Banana slugs (Ariolimax columbianus) are mollusks. They are the second largest slug in the world, and they can be up to 25cm in length. Their body is bright yellow, with black spots, somewhat resembling a banana. However, banana slugs can also be green, brown, or even white. Their color adjusts based on light exposure, food intake, and moisture.
Banana slugs have a single lung which opens externally with a pneumostone. The pneumostone holds air which is passed through the lung cavity. Banana slugs live on the floors of forests along the Pacific Coast of North America.
They are decomposers; they chew up leaves, animal droppings, and dead plant material, and recycle them into soil. They seem to have an affinity for mushrooms, and they spread seeds and spores when they eat. They move relatively slow since banana slugs, like all slugs, have only one muscular foot.
Slugs use two pairs of tentacles to sense their environment. The larger pair is used to detect light for movement. The second pair is used to detect pheromones. The tentacles can retract and extend themselves to avoid damage from leaves and twigs.
Banana slugs excrete a thick coating of slime around their bodies. The slime keeps the skin moist, so the slug can breathe through it. If the skin is not moist, the slug cannot exchange gases. The slime gathers moisture from the air on damp days, and from soil beneath logs on dry days. Slugs can travel across the sharp edge of a razor blade or piece of glass, because of their thick slime.
The slime also protects the slug from predators, by excreting thick mucous and humping their body up, to appear larger. When the slime comes into contact with a moist surface, it produces an anasthetic which causes the membranes to go numb.
Racoons, 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 eaten by shrews and moless.
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. Some researchers are attempting to reproduce slug slime, since it is one of the best natural glues, and may have a potential use in medicine. These attempts have been unsuccessful, thus far.
To prevent themselves from drying out, slugs estivate. They secrete a protective layer of mucous, and insulate themselves with a layer of soil and leaves. They remain inactive in this state until the environment is moist again.
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 twenty translucent eggs, which is laid in a log or in leaves. Slugs mate and lay eggs throughout the year. The eggs and young of banana slugs are not protected by their parents.
Salt is harmful to all slugs; it causes the slug to dehydrate. Blood rushes to the surface of the skin to dilute the salt. This process is only effective with small quantities of salt.
The University of California, Santa Cruz prides itself on its uniqueness and non-conformity, and chose the banana slug as its mascot (in contrast to aggressive mascots like the UCLA Bruins). Thus its competetive teams are also known as Banana Slugs.
