| Reële kans op vestiging? |
Ja |
|
| Betrouwbaarheid beoordeling |
Grote mate van zekerheid (meerdere bronnen) |
|
| Vestigingsstatus |
Niet gevestigd |
|
| Zeldzaamheid |
Lokaal |
|
| Invasiviteit |
Potentieel invasief |
|
| Invasiviteit (toelichting) |
P. japonica originates from the North Pacific Ocean. It is native to Japan, Korea, Russia (Sanamyan 1998). It is introduced in 2003 to North America and parts of Europe (a.o. in 1982 in France; 1999 in the UK; 2008 in Spain). The species forms colonies of apparently solitair individuals, which are however interconnected by stolons and form actually one larger colonial (compound) tunicate consisting of many zooids. Its invasiveness is induced by the rapid spread in America and Europe. Other indicators are: it is a fast growing, adaptable species, it has a broad salinity range (polyhaline-euhaline), a broad temperature range (cold temperate-warm temperate), it is hermaphroditic and can reproduce both asexually (by budding), and sexually (fertilized eggs - able to self-fertilize - developing into larvae), it has the potential to cover large surfaces (small colonies of zooids to large spreading masses). The species most probably is dispersed as a fouling organism on the hull of ships. |
|
| Type introductie |
Niet opzettelijk |
|
| Jaar van eerste introductie |
2000 |
|
| Jaar van eerste melding |
2007 |
|
| Natuurlijke verspreiding |
Azië |
|
Noordelijke Stille Oceaan |
|
| Verspreiding in Nederland |
Zeeland |
|
| Verspreiding in Nederland (toelichting) |
P. japonica probably reached the Netherlands as fouling species on hulls of ships or accidentally as a result of aquacultural operations. Further spread through attachment to oysters and mussels (aquaculture) is a possibility (Gittenberger 2009). Dispersion in a more natural way or in ballast water is restricted by the larvae being lecithotrophic (non-feeding, yolk-dependent) being capable only to swim briefly (one day) before settlement, although the larval period seems to be be longer at lower temperatures (Van Name 1945). The species was recorded in 2004 for the first time in the Netherlands, at two different localities in the Eastern Scheldt (Neeltje Jans). Within two months it was also recorded at another locality (Wemeldinge). At present, the species is still locally restricted to the Eastern Scheldt. |
|
| Habitats |
Mariene habitats |
|
Estuaria en brakwatergebieden |
|
| Wijze van introductie |
Aquacultuur |
|
Aangroei op scheepsrompen |
|
| Impact |
Concurrentie |
|
| Ecologische impact (toelichting) |
This species is found in marinas and docks, where they grow on ropes, woody debris, brown seaweeds as Sargassum muticum, species of Fucus and Laminaria, sponges, solitary tunicates, shellfish and on pontoons and other hard substrates. The species is able to overgrow other species and compete for food and space. The main food source for this epibenthic suspensionfeeder is plankton. As yet there are no indications on the ecological impact in European (and Dutch) waters. |
|
| Economische impact (toelichting) |
In Japan, where the species is native, it has been reported to foul cultured oysters (da Rocha et al. 2009). From introduced populations, in the Netherlands as well as elsewhere in Europe, as yet no impacts have been reported upon. |
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