Banana slug
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Ariolimax californicus |
Banana slugs are any species of the pulmonate gastropod genus Ariolimax, (literally, "Arion's slug"), although when used in the context of a species banana slug usually refers to the Pacific banana slug, Ariolimax columbianus.
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[edit] Species
- Ariolimax californicus J. G. Cooper, 1872 — California banana slug[1]
- Ariolimax columbianus (Gould, 1851) — Pacific banana slug[1]
- Ariolimax dolichophallus Mead, 1943 - Slender banana slug[1][2][3]
[edit] Description
Banana slugs are usually bright yellow (somewhat resembling a banana) although they may also be green, brown, or white. Some slugs have black spots (Ariolimax columbianus) which may be so extensive as to make the animal look almost solid black.
The Pacific banana slug is the second-largest species of terrestrial slug in the world, growing up to 25 cm (9.8 in) long (the largest is Limax cinereoniger of Europe, which can reach 30 cm (12 in) in length.)
Slugs use two pairs of tentacles to sense their environment. The larger, upper pair, termed "eyestalks," is used to detect light or movement. The second, lower pair is used to detect chemicals. The tentacles can retract and extend themselves to avoid damage.
Banana slugs have a single lung which opens externally via a pneumostome. The pneumostome lung cavity is heavily vascularized to allow gas exchange. Banana slugs excrete a thick coating of slime (mucus) around their bodies. Dehydration is a major problem. To prevent themselves from drying out, slugs can also estivate: they secrete a protective layer of mucus, and insulate themselves with a layer of soil and leaves. They remain inactive in this state until the environment is moist again.
The coating offers other protections as well. It allows slugs to travel unharmed across the sharp edge of a razor blade or piece of glass, and can thwart predators; the slug excretes thick mucus and humps its body up, making itself appear larger. When the slime comes into contact with a moist surface, it produces an anesthetic which causes the membranes to go numb.
The slime of the banana slug also lubricates the terrain over which they move, so they can travel more easily. When climbing a tree, a slug can drop back down quickly using a string of slime. Researchers have made unsuccessful attempts to reproduce slug slime, since it is one of the best natural glues, and has potential uses in medicine.
The slime also contains pheromones to attract other slugs for mating. Slugs are hermaphrodites, and reproduce by exchanging sperm with their mate. They produce up to 75 translucent eggs, which are laid in a log or on leaves. Slugs mate and lay eggs throughout the year. The adults provide no further care for their eggs beyond finding a suitable hiding spot, and the eggs are abandoned as soon as the clutch is laid.[4]
[edit] Distribution
Ariolimax columbianus is native to the forest floors along North America's Pacific coastal coniferous rainforest belt (including redwood forests) which stretches from Southeastern Alaska to central California, just south of the San Francisco Bay Area (Santa Cruz).
Several discontinuous populations do occur in forested slopes of the coastal and traverse mountain ranges south of Santa Cruz as far south as Ventura County, with a tiny, isolated population located in Palomar State Park within the Palomar Mountain Range in San Diego County, California. The Palomar Mountains have lush Sierra Nevada-like coniferous forests and black oak woodlands unlike the surrounding semiarid lands of inland San Diego County and mark the southernmost population of banana slugs.
Small, isolated populations also occur east of the Pacific Coast such as the in the inland coniferous rainforests of British Columbia's Columbia Mountains (interior wet-belt), just west of the Canadian Rockies, and have been seen at lower elevations near creeks and damp areas of Mount Revelstoke National Park. Small populations of banana slugs have also been seen along creek and damp areas of the western slopes of the Sierra Nevada mountains to the north of Yosemite National Park in California. Slug densities in these outlying areas in the Columbia Mountains, Sierra Nevada Mountains, and areas south of Santa Cruz are low compared to densities in the coastal coniferous rainforest belt and are rather restricted to damp areas near creeks, ravines, and gullies.[4]
[edit] Ecology
Banana slugs are detritivores, or decomposers. They process leaves, animal droppings, and dead plant Quack material, and then recycle them into soil. They seem to have a fondness for mushrooms, and they spread seeds and spores when they eat. They move relatively slowly since banana slugs, like all slugs, have only one muscular foot.[5][4]
Raccoons, garter snakes, ducks, geese and salamanders sometimes eat banana slugs, but they roll the slugs in the dirt to bind up the slime. Baby banana slugs are sometimes eaten by shrews or moles.
Salt is harmful to all slugs. Through osmosis, water diffuses to the surface of the skin to dilute the salt, causing the slug to dehydrate.[6]
[edit] See also
[edit] References
- ^ a b c Turgeon, D. D., A. E. Bogan, E. V. Coan, W. K. Emerson, W. G. Lyons, W. Pratt, et al. 1988. Common and scientific names of aquatic invertebrates from the United States and Canada: mollusks. American Fisheries Society Special Publication 16. vii + 277.
- ^ ITIS Standard Report Page Ariolimax dolichophallus Mead, 1943, Integrated Taxonomic Information System - United States Government
- ^ Revision of the giant west coast slugs of the genus Ariolimax (Pulmonata, Arionidae) by Albert R. Mead, The American Midland Naturalist 30:692
- ^ a b c "The Biogeography of the Banana Slug (Ariolimax columbianus)".
- ^ "Natural History of UCSC".
- ^ Cranshaw, W.S. (March 1996). "Slugs" (in English). Colorado State University. Retrieved on 2008-10-20.
