snail (Helix), as all land snails are mollusks gasterópodos, which means that they belong to the same group of octopuses, which are part of the Mollusk phylum. At the same time, they are members of the Gastropoda class, which includes all snails and slugs. Being a mollusk means lacking internal skeleton and bones, but snails are not unprotected.

Gastropods can adapt to a variety of living conditions and do not require large amounts of food. They have been able to continually evolve to survive the conditions around them that many researchers find fascinating.

Gastropods belong to the phylum Mollusc (or Mollusks), a classification of invertebrate animals with a soft non-segmented body, sometimes covered with an exoskeleton or shell. This phylum, Mollusca, includes animals such as squid, octopus, clams, and cuttlefish among others. Snails and slugs are both gastropods. Therefore, they are closely related, despite the fact that slugs lack a protective shell.

The giant African snail is the largest snail in the world.

The giant African snail is the largest snail in the world.

Species

There are many types of snail, but they differ fundamentally because they are aquatic or terrestrial. The former are adapted to live in the sea or in freshwater bodies, but the latter live exclusively on land, although in humid areas.

There are many species, but we are going to name only the most important:

Giant African snail (Achatina fulica)

The giant African snail is a 20 cm long snail native to Africa, and is one of the largest snail species. In some places, it is considered an invasive animal due to its high reproductive rate and voracious appetite for crops and vegetation.

Garden snail (Helix aspersa)

The garden snail is a small species with a height of up to 3 centimeters and a particular shell design that distinguishes it from other species. They are native to the Mediterranean region, Western Europe, part of Asia, and northern Egypt.

Roman snail (Helix pomatia)

The Roman snail has a beautiful shell that represents almost a third of its total weight. Originally native to Europe, it is found in most of the world today. It lives in temperate forests with humid temperatures but with little rainfall.

Features

The most striking physical characteristic of snails is their spiral shell that they carry on their back. It is a hard structure composed of calcium carbonate, which protects your soft body and internal organs. Among these organs is the lung because land snails breathe air from the atmosphere that then passes into a lung to obtain oxygen; This is one of the main differences with aquatic snails, that only a few species of water snails breathe air.

The snail varies greatly in size. While some of them are only a few centimeters long and often weigh only a few grams, there are land snails that reach almost 30 cm, such as the giant african snail, an endemic species to Africa.

Although snails do not have legs, they can move thanks to a "muscular foot" that, based on the movements of the waves, allows the snail to go from one place to another. This action is gentler and safer for the snails with the help of the "mucus" that the snail secretes to slide on all types of surfaces and maintain its moisture, reduces friction and prevents damage to your body.

The shell of the snail is made of calcium carbonate and continues to grow as the snail grows. They keep adding more calcium carbonate to the edge until the snail reaches adult size.

Anatomy

The anatomy of a land snail is very different from that of most animals. Most of us recognize snails by their spiral shells, but this is not the only interesting thing about them. His body is a set of surprising quirks and facts, not found in other animals.

Some people find them fascinating while others think they are pretty ugly. However, when you start to analyze all the parts of their body, they have unique anatomy and physiology.

External anatomy

To analyze the external anatomy of snails, we will divide their body into the shell and soft body holding it. The first is a solid, spiral-shaped back-worn structure made in one piece and composed primarily of calcium carbonate. The central layer of the shell, called ostracum, has two layers of crystals of the same substance, calcium carbonate. He Hipostracum is below, and the most superficial layer is the periostracum, made up of many proteins.

The shell of a land snail can be very different in size and shape depending on the species. Some of them are cone-shaped while others are round. However, they all have a spiral design, caused by the way that land snails produce and grow their shells.

This structure protects the snail from the environment and even from predators. It is composed of calcium carbonate which makes it strong and remains so as long as the snail eats food with calcium.

Their surface may show different colors with fringed designs, but they are generally brown or yellow. The shell protects the body and internal organs of the animal and has an opening to one side, usually the right.

The rest of the body is smooth, with a slimy texture and dark colors with gray or light spots. It has no legs but is moved by a "muscular ventral foot." The foot has a wave-like motion produced by muscle contractions that cause the snail to glide, while the foot secretes a slippery mucus that reduces friction on the surface on which it moves. This mucus is the "trail" that the mollusk leaves on the ground as it moves.

The head, at one end of the body, has one or two pairs of tentacles (retractable and equipped with touch receptors), which have the eyes at the tips. The lower pair function as olfactory organs for smelling. It also has a fold of outer skin tissue, which covers the internal organs and also usually covers the shell and the cavity of the mantle. Their tentacles may not always be visible because all land snails have the ability to retract them.

Some terrestrial species secrete a layer of mucus, which when hardened blocks the entrance of the shell and is called epifragma.

When snails sense danger around them, they hide in the shell. Snails spend a lot of time in their shell when the weather is hot and dry. Otherwise, their wet bodies could dry out.

Internal anatomy

Inside, the body of the snails is devoid of divisions. Internal organs, including the gonads, intestines, the corazón and esophagus, create an organic mass protected by the mantle.

They are pulmonary animals, which means that they have a lung specialized in using the oxygen obtained by breathing the air in the atmosphere.

On the contrary, they do not have a brain like that of dogs or humans. Instead, nerve cells are concentrated in a set of ganglia and emit neurosecreciones that trigger necessary actions such as the release of hormones. The ganglia are interconnected by bundles of nerve fibers that carry signals at high speed. Although it is a rudimentary brain, they have an excellent capacity for associative thinking.

The snails sense of sight is useful but they only detect changes in the intensity of light to recognize whether it is day or night; they can move their tentacles up or down to improve their ability to see. However, they are practically deaf, since they do not have ears or ear canal. To compensate for this lack of hearing, they have excellent associative thinking that helps them remember the places where they were or where objects in their environment are.

A snail's mouth is at the bottom of its head, just below the tentacles. The radula is a structure in the mouth of snails. Similar to an elongated sac that has several rows of tiny teeth inside it that help dispose of food rather than chew it; the food then passes into the esophagus and other organs in your digestive tract. In the lower part of their soft body, they have the anus.

Most land snails are hermaphrodites because they each have male and female reproductive organs that produce eggs and sperm. They are capable of self-fertilization, but generally copulate with each other.

The mantle is a protective layer that covers the foot and some internal organs. In some cases, it is also found covering the shell to offer you additional protection.

There is a unique process in gastropod mollusks during larval development, known as torsion. The body moves from the back area to the frontal region, which causes a rotation so that the cavity of the mantle, which includes the anus, the shell and the visceral mass, rotates around 180 degrees and is suddenly placed above the head and it looks like the shell is back.

Behavior

Certainly the snail is incredibly slow. Their speed of advance depends on the species, but it is generally between 0,5 and 0,7 centimeters per second. Its slowness is another of the characteristics that have made it famous, and some people have known how to play with it. For example, in many places in the UK snail races are organized.

As they move, the snails leave a trail of slime, a lubricant they produce so that they can circulate on any terrain without damaging their bodies. Land snails can't hear anything, but they do have eyes and olfactory organs. They use their sense of smell to help them find food as their most important sense organ.

Snails are most active at night. They can also go out during the early hours of the morning.

Habitat

Earth offers a great diversity of habitats for the snail. Surely you have found small snails under a stone, but also climbing a stem or leaf of a plant. They can survive in natural environments or in places frequented by man, such as parks and public gardens

Distribution

Snails can be found all over the world. In fact, gastropods are second only to insects when it comes to the number of named species. As an obvious result of this they are found in many places, living in a very diverse type of habitat and even having particular eating habits.

Food

The snail bases its diet on a wide variety of foods found in its natural habitat. What they consume depends on where they live and what species of snail they are. Some conventional foods are plants, fruits, vegetables, and algae. Plants that are dying are often good food for them, and they also eat sand or dirt when looking for calcium for a thicker husk.

Diet according to species

Most land snails are herbivores, but others are omnivores and some are even carnivores. Each species has different eating habits, depending on its size, age, habitat, and individual nutritional requirements.

Herbivorous snails eat a wide variety of living plant parts: leaves, stems, plant crops, bark, and fruit. Many consume mushrooms and mushrooms, and others may occasionally add algae, although these are an important food for freshwater snails.

Some species of snail enjoy plants that are already dead, as well as animals or any dead organic matter. These individuals are detrivores because they feed on rubble or solid waste that remains on the ground.

Carnivorous snails eat various types of small animals; this is the case of species of the genus Powelliphanta, which live in New Zealand and feed on other gastropod mollusks such as slugs and earthworms, among other land animals.

On the other hand, omnivores can include plants and animals in their diet, but in general, these animals prefer other land animals, so they are practically predators. For example, the species Rumina took off it can eat other species of conches, slugs, annelids such as worms and, to a lesser extent, plants.

The snail has to eat foods that include significant amounts of calcium to keep its shell hard. When they search for food, they use their powerful sense of smell.

They are nocturnal, so they forage for food at night or very early in the morning. They eat more food than usual as winter approaches, so they can store fat stores to live on while they hibernate.

When food sources are very low in the summer or spring months, they can also voluntarily put your body into a state of estivation. This process allows them to survive in severe drought conditions.

How does a snail eat?

These mollusks have an organ in the mouth with rows of tiny teeth, sometimes compared to a tongue, fully functional when eating.

radula It is this structure inside the snail's mouth that has rows of chitin teeth. When food reaches this sac-like structure, the teeth do not cut or grind it like human teeth would. Instead of being chewed, the rabula scrapes the food and breaks it, before it passes through the esophagus to continue the digestion process.

These small teeth suffer a lot of wear over time. Therefore, they are continually replaced by others. Not all species have the same number of teeth. Some have ranks with a few, but in others the number reaches the hundreds.

Snails are often said to eat very loudly. However, the sounds you hear are not the ones that consume the food. It is the radula ripping and scraping the food.

Predators

Land snails have a large number of predators. They are small, slow animals, and lack agility or physical defense skills. For these reasons, they are preyed upon by other larger, stronger and faster animals. From an ecological point of view, land snails are at the bottom of the food chain.

The most common enemies of land snails are small vertebrates, invertebrates, birds, and mammals. They are not usually victims of large animals. Predators include flies, mites, nematodes, millipedes, centipedes, some caterpillars and fireflies, leeches, beetles and their larvae, rats, mice, weasels, squirrels, toads, salamanders, turtles, blackbirds, wild turkeys and other birds of the subfamily Tetraoninae.

And they also eat each other. Well, in some cases. Certain species such as the Rumina conch shell enjoy eating other relatives, usually garden snails (Helix aspersa). Haplotrema concavum is an American carnivorous predatory snail that, in addition to worms, enjoys eating other snails that may be of the same species. Many of the smaller species of snails end up being eaten by the larger ones, such as the hung snail, which is a voracious predator that feeds on garden snails and slugs, as well as their eggs.

Predators attack snails based on their size and capacity. For the smallest ones, such as nematodes or larvae, it is relatively easy to enter through the opening of the shell and start eating the snail. The larger ones can crush them or poke a hole in the shell to extract the soft body.

In some cases, snails are victims of predators introduced into their habitat, that is, animals that do not belong to their natural environment and that can be very dangerous for them. As has happened with the snail species Pseudocharopa whiteleggei, highly vulnerable to black rat (Rattus rattus) introduced to Australia in the early XNUMXth century. This black rat has been key to the decline in the population of this species of snail.

In residential areas, pets can also be snail predators. They include cats and dogs. They may not need to consume them for food, but they are often curious as well as territorial. Some may eat them, but others just kill them or just play with them.

Defense

They may not appear fierce, but they are not completely defenseless against predators either. To do this, they can use strategies such as the following:

  • Shrink back into their shells: As we know, they are not fast; then when they sense danger nearby, they encase themselves in their shell and cover the opening with a layer of mucus called epifragma.
  • Secretes extra mucus: When an animal attacks a snail, it releases large amounts of mucus, perhaps to confuse or suffocate the attacker. So far, it has not been confirmed whether the secretions of land snails contain toxic substances.
  • They hide under the ground: It is always effective to disappear from the sight of your predator.
  • Live in areas with places to hide like rocks and plants: Some live in hard-to-reach places like crevices or crevices or on the roofs of some structures.
  • Cryptic coloring: The shell of most snails is brown or light brown, which sometimes makes them difficult to see on the ground or on tree trunks.
  • Huye: Some snails prefer to escape a direct attack. They can move quickly if there is another snail on top of them. Some manage to do it without their attacker noticing.

Reproduction

The reproduction of non-mammalian animals attracts the attention of some people because they are usually unique processes. Snails look striking, but their reproductive habits are also rare. One of the keys to the survival of the snail through time is the characteristics of its reproduction process.

The first thing to know about these terrestrial gastropod mollusks is that most are hermaphrodites. Any organism that has male and female reproductive organs and can therefore produce eggs and sperm is called a hermaphrodite. In other words: Snails are male and female at the same time.

However, there are exceptions. The snails of the family Pomatiidae They differ from their relatives because they have separate genera, that is, each snail is a male or a female according to the reproductive organs it possesses. It is relatively easy to recognize the genus since the species is sexually dimorphic: the shell of the males is smaller than that of the females.

Most terrestrial gastropods are hermaphrodites, but some snails do not have this attribute, specifically some freshwater snails such as apple snails and periwinkles. These two types of snails still have separate male and female individuals.

The reproductive system ends in an external opening located in the lower part of the body near the head, called the genital pore. Individuals reach sexual maturity at different ages, according to their species and their particular conditions. Once they are sexually mature, their sexual organs acquire the necessary conditions to reproduce, but they can begin to mate later. Land snails generally reach maturity between 6 weeks and 5 years of age. Some mature sooner or later if the conditions of their external environment are favorable or not for their development.

Courtship

When a snail is mature it can begin to mate, that is clear, but how do they approach each other?

Before sexual intercourse, both approach each other to start the courtship process that consists of a series of movements and attitudes that will or will not end in mating. The entire process can take as little as 2 hours or as long as 12 hours. To find a partner, they rely mainly on their sense of smell and touch, since their visual capacity is underdeveloped and they lack hearing. They can recognize chemicals in the air that communicate the receptivity of some other snail nearby.

During the process, both land snails get closer, recognize each other, and "test the odds." As they get closer, they begin to interact in a more physical way and can be touched with the help of their tentacles. Some move in circles and can bite into the genital pore area.

In the final stage of courtship and before mating, some species use a unique weapon: the «love darts«. No, it is not a metaphor, it is a calcium or chitin structure that only sexually mature snails have, and usually they have mated more than once. Viewed in detail, they resemble pointed darts.

When they are both close enough to touch her genitals, they fire their love darts. Darts are not fired, but are a contact shot. Usually, the two snails shoot at the structures, and pierce the skin of the other so that they join. The dangerous thing about this is that sometimes darts can damage an internal organ or go through the body and out the other side.

The function of love darts is not sperm transfer, but a form of sexual selection, and observations concluded that the garden snails (Helix aspersa) could increase your reproductive success. The mucus that covers a dart contains a type of hormones capable of increasing the chances of success in having children.

Mating

After the snails fire their "love darts," copulation follows. Sperm transfer through the penis can be reciprocal or unilateral; this means that both of them transfer it, or only one of the snails. It depends on the species. Others prefer to self-fertilize, so they do not need another individual to lay eggs.

After fertilization, the eggs go through a growth process inside the snail, until they are ready to be delivered. After that, both snails lay their eggs and bury them in separate places inside a small hole made in the top layer of the earth in a cool place. The snails' mating process allows them to deliver eggs at a consistent rate.

Generally, a snail egg takes two to four weeks to develop. As soon as they hatch, they immediately go into survival mode, because their shells are still soft. Their first reaction as soon as they hatch is to find sources of calcium either by eating the remains of their egg or by eating other eggs that have not hatched to get the additional nutrients.

In conclusion, the mating process of snails begins when they reach sexual maturity, followed by the search for the right mate, copulating, locating and creating a place to deliver the eggs, incubating the eggs and ending with the development of small snails.

We can appreciate the mating of the snail.

We can appreciate the mating of the snail.

Lifecycle

The life cycle of any animal is the period that involves the succession from one generation to the next through reproduction.

In summary, the snail life cycle has the following steps:

  1. Born and develop.
  2. Reach sexual maturity.
  3. Find a mate to mate with.
  4. Mating process.
  5. Gestation period.
  6. Egg drop.
  7. Incubation of eggs.

From young to adulthood.

The shell of the snail develops as it is an embryo within its egg. Under favorable conditions, the eggs hatch after about two weeks to a month and the snails emerge with a soft shell. Therefore, they need to feed to obtain calcium, and the first source to obtain it is consuming the remains of their egg and even other eggs that have not yet hatched.

The shells continue to grow with the snail throughout its life.

Baby snails have, in addition to a soft shell, an almost transparent body that acquires strength and color as it grows. The first color they usually have is bluish, but then it turns brown or the color that characterizes their species. They grow remarkably fast, but very few ever reach one year of age. In general, snails are victims of numerous predators, and young individuals are even more vulnerable due to their incomplete development.

The shells continue to grow with the snail throughout its life, and the rings it has are indicators of its age.

The complete life cycle of a land snail is not very long in human terms. A single snail can live from 2 to 7 years depending on its species, but in captivity, the life expectancy extends to 10 or 15 years. They rarely live longer.

Hibernation and estivation

Some land snails go into a period of torpor in which their metabolic rate slows, and both respiration and heart rate slow down than usual. If it occurs in summer it is called stowage, but if it happens in winter, it is hibernation. During this process, to maintain moisture and protect themselves from predators, snails retract into their shells and secrete a layer of mucus called the epiphragm, which closes the opening.

Some young snails show a tendency to stay close to where their eggs hatched, and if they leave, they return in the morning.

A common snail

A common snail

State of conservation

They are listed as Least Concern (LC) according to the IUCN red list.

Relationship with humans

Humans have eaten land snails for centuries, though not everywhere. They are common in gastronomy, in some parts of Europe such as France and Spain where they are considered a delicacy. However, its consumption must be careful, since some snails harbor parasites that, once in the human body or in that of other animals, can cause serious diseases. Therefore, when handling land snails, especially those found in the wild, you must observe adequate hygiene precautions to avoid dangerous diseases such as meningitis, among others.

When snails multiply and damage crops or affect species in a region or humans in any way, they are considered pests. Some species grow to the size of an adult hand and, of course, their food needs increase as well. That is why it is important to pay attention to the recommendations on handling and caring for snails.

Some terrestrial species, such as the giant african snail (Achatina fulica), are a headache for farmers and crop owners, as they have no scruples when it comes to consuming plant species of economic value such as cocoa, cucumber, papaya, beans, squash, cauliflower and some cereals, to name just a few. This species, considered in many countries as an invasive animal, generates significant economic losses.

A typical gastronomic dish in France and Spain.

A typical gastronomic dish in France and Spain.

Popular culture

Gary, the mascot of sponge BobIt is a type of snail, and surely the most famous snail, but it is a marine snail.

Land snails have been present in various aspects of human culture, including legends, myths, movies, books, and graphic works. However, not only fictitious snails are important, but also anonymous ones that are part of the customs and traditions of a region.

One of the clearest examples of the latter is snail racing. Snail racing may lack the relevance of other types of events, but they attract curious onlookers from around the world, and have become a unique tradition in some places. One of the most famous is the World Snail Racing Championship, which has been organized every year since the XNUMXs. These events may appear to be boring or very long, but in reality, usually slow competitors take no more than a few minutes to cross the finish line.

In addition to its spiral shell, the snail's slowness has made it stand out from other animals. These were known to the men of ancient cultures, who began to attribute symbolisms related to snails. To this day, the snail is a symbol of laziness, one of the deadly sins of Christianity.

In fact, the snail's slowness has made it an animal frequently associated with inactivity, used as part of metaphorical language. Although a very slow person is commonly called a "tortoise" in some places, in other areas a person with slow movements, or who walks like a "snail," is also called a "snail."

On the other hand, the habits of land snails could be indicators of some events. Hesiod, a poet from ancient Greece, recorded that when snails climbed the stems of plants, it was harvest time.

Gastronomy is also part of our culture, and although the consumption of land snails is not a widespread practice throughout the world, it is not as vilified as the consumption of other animals and has been carried out for several centuries. The ancient Romans made dishes with snails, and even the historian Pliny the Elder mentioned the existence of a farm where the owner raised land snails.

Currently, the giant African snail (Achatina fulica) is part of some religious ceremonies in Brazil, where it is an offering to the deity called Oxalá.

Art

From still lifes to contemporary works of art, land snails have been present in various artistic disciplines. They had a prominent role in many works of Christian art, where they were considered a symbol of sin, as well as laziness, since it is an animal that does not strive for food because it eats almost anything organic in the ground. It was also believed that they were born from clay.

In the "Annunciation and Nativity", from Francesco Del Cossa, and in "Madonna with Child and Saints", from Carlo Crivelli, both Italian Renaissance painters, a snail can be seen. In the last times, The snail (The snail), the work of Henri Matisse, stands out as one of the works made with paper cuts by the great artist.

Brief History

The ancestors of snails are one of the earliest types of animals known to the world. There is fossil evidence of primitive gastropods dating from the late Cambrian period; this means that they lived almost 500 million years ago.

List of other interesting animals