Invasion
Invasion Description
1st Record: Avery Point, Groton/CT/Long Island Sound (2000, Osman and Whitlatch 2007)
Geographic Extent
Avery Point, Groton/CT/Long Island Sound (2000, Osman and Whitlatch 2007); Brewer Mysyic Marina, Mystic/CT/Fishers Island Sound (209, Pederson et al. 2021)
Vectors
| Level | Vector |
|---|---|
| Probable | Hull Fouling |
Regional Impacts
| Ecological Impact | Competition | |
| On bare experimental plates in Fishers Island Sound, Connecticut, Didemnum was most competitive at sites with cooler temperatures, where it outgrew other tunicates, such as Botrylloides violaceus, Botryllus schlosseri, and Ascidiella aspera. However, Didemnum was less dominant on plates in which colonies of other species were already established (Osman and Whitlatch 2007). Invasion success of D. vexillum in experimental fouling communities was dependent on the presence of large amounts of unoccupied space (Janiak et al. 2013). In field experiments with a diversity of competitors and predators, Didemnum vexillum was less successful than when competitors and predators were excluded. However, the ability of colonies to form tendrils for dispersal, to fuse, to form extensive colonies on pebble and cobble surfaces, and to resist grazing, due to calcareous spicules in the tunic, enable D. vexillum to form extensive colonies (Stefaniak 2017). | ||
| Ecological Impact | Food/Prey | |
| Some predation occurred on Didemnum, by the snail Mitrella lunata and probably by fish on uncaged plates, but this tunicate appears less limited by predation than other tunicates, whose recruits are less likely to survive in open, deeper waters than Didemnum (Osman and Whitlatch 2007). | ||