Annelida (Segmented worms)
Earthworms are annelid worms (family Lumbricidae). There are no earthworms on Svalbard but close relatives, the potworms (family Enchytraeidae), are often found in large numbers. These look like small white earthworms but few are longer than two or three centimetres. They live anywhere where there is organic soil, feeding on dead plant material and microbes. The enchytraeid worms perform a vital role in the ecosystem replacing the absent earthworms role in decomposition processes and the formation of organic soil facilitating the establishment of higher plants and other invertebrates.
Although earthworms are not naturally present in Svalbard they have been imported to Barentsburg, presumably with soil brought to the town to be used in the greenhouses. These green houses are now derelict but once provided fresh vegetables for the towns population. The soil had a limited life span before it became nutrient poor or diseased to be used further. These soils were deposited on the slopes in front of the greenhouses. Along with manure from the cow and pig houses these soils form a deep organic soil not found naturally in Svalbard. In these soils there are several species of invertebrate not seen elsewhere in Svalbard and a legacy of the import of these soils from what was formerly the Ukraine region of the Soviet Union. Two of these species of invertebrate are the earthworms Dendrodrilus rubidus and Dendrobaena hortensis. However, due to their limited cold-hardiness and requirement for deep moist organic soils it is not expected that they will spread far beyond the anthropogenic soils close to the greenhouses.
Many species of Nematoda can be found in Svalbard. Close to 100 species have been identified from the archipelago but the taxonomy is unclear and often identifications remain to be confirmed. The majority are free living in the soil but parasitic species, either plant or animal, exist. Two species have been studied in considerable depth, Ostertagia gruhneri Skrjabin, 1929 and Marshallagia marshalli(Ransom, 1907), both intestinal parasites of the Svalbard reindeer. Unusually, M. marshalli is transmitted during the winter, the eggs being deposited on the winter pastures when the reindeer gather to feed along the wind blown ridge tops.
One of the few species of invertebrate introduced to Svalbard by man came with the accidental introduction of the Sibling vole (Microtus rossiameridinalis). The invertebrate goes by the name of Echinococcus multilocularis Leuckart, 1863 and has a complicated life cycle involving both the vole and the arctic fox (Alopex lagopus). The parasite is an adult tapeworm in the gut of the fox. These adults produce eggs which pass out of the fox with the faeces and become attached the vegetation. The eggs can now be eaten by the vole while it is grazing on the grasses. Once in the gut of the vole the eggs hatch and the larvae migrate through the gut lining into the blood stream and to the liver. On arrival here they develop into a hydatid cyst, a large mass of tissue that swells and eventually kills the vole. The vole is then scavenged by the fox, eaten and the cysts develops into the adult tapeworm in the gut of the fox and is ready to produce more eggs. The parasite is potentially dangerous to humans since it is possible to become infected with the eggs. The subsequent illness is termed alveolar hydatid disease and is often fatal unless treated early. It is extremely difficult to surgically remove the hydatid cysts and main treatments rely on drugs that prevent development of the parasite. However, infection is rare. First one must ingest the eggs so normal hygiene procedures in known risk areas will reduce the likelihood of infection significantly. Also, in most cases the immune response of the body detects and removes the parasite.
The vole is thought to have been brought to Svalbard with feed for the horses in the now derelict Russian mine at Grumont. Eggs of the parasite may be found where voles and foxes live in closed contact. Voles have established themselves along the coastline from Colesdalen to Adventfjord. It seems unlikely that the vole will be able to spread much further since the vole requires access to vegetation throughout the winter on which it feeds and a deep insulating snow layer to protect against extremes of low temperature. These conditions are found under the bird cliffs but are rare elsewhere. Since the foxes roam over large areas infected foxes may in principle be found almost anywhere but it seems the chances of being infected are low.