Қара жұмырқа құрт және оның экологиялық рөлі

Species of gastropod

The black slug (also known as black arion, European black slug, or large black slug), Arion ater, is a large terrestrial gastropod mollusk in the family Arionidae, the round back slugs. Many land slugs lack external shells, having a vestigial shell. Most slugs retain a remnant of their shell, which is usually internalized, unlike other terrestrial mollusks (such as snails) which have external shells. Without such shells, slugs produce mucus, that may also contain toxins—to deter predators. Terrestrial slugs produce two other forms of mucus that facilitate locomotion and prevent death from drying. Such mollusks are hermaphroditic. Slugs most often function as decomposers but are also often omnivores. Arion ater is one such slug, decomposing organic matter, preying on other organisms, and consuming vegetative matter including agricultural crops. Native to Europe, the black slug is an invasive species in Australia, Canada (British Columbia, Newfoundland, Quebec), and the United States (Pacific Northwest).

The black slug is mainly nocturnal and avoids exposure to sunlight, although in introduced areas, it has been observed to be active all parts of the day and night. It is omnivorous, eating carrion, fungi, animal feces, algae, lichen, and vegetation (living or decaying). These slugs prefer to eat on cloudy days or at night when temperatures are above 10 degrees Celsius. Mucus production necessitates moist habitats, such as among leaf litter, mosses, or fallen trees. Consequently, the black slug becomes most active after rainfall. A 1976 study compared black slug assimilation rates to that of similar slugs in the UK. Microbiota within black slug digestive systems produce these enzymes—such as the bacteria that produce cellulose—enabling the slugs to break down lignocellulose. A recent study further explored Arion ater’s gut microbiome and discovered the black slug to have far more bacteria within its gut than did neighboring, northern European insects, including members of the orders Coleoptera, Isoptera, Orthoptera, and Diptera. This study learned the black slug’s gut microbiome to be functional at a wide range of temperatures and pH levels, and its results suggest that the mycobacterial culture may be uniform throughout the black slug’s gut and that Gammaproteobacteria composes most of this culture. This study contrasted its results to studies of North American black slugs that presented higher levels of cellulolytic activity at a narrower pH range. In summary, Arion ater can digest diverse food material such as cellulose because gut bacteria produce digestive enzymes. As decomposers/consumers, slugs engage an important niche, contributing to ecosystem health. A 2005 study looked at another Arion slug species and concluded slugs may promote plant biodiversity. This study suggested that slugs promote plant—especially forb—species diversity and that slugs support annual plant species’ fitness, reducing rates of successional change. Additionally, slugs help disperse seeds and spores through their waste, and slugs facilitate nutrient cycling by being an omnivorous consumer (especially a decomposer) and by leaving behind their mucus, which also facilitates decomposition. Slugs are common agricultural and horticultural pests. When picked up or touched, the black slug will contract to a hemispherical shape and begin to rock from side to side. This defensive behavior confuses predators, and is unique in the family Arionidae.

Arion ater has been introduced to southeastern Australia and to North America, where it occurs in Newfoundland, southern British Columbia, the Pacific Northwest of the United States and some parts of Alaska. In the past two decades, its mating with the non native (at northern latitudes) pest species Arion vulgaris (or Spanish slug) has resulted in a more resilient hybrid exhibiting increased tolerance to cold. These slugs might endanger sensitive ecosystems, especially as an invasive species, and it is yet unclear how drastically these slugs might alter plant community compositions. The black slug is a voracious seedling predator. Terrestrial slugs are considered to be especially dangerous because they alter plant species abundance, adult plant fecundity, and the production of plant defensive compounds. Black slugs are of special concern in fragmented ecosystems and areas with high shrub and tree cover. In Alaska, the black slug threatens seedling populations of lilies and orchids after already having diminished sensitive populations of deltoid balsamroot and yellow montane violet in BC Canada. This report stated the black slug can often be found in disturbed soils or areas with well irrigated soils such as lawns. Frequent sightings along roads suggest the black slug might move more easily along human traffic corridors; however, the black slug is believed to migrate little during its one year life span. Their study found black slugs were more abundant and consumed a greater quantity of mushrooms than native banana slugs but could not determine reasons for differences in population sizes. They theorized the greater abundance of black slugs could be because the black slug displaced banana slugs or because the black slug might be invading areas with previously low banana slug numbers; however, there is no data for banana slug population sizes prior to the arrival of Arion ater. This complicates determining whether alien slugs have a negative or negligible effect upon native slug numbers. Additionally, this study could not determine whether high fungi consumption resulted from dietary preference or from higher concentrations of alien slugs amidst Douglas fir forests, which promote fungal growth. The study also concluded that black and banana slugs compete for under story berries. The study demonstrated neither native nor alien slugs consume conifer or fern seedlings. It also demonstrated no significant difference between metabolic rates. However, they concluded the black slug may eat more because of its shorter life span (one compared to several years), requiring faster consumption rates to reach sexual maturity. The study demonstrated both slugs benefit ecosystems by dispersing seeds and spores. This study demonstrates the two slugs to be functionally different; however, this study proposed further research on the following to determine if black slugs are displacing banana slugs: interactions between Arion ater and fungal communities and comparative studies looking at seed dispersal rates to determine their effect on native, fruit bearing plant communities. Hand collecting is most effective at dusk or dawn when slugs feed most actively. Traps are also effective. Commercial traps can be used, or homemade traps can be made using beer. Fences can be used to protect small areas and can be commercial (often electrical) or easily homemade with sawdust, crushed eggshells, ground oyster shells, soap, cinders, or diatomaceous earth. Such fences are especially effective at protecting important seedlings or home gardens. European nematodes (Phasmarhabditis hermaphrodita) parasitize slugs, and in European agriculture, these nematodes have been mass produced as a biological control; however, European nematodes are neither native to North America nor commercially available. In addition to nematodes, there may be other biological control methods. Sciomyzids (marsh flies) larvae kill slugs and live in environments similar to slugs. Additionally, carabid beetles consume slug eggs. Large carabid beetles, such as Abax parallelepipedus predate slugs. Black slugs are edible but rarely consumed by humans; they taste horrible, may bioaccumulate pesticides, and potentially carry French heartworm (Angiostrongylus vasorum). Researching the black slug has provided human and ecological value. For example, a 1996 study investigated the bioaccumulation of mercury in black slugs and determined these slugs could be used to monitor levels of heavy metals in terrestrial systems—similar to how ecologists use aquatic mollusks. And a 2014 study researched the black slug gut's microbiology in hopes of catalyzing other studies of cellulolytic activity that could improve biofuel technology.