Alien worms - frequent international travellers


Helobdella europaea with proboscis. Unlike blood-feeding leeches it doesn’t have sharp teeth. The leech is about 15 mm long. (Photo: Geoff Read, NIWA)

NIWA scientists are often the first to detect and identify new alien aquatic organisms after they arrive in New Zealand and establish in our marine and freshwater environments. Many worms are among the animals that frequently arrive on our shores.

For instance, three very different foreign worms have all been found here recently. The freshwater leech Helobdella europaea (pictured) has been found in Taupo and Auckland. It had previously managed to arrive so inconspicuously in Australia and Germany that it was thought to be a native in each country and was given a new name, but study of its DNA showed it probably originated in South America. The marine scaleworm, Paralepidonotus ampulliferus, has established on Auckland Harbour beaches, and probably arrived from Australia, while the marine tubeworm, Hydroides sanctaecrucis, arrived on a boat hull. The tubeworm is a potential fouling pest, but New Zealand seas may be too cold for it to establish permanently.