Over time these mutations can change the identity of the organism. This is how we got slugs. Slugs evolved from snails that gradually over time accumulated mutations that caused them to lose their shells. And this didn't just happen once.
Snails and Slugs
Both animals belong to the phylum mollusks and to the class gastropods. However, they are completely different animals. That is why by taking a snail out of its shell, you will not turn it into a slug!
All terrestrial slugs have evolved directly from terrestrial snails; with the most obvious evolutionary shift being the loss of their large external protective shells; however modern slug species do still have a vestigial shell, a remnant left over from their evolutionary past.
Slugs and snails are mollusks that are related to clams, oysters, and other shellfish. Snails have coiled shells on their backs for protection from predators. Slugs have a soft shell that is hidden underneath their fleshy mantle. Both creatures leave slimy trails of mucus wherever they travel.
Slugs have both male and female reproductive cells (hermaphrodite), but must find a mate to exchange sperm before they can reproduce. They lay batches of gelatinous, watery eggs in moist crevices. The climatic conditions determine how quickly the eggs develop and hatch – the warmer it is, the quicker they develop.
How did I get snails and slugs? Moist plant debris, underneath rocks, low weeds, mulch and fallen logs all provide hiding places for snails and slugs. Moisture is a key requirement for snails and slugs since they are adversely affected by dry conditions and the loss of body moisture.
Some researchers even suggest that slugs once had external shells, as they evolved from snails and lost their shells over time. Today, most slugs have a remnant of a shell, although it's usually internal.
Slugs can be a vector for transmission of parasitic nematodes that cause lungworm in various mammals, so they are usually avoided by hedgehogs and other mammals when other food is available. In a few rare cases, humans have contracted parasite-induced meningitis from eating raw slugs.
They don't actually need to mate with another snail in order to reproduce, self fertilisation is possible. After mating they lay around 80 white eggs in a damp, underground nest. The newly-hatched snails have fragile shells and take about two year to mature.
Slugs and snails are very important. They provide food for all sorts of mammals, birds, slow worms, earthworms, insects and they are part of the natural balance. Upset that balance by removing them and we can do a lot of harm. Thrushes in particular thrive on them!
Never pick up a snail by its shell, as this can damage the muscle that attaches the body to the shell. If this muscle, called the mantle, is damaged, death can result.
After the 2-4 weeks that it takes for baby snails to hatch, they emerge from their eggs as tiny creatures, but they have equally tiny shells atop their bodies. Snails are born with shells, although they are significantly smaller than they will soon grow to be.
Snails may have opioid responses and mussels release morphine when confronted with noxious stimuli. Both reactions suggest that these animals do, in fact, feel pain. While mollusks don't have brains per se, they do exhibit some nervous system centralization. They have several pairs of ganglia connected to a nerve cord.
Lifespan. Most species of land snail are annual, others are known to live 2 or 3 years, but some of the larger species may live over 10 years in the wild. For instance, 10-year old individuals of the Roman snail Helix pomatia are probably not uncommon in natural populations.
Snails can't survive for very long without a shell on its back. The shell is their home, their protection, and their way of not drying out in the burning heat of the sun. Without the shell, most snails won't last longer than a few hours before dying.
Snails typically live 2-5 years in the wild. Some of the larger species live up 15 years and up to 25 years in captivity.
Contamination of the hands during the preparation of uncooked snails or slugs could also lead to ingestion of the parasite. People who handle snails or slugs while gardening should wash their hands thoroughly before eating or preparing food.
Slugs do not bite in a traditional way. Yet, they use a ribbon-like organ to scrape rocks and other surfaces, which can include human skin. Slug bites are not as dangerous as you would think. Among the few occurrences of slug bites, only some people experienced tingling and pulsation in the bitten area.
People, especially children, should be cautioned not to handle snails and slugs, and if they do to wash their hands thoroughly afterwards.
Slugs are hermaphrodites, having both female and male reproductive organs. Once a slug has located a mate, they encircle each other and sperm is exchanged through their protruded genitalia.
Where to Keep a Pet Slug. The container you use can be a small aquarium or another spacious container at least 20 cm by 20 cm with a lid that has tiny holes for ventilation. Make sure that the holes are not too big, as your pet can escape through bigger holes.
In captivity, people have been known to use plasters and even normal sticking tape to hold minor broken shells together allowing the snail to fill and seal the cracks in their shells.