[5] It is thought to be native to Japan, but it has been reported as an invasive species in a number of places in Europe, North America and New Zealand.

The colour can be orange, pink, tan, creamy yellow or greyish-white and the tunic is sparsely strengthened by stellate spicules with nine to eleven rays.

In places with stronger currents, they cover the surface of rocks, boulders, pebbles, gravel, and oysterbeds in a thin, encrusting layer.

[8] The Portuguese oyster (Crassostrea angulata) cultivated off the Atlantic coast of France and Portugal was largely killed by an iridoviral disease in 1969.

On the east coast of North America its range extended from New Jersey, New York, Connecticut, Rhode Island, Massachusetts and New Hampshire, to Maine.

[10] The Massachusetts Institute of Technology (MIT) built an autonomous underwater vehicle, named "Odyssey IV" that was used to monitor the spread of Didemnum at George's Bank.

When they hatch, after about two weeks, the larvae have a short free-living stage lasting up to a few hours, before undergoing metamorphosis into a zooid ready to found a new colony.

[8] Didemnum vexillum is capable of forming large colonies which can overgrow rocks and gravel, smother benthic organisms and change the marine balance of the seafloor community.

In some places in the Netherlands it covers 95% of the seabed and there is a marked decrease in populations of the sea urchin Psammechinus miliaris and the brittle star Ophiothrix fragilis.

On the Georges Bank, Massachusetts, the seabed community is also changed, with some invertebrates decreasing but others, such as two species of polychaete worm, increasing in abundance.

[15] To this end a combination of several computational approaches, including blast searches with a wide range of parameters, and secondary structured-centred survey with infernal.