With a top speed of only 16.5 cm per min or 10 meters per hour, slugs are among the slowest creatures on the planet. Like all gastropod, the African Banana slug has one lung, one foot, and no spine. It is about 5 cm long but can stretch up to about 15 cm. It is variable in color and patterning, being yellow, white, orange, or gray, with or without banding, and it has gray or yellow tentacles and a yellow or orange sole.
Slugs
have four tentacles. A pair of upper tentacles, which is longer, protrude from
the top of their heads and are optical. Tiny black dots, or “eyes,” at the ends
of the tentacles detect light and movement. A pair of smaller, lower tentacles,
protruding straight out in front of their “face” are able to feel and smell. If
the slug loses a tentacle to a predator or accident, the tentacle grows back.
On
top of the slug, behind the head, is the saddle-shaped mantle. A respiratory
opening called a pneumostome is located on the right side of the mantle and is
more visible when it is open. On the mantle also are the genital opening and
anus. The part of a slug behind the mantle is called the 'tail'.
Parts of the slug
The
bottom side of a slug, which is flat, is called the 'foot'. A slug moves by
rhythmic waves of muscular contraction on the underside of its foot. It
simultaneously secretes a layer of mucus that
it travels on, which helps prevent damage to the foot tissues. Slugs produce
two types of mucus: one is thin and watery, and the
other thick and sticky. While the heavy mucus spreads from front to back, the
thin mucus spreads from the center of the foot to its margins. Additionally,
slugs secrete a viscous mucus that covers their entire body. Additionally, the
slime facilitates slug mobility while deterring predators.
The
"slime trail" a slug leaves behind have some secondary effects: other
slugs coming across a slime trail can recognize the slime trail as produced by
one of the same species, which is useful in finding a mate.
Slugs
are hermaphrodite. They possess both male and female sex organs simultaneously.
They are able to mate with themselves and self-fertilize. They however like to
court and mate with other individuals. When the encounter each other, they push
out and entwine their overly sized penis from their openings on the side of
their head, before exchanging sperms to fertilize each other’s eggs. Occasionally,
the penis gets stuck inside the partner's body. To separate themselves one or
both of the slugs chew off the other's or its own penis. Once the penis has
been discarded, the slugs are still able to mate using only the female parts of
the reproductive system. They lay clutches of about 30 eggs under leaves and
soil, and leave the clutch once laid.
Slugs
mating
While snails have shells to help protect their skin from drying out, slugs must stay moist to stay alive. To avoid dehydration, they secrete a layer of mucus, or slime, which covers their bodies. This is why most slugs are active just after a rain because of the moist ground or during nighttime. In dry conditions, slugs insulate themselves in dirt and leaves until their environment becomes moist again.
They
eat detritus (dead organic matter), including fallen leaves and plants, animal
feces, moss, and mushroom spores. They
also feed on a wide dead organic matter and a variety of vegetables, including flowers, cabbages and
strawberries.
The
slugs are essentially harmless to humans, but can be serious pests of agriculture and
horticulture. They can destroy foliage faster than plants can grow, thus
killing even fairly large plants. They also feed on fruits and vegetables prior
to harvest, making holes in the crop.
Slug control methods useful in small gardens include beer traps, crushed eggshells and coffee grounds. Salt kills slugs by causing water to leave the body through osmosis but this is not used for agricultural control as soil salinity is detrimental to crops.
In few rare cases, humans have developed rat lungworm induced meningitis from eating raw slugs. Slugs and snails are the primary intermediate hosts of the Angiostrongylus cantonensis- induced meningitis, where the larvae develop until they are infectious. Live slugs that are accidentally eaten with improperly cleaned vegetables (such as cabbages and kales), or improperly cooked slugs, can act as a vector for a parasitic infection in humans.
