Topical Tens: 28th May: Slugs

Monday 22 May 2017

28th May: Slugs

Today, according to tradition, slugs return to people's gardens from Capistrano after spending the winter there.

Slugs belong to the gastropod family, and are, not surprisingly, related to Snails. Some species of slug even have shells - inside their bodies.
While gardeners see slugs as pests, only a few species want to chomp away at your prize veggies. Most eat rotting vegetation and are vital to the ecosystem. A few species are carnivorous and will eat worms or other slugs. There is a species of sea slug that eats hydroids. A hydroid is a marine creature with a sting. The Spanish shawl sea slug eats the hydroid except for the sting, which it keeps and uses to defend itself.
There are about 30 species of slug in Britain and an average garden will contain 200 slugs per cubic metre. An acre of farmland will probably have over 250,000.
The smallest slugs are about a quarter of an inch long, but some species can reach 10 inches in length. Sea slugs get even bigger - there is a species found in California which can reach 40 inches long.
Slugs are known for being slimy. The slime is a type of liquid crystal, and contains fibres to help the slug climb things like walls or plant stalks. The slime allows it to get over sharp edges like razor blades and broken glass. It absorbs Water, so if you get it on your hands it can be nearly impossible to wash off, but it will come off if you use vinegar. Finally the slime trails slugs leave behind are actually helpful to the slug. They use their slime as a scent trail to find their way home, and the trails of other slugs to find mates, or in the case of the carnivorous ones, a meal.
Slugs have remarkably exciting sex lives. They are hermaphrodite, having both male and female reproductive organs, so they can reproduce on their own if they have to, but they prefer to do it with another slug. Some species like the leopard slug use their slime to make a thread which they dangle from while mating. The banana slug chews off its partner's penis when it's finished and there is a species of sea slug that chews its own penis off after mating and grows a new one for its next partner. A slug lays 20-100 eggs several times a year. Slug eggs can lay dormant in the soil for years and hatch when conditions are favourable.
Slugs like moisture, which is why they are so active when it has been raining. Even then, the ones you see on the wet path only amount to about 5% of the local slug population. The rest are underground eating or laying their eggs. When it is dry, slugs hide under things like logs or stones where it is damp. They don't hibernate in winter - if it's above five degrees centigrade the slugs are active.
A slug can stretch out to 20 times its normal length, so it can squeeze through small openings.
A slug has four tentacles which are retractable, and if it loses one, it will grow back. Two are for seeing and smelling and two are for touching and tasting. The eye stalks can move independently so a slug can look at and/or smell, two different things at once.
The University of California at Santa Cruz has the banana slug as the mascot for its sports teams. In 1980, however, when the university joined the National Collegiate Athletic Association, officials thought the slug wasn't athletic or pretty enough to use as an official mascot and proposed the sea lion instead. Many of the students had become fond of the slug mascot; “Slime 'em!” and “Go slugs!” were common shouts of encouragement during matches and the debate about whether the slug or the sea lion should be the mascot was so hotly debated that it reached the national newspapers. In 1986, they settled it by having a vote. The slug supporters won by a landslide.