- Summary of Invasiveness
- Taxonomic Tree
- Diseases Table
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Pathogen Characteristics
- Host Animals
- Notes on Natural Enemies
- Pathway Causes
- Pathway Vectors
- Vectors and Intermediate Hosts
- Impact Summary
- Economic Impact
- Environmental Impact
- Social Impact
- Risk and Impact Factors
- Links to Websites
- Distribution Maps
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IdentityTop of page
Preferred Scientific Name
- Myicola ostreae Hoshina & Sugiura, 1953
Summary of InvasivenessTop of page
Myicola ostreae is a copepod parasite of the gills of a number of bivalve mollusc species, particularly Crassostrea gigas. It is native to the Far East (Korea and Japan). It was first noted in France in the early 1970s following several imports of C. gigas spat from Japan into France for aquacultural purposes between 1971 and 1975 (Grizel and Heral, 1991; His, 1979). It was recorded in Marennes-Oléron, France in populations of Crassostrea angulata (now considered a junior synonym of C. gigas) by Comps (1972). Subsequently His (1979) recorded it in the gills of Ostrea edulis from the Bay of Arcachon at prevalences of 4-40% with up to 4 parasites per host. Crassostrea gigas were imported from France to Ireland in January 1993; M. ostreae was found the following month in Dungarvan Bay (south coast of Eire) where it has become established (Holmes and Minchin, 1995). Through the anthropogenic movements of the host, the parasite has become established in a number of countries. It does not appear to be able to translocate without the movement of the host.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Arthropoda
- Subphylum: Crustacea
- Class: Copepoda
- Order: Poecilostomatoida
- Family: Myicolidae
- Genus: Myicola
- Species: Myicola ostreae
DistributionTop of page
M. ostreae is native to Korea and Japan, and has been translocated to Europe via the movement of infected Crassostrea gigas. Clear data are lacking for its exact distribution in the Mediterranean; it appears to have been found in the Thau Lagoon, France in 1980 but no further reports appear to have been made (DAISIE, 2010). Data is lacking on parasite distribution in all areas where C. gigas has been translocated and become established.
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|
|Japan||Present||Native||Yamaguti (1936)||First reported from here|
|South Korea||Present, Widespread||Native||Kim (2004)||Found in Crassostrea gigas and Sinonovacula constricta from the Yellow Sea, Korea Strait and Sea of Japan.|
|France||Present||Introduced||Comps (1972); His (1979); DAISIE (2010)||Reported on Atlantic coast of France. Present on the gills of Ostrea edulis and Crassostrea gigas; also in Thau lagoon, Mediterranean coast.|
|Ireland||Present||Introduced||Invasive||Holmes and Minchin (1995)||Reported on the gills of Crassostrea gigas.|
|Netherlands||Present||Introduced||Stock (1993); Gollasch et al. (2009)||Reported on gills of Crassostrea gigas|
|Portugal||Present||2004||Introduced||Batista et al. (2009)||Present on gills of Crassostrea gigas|
|Spain||Present||1986||Introduced||Villalba et al. (1993)||Reported in gills of Crassostrea gigas|
|Atlantic - Northeast||Present||Introduced||Invasive||Streftaris et al. (2005)||Transferred to area via translocation of Crassostrea gigas.|
|Mediterranean and Black Sea||Present||Introduced||Invasive||CABI (Undated)||Transferred to area via translocation of Crassostrea gigas; Original citation: Zenetos (2005)|
|Pacific - Northwest||Present, Widespread||Native||Kim (2004)||Found in Crassostrea gigas and Sinonovacula constricta from the Yellow Sea, Korea Strait and Sea of Japan.|
History of Introduction and SpreadTop of page
Crassostrea gigas, the main host for M. ostreae, has been imported into Europe for aquacultural purposes from 2 main sources – British Columbia and Japan. As a direct result of importation of spat from Japan into France between 1971 and 1975, M. ostreae was most probably introduced, being first recorded in Marennes-Oléron, France (Comps, 1972; His, 1979). It is probable that the anthropogenic movement of oyster stocks within France led to the transfer of the parasite to the Bay of Arcachon (Atlantic coast) and to the Thau Lagoon (Mediterranean Sea). The route of entry of M. ostreae into the Netherlands is unclear. C. gigas spat was imported from Canada into the Netherlands from 1964; all imports of Pacific oysters into the Netherlands from overseas ceased in 1977 so it is probable that the parasite was introduced prior to 1977 (Drinkwaard, 1998). There were movements of Pacific oysters from France to Ireland in January 1993; by February 1993 it was clear that M. ostreae was present in Ireland (Holmes and Minchin, 1995). Reports of its presence in other countries such as Spain and Portugal have not provided evidence of the possible route of infection; presumably this has been through the extensive anthropogenic movements of C. gigas into these countries.
IntroductionsTop of page
|Introduced to||Introduced from||Year||Reason||Introduced by||Established in wild through||References||Notes|
|Natural reproduction||Continuous restocking|
|France||Japan||1971-1975||Aquaculture (pathway cause)||Yes||Comps (1972); Grizel and Héral (1991); His (1979)||Date of introduction not absolutely known but first recorded in France in 1972 in the gills of Crassostrea angulata [C. gigas] – route of entry is likely to have been through the mass introduction of C. gigas spat from Japan between 1971 and 1975.|
|Ireland||France||1993||Aquaculture (pathway cause)||Yes||Holmes and Minchin (1995)|
|Netherlands||before 1992||Aquaculture (pathway cause)||Faasse (2003); Gollasch et al. (2009); Stock (1993)||Probably introduced from Japan. Not reported in Netherlands since, although Faasse (2003) lists M. ostreae as being present in the Netherlands|
|Portugal||before 1994||Aquaculture (pathway cause)||Yes||Batista et al. (2009)||Date of introduction not known|
|Spain||1985||Aquaculture (pathway cause)||Villalba et al. (1993)||Date of introduction not known but C. gigas have been imported into Spain from 1985 onwards. Parasite was noted in C. gigas that were laid in the Eo estuary between 1986 and 1990|
Risk of IntroductionTop of page
Intentional introduction of M. ostreae should not occur -- it is recognised as being pathogenic under selected conditions and has no economic or ecological benefit. Without doubt it will be able to readily transfer to and establish in new areas through the anthropogenic movement of infected hosts for aquaculture, which is the main pathway for introduction; the lack of data on its distribution makes it more likely that such accidental transfers will occur. Its wide host range would suggest that it is able to infect other host species which may be accidentally transferred between infected and non-infected zones.
Assuming the presence of other suitable hosts, transmission of M. ostreae is likely to occur at a local level via the production of infective free-swimming copepodid stages. Rates of transmission are unknown but are likely to be high under optimum conditions for the parasite and high stocking densities of the host. The free-swimming stage is unlikely to be able to travel the vast distances that would allow transfer to new areas and thus this route of transfer is considered negligible for long-distance introduction
M. ostreae is not considered a quarantine pest.
Pathogen CharacteristicsTop of page
Limited data exist on basic biology of M. ostreae.
Notes on taxonomy and nomenclature
Myicola ostreae was described from the gills of Crassostrea gigas by Hoshina and Sugiura (1953). Whilst no major nomenclatural changes have been made to M. ostreae, there have been some issues surrounding the family. Yamaguti (1936) erected the family Myicolidae but failed to provide a diagnosis for it; this was subsequently provided by Humes (1986). Ho and Kim (1992) provided a key for the six genera occurring in the family; a more recent key to include all 8 recognised genera and 20 species in the family is provided by Boxshall and Halsey (2004). The genus Myicola currently contains four species according to Boxshall and Halsey (2004).
The morphology of M. ostreae is typical of cyclopoid copepods. There is limited data on its biology but it is likely that the life cycle consists of six naupliar stages, five copepodid stages and separate sexes at the adult stage (Ho, 2000). Detailed descriptions are provided in Ho (2000), Ho and Kim (1991) and Yamaguti (1936). Keys to the genera or species of the family are provided in Boxshall and Halsey (2004), Gotto (2004), Ho and Kim (1992), Ho (2000) and Humes (1986). Pathology associated with the parasite is described in Batista et al. (2009) and Villalba et al. (1993).
This description follows that of Ho and Kim (1991). Sexes are separate. Adult females possess an inflated cylindrical prosome with obscured body segmentation; constriction between pedigers 3 and 4. Body length (excluding setae of caudal rami) 1.6-2 mm × width 0.4-0.6 mm. Urosome possesses ventral spinulation and genital area contains 2 spinules. Tapered caudal rami about 5 times longer than wide, with 6 naked setae. Egg sac is multiseriate and measures around 1 mm in length. Antennule is 7-segmented with armature formulation of 4, 13, 5, 3, 4 + 1 aesthete, 2 + 1 aesthete and 7 + 1 aesthete. Antenna is 3-segmented with first segment having several lateral spinules and 1 small inner distal seta; second segment has a single inner distal seta and 3rd segment has spinules on outer proximal surface, a small inner seta, a small outer distal seta and 2 unequal inner distal setae. Mandible has 4 barbed elements and maxilllule has 4 setae. Maxilla has 2 segments, the first of which has two groups of spinules whilst the second has 2 unequal sized but barbed setae plus a single naked seta. Rudimentary maxilliped. First 4 swimming legs have 3-segmented rami. Armature formula provided in Ho and Kim (1991). Leg 5 is armed on outer margin of proximal segment with a single seta and several spinules. Second segment of leg 5 has 2 spines, 2 setae and spinules.
Adult male is uninflated and has distinct body segmentation. Males are smaller than females, measuring only around 1 mm × 0.25 mm. Urosome is 60-segemented and genital area has 2 setae on each distal corner. Caudal rami, antennules, antenna, labrum, mandible, maxillule, maxilla and legs 1-4 as per female. Four segments to maxilliped.
Similarities to Other Species/Conditions
Only three other species in the genus are recognised by Boxshall and Halsey (2004): M. metisiensis (from Mya arenaria), M. intumidus (from Dosinia penicillata) and M. formosanus (from Cyclina sinensis). They can be discriminated from M. ostreae on the basis of the caudal ramus size, length of the female urosome and length of the longest spine on the exopod of leg 5. The genus can be distinguished from the closely related Ostrincola by the structure of the egg sacs – Myicola egg sacs are multiseriate, and those of Ostrincola are uniseriate.
No genetic data exists for M. ostreae. Research on genetic variation within the species might be useful in tracing routes of introduction.
It is believed that M. ostreae has 6 naupliar stages, five copepodid stages and a single adult stage (with separate sexes). It is presumed that transmission to another host occurs via the first copepodid stage. No data is available on reproductive strategy, fecundity, cues or periods of development in relation to environmental factors.
Physiology and phenology
No data on physiology and phenology exist. No comparative studies have been completed on M. ostreae in its native and exotic range. It appears to be adaptable as it is able to infect at least four different bivalve hosts across its range.
M. ostreae feeds on host cells.
Other than a prerequisite to infect its bivalve host, this obligate parasite does not appear to have any other associations.
No data exist.
Host AnimalsTop of page
Notes on Natural EnemiesTop of page
No natural enemies of M. ostreae are known to exist.
Pathway CausesTop of page
|Aquaculture||Through anthropogenic movements of infected hosts.||Yes||Yes||Batista et al., 2009; Comps, 1972; Faasse, 2003; Gollasch et al., 2009; His, 1979; Ho and Kim, 1991; Holmes and Minchin, 1995; Hoshina and Sugiura, 1953; Kim, 2004; Villalba et al., 1993; Wolff, 2005; Zenetos, 2005|
Pathway VectorsTop of page
|Aquaculture stock||Possibly many introductions by movement of natural host and other infected stock. All life stages.||Yes||Yes||Comps, 1972; Faasse, 2003; Gollasch et al., 2009; His, 1979; Ho and Kim, 1991; Holmes and Minchin, 1995; Kim, 2004; Preisler et al., 2009; Stock, 1993; Streftaris et al., 2005; Torchin and Mitchell, 2004; Torchin et al., 2002; Villalba et al., 1993; Wolff, 2005; Zenetos, 2005|
|Host and vector organisms||Through transfer of infected hosts||Yes||Yes||Comps, 1972; Faasse, 2003; Gollasch et al., 2009; His, 1979; Ho and Kim, 1991; Holmes and Minchin, 1995; Kim, 2004; Preisler et al., 2009; Stock, 1993; Streftaris et al., 2005; Torchin and Mitchell, 2004; Torchin et al., 2002; Villalba et al., 1993; Wolff, 2005; Zenetos, 2005|
Vectors and Intermediate HostsTop of page
Impact SummaryTop of page
|Fisheries / aquaculture||Negative|
Economic ImpactTop of page
No clear data exist on the economic impact of M. ostreae on oyster cultivation. It reduces growth rates of the host and can lead to mortality, thus reducing the market value of shellfish. The economic impact is unknown, but does not appear to be large.
Environmental ImpactTop of page
Impact on habitats
M. ostreae has limited direct impact on habitats. Affected hosts are generally farmed.
Impact on biodiversity
M. ostreae has limited impact on biodiversity. It is not considered a limiting factor in the development and survivability of flat oysters.
Social ImpactTop of page
No social impacts are noted for M. ostreae.
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Abundant in its native range
- Has high reproductive potential
- Host damage
- Negatively impacts animal health
- Negatively impacts livelihoods
- Negatively impacts aquaculture/fisheries
- Parasitism (incl. parasitoid)
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect as a commodity contaminant
- Difficult to identify/detect in the field
ReferencesTop of page
Batista FM; Boudry P; Santos A dos; Renault T; Ruano F, 2009. Infestation of the cupped oysters Crassostrea angulata, C. gigas and their first-generation hybrids by the copepod Myicola ostreae: differences in susceptibility and host response. Parasitology, 136(5):537-543. http://journals.cambridge.org/action/displayJournal?jid=par
Boxshall GA; Halsey SH, 2004. Copepod orders and families - Family Myicolidae Yamaguti, 1936. In: An Introduction to Copepod diversity, Part II [ed. by Boxshall, G. A.; Halsey, S. H.]. London, UK: The Ray Society, 588-591.
Comps M, 1972. On a copepod parasitizing the Portuguese Oyster (Crassostrea angulata Lmk) in the Marennes-Oléron Basin. (Sur un copépode parasite de l'huître portugaise (Crassostrea angulata Lmk) dans le Bassin de Marennes-Oléron.) In: Congrès International pour l'Exploration de la Mer, Comité des Crustacés, coquillages et benthos. CM 1972.
Gollasch S; Haydar D; Minchin D; Wolff WJ; Reise K, 2009. Introduced Aquatic Species of the North Sea Coasts and Adjacent Brackish Waters. In: Biological Invasions in Marine Ecosystems. Ecological Studies [ed. by Rilov G, Crooks JA] Berlin/Heidelberg, Germany: Springer-Verlag, 507-528.
His E, 1979. Mytilicolides and myicolides, parasites of bivalves of commercial interest in the Bassin d'Arcachon. (Mytilicolides et myicolides parasites des lamellibranches d'intérêt commercial du Bassin d'Arcachon.) Haliotis, 8:99-102.
Humes AG, 1986. Myicola metisiensis (Copepoda: Poecilostomatoida), a parasite of the bivalve Mya arenaria in eastern Canada, redefinition of the Myicolidae, and diagnosis of the Anthessiidae n. fam. Canadian Journal of Zoology, 64:1021-1033.
Preisler RK; Wasson K; Wolff WJ; Tyrrell MC, 2009. Invasions of Estuaries vs the Adjacent Open Coast: A Global Perspective. In: Biological Invasions in Marine Ecosystems [ed. by Rilov, G. \Crooks, J. A.]. Berlin, Germany: Springer-Verlag, 587-617.
Streftaris N; Zenetos A; Papathanassiou E, 2005. Globalisation in marine ecosystems: the story of non-indigenous marine species across European seas. Oceanography and Marine Biology: An Annual Review, 43:419-453.
Torchin ME; Mitchell CE, 2004. Parasites, pathogens, and invasions by plants and animals. Frontiers in Ecology and the Environment, 2(4):183-190. http://www.esajournals.org/perlserv/?request=get-abstract&doi=10.1890%2F1540-9295%282004%29002%5B0183%3APPAIBP%5D2.0.CO%3B2
Villalba A; Azevedo C; Rodríguez C, 1993. Occurrence of multiple hyperplastic growths on the gills of Pacific oyster, Crassostrea gigas, and their relationship with associated pathologic conditions. Journal of Invertebrate Pathology, 61(3):296-302.
Zenetos A; Cinar ME; Panucci-Papadopoulou MA; Harmelin JG; Furnari G; Andaloro F; Bellou N; Streftaris N; Zibrowius H, 2005. Annotated list of marine alien species in the Mediterranean with records of the worst invasive species. Mediterranean Marine Science, 6:63-118.
Batista F M, Boudry P, Santos A dos, Renault T, Ruano F, 2009. Infestation of the cupped oysters Crassostrea angulata, C. gigas and their first-generation hybrids by the copepod Myicola ostreae: differences in susceptibility and host response. Parasitology. 136 (5), 537-543. http://journals.cambridge.org/action/displayJournal?jid=par DOI:10.1017/S0031182009005691
CABI, Undated. Compendium record. Wallingford, UK: CABI
CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI
Comps M, 1972. On a copepod parasitizing the Portuguese Oyster (Crassostrea angulata Lmk) in the Marennes-Oléron Basin. (Sur un copépode parasite de l'huître portugaise (Crassostrea angulata Lmk) dans le Bassin de Marennes-Oléron.). In: Congrès International pour l'Exploration de la Mer, Comité des Crustacés, coquillages et benthos. CM 1972. [Congrès International pour l'Exploration de la Mer, Comité des Crustacés, coquillages et benthos. CM 1972.],
Gollasch S, Haydar D, Minchin D, Wolff W J, Reise K, 2009. Introduced Aquatic Species of the North Sea Coasts and Adjacent Brackish Waters. In: Biological Invasions in Marine Ecosystems. Ecological Studies. 204 [ed. by Rilov G, Crooks J A]. Berlin Heidelberg, Germany: Springer-Verlag. 507-528.
His E, 1979. Mytilicolides and Myicolides, parasites of bivalves of commercial interest in the Bassin d'Arcachon. (Mytilicolides et myicolides parasites des lamellibranches d'intérêt commercial du Bassin d'Arcachon.). Haliotis. 99-102.
Streftaris N, Zenetos A, Papathanassiou E, 2005. Globalisation in marine ecosystems: the story of non-indigenous marine species across European seas. Oceanography and Marine Biology: An Annual Review. 419-453.
Villalba A, Azevedo C, Rodríguez C, 1993. Occurrence of multiple hyperplastic growths on the gills of Pacific oyster, Crassostrea gigas, and their relationship with associated pathologic conditions. Journal of Invertebrate Pathology. 61 (3), 296-302. DOI:10.1006/jipa.1993.1054
ContributorsTop of page
11/08/10 Original text by:
Matt Longshaw, Cefas Weymouth Laboratory, Environment and Animal Health Team, Barrack Road, The Nothe, Weymouth, Dorset, DT4 8UB, UK
Distribution MapsTop of page
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