin | First Reported | Invasive | Reference | Notes |
---|---|---|---|---|---|---|---|
Europe |
|||||||
Faroe Islands | Present, Widespread | Introduced | 1982 | Invasive | First record from the downpipes of the parliament building in Tórshavn | ||
Iceland | Present, Only in captivity/cultivation | Introduced | Reported from a glasshouse in Iceland. Either an isolated or unconfirmed report | ||||
Ireland | Present, Widespread | Introduced | Invasive | Summary of records in Ireland (both North and South) | |||
United Kingdom | Present, Widespread | Introduced | Invasive | Distribution in Scotland – mainly in the populated central belt from Glasgow to Edinburgh but also records from the islands | |||
-Northern Ireland | Present, Widespread | Introduced | 1963 | Invasive | Northern Ireland -first record outside New Zealand | ||
Oceania |
|||||||
New Zealand | Present, Widespread | Native | Specimens collected from Christchurch, Rapaki and Ashburton on the South Island |
History of Introduction and Spread
Top of pageA. triangulatus was first found outside of New Zealand in Belfast, Northern Ireland, in 1963. Exactly how this species came to be in Belfast is unknown but it is thought to have been carried inadvertently with ornamental plants such as daffodils, roses or rhododendrons (Willis and Edwards, 1977; Blackshaw and Stewart, 1992). A similar situation is likely to have happened in Scotland. The first record was from the Royal Botanic Gardens in Edinburgh, and many flatworm records have been associated with botanic gardens, garden centres and nurseries (Boag and Yeates, 2001). As an example, 22 live flatworms (though not A. triangulatus) were found within a Dicksonia antarctica (tree fern) from Australia (Parker et al., 2005). The spread of A. triangulatus to the relatively isolated Faroe Islands, was thought to have occurred via goods from Scotland, although direct transmission from New Zealand cannot be excluded (Mather and Christensen, 1992).
Introductions
Top of pageIntroduced to | Introduced from | Year | Reason | Introduced by | Established in wild through | References | Notes | |
---|---|---|---|---|---|---|---|---|
Natural reproduction | Continuous restocking | |||||||
Faroe Islands | 1982 | Yes | Bloch (1992); Mather and Christensen (1992) | May have been introduced accidentally from Scotland or New Zealand | ||||
Northern Ireland | New Zealand | 1963 | Horticulture (pathway cause) | Yes | Ministry and Northern (1964) | Accidental introduction (Blackshaw and Stewart, 1992). First confirmed record of this species outside of its native range in New Zealand | ||
UK | 1965 | Horticulture (pathway cause) | Yes | Boag et al. (1994a); Boag et al. (1994b); Willis and Edwards (1977) | To Scotland and England, associated with botanic gardens and nurseries |
Risk of Introduction
Top of pageA. triangulatus has been present in Ireland and Great Britain since the early 1960s. It has become almost ubiquitous within the populated areas of Northern Ireland (Moore et al., 1998) and has a cosmopolitan distribution in Scotland (Jones and Boag, 1996; Boag et al., 2006a). The colonisation of the Scottish and Faroe Islands demonstrates how this species can be easily spread from infected areas to relatively isolated regions. The risk of introduction of A. triangulatus is most severe in local regions of Ireland, Scotland, England and Wales. Unless steps are taken to limit local movement of this species, it is likely to continue to spread in Ireland and Great Britain.
A. triangulatus has not established on continental Europe, despite being present in Ireland and GB since the 1960s. Climate matching would suggest that A. triangulatus could establish in large areas of north-western continental Europe such as Denmark, Germany, the Netherlands and Belgium (Boag et al., 1995a; Boag and Yeates, 2001). The fact that A. triangulatus has not already been found on continental Europe is a puzzle and may suggest more stringent environmental conditions necessary for establishment. Outside of Europe, there are regions in the United States, Canada, Japan, Argentina and Australia, which are theoretically at risk from invasion by this species (Boag et al., 1995b). Perhaps of particular risk is Tasmania, which would be climatically similar to the South Island of New Zealand. A. vegrandis, another New Zealand species, has been found on the Australian subantarctic Macquarie Island (Greenslade et al., 2007).
Habitat
Top of pageTypically found under debris on the soil surface, mostly in gardens or on the margins of agricultural land. Increasingly found in pasture in Northern Ireland (Murchie et al., 2003) and in potato fields in the Faroe Islands (Christensen and Mather, 1998). A. triangulatus may be active on the soil surface at night.
Habitat List
Top of pageCategory | Sub-Category | Habitat | Presence | Status |
---|---|---|---|---|
Terrestrial | ||||
Terrestrial | Managed | Cultivated / agricultural land | Principal habitat | Harmful (pest or invasive) |
Terrestrial | Managed | Managed forests, plantations and orchards | Secondary/tolerated habitat | Harmful (pest or invasive) |
Terrestrial | Managed | Managed grasslands (grazing systems) | Principal habitat | Harmful (pest or invasive) |
Hosts/Species Affected
Top of pageA. triangulatus is a predator of earthworms and therefore an indirect plant pest. That is, the flatworm does not attack plants directly but by reducing earthworm numbers, soil fertility and hence plant productivity are also reduced. The concept of an indirect plant pest has been accepted by the European and Mediterranean Plant Protection Organisation (EPPO) (Schrader and Unger, 2003; IPPC-Secretariat, 2005; Murchie, 2008).
List of Symptoms/Signs
Top of pageSign | Life Stages | Type |
---|---|---|
Roots / reduced root system | ||
Whole plant / dwarfing |
Biology and Ecology
Top of pageThe main factors limiting A. triangulatus dispersal are soil temperature, soil moisture and the availability of prey (Boag et al., 1998a). Soil temperatures greater than 20°C are detrimental to A. triangulatus, with 100% mortality after 3 weeks (Blackshaw and Stewart, 1992). Similarly, consistent low temperatures of -2°C caused 100% mortality after 3 days, whereas at -1°C mortality had only reached c. 50% after 21 days (Scottish Executive Rural Affairs Department, 2000). There has been little quantitative work on the effects of soil moisture on A. triangulatus, although it is clearly important (Boag et al., 2005). Part of the reason for this, is that in the UK and Ireland, soil moisture and temperature are often correlated, with high temperatures corresponding to low soil moisture.
Climate
Top of pageClimate | Status | Description | Remark |
---|---|---|---|
Cs - Warm temperate climate with dry summer | Preferred | Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers |
Notes on Natural Enemies
Top of pagePredatory ground beetles of the families Carabidae and Staphylinidae will prey on A. triangulatus (Blackshaw, 1996; Gibson et al., 1997) but it is unlikely that they will do so in sufficient numbers to limit flatworm spread. There are also consistent reports of birds and other generalist worm predators such as shrews feeding on flatworms (Cannon et al., 1999). However, it would seem that flatworms are not choice prey and are distasteful to most predators (Cannon et al., 1999). Arthur Dendy, who described A. triangulatus and in whose honour the genus is named, describes tasting two specimens of land planarian. He found it to be “an exceedingly unpleasant sensation” (Dendy, 1891). Ducks, geese and even ferrets are known to feed on them without ill effects (B Boag, The James Hutton Institute, UK, personal communication, 2013).
Little is known about the natural enemies of A. triangulatus in New Zealand, although they are presumed to be ground beetles and other flatworms. Planarivora insignis (Diptera: Keroplatidae) is a parasitoid of terrestrial flatworms in Tasmania (Hickman, 1965). It is possible that a similar species may exist in the native habitat of A. triangulatus.
Means of Movement and Dispersal
Top of pageNatural Dispersal (Non-Biotic)
There have been anecdotal stories about greenkeepers releasing flatworms in order to reduce earthworm casting on golf and bowling greens, but these are unsubstantiated.
Pathway Causes
Top of pageCause | Notes | Long Distance | Local | References |
---|---|---|---|---|
Crop production | Possibly from Scotland to the Faroe Islands with potatoes, also via manure, silage & machinery | Yes | Yes | Boag et al., 1999; Mather and Christensen, 1992; Moore et al., 1998; Murchie et al., 2003 |
Horticulture | Movement of containerised plants | Yes | Yes | Blackshaw, 1992; Cannon et al., 1999; Dynes et al., 2001; Willis and Edwards, 1977 |
Landscape improvement | Movement of topsoil | Yes | Christensen and Mather, 1995 | |
Nursery trade | Importation of containerised plants from New Zealand seems the most likely mechanism of invasion | Yes | Yes | Blackshaw and Stewart, 1992; Cannon et al., 1999; Dynes et al., 2001; Stewart and Blackshaw, 1993; Willis and Edwards, 1977 |
Ornamental purposes | Associated with botanic gardens | Yes | Boag et al., 1994a; Willis and Edwards, 1977 |
Pathway Vectors
Top of pageVector | Notes | Long Distance | Local | References |
---|---|---|---|---|
Land vehicles | Could be moved on soil attached to farm equipment | Yes | ||
Plants or parts of plants | Probably both adults and egg capsules could be introduced in this way | Yes | Yes | Blackshaw and Stewart, 1992; Cannon et al., 1999; Dynes et al., 2001; Willis and Edwards, 1977 |
Soil, sand and gravel | Local movement of topsoil and dung can facilitate flatworm spread | Yes | Murchie et al., 2003 |
Plant Trade
Top of pagePlant parts liable to carry the pest in trade/transport | Pest stages | Borne internally | Borne externally | Visibility of pest or symptoms |
---|---|---|---|---|
Bulbs/Tubers/Corms/Rhizomes | adults; eggs | Yes | Pest or symptoms usually visible to the naked eye | |
Growing medium accompanying plants | adults; eggs | Yes | Pest or symptoms usually visible to the naked eye | |
Roots | adults; eggs | Yes | Pest or symptoms usually visible to the naked eye |
Plant parts not known to carry the pest in trade/transport |
---|
Leaves |
Stems (above ground)/Shoots/Trunks/Branches |
Impact Summary
Top of pageCategory | Impact |
---|---|
Economic/livelihood | Negative |
Environment (generally) | Negative |
Economic Impact
Top of pageThe economic impact of A. triangulatus is by reducing earthworm activity, which then limits plant growth. It is likely that the most serious impact will be in pasture. There are two reasons for this. First, A. triangulatus is commonest in relatively wet mild climates that are suited for grass production. Second, arable cultivation in itself is physically damaging to both earthworms and flatworms.
As highlighted by Alford (1998), one of the main economic effects of flatworm infestation could be limitations on trade. This applies to international trade and also to local trade in the sense that a garden centre, nursery or topsoil distributor may be held liable for distributing a harmful invasive species.
Environmental Impact
Top of pageImpact on Habitats
A decline in earthworms could have knock-on effects on earthworm-feeding wildlife (Alford, 1998). In the UK and Ireland, most vulnerable are badgers, hedgehogs, moles (not Ireland) and many familiar garden and farmland bird species (e.g. blackbirds, thrushes, rooks and lapwings). Earthworms are also an important food source for many invertebrates: e.g. carabid beeles (Symondson et al., 2000), testacellid snails and indigenous flatworm species. The only specific study on this topic was done on moles (Talpa europaea) in southwest Scotland. Boag (2000) found a significant negative relationship between the presence of A. triangulatus and that of moles.
Threatened Species
Top of pageThreatened Species | Conservation Status | Where Threatened | Mechanism | References | Notes |
---|---|---|---|---|---|
Lumbricus terrestris | No Details | Faroe Islands; UK | Predation | Blackshaw, 1990; Fraser and Boag, 1998; Jones et al., 2001; Lillico et al., 1996 |
Social Impact
Top of pageA. triangulatus is a garden pest spread by the movement of plants. Gardening is a popular hobby and many gardeners exchange plants through semi-formal networks such as gardening societies. Inadvertent spread of A. triangulatus has happened by this mechanism and therefore, where A. triangulatus is present, movement of containerised plants should be minimised.
Risk and Impact Factors
Top of page- Proved invasive outside its native range
- Has a broad native range
- Highly mobile locally
- Benefits from human association (i.e. it is a human commensal)
- Long lived
- Has high reproductive potential
- Changed gene pool/ selective loss of genotypes
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Host damage
- Modification of hydrology
- Modification of nutrient regime
- Negatively impacts agriculture
- Negatively impacts livelihoods
- Reduced native biodiversity
- Threat to/ loss of native species
- Negatively impacts trade/international relations
- Predation
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect as a commodity contaminant
- Difficult/costly to control
Uses
Top of pageEconomic Value
A. triangulatus does not burrow but rather squeezes through gaps in the soil. It therefore does not confer the same aeration and drainage benefits as earthworm burrowing.
Diagnosis
Top of pageDiagnosis is by morphological features or species-specific DNA diagnostic primers. A. triangulatus is a distinctive species and microscope or molecular means for identification are rarely necessary. Jones (2005) provides user-friendly description of British terrestrial flatworms, including A. triangulatus.
Detection and Inspection
Top of pageA. triangulatus is mainly detected by visual inspection under plant pots, stones, wood, plastic sheeting and other debris on the soil surface (EPPO, 2001). The flatworm may also be detected by use of the expulsion techniques (e.g. formalin or mustard) used to assess earthworm populations (Gunn, 1992; Murchie et al., 2003). Shelter traps may be placed on the soil surface, these can be pieces of wood, tiles or plastic bags filled with soil. A sampling strategy to quantify the detection of the New Zealand flatworm was published by Boag et al. (2010).
Similarities to Other Species/Conditions
Top of pageA. triangulatus could be confused with other flatworm species but is considerably larger that the native Microplana flatworms in Ireland and GB. The ‘Australian flatworm’, Australoplana sanguinea is similar in body shape but is orange. Terrestrial leeches also have a cursory similarity but are segmented.
Prevention and Control
Top of pageDue 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.
A. triangulatus is considered an indirect plant pest by the European and Mediterranean Plant Protection Organisation (EPPO). The EPPO standard ‘Import requirements concerning A. triangulatus’ relate to the importation of containerised plants and specify: 1) plants should be grown on raised and slatted benches; 2) or come from an area free from A. triangulatus; 3) or a representative sample of the product should be examined and found free of A. triangulatus; 4) or the consignment should be subject to heat treatment.
Cultural Control and Sanitary Measures
It is possible to inoculate depleted sites with earthworms (van der Werff et al., 1998), although this would only be justified if A. triangulatus were removed and would be dependent on the scale of their impact on the earthworm population. Given time and removal of flatworm predation, it is expected that earthworms will naturally recolonise infested areas.
Gaps in Knowledge/Research Needs
Top of pageMore research is required on mechanisms to control A. triangulatus or prevent spread. From a practical viewpoint, hot-water phytosanitation provides a relatively cheap and easy means of disinfecting containerised plants. However, the precise temperatures required, the penetration of heat into compost or soil and the resilience of egg capsules to this treatment need to be determined.
References
Top of pageBoag B; Jones HD; Neilson R, 2006. Proceedings of the 10th International Symposium on Flatworm Biology, Innsbruck, Austria, July 2006. Innsbruck, Austria: The James Hutton Institute.
Boag B; MacKenzie K; McNicol JW; Neilson R, 2010. Proceedings of Crop Protection in Northern Britain., UK 45-50.
Boag B; Neilson R, 2006. Impact of New Zealand flatworm on agriculture and wildlife in Scotland. Proceedings Crop Protection in Northern Britain, 51-55.
Boag B; Neilson R; Scrimgeour CM, 2006. Degrowth phenomenon in the planarian Arthurdendyus triangulatus (Tricladida: Terricola) as measured by stable isotopes. Biology and Fertility of Soils, 43:267-270.
Gunn A, 1992. The use of mustard to estimate earthworm populations. Pedobiologia, 36(2):65-67.
Jones HD, 2005. Identification of British land flatworms. British Wildlife, 16:189-194.
Ministry of Agriculture; Northern Ireland, 1964. .
Murchie AK; Gordon AW, 2013. The impact of New Zealand flatworms Arthurdendyus triangulatus on earthworm populations in the field. Biological Invasions, 15(3):569-586.
Neilson R; Boag B; Smith M, 2000. Earthworm 13C and 15N analyses suggest that putative functional classifications of earthworms are site-specific and may also indicate habitat diversity. Soil Biology and Biochemistry, 32:1053-1061.
Distribution References
Links to Websites
Top of pageWebsite | URL | Comment |
---|---|---|
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gateway | https://doi.org/10.5061/dryad.m93f6 | Data source for updated system data added to species habitat list. |
Habitas – Invasive Species in Northern Ireland | http://www.habitas.org.uk/invasive/index.html | |
Invasive Species Ireland | http://www.invasivespeciesireland.com | |
North European and Baltic Network on Invasive Alien Species (NOBANIS) | http://nobanis.org | |
The Food and Environment Research Agency, UK. Flatworm webpage | http://flatworm.csl.gov.uk/ |
Organizations
Top of pageDenmark: Aarhus University, Nordre Ringgade 1, 8000 Aarhus C, http://www.au.dl/en
UK: FERA (The Food and Environment Research Agency), Sand Hutton, York, Y0411LZ, http://www.fera.defra.gov.uk
UK: The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, http://www.hutton.ac.uk/
Northern Ireland: Agri-Food & Biosciences Institute (AFBI), Newforge Lane, Belfast, BT9 5PX, http://www.afbini.gov.uk
Scotland: Science and Advice for Scottish Agriculture (SASA), 1 Roddinglaw Road, Edinburgh, EH12 9FJ, http://www.sasa.gov.uk
New Zealand: University of Canterbury UC, Private Bag 4800, Christchurch 8140, http://www.canterbury.ac.nz
Contributors
Top of page29/09/09 Original text by:
Archie Murchie, Agri-Food and Biosciences Institute, Applied Plant Science Division, Newforge Lane, Belfast, BT9 5PX. Northern Ireland, UK
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