Invasive species

Invasive?

The American bullfrog was deliberately imported from its native area the eastern part of North America, from the 19th century to Europe, bred and repeatedly released. It was an asset for gastronomy, ornamental trade and served as fishing bait. They compete with native frog and amphibian species for spawning sites, food, and habitat. The frogs' abundance is probably boosted by warm winters, when fewer hibernating American bullfrogs die.

Where?

The American bullfrog lives in still waters rich in plants, such as lakes, ponds and swamps. It prefers warmer waters. The call of the males is quite loud and reminds of ox calls.

Aussehen?

It is one of the largest frog species in the world (15-20 cm in body size), making it larger than all native frog species. The tadpole can also grow up to 14 cm. Recognizing feature of adult animals is the strikingly large eardrum below the eyes. The body is olive green to gray-brown in color and often dark spotted. The sound bladder in males is located on the throat and not on the side as in native water frogs.

Distribution in Luxembourg:https://neobiota.lu/lithobates-catesbeianus/

Invasive?

The Black bullhead originates from the Great Lakes region in North America. It can be bought in pet stores for aquariums and garden ponds, over these ways it probably also found its way into wild waters. In 1934 the first Black bullheads were found in Northern Europe, in Southern Europe they have been established for a long time. Black bullhead are omnivorous and feed on insect larvae, leeches and crustaceans as well as the spawn of other animals and usually prevail in competition with other fish species. In smaller waters, Black bullhead can become the dominant fish species, displacing other fish species and amphibians. They also tolerate high CO₂ and low O₂ levels in water bodies as well as pollution from sewage. The species populations are currently still insignificantly small, but due to the high "invasive potential" they should remain under observation.

Where?

Black bullhead live in larger lakes and ponds, but also in slow-flowing waters with soft or muddy bottoms.

Appearance?

The Black bullhead is easily confused with the Brown bullhead (Ameiurus nebulosus). It has 8 barbels (whiskers), the back is dark gray to black, the belly is light. Adult animals grow between 25 and 35 cm long. The base of the whiskers is black in A. melas, light in A. nebulosus.

Distribution in Luxembourg: https://neobiota.lu/ameiurus-melas-rafinesque-1820/

Invasive?

Orconectes limosus, the Spiny-cheek crayfish and its congeners Pacifastacus leniusculus, the Signal crayfish and Procambarus fallax, the Marbled crayfish all originate from North America and nowadays inhabit almost all flowing waters. They are carriers of the deadly fungus "crayfish plague", to which they themselves are resistant. Since the crayfish grow faster, reproduce more strongly and are much more aggressive, they are biologically superior to the native European crayfish Astacus astacus and displace it even without transmission of the crayfish plague. Since the signal crayfish is very similar to the noble crayfish, it has also been released by humans into various lakes.

Where?

The crayfish are quite shy, which is why you can often only spot dead animals or moulting carapaces. Being nocturnal animals, they like to stay hidden in their hiding places or among aquatic plants during the day. They are omnivores. Both crayfish prefer cool rivers, but can also cope with warmer still waters.

Appearance?

Invasive?

The Himalayan balsam is originally from the Himalayas and was brought to Europe as an ornamental plant. It has a very professional way of spreading ( watch the Video) and that is what makes it so dangerous to native plant life, as it threatens to out compete other plants. The flowers of the Himalaya balsam have the highest nectar production in Europe and attract numerous pollinators.
Since the end of the first decade of the 21st century, the Himalayan balsam has been increasingly spreading across the landscape, leaving riverbanks and colonizing other habitats such as roadsides and forests. An example of this is the Our valley between Stolzembourg and Dasbourg-Pont, where the balsam has managed to "jump" over the main road, climb the steep slopes and "invade" the oak forests. Meanwhile, Impatiens glandulifera also occurs in many forests and forest edges. Over the past 20 years, the spread of I. glandulifera into forest habitats has accelerated and may have been aided by the strong dispersal tendency of riparian populations, major anthropogenic or natural disturbance of forest ecosystems, increased use of forestry equipment capable of transporting seeds, and the high environmental tolerance of the species. Impacts of I. glandulifera in forest habitats may include negative effects on native plant and mycorrhizal fungal diversity. I. glandulifera may also have a negative impact on the growth of planted forest plants.

Where?

Found frequently in masses especially on the banks of many waterbodies, but also on roadsides, slopes, cities and forests. It prefers moist and relatively nutrient-rich soil.

Appearance?

The Himalayan balsam is an annual plant, it can be found from spring to summer. It grows quickly and can grow up to 3 meters high. The leaves grow opposite and are strongly serrated. The white, purple or pink flowers grow in flower groups  (inflorescences) of 2- 14 flowers. The stem is mostly reddish, hollow and hairless.

Video of bursting capsule fruit

Distribution in Luxembourg / Action Plan: https://neobiota.lu/helianthus-tuberosus/

Invasive?

Helianthus tuberosus is native to central and eastern North America. Probably cultivation for eating the root tubers brought him to Europe. Under Western European climatic conditions, the plant does not produce viable seeds and reproduces vegetatively. Tubers and root pieces (rhizomes) are transported by rodents and running water, especially during winter floods. The plant can form dense and persistent monocultures along rivers, where it usually displaces native species by shading and competing for other resources..

Where?

Helianthus tuberosus, prefers light-rich, sandy, moist and nutrient-rich soils. It thrives best in locations that are repeatedly flooded by high water (riverbanks), but can also be found in ruderal areas and in agriculture.

Appearance?

The plant grows up to 3 m high, the stem is round and rough hairy. The stalked leaves are broad-lanceolate, with serrated margins, rough on top and finely soft-hairy underneath. They grow up to 25 cm long and 10 cm wide and are opposite in the lower part of the stem, alternate above. The yellow flowers are erect and 4 to 8 cm in diameter. Tongue and tube flowers are yellow. The plant blooms from September to October.

Distribution in Luxembourg / Action Plan: https://neobiota.lu/helianthus-tuberosus/

Invasive?

The jellyfish probably originated in the Yangtze River in China. How the freshwater jellyfish came to Europe is unclear - but probably as a stowaway of an imported pond plant. Since it reproduces asexually by division, it can spread rapidly. The freshwater jellyfish probably has no major ecological impact on native animal and plant species.

Where?

It is found in warm, clear, slow-moving and stagnant waters. Most of the time it lives in the polyp stage attached to plants. It needs water temperatures of at least 25°C to develop into a medusa. In warm summers the jellyfish often appear in masses, they are harmless to humans.

Appearance?

Their rather small whitish, transparent umbrella has a diameter of about 6 mm to 20 mm. It is the only species of the native cnidarians that besides the polyp stage has a medusa stage, so it looks like a classic jellyfish.

Invasive?

The quagga mussel is apparently displacing the zebra mussel (D. polymorpha), which was introduced more than 100 years ago and is found almost everywhere. It is spreading further and further south via large rivers and canals.

Where?

With the help of its adhesive foot, it can attach itself to stones, concrete walls or ship hulls. It owes its rapid spread to its dispersal mechanism via the free larvae, which only attach themselves to a substrate after about over a week.

Appearance?

The colors are very different, the has a beige to dark brown shell and is often clear longitudinally striped. The quagga mussel is recognizable by rounded shell sides. The shell sides are also asymmetrical, if you look at the shell from the side they are wavy and not flat on top of each other as in the native triangular mussel.

Invasive?

This perennial submerged plant forms dense populations that often colonize entire water bodies, restricting water movement, blocking light, creating anoxic conditions, and accelerating sediment deposition. Because of its rapid nutrient uptake and very high growth rate, the species displaces native aquatic plants.
The species' original range in North America extends from Quebec through Montana to Washington, and south to North Carolina and California. Spread is by vegetative propagation: shoot parts are transported widely by flowing water, marine traffic, water sports equipment (including fishing), and waterfowl. A new waterweed population grows from the shoot fragments.

Where?

Elodea nuttallii is an underwater plant that grows in various types of freshwater habitats, from stagnant to slow-flowing waters. It is very tolerant of water pollution and prefers warm, eutrophic and calcareous waters. It is often found in species-poor aquatic plant communities. It is more nutrient tolerant than its sister species Elodea canadiensis and can even survive in wastewater with concentrations up to 27.2 mg NH4+-N/l. Thus, it benefits more from water pollution than E. canadensis. Elodea nuttallii can form dominant stands in nutrient-rich, stagnant or slow-flowing waters. In hypertrophic waters, dominance stands of narrowleaf waterweed can occur especially after nutrient levels are reduced.

Appearance?

In addition to the Canadian pondweed (E. canadensis) and the Western waterweed, the Argentine waterweed (E. callitrichoides; with flat, longer leaves) is also found in our area, but all species are quite difficult to distinguish. Waterweed species are perennial submerged aquatic plants. Their densely leafy shoots creep or grow erect. They are about 1 mm thick and up to 300 cm long. The light green narrow leaves of this species are 3-cornered to linear, long-pointed, up to 10 mm long and 0.4 - 1.5 (-2.4) mm wide. In the lower stem area they are alternately arranged, in the upper area they are in mostly 3-fold whorls. In contrast to the Canadian pondweed (E. canadensis), the leaves of the Western waterweed are narrower, long-pointed, recurved and more or less strongly spirally twisted.

Distribution in Luxembourg: https://neobiota.lu/elodea-nuttallii/