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Amathia gracilis


Amathia [genus] (3/3)
gracilis [soort]

Exotenpaspoort ?

Reële kans op vestiging? Ja
Betrouwbaarheid beoordeling Grote mate van zekerheid (meerdere bronnen)
Vestigingsstatus Gevestigd
Zeldzaamheid Algemeen
Invasiviteit Niet invasief
Invasiviteit (toelichting) This is a cosmopolitan species, of which the origin is considered unclear (Wolff 2005). It may however, prove to be native to the Northern Atlantic or even to the North Sea area. It has been present in Europe for a long time, although in early literature usually under the name of Bowerbankia caudata (Faasse en De Blauwe 2004). In the eastern Atlantic the species occurs from the Arctic into the Mediterranean and perhaps also the Black Sea and the Caspian Sea, in the western Atlantic its range extends from Greenland south to Brazil. There are several factors that contribute to its abundancy and dispersal (or invasiveness). It is highly adaptable to all kins of habitats and substrates, living on solid materials as well as on seaweeds, hydroïds and other species. Its reproduction strategy includes both sexual and asexual reproduction: the colonies consist of replicated series of zooids, each budded asexually from a predecessor. Founding zooids metamorphose from sexually produced larvae. Furthermore the species is considered to be tolerant of a broad temperature-range (eurythermal) and is particularly tolerant of widely ranging salinities (euryhaline): it occurs in brackish and estuarine habitats with highly variable salinities, as well as in marine habitats with high and a stable salinities (Winston 1995). If introduced, it probably arrived on ships’ hulls (Wolff 2005).
Type introductie Niet opzettelijk
Jaar van eerste melding 1936
Natuurlijke verspreiding Onbekend
Verspreiding in Nederland
  • Friesland
  • Groningen
  • Noord-Holland
  • Zuid-Holland
  • Zeeland
  • Verspreiding in Nederland (toelichting) This species is already mentioned by Vorstman (1936) from the brackish water in the former Zuiderzee, before this was converted to a freshwater lake. The species is rather abundant at many localities in the province of Zeeland (Lake Grevelingen; Eastern Scheldt, Western Scheldt; Lake Veere; several brackish inland creeks, lakes and ponds; Nieuwe Waterweg; some brackish localities in Zuid-Holland and Noord-Holland. But it is also present along the North Sea Coast in almost every harbour and marina (for instance IJmuiden), on groynes, peers and other coastal constructions and from the artificial reefs near Katwijk-Noordwijk. It is also present in the Wadden Sea (a.o. on the island of Texel, Ouderschild).
  • Mariene habitats
  • Estuaria en brakwatergebieden
  • Wijze van introductie Aangroei op scheepsrompen
    Ecologische impact (toelichting) B. gracilis is a suspension feeder, capable of filtering rather a large quantity of water. Winston (1995) reported in general that bryozoan colonies located in one square meter of seagrass bed could potentially filter and recirculate an average of 48,000 gallons (approximately 200.000 liter) of seawater per day. If not attached on solid substrates (stones, shells, wood, hulls of boats), also submerged or even floating macroalgae can provide support for the bryozoan colonies. In turn, bryozoans provide habitat for several small organisms like polychaete worms, amphipods and copepods (Winston 1995). Nothing is known about the impact of this species on the environment.
    Economische impact (toelichting) As there are no reports on economic impact.


    • Blauwe, H. De 2009. Mosdiertjes van de Zuidelijke bocht van de Noordzee. Determinatiewerk voor België en Nederland. 464pp. Vlaams Instituut voor de Zee, Oostende.
    • Faasse, M. & H. de Blauwe 2004. Faunistisch overzicht van de mariene mosdiertjes van Nederland (Bryozoa: Stenolaemata, Gymnolaemata). Nederlandse Faunistische Mededelingen 21: 17-54.
    • Hartog, C. den & G. van der Velde 1987. Invasions by plants and animals into coastal, brackish and fresh waters of The Netherlands. Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen, Series C: Biological and Medical Sciences 90: 31-37.
    • Vorstman, A.G. 1936. Bryozoa. In: H.C. Redeke et al. (red.), Flora en fauna der Zuiderzee, Supplement. 145-149. De Boer, Den Helder.
    • Vorstman, A.G. 1954. Spongiaria en Bryozoa. In: L.F. De Beaufort (eds.), Veranderingen in de flora en fauna van de Zuiderzee (thans IJsselmeer) na de afsluiting in 1932. 156-157. Nederlandse Dierkundige Vereniging, Den Helder.
    • Winston, J.E. 1995. Ectoproct diversity of the Indian River Coastal Lagoon. Bulletin of Marine Science 57: 84-93.
    • Wolff, W.J. 1999. Exotic invaders of the meso-oligohaline zone of estuaries in the Netherlands: why are there so many? Helgo Meeresunters 52: 393–400.
    • Wolff, W.J. 2005. Non-indigenous marine and estuarine species in The Netherlands. Zoölogische Mededelingen 79: 1-116. [link]