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Snails biology

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Snails biology

  1. 1. TYPES OF SNAILS Types of Land Snails -Giant African Land Snail – Achatina fulica The Giant African land snail is a large species native of East Africa, but it has been widely distributed to other parts of the world. -Garden Snail – Helix aspersa Snails are quite plentiful in the world so it shouldn’t come as a surprise to learn they are found in very diverse habitats. -Roman Snail – Helix pomatia The anatomy of a snail is very different from many other animals in the world. Some people find them to be fascinating while others thing they are ugly. Snail Information -Snail Feeding Snails tend to feed on a variety of items found in their natural habitat. What they will actually consume depends on where they live and the species of snail that they are. -Snail Habitat Snails are quite plentiful in the world so it shouldn’t come as a surprise to learn they are found in very diverse habitats. -Snail Anatomy The anatomy of a snail is very different from many other animals in the world. Some people find them to be fascinating while others thing they are ugly. -Snail Reproduction If you are entering into the wild world of snails, you will also begin to notice that the way in which they are built has allowed for their survival through centuries. -Snail Lifecycle The reproduction process of the snail is one that has some unusual patterns to it when compared to that of other land animals. -Snail Predators One of the main reasons why snails die is due to becoming a meal for other animals. We all know that snails are extremely slow creatures so they definitely aren’t going to be able to out
  2. 2. run other animals in the wild. ROMAN SNAIL Roman Snail – Helix pomatia -Description: The helix pomatia is very famous because it is the snail used in the exclusive French cuisine where is called “Escargot”. This species of snail is also known as Roman Snail, Burgundy snail or Apple snail. As we can infer, this snail is edible and highly valued. It has been farmed and it has created an industry to supply restaurants around the world. The Roman snail is classified as a terrestrial gastropod mollusk. -Anatomy: The Helix pomatia is an air breathing land snail that has a creamy to light brown shell with darker brown bands. The shell is almost rounded with a width of 1.2-2 inches and a height of 1.2-1.8 inches. They have a single lung and a muscular foot that helps with locomotion. The foot contracts to produce movement and glands within it release a mucus that reduce friction with the underneath surface, reducing risks of damaging their skin. Another important anatomy characteristic is a couple of tentacles in the head. The upper pair is used for vision, while the lower contains smell sensors. Roman snail in garden. -Behavior: The trail followed by the Roman snail can be easily followed because they leave behind a mark of slime, which actually is the mucus produced by the foot to ease the movement. When a helix pomatia moves above dry surfaces, they tend to reduce the foot contact with the surface to avoid the loose of water. Burgundy snails usually are active during night time, but they can be out on a rainy day or in early mornings, especially if it is a cloudy day. -Habitat and Distribution: This gastropod mollusk also known as apple snail is native of Europe including countries like Austria, Belgium, Germany, Romania, Sweden, Spain, Ukraine, United Kingdom, Luxembourg and most territories in the continent. However has been moved by humans to Asia, Africa, Oceania and the Americas, where there is a huge industry of snail farming of this and some other edible species. The helix pomatia habitat usually will be below 2,000 meters above the sea level in places with mild temperature and high humidity. They won’t be find in places with a lot of sun as they cannot tolerate direct sunlight or heavy rains Roman snail or escargot -Diet and Feeding Habits: Usually the feeding activity of a Roman snail will be during the night, but you can find them during early morning hours or during rainy days. To scrap their food, the helix pomatia will use
  3. 3. an organ inside its mouth with micro teeth called the radula. These snails feed on a variety of plants, vegetables, flowers and leaves. However, they need to consume a considerable amount of calcium to preserve their shells as hard as possible and when they are not able to get it from their food, they will feed on some other materials which contain calcium, even soil or rocks. -Reproduction This snail, as most land gastropods is hermaphrodite; this means that they have both reproductive organs. However, they need to mate with other snails to fertilize their eggs. During the mating process, both snails will fertilize each other making them both able to release eggs. The mating process can last for several hours. During that time, both will exchange “love darts”, a calcareus structure that is injected to each other. Two to eight weeks after mating, they will lay 30 to 50 eggs in holes dug out in the ground with their foot. After 3 to 4 weeks of this, newborn snails will hatch their eggs and will appear out from the soil. It is believed that this process can be repeated from 2 to 6 times in a year, depending on the climate conditions. -Predators: Roman snails main predators are insects, toads, centipedes, ground beetles, mice and birds, being the eggs the most attacked. One of the major threats their have, is the continuous habitat destruction. However, they are pretty good surviving and are least concern regarding conservation. GARDEN SNAIL Garden Snail – Helix aspersa -Description The garden snail (helix aspersa) is one of the best-known species of snails in the world. As all terrestrial snails is a gastropod mollusk. It is so common, that it is one of the most proliferated
  4. 4. terrestrial mollusks. The helix aspersa is also known with the common name of “European Brown Garden Snail”, but its scientific name is has alternative versions. Some scientist name this snail as Cornu aspersum, Cantareus aspersus or Cryptomphalus aspersus. This species is native of Europe but it has been introduced in several parts of the world where it has become a pest for crops and gardens. -Anatomy The Helix aspersa is an air-breathing snail, which has a single lung. They have a brownish soft body, which is usually covered with slimy mucus. They have yellow or cream-colored shells with brown spiral stripes. When a snail is old enough, a lip is formed at the edge of the shell aperture. The shell of this species has a height of about 1-1.4 inches and a width of 1-1.5 inches. The garden snail has a flat muscular organ called a foot that helps it move with a gliding motion helped by the release of a mucus to reduce friction with the rough surface. This mucus is the reason why snails leave a wet trace of slime when they move around. -Behavior Garden snails are mainly active during nights or early mornings when the sun is not shinning, however they can be active during cloudy or rainy days. Some Helix aspersa hibernate during winter months, especially when they are mature, but they return to activity with the spring. They are extremely slow as their fastest speed is only 1.3 centimeters per second. -Habitat and Distribution The Helix aspersa was originally found in the British islands, western Europe and the Mediterraneo, reaching some regions of north Africa, and the middle east. However, this snail has been introduced to several places where they have become agricultural pests. These places include the United States, Canada, South Africa, Australia, New Zealand, Mexico, Chile, Argentina and some others. This snail has arrived to these places either by accidentally hidden in plant or vegetable shipments or intentionally imported for some purpose. -Diet and Feeding Habits Garden snails are herbivorous and feed on several kinds of fruit trees, garden plants, crop vegetables and some cereals. Snail mouth is beneath its tentacles and it has a toothed ribbon called the radula, which is used to fragment its food. This structure is exclusive of mollusks and most of them have one. Close up to garden snail on green background -Reproduction Like other gastropod mollusks, the Helix aspersa is hermaphrodite; this means that it has both male and female organs. However, mating is required for fertilization, even tough self- fertilization is possible for this species. The mating process is complex and interesting. After some pairing and courtship, this species start the mating process that can last from four to twelve hours and usually includes the exchange of a love dart, a kind of calcareous arrow with a purpose still unclear. During the mating process they fertilize each other and they both will lay around 80 eggs 3 to 6 days after the mating occurs. To deliver his eggs, each snail will create a nest digging a hole in the soil with its foot. The nest will be 1 to 1.5 inches deep where the eggs will be delivered.
  5. 5. Gardens snails are able to deliver up to six batches of eggs in a single year. Each newborn, will take one to two years to mature. -Predators Garden snails are food source for some animals like lizards, frogs and worms. Predatory insects and other species of snails will also eat garden snails. Some birds, especially ducks will feed on these snails. Relation with humans This species is edible and it is sometimes used for cooking, although it should not be confused with the helix pomatia, the “Escargot”. Although is considered a pest in most places, it has acquired popularity in the cosmetic industry because the regenerative properties of their mucus. GIANT AFRICAN LAND SNAIL Giant African Land Snail – Achatina fulica -Description The Giant African Land Snail is one of the largest of all the terrestrial species out there. It is very rare that you will come across one but if you do pay close attention to the very unique markings that they offer. They have a light to dark brown shells with vertical stripes of a darker shade of brown on them. The average adult shell has a conical shape and its length is 4 inches although exceptional individuals have reached up to inches 7 inches. They can range in size from about 3 inches long to about 8 inches long. They have an average life span of about 5-7 years. When they have enough food and the weather is comfortable, they tend to live much longer. Some of them have been known to live up to 10 years. It is not easy to have them in captivity because people aren’t usually educated about the temperature and the moisture that they need. The “Achatina fulica” is considered one of the most invasive species in the world and it is considered by the United States Department of Agriculture as one of the most damaging species for the agriculture and crops in the country. It is known to eat at least 500 different
  6. 6. species of plants. -Anatomy A very important part of the anatomy of this snail is the tongue, which is called the radula. They have small spikes on the tongue that allow it to grab food easily. They are able to sense movement because they don’t have ears. They do have a very good sense of smell though. They have very powerful foot muscles and this is what allows them to be able to move forward. They also release a slippery substance, a kind of mucus, as they move to help them move through rough materials without damage. Their movements are very slow which is where the saying moving at a snails pace comes in. They often blend in very well to their surroundings though which helps to make up for the fact that they can’t move very fast. The shell is the location where the Giant African Land Snail takes refuge from predators. They will also spend time inside of their shells when the temperatures begin to dip too low at night for their comfort. While this shell is very hard, it can dry out if they don’t get enough moisture. There are several layers of this shell. Each one has its own process so that the outer shell can be strong. The shell will continue to grow as the snail does for almost one year, when you can guess how big the snail will be. -Behavior Besides the USDA, several state governments like Idaho, Georgia and Florida among others have listed this species as highly invasive and set controls to avoid their proliferation. The global invasive species database, have listed the Achatina fulica in the top 100 of their rank and associations like invasive.org have made similar warnings. The Giant African Land Snails don’t seem to interact with each other except for when they are going to mate. They don’t have any sounds and they spend their time moving, eating, and resting. They are considered to be active between 9 C and 29 C degrees but they are able to survive above 2 C degrees by hibernating inside of the shell during the colder months. During this time, they are able to slow their bodies down enough that they don’t need to eat or to move during that period of time. They can remain inside of the shell for several months before they emerge again. Sometimes, you will find that these snails may aestivate in the summer months as well. This is caused by drought conditions because their shell will dry out. They are able to keep it moist by creating a barrier with a thin layer of mucus that their bodies create. In case of severe drought, they are able to aestivate up to three years. Even so, many experts believe there has to be much more than meets the eye when it comes to these snails. Yet there hasn’t been very much in the way of research conducted on them. Many people would rather spend the time and money investigating other types of animals that seem to be more interesting to the public in general. -Habitat and Distribution As you may have guessed by the name, The Giant African Land Snail is found in Africa. The Achatina fulica is originally native of East Africa, from Mozambique in the south to Kenia and Somalia in the north. However, they have been introduced in recent years to several locations and seem to have adapted extremely well. These areas include the Caribbean and Pacific islands. They often end up in places where they shouldn’t though due to people transporting
  7. 7. them, either as pet trade or inadvertently. It may surprise you to learn that it is illegal to have one of them in the United States as a pet. This is because they are considered as one of the most invasive species in the world and they have produced great damage to crops in states like Florida, Georgia or Idaho. While you may think it is no big deal, they can deposit a very large amount of eggs, up to 200 every time they deliver a batch of eggs, and this can happen in a short span of time. Then instead of having one Giant African Land Snail you will have many munching around. Some people turn them loose to get rid of them and that is were the real trouble starts. Instead you should contact your local animal shelter and they can come pick them up. -Diet and Feeding Habits These snails are herbivorous. They consume a wide variety of plants, fruits and vegetables. They also need calcium in order to ensure their shell stays very strong, so they will consume more of particular types of plants in order to get enough of the calcium they need. When they aren’t able to get enough calcium in their diet from plants, they may feed on bones from carcasses, sand or small stones to get it. They also consume small amounts of water that they can get from the food they consume as well. Giant African Land Snail / Photo taken by Sonel.SA -Reproduction The Giant African Land Snail is categorized as a hermaphrodite. This means that they possess the reproduction organs for both males and females. While you still will need to have two of them for successful breeding, they can take on either role in the process or get them both fertilized, depending mainly on the size difference between the mating couple. They don’t have a set breeding period and on average they lay 5-6 clutches of eggs per year, containing each one close to 200 eggs per clutch with the right conditions. Delivering close to 1,200 eggs per year and with a hatch success probability of 90%, this species can quickly become a pest. -Predators It may surprise you to learn who the various predators are of the Giant African Land Snail. They include the caterpillar, ground beetles, other species of snails, and many types of vertebrates. In Africa, the Giant African Land Snail is considered to be a very delicious source of food. It is nutritional in value and in many areas it is also very expensive. Many villagers will harvest these snails in order to either eat them themselves or to sell them to make money. It is important to note that this particular type of snail has been associated with different types of parasites. The failure to cook them completely can result in humans becoming very ill called meningitis. Most humans don’t realize how delicate the protective shell of a Giant African Land Snail can be. When a person is holding one it can dry out faster. One way to prevent that is to wet your hands before picking one up to closely examine it. Failure to do so can result in the shells drying up and then these snails don’t have any way to protect their bodies. Since they also feed on plant life, the use of pesticides is a common cause of death for the Giant African Land Snail. In most areas they are considered to be nothing more than destructive pests. They can affect the quality of foods being grown so preventing them from being in the area often takes drastic measures.
  8. 8. SNAILS AS FOOD Land Snails as Food, Escargots Since prehistoric times, man all over the world consumed what they could for survival, and that sometimes included snails. In several parts of the ancient world including the Roman Empire, snails were eaten frequently. In fact, they were harvested so that there would be a huge supply of them all the time to meet the demand. That desire to consume them hasn’t stopped there. They continue to be a huge industry for the restaurant business. Offering snails is getting usual for unusual receptions and other elaborate affairs. If you haven’t tried them, the idea may not be very appealing to you. However, you may find that your taste buds are really impressed by them. Land snails are regularly consumed in the European cuisine. It is no secret that many people find snails to be delicious as an appetizer or as a main course. There are plenty of well known recipes out there for making them and many people do so at home. Such dishes are common in many types of fine restaurants as well. For example in France they are very popular and they are called with the French word “Escargot”. When cooked, snails are prepared with garlic and parsley butter, added for seasoning and they are server in their own shell. They are very expensive due to the fact that they are considered a delicacy. In Greece and Italy they are often consumed in a diversity of dishes and sometimes they are even used in sauces and poured over various types of pasta. Other countries like Spain, Portugal and Germany also consume them, where people create a variety of dishes. In the US there is huge market for Escargots where they are imported from many countries. Many of the recipes found in some restaurants are spin offs from what is cooked in the European countries. Escargot is the common name for snails when they are to be eaten in a dish. Millions of pounds of snails are consumed around the world annually. In fact, there is even a day to celebrate it! May 24th is the National Escargot Day. Recipes like the ones below are cooked that day: - Escargots Gratin - Escargots in Herbed Cream - Escargot a la Bourguignonne - Saffron Tagliarini With Snails & Sorrel
  9. 9. - Mushroom & Escargot Soup - Burgundian Escargots With Spaghetti It is believed that snails for eating were brought to the United States (California) in the 1850’s. Either by immigrants or by consumers, but some of them escaped though and it didn’t take long for them to be all over the country. Many people viewed them as pests which is why they don’t have any problems eating them. Instead of paying money for them, they started to harvest their own from gardens and farms. In fact, some of the farmers in California were making a nice amount of money on the side by collecting the snails and selling them on the market along with their fruits and vegetables. However, wild snails can carry deadly diseases, therefore regulations in the U.S. to sell and harvest them where established to avoid improper handling. The most common type of snail used is the garden variety. However, if you have a garden and they are present do not try to trap them and process them yourself. This would be a great way to take care of the problem you are having with the pests harming your fruits and vegetables, but as we mentioned above, wild snails can carry a parasite that can cause meningitis. As a note of caution it is important to mention that you need to properly cook snails before you consume them, even if they are purchased. The failure to do so can result in parasites entering the body, which have been linked to the development of meningitis. The failure to cook them properly can result in people becoming very ill. When you buy snails to cook you need to prepared them well done, so if present the parasite would be killed. Before cooking snails, chefs put them on fasting for three days only with water and then feed them with flour and water for one week to purify them. After that, they are cooked with one of the recipes mentioned before. FACTS ABOUT SNAILS Interesting facts about Snails 1. Some snails Hibernate. Some species of snails actually hibernate during the colder months of the year. They cover their bodies with a thin layer of mucus, which prevents them from drying out. Sometimes snails are also able to hibernate in the summer to survive if they are faced with a severe drought. They live off of the stored up fat during this time of year. This process is one of the many reasons why they have been able to survive for million years. 2. Snails can have a long life. The life span for snails depends on their habitat and the species. Some of them only live for about 5 years. However, others in the wild are believed to be up to 25 years old in unusual occasions. 3. There are huge snails. The largest land snail recorded was 12 inches long and weighed near 2 pounds. It belonged to the Giant African Land Snail species. Other species are extremely small being only a few centimeters long when they are adults and weighing just a couple of ounces. 4. Snail Moving. While moving, snails they leave behind a trail of mucus. This mucus acts as a powerful lubricant to reduce friction against the surface. This is why they are able to move upside down, around
  10. 10. corners, and other situations. 5. Snail Mucus. It is a myth that this mucus is going to make humans ill. Many people worry that snails being in their garden will ruin the foods grown there and make them unfit for consumption but that is all false. 6. Living with no rush. Garden snails (helix apersa) a top speed of 50 yards per hour, this is about 1.3 cm. per second. While they don’t move fast, they do move at a very steady pace. The snails are one of the slowest creatures on the entire Earth. 7. Snails are Hermaphrodites. Snails have the reproductive organs of both, males and females, which categorize them as hermaphrodites. However, they cannot create offspring on their own. They must mate with another and then both of them will have the ability to lay eggs. 8. Snail can see but can’t hear. Most land snails have two set of tentacles, the upper one carry the eyes, while the lower one has the olfactory organs. 9. Snails are nocturnal They are nocturnal animals, which means most of their movements take place at night. Snails don’t like the brightness of sunlight, which is why you will find them out more on cloudy days. If you keep on in an aquarium you want to make sure that too much sunlight doesn’t filter into the room. This can cause the snail to stop eating and to spend most of its time inside of the shell. 10. Get your size. Snails range in size from a few centimeters to 12 inches in length. 11. Snail Care. Snails will die if you put salt on them. Make sure you don’t offer these types of items to them when you see them or when you have one in captivity because their body can´t process these items. 12. Very Hungry. The Giant African Land Snail is known to eat more than 500 different types of plants. 13. Small, not weak. Snails are very strong and can lift up to 10 times their own body weight in a vertical position. 14. Big family. It is believed that there are at least 200,000 species of mollusks out there including snails. Although only 50,000 have been classified.
  11. 11. Realizado por: Álvaro Montoya Piqueras y Fermín Nogales Jiménez.

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