Lesson: Molluscs: Snails, Bivalves and Octopus Lesson: Molluscs: General Lesson Plan BY: Avril Bourquin and Robynn Honeychurch First things first! Printout and use the lesson plan checklist to assist you in making the most out of your lesson plan Length of Lesson: Approximately 3 hours for the general lesson plan. This however, can be any length depending on the plan you choose to use or make up from the materials presented here. Their is more than enough information and additional resources presented here, that it can quite easily be split into many different lesson plans formats. *Please note that this is an extensive lesson plan containing a lot of information and ideas. You, as the teacher should take the time to read through the following pages and determine which format and which activities will work best for you and your students. TEACHERS:By no means try to present all the information in one lesson plan. Scan this lesson plan, then decide which lesson plan format and materials you wish to use for your class.

Lesson Plans presented in this package Lesson Plan Format 2 hours plus Suggested lesson plans that can be created from the information found in this general lesson plan Snails, Bivalves and Octopus: decide which grade level and materials are most appropriate for you. A lot of information and activities have been placed here so that you may easily personalize a lesson plan best suited for you and your class and time available for this subject. Gastropods (Marine Gastropods lesson plan information is coded brown) Bivalves (Bivalve lesson plan information is Coded Green) Cephalopods (Cephalopod information is coded Navy Blue) Instructional Goal To provide students with an introduction to the invertebrate phylum, mollusca and to help them gain a basic understanding of molluscs in general. In most of these lesson plans, three main classes will be discussed in general. Those classes are; the gastropods, bivalves and cephalopods. The main emphasis in the K to 8 lesson plans will be on the terrestrial (land snail) gastropods mainly. The 8 - 12 lesson plan will also include a discussion on the other classes.

Those of the Polyplacophora, Scaphopoda, Monoplacophora and Aplacophora. Discussions and materials presented will cover such things as anatomy of the mollusc, needs of the mollusc and procreation of the molluscs. Your students will also learn how and why molluscs are important to humans and the environment. They will also be presented with the habitat and environmental problems involved around and with molllusc. Performance Objective Students will create a report, including drawings and notes based on the information presented to them and the observations they make of their molluscs, shells, habitats and work sheets presented in this lesson plan. Students should be encouraged to participate in discussions about molluscs, their value to humans and the environment and a bit on "Molluscs: Friend or foes?". Students should also help out in making a molluscan habitat and other classroom projects (e.g. posters) based on molluscs. Rationale Molluscs are an integral part of our environment. In studying this life form, students will observe the way these animals are a very important member of our world today.

The mollusc's reliance upon the environment in which they live, and the way in which we humans rely on them, exemplifies the interconnectedness of all the ecosystems of the earth. Lesson Content Students will be presented information, visual, and written plus worksheet projects on the main classes of molluscs: gastropods (ex.: snails), bivalves (ex.: oysters and clams), and cephalopods (ex.: octopuses). Senior levels will also include the the other four classes of molluscs. Students will: discuss what molluscs require to live and stay healthy hear (younger students) or read the educational story about snails "Sammy's Adventure" observe molluscs in a simulated natural environment (terrarium, aquarium, etc.) discuss how humans now use and have used molluscs in the past discuss the importance of a healthy environment to molluscs and thus to humans, study, label and draw collected shells and help to create a classroom display colour pictures and complete worksheets which are passed out and which are available on the worksheet checklist draw a mollusc/s they have seen and record facts they've learned about molluscs. This can be in report form.

continue with other suggested projects to further explore the subject of molluscs. Planning Ahead The following steps should be taken well in advance of teaching this lesson: Print out a copy of this lesson plan for yourself to follow. Decide what printed materials will be used for your lesson and have the appropriate pages photocopied. (See the enclosed in the the lesson plan checklist ) Research your locality for available resources such as, museums with shell collections, local aquariums, local shell clubs and or shell collectors in your vicinity. Often you can find someone willing to come into your classroom to present and display their shell collection. Field trips may also be planned as part of your lesson plan. Teachers should also collect some shells to share with their students. Do this a few weeks before you first lesson. Check your local museums, ask friends, look for shell clubs in your area. Many people collect shells and may have some to lend you. To find local shell clubs: go to: Man and Mollusc International Shell clubs at: /links_mala.html For museums and aquariums, go to: /links_museum.html Often there are shells to be found on lake shores, by creeks and rivers and always near the seashore, should you have access.

Live clams, oysters, mussels and many other shells can be collected. To preserve in an intact mollusc, place the entire specimen in rubbing alcohol or you may take out the inside mollusc and just preserve it in rubbing alcohol or formaldehyde to show your students. Shells can be cleaned as well and shared with the class. Be aware of collecting bans or bag limits for your area as many molluscs are on the endangered or protected species list. (Smelly shells are easily cleaned in a few hour or overnight by placing them in a strong bleach solution. However, if a shell has a skin covering it (Called a periostracum) just clean the inside of the shell with a soft tooth brush and mild soapy dish detergent then place the shell in rubbing alcohol for a few hours then coat the skin with baby oil or mineral oil. This will help to preserve the shell's skin) Several weeks before your first Mollusc lesson, encourage your students to look for shells of all kinds. Perhaps their relatives or friends will have shells which they are willing to lend out. Place each student's contribution in their own labeled bag, so that shells can be returned to the rightful owner after the completion of the lesson.

If you live by the seashore, lakes, rivers or other bountiful snail and slug areas,encourage students to bring in their own shells to class. Make sure these shells are clean and not inhabited or filled with decaying matter (soaking shells in a bleach and water solution used under strict adult supervision, cleans up most shells). Unshelled molluscs such as slugs should be placed in an air tight jar filled with rubbing alcohol. These shells should also be placed in bags and labeled with the students name. You should also encourage the student to place a paper with their find as to where the shell was found the date it was found and if it was alive or dead when collected. Have them write down as many details as they can in regards to their finds. If they become a shell collector, collection data slips help to increase the educational and economical value of their collection. *** Be sure to heed this, and share this with students: if shells are brought from far away, make sure there is nothing living in them! Clean out the shells before they leave their place of origin. The propagation of misplaced molluscs can cause serious environmental and ecological damage!

If in your lesson plan you are going to include living snails in a terrarium or aquarium; be sure you have the appropriate food, water and other necessities such as a calcium source available for feeding the snails that you will collect and house.. Have your snail's terrarium or aquarium created BEFORE you collect or purchase your snails. (See the habitat preparations in the next section). If you plan to use garden snails for your students to observe, plan to collect them well before you want to use them in the classroom. Sudden changes in the weather can send an apparently plentiful supply into hiding so that none will be available. This is also good advise if using live freshwater snails. Often live terrarium or aquarium snails can be purchased at pet stores. See details of collecting and looking after snails. (See the habitat preparations in the next section). If teaching younger children, be sure to print out "Sammy's Adventure" story, and any additional worksheets , colouring sheets, etc. that you plan to use (see the lesson plan checklist ) . All materials found on this lesson plan are the property of Man and Mollusc and are not copyrighted for educational use and can be freely used for all educational needs.

The exception is "Sammy's Adventure". This story is copyrighted but may be used freely for all classroom lessons. An illustrated "Sammy's Adventure" story book will be published within the next year (2002). To learn where and when this book will be available, check with the owner, Avril Bourquin: avril@rockies.net Optional: A few weeks before you teach this lesson, check through some of the sites listed on the Additional Resources section at the end of this lesson plan. There are extra more games, puzzles, pictures and much more information about molluscs that you may wish to use. A few days before your first class, search out books at your school or community library on molluscs to bring into your classroom and share with your students. Bring as many of your School Library books on molluscs to your class as possible. This way students will know what to look for in their own school library. Optional Ideas that take some preplanning Escargot (canned) can usually be bought ahead of time at most grocery stores and can be brought in to class to show students an example of edible terrestrial snails.

For class use; open a container of escargot, wash and place them in a clean container filled with rubbing alcohol. Replace alcohol, as needed, when it begins to go brown. Oysters, clams, scallops and mussels can usually be bought ahead of time at most grocery stores or fish markets to be preserved for class as well in alcohol or formaldehyde. Living marine molluscs can also be purchased or found nearby if you live at the ocean and these may be kept in a saltwater aquarium and kept alive for the classroom (see habitat info in next section) . Use local beach water for these specimens unless you are used to maintaining a salt water aquarium. This water must be replaced regularity and an aeration stone is a must. I would only encourage you to keep such living specimens for one day only unless you are proficient at salt water aquarium keeping. Plan to return these to their original home. If you are a really ambitious and creative teacher you may even decide to cook up a seafood meal for your students as an introduction to this mollusc unit. Parents may be of help in preparing a seafood or molluscan feast .

Notes sent home with a student well in advance of this lesson may help you to present the idea and help you locate volunteers. A field trip could be planned to search out molluscs and to observe them in their natural habitat. Seashore rock pool or tide pools, lake shores creeks, and rivers make an excellent field trips. A word of advise: visit these areas well in advance of taking your students so that you know for sure where to locate snails. If going to a beach, be sure to know what the tide status will before this day as well. Tide and rock pools may totally disappear if you have a high tide. Also be sure to have adequate supervision for all students if undergoing such a field trip. Once again, check whether or not you have a local shell club which might be of help to you on such a trip and if their are collecting bans or bag limits. Museums or aquariums with a focus on sea life or molluscs can also make a good field trip destination for this unit. Often if you speak to the curators of such facilities, special arrangements can be made to have a special displays and onsite talks for your class. Give these people as much time as you can for arranging such a visit.

Library books Making a terrarium habitat: This can be kept as simple as a jar or as complex and imaginative as you and your students wish. These are just guidelines. Active snails can be kept for classroom viewing in a terrarium made from an aquarium, a large, wide-mouth jar turned on its side, plastic tubs, fish bowls,etc. The top should be securely covered with a fine meshed nylon screen or part of a nylon stocking. Lids which have holes punched in them do not allow for adequate ventilation and the sharp edges on the interior are a safety risk to both snails and students. To collect terrestrial snails, you will need a shovel and a container (to put your snails in). Make sure your container is not airtight so that the snails can breathe by making tiny holes in the lid. Use a plastic container to avoid sharp edges. (You need a lid to cover your container because snails can crawl on any texture or surface.) To find the snails; choose a damp spot such as, under leaf litter or near a pond. Use your shovel to loosen the ground and you should find many snails just beneath the surface.

Be sure to collect some of the soil or leaf litter for use in your terrarium. Terrestrial snails may be collected around gardens and in trees in your own area. Be sure to locate these snails well in advance so you know where to find them for your classroom. Looking for them at night time is best as most are nocturnal and or like to like in dark damp places so that they don't dry out so fast. Be sure to know what they eat and collect as much food from their natural environment as possible to include in your terrarium. Non-clohorinated or natural (Rain, lake or stream) water is also a must, so collect enough for the entire time you plan to keep your snails. Herbivores also will generally enjoy lettuce broccoli, fruits etc. Keep the terrarium clean and food and water supplies fresh and clean. Plan to release these snails back to their original home upon completion of the lesson. If they are a known pest, you might well have them properly destroyed and keep the shell for future class use.

In your terrarium, drinking water can be supplied in a shallow dish, plastic lid or in a deeper dish containing a water soaked sponge, or by generously sprinkling lettuce or other fresh, leafy food with water. Create a sample habitat by including damp soil, or sand, plants, and rocks preferably from the snail's original habitat. Food can also be placed into a shallow plastic lid in the terrarium. Most terrestrial snails are vegetarians and eat many kinds of plant material. Cornmeal, oatmeal, and fresh green leaves (Lettuce, broccoli, fruit, etc.) are all appropriate foods. Chalk, a cuttlefish bone from pet store (NOTE: this is a mollusc) or eggshells should be placed into the terrarium to provide the calcium necessary for healthy shells. Snails need calcium for healthy strong bones, much as we need calcium for strong, healthy bones. Cleaning to remove stale or moldy food, the build up of mucus, and droppings, should be done on a regular basis. Water should also be kept clean and fresh. Encourage your students to help with this chore.

Snails which withdraw into their shells during class can usually be coaxed out by a brief dip in a shallow container of water. Overcrowding snails should be avoided. In terrariums, too many snails in too small a space, or inadequate ventilation can cause the humidity to rise to unacceptable levels and the snails will die. If time permits, (are you keeping the snail for a few weeks or more), the lifecycle of the snail can be observed in the classroom. Adult snails can be recognized by a small lip that is added to the open end of their shell when growth is complete. Most terrestrial snails are hermaphroditic (each snail had both male and female sex organs), any two snails can mate. Each fertilizes the eggs of the other. The eggs are usually laid in a hole that the snail digs in the damp soil or under bark or damp leaf litter The small, translucent white eggs about the size of small peas. Upon completion of your lesson, plan to return all snails to their original home. If they happen to be a known pest species, they may be disposed of appropriately and their shells cleaned and kept for future lessons.

Soft parts may also be kept in formaldehyde or rubbing alcohol. Make a Freshwater Aquarium Habitat: This can again be kept very simple or as complex and fancy as you wish to be. For freshwater snails, search along the lake shores river or creeks. Be sure to look under wharfs, stones and on water plants. Use a fine meshed collecting net to retrieve snails. Be sure to collect a good supply of the water the snail is found in. This is the best way to make sure the snail remains healthy. Use only this water (you may add an aeration stone, and filter system to keep the snails healthy and happy. Rocks covered with mosses and algae found around the snail should also be added to the aquarium. This aquarium should also have a lid or stocking cover as pond snails sometime do crawl out of the water. Aquariums, large glass jars, fish bowls or any solid water proof container can be used. Just make sure it has a fine meshed top or stocking top for a lid. Molluscs are great escape artists.

You may have a fully water-filled aquarium or just a pool of water around such things as rocks and old tree branches from the area where you found the snail. This allows the snail to crawl on and up out of the water. An aquarium lid or mesh top to prevent escapes is still a vital part of this setup. Be sure to return all living snails to their place of origin or have them properly disposed of, if they by chance are a known pest species, at the completion of your lesson. Saltwater Aquariums: Unless you are just keeping a salt water habitat for a few hours, it is best to have a well established saltwater aquarium or at minimum a lot of replacement water from where you caught the molluscs. Sometimes salt water molluscs can be found at a pet stores or if you live by the ocean, they may also be collected on the seashore around rocks in the inter-tidal zone. Be sure to collect a good supply of the water where they live for your aquarium. These molluscs should be returned back to the ocean ASAP as they will not survive long in a simple aquarium. You should also collect a few rocks, sea weed and a bit of bottom sand or detritus to add to your habitat.

If you are going to use an established salt water aquarium, I would strongly suggest that you understand the basics of maintaining such an aquarium. Another option would be to have a knowledge person placed in charge of your aquarium for you. Check at your local pet shops for such help. If self-collecting molluscs, be sure to know and observe local collecting bag limits and restrictions. Usually this can be found out a government offices. Permits to collect may also be required. Salt Water Tide Pools: If you live near the ocean, you may wish to set up a classroom tide pool. Collect molluscs, rocks, algae, sand, water weeds or whatever else you find in the natural tide pool . Be sure to check with the authorities on legalities of live collecting and disturbing a habitat. If you explain that it is a school project, and that everything will be returned to it's original place after the lesson, there is generally no problem. Something like a large plastic Rubbermaid container or baby bath makes for an excellent tide pool. Make sure you collect lots of water to keep it fresh and well aerated. You may also use an aeration stone however, the water still becomes fouled very quickly.

Artificial tide pools should only be kept about 24 to 48 hours unless you are familiar with caring for such a habitat and know what molluscs you have and what their needs are. Again, make sure you have a good mesh cover as these molluscs also love to wonder about especially if you happen to have picked up a shell inhabited by a hermit crab.. Teaching Procedures Teachers should encourage students to share what knowledge they already have about molluscs ahead of actually starting the lesson. Have students bring in shells and bag and label them as discussed above. This may be done any time before the beginning of the actual lesson plan. Teachers may have the students help to set up a live habitat or do something like a diorama ahead of the actual lesson as well. Teachers should read "Sammy's Adventure" to younger students (also enclosed in the the lesson plan checklist ), first instructing students to listen for the facts about snails that are hidden throughout the story.

Teachers should ask students what they have learned about a snail from this story or about other molluscs from materials you present Students will be asked to carefully observe the molluscs in their habitat (the terrarium or aquarium or other habitat that the teacher and they have set up). Send students up in small groups to study the habitat, while the other students remain in their seats and record, in note form on the same sheet where they will draw their snails, the facts they've learned about snails from the story they heard. If there's time and you're using terrestrial or pond snails, teacher can remove several snails from the habitat, and place them on moist surface such as a big leaf from a head of lettuce to also observe then move about and eat. Encourage students to gently touch and pick up the snails so that they can closely observe their colours, shell pattern, body shape, size and texture. Have the students carefully place the mollusc onto the piece of prepared glass so they can observe the snail moving. A small bit of cornmeal or cornstarch can also be placed on the glass and you might actually see the mollusc feed by using it's radula. Small scratch marks will be left visible if they do feed.

Remind students that they will be returning to their seats to do a detailed drawing of the snails they've observed. Have students also observe the contents of the habitat as well , so that they can draw these in as well. If including this part of the lesson, YOU MUST have a place for the children to wash their hands well or at minimum have good disinfecting hand wipes available for use after handling the snails. Upon returning to their seats, students should draw the molluscs in its habitat from memory, and write any additional facts or observations that they have made from observing the snails. Encourage students to draw in as many details as they can: including the foot, tentacles, eyes, body and shell of the mollusc, plus whatever else is in their habitat to keep the snail alive and happy. Handout the snail diagrams, other work sheets stories or quizzes that you plan to use for students to study and label. Be sure to cover such facts with your students such as: Terrestrial Snails such as "Sammy" are part of the Gastropod family, a class of mollusc, with a one- piece shell (univalve), or no shell at all (like a slug).

Molluscs are soft-bodied animals without bones, and often with shells, that live in almost all the habitats of the world. Molluscs, such as "Sammy Snail" , live in the woods near a lake or stream,; however,some molluscs even live in the desert. Examples of molluscs that live in the ocean: cvonch (gastropods),clams, scallops and oysters(which are in the bivalve family), octopus and squid(which are in the cephalopod family and may not have a shell). There are four other, less well-known families in the mollusc class, which we will not cover here. (For your information, these are: the Scaphopods or the tusk shells, the Polyplacophoras or chitons, the Aplacophorans are relatively rare and deepwater mollusc and the Monoplacophoras another relatively scarce mollusc that until the 1950s had actually been classified as extinct) Present as many facts from the Facts section of this molluscan lesson plan as is appropriate for the students age level and comprehension level as time will permit.

Teachers should encourage students to brainstorm: (If desired and have them prepared, hand out the pages on Introduction to Molluscs, Cephalopoda, Bivalves, and Gastropoda. These pages are from Man and Molluscs Beginner's (and are also enclosed in the the lesson plan checklist ) Discuss what other sea creatures and land beasties can your students think of that might be molluscs? (be sure not to get mixed up with such things as starfish, sea biscuits and sand dollars etc., which are echinoderms) (Ex: slugs, nudibranchs, sea butterflies, nudibranchs, etc.) What do your students think molluscs eat? ( you may want to talk about herbivores, carnivores. Omnivores and parasites if the age group lends to this. Filter feeding bivalves to the hunting carnivores such as fish-eating cone shells may be touched upon here as well.) What do molluscs need to live? (food, moisture, and a clean oxygen supply) Can students think of ways in which humans use molluscs? And their shells? Most molluscs can be eaten by humans.

Some of our favorites are scallops, oysters, clams and escargot (land snails - Helix aspersa L.) To give you an idea of the extent of this food source, you may want to visit the Data Base of Edible Molluscs on the Man and Mollusc web site. The URL for this is: molluscan_food_mp.html Shells have long been used by man as tools, and buttons,jewelry, etc. See the Man and Mollusc Article: Uses of Shell-Bearing Molluscs - Past, Present & Future also enclosed in the the lesson plan checklist ) Shell collecting as a hobby Occupations using and studying molluscs What do your students think happens when the environment (ocean) where molluscs live becomes polluted: like with an oil spill or when sewage from homes or industrial pollutants and garbage gets dumped into the earth's water systems? Ballast water from ocean liners is also another danger to ports. This is how such things as the zebra mussel got into the Great Lakes where they have created massive damage. Snails moved from one habitat to another may become bad pests and devastate crops and other vegetation.

Discuss with your students what happens when the environment is disrupted due to lack of molluscs that were once present or when new introduced species overruns an area. Animals and man that feed upon this mollusc are losing a food supply. Where invasive molluscs go, food supplies that other rely on are jeprodised and or crops may also be destroyed. How does all this affect man? What happens to terrestrial snails when their habitats are destroyed? Tree snails in areas of deforestation, or freshwater molluscs when their marshlands are drained, or chaparral areas that are torched, or beaches that are restored by dredging sand where molluscs normally live(both where the sand is collected and where the sand is dumped). There are many great environmental ramifications that can be studied about and discussed with your class in this area. Age level and time permitting, you may even want to touch upon some ways in which the medical world is presently studying molluscs. Such things as pain killers, cancer cures, skin adhesives for operations and materials for healing broken bones are just a few medical objectives being developed from molluscs. Ancient and traditional medicine use many molluscs for their curative powers.

Medically, molluscs are also responsible for spreading many illnesses such as schistosomiasis. More information on Molluscs and Medicine can be found on the Man and Mollusc site at: /links_medicine.html NOTE: Students can write down additional facts on the report they are creating about snails, as the discussion progresses. Teacher should prompt for this by writing key words and ideas on the board. General Mollusc Information That Should Be Covered: This is a more comprehensive list of molluscan facts to cover is in the next section on" Snail Facts to Refer to When Discussing and Marking Projects": Molluscs have been around for over 500 million years. To live, all molluscs must have: food, oxygen and moisture. Most molluscs live in the ocean or, if on land, in moist places such as in lakes, rives, marshes or under leaves or in soil. All molluscs require moisture to stay alive. Even the desert dwelling snails are no exception and they maintain their own moisture inside their shell by means of a trap doors and or a or creating a mucus cocoon and a mucus plugs.

Many molluscs eat: plants (herbivores) or plant cell material in the water. Terrestrial snails like to eat fresh leaves and decomposing material. This can be beneficial because they break down decomposable materials, but snails can also become pests when they turn their attention to garden greens. Many water molluscs eats mosses, algae and such other microscopic plants. Other molluscs are carnivores (eating such things as fish and other molluscs) and some are even parasites (living within another living host) Most aquatic molluscs filter oxygen from the water to "breathe" by means of gills . Terrestrial and some pond snails breathe using lungs (Pulmonary sacs) just as we do. Some pond snails have both gills and modified lungs. Deep ocean trenches do have molluscs that do not utilize oxygen. Polluted waters lack oxygen and food for molluscs and other water creatures to eat and "breathe". This makes them sick and they die and their babies don't hatch or don't live long. When molluscs disappear, the fish and birds and mammals (like otters) that eat them have less food and some of these animals begin to die.

Then there is less fish and molluscs for us to eat, too. If the water they live in is really polluted, the molluscs and fish that survive won't be safe to eat. All the parts of our environment are connected and so you can see how important molluscs are, and how important a clean environment for them to live in is. Most molluscs can be eaten by humans. Some of our favorites are scallops, oysters, clams and escargot (land snails - Helix aspersa L.) To give you an idea of the extent of this food source, you may want to visit the Data Base of Edible Molluscs on the Man and Mollusc web site. The URL for this is: molluscan_food_mp.html Today as in the years past, many people love to collect shells for their beauty and interesting shapes. People who study the shells are called Conchologists. Those scientists that study the molluscan animal are called Malacologists Shells have long been used by man as tools, meidicone, trade goods, buttons, jewelry (pearls and cameos), etc.

See the Man and Mollusc Article: Uses of Shell-Bearing Molluscs - Past, Present & Future located at: man_and_molluscs_a.html Dyes from some molluscs (mostly murex) can be produced from shells for use in colouring cloth. This is not so important today as we have much cheaper synthetic dyes. The Royal Purple garbs of monarchs and priests of old were made from molluscan dyes. This is discussed further in The Man's Uses of Molluscs article ( man_and_mollusc.html) in the section: Personal Adornment (8); personal_adornment.html More Snail Facts to Refer to When Discussing and Marking Projects: More detailed anatomy and physiology facts both for beginners ( A Beginner's Guide to the Molluscs ) and seniors (The Phylum Mollusc) can be found on the Man and Mollusc Lesson Plan-Checklist for Printouts Molluscs (Mollusks; both spellings are correct) Molluscs can be found in gardens, in ponds, deserts and oceans. Some live in the tops of trees and others high in the mountains-and there are probably some in your back yard!

They belong to the group (phylum) of invertebrate animals with a soft bodies known as molluscs Characteristically they have soft, unsegmented bodies. Often, their soft bodies are protected by a hard shell. A gastropod in Latin means, gastro for stomach and pod for foot. A cephalopod in Latin means head - foot Bivalves or Pelecypoda in Latin are called hatchet - foot Gastropods: Terrestrial or Garden Snail Facts : Achitina fulica (Giant African Land Snail) Terrestrial gastropods often have a shell to protect their soft body. Some like slugs have no shells. The body of the snail is usually moist and often slimy. Snails have tentacles. They have a very developed sense of smell, but do not feel much sensation/touch-wise. They do not hear or taste food like we do and their behavior is instinctive. Eyes are usually on the tip of the tentacles. The snail has two pairs of tentacles on its head. One pair is longer than the other pair. The eyes are on the longer pair. The shorter pair is used for smelling and feeling its way around.

The tentacles are very important to a snail. Many gastropods are autonomous, meaning they can regrow lost body parts. When the snail is disturbed, it simply withdraws or pulls its body back into its shell. The snail then seals the entrance with a mucus plug or a trap door, called an operculum. Many snails also use this trap door, to hold in valuable moisture during dry spells. This door is located on the top of their foot and when danger is around or they are required to maintain moisture, this operculum closes them into their shell. When land snails are threatened and want to hide, they go beneath leaves, stones or logs and if possible pull into their shells and hide. The majority of snails are most active at night and on cloudy days. They do not like the sunshine very much as it dries them out too fast. Snails do not like hot and dry conditions. They like it moist or humid and not too bright. During very cold weather or winter, they hibernate in the ground. During dry periods (droughts) molluscs pull into their shells or create a mucus cocoon to keep in valuable moisture. This kind of hibernation is called aestivation.

Snails have different shaped shells. It can be a single shell that is rounded or a pointed spiral or flat. They are often brightly coloured and some even have spines and ridges as well. A snail has fingernail file like tongue called a radula in its mouth for scraping food particles off. This radula is like a rough tongue-like ribbon, something like a file with rows of tiny teeth, which it uses to scrape off bits of leaves and flowers to eat. Snails eat mostly living plants as well as decaying plants. They also chew on fruits and young succulent plant barks. The snail moves by creeping or gliding along on a flat "foot" underneath it's body. The band of muscles in the foot contracts and expands and this creates a kind of rippling movement that pushes the snail forward. The "foot" has a special gland that produces slimy mucus to make a slippery track. You can often see these silvery tracks in the garden. The slime comes out from the front and hardens when it comes into contact with air. The snail is able to move on very sharp pointed needles, knife, razors and vines without being injured because the mucus-like secretion helps to protect its body.

The garden snail travels about 70 cm every 3 minutes-that's 1 km every three and a half days. Many snails are both male and female. Therefore, it can produce sperms and eggs at the same time! However, to fertilize the eggs, the snails need to exchange sperms with each other. An animal that is both a male and a female is called a hermaphrodite. This method of reproduction comes in very handy as these snails are very slow moving and dont like moving around too much. If they had to go looking for a boyfriend or girlfriend, it could take them a very, very long time to have babies. The brown garden snail (Escargot: Helicidae family) lays about 80 spherical shaped white or yellowish coloured eggs at a time into the topsoil of the ground. It can lay eggs up to six times a year. Snails take about 2 years to become adults. After mating, each snail will go search for soft ground to dig and lay its eggs in. The snail lays its eggs in a nest, 2.5 to 4 cm deep in the soil or under tree bark o4 ground leaf litter.

Each snail can lay an average of 85 eggs and they hatch in 2 to 4 weeks, depending on the temperature and moisture of the soil. The first thing that a newly hatched snail does is to find food. It will eat whatever is left of its eggshell too. As the snail grows, its shell grows too, in a spiral shape. The new shell is added at the opening of the shell. The part of the shell the baby snail was born with, ends up in the middle of the spiral. Snails have many natural enemies. They include ground beetles, snakes, toads, turtles, and birds, including chickens, ducks and geese. The largest known land snail is the Giant African Land Snail. It can weight up to 2lb (900g) and measure up to 15.5 inches (39.3cm) from snout to tail. Many land snails are very strong: they can lift 10 times their own weight, even moving up the side of something-like a tree. Snails can live up to 10 years depending on which species you look at. Some have been known to live up to 15 years or longer.

Many people get upset and farmers get angry when snails eat their plants and crops. Snails can cause serious damage to crops. Terrestrial snails are the food humans eat as escargot. The flesh of the snail is very delicious. The French people, especially, love to eat these snails. Some people keep snails in aquariums together with their fish. However, they must make sure that they control the number because snails reproduce rapidly !! Many types of terrestrial snails such as the helicidae or escargot snails are actually farmed today. This farming method is called Heliciculture. Gastropods: Aquatic (Pond or other Freshwater) SNAIL Facts: Pomacea bridgesi (Golden apple snail) The pond snail is, in many ways, like the garden snail. Pond snails are usually tan or dark brown in colour, but some are very brightly coloured as is the golden apple snail seen above. Some pond snails have gills to breathe in water. Those with gills will live at the bottom of the pond. Those that do not have gills will come up to the surface to breathe and have pulmonary sacs which act like our lungs.

These snails will live on the surface so that they can come up to breathe easily. You can often buy pond snails from a pet or aquarium stores. One common pond snail often sold is called "Apple" snail or golden snail. The pond snail feeds mainly on plants like algae and microscopic creatures that are found on the surface of waterweeds. They eat by scraping bits off with their rough, sandpaper-like tongue, just like the garden snails. When pond snails are threatened and want to hide, they bury in the sand, or hide beneath rocks or logs on the bottom of the pond. In the ocean, snails will hide in caves, or on rock ledges. Most pond snails reproduce just like the garden snail. It is a hermaphrodite. The only difference is that, unlike the garden snail, the pond snail carries its fertilized eggs with it or stick them onto or under foliage or stones. If carried around on their mother's shell, the baby snails will only leave their mother when they are hatched. Some pond snails can swim and others can bury themselves in the sand very quickly.

Marine Gastropods Facts (these are the conchs (Strombidae), whelks (Buccinidae), limpets (Lotiidae), periwinkles (Littorinidae), cones (Conidae), volutes (Volutidae), and cowries (Cypraeidae) that we mostly know) Cypraea moneta (Money cowrie) Most seashells that people recognize and pick up along our beaches fit into this group of molluscs Most have a coiled shell. Their soft bodies have a head usually complete with two eyes Some snails have pointy spines on their shells to keep their enemies from eating them; some have very heavy shells that discourage their prey. Some snails have a body that comes over their shells to camouflage them from those that would eat them, and some are poisonous to fend off prey.

They have a big flat foot, which they use for locomotion and on the back end of this foot is a structure called an operculum, which acts as a trap door Most breathe through gills; however, some absorb oxygen from the water directly through a specialized membrane (something like the thin skin lining the insides of your cheeks) lining their mantle cavity. Many of these molluscs have very colorful bodies. Some members in this class only have a very small, fragile shell (such as bubble shells ) and it is often contained right inside their soft bodies or they may not have a shell at all. We know some of the Opisthobranches as: sea hares, sea butterflies (Thecostoma), sea slugs (saccoglossans and nudibranchs), and canoe shells (Scaphandridae). All cone shells possess a poisonous dart (a modified radula) with which they harpoon, inject venom and thus killing their prey. Most are herbivores. Some cone shell possess venom is so toxic that if stung, it can severely harm or even be fatal to man. Many members of the Carrier shell family collect seashells.

These shells scientists call Xenophoridae attach other shells or stones to their own shell for protection and camouflage. Sometimes they even use man-made objects such as glass and bottle caps! The largest snail (univalve) known attained a length of 78 cm (two and one half feet) with a girth of nearly forty inches. This trumpet conch, Syrinx aruanus (Linneus, 1758), weighed in at nearly forty pounds. The smallest known snail shell is the Ammonicera rota and measures only 0.02 inches in diameter. Fifty of them laid end to end would measure one inch! "Pelagic" gastropods live their entire life without ever touching bottom or shore! They float and travel on the ocean's currents. The violet snail, the Janthina, can travel hundreds of miles in its lifetime as it floats around on the ocean's currents. Its delicate shell only touches land when it gets washed up onto beaches during storms. Money cowries were the first item used by man for trade and a monetary system. Other examples of this is the wampum trade beads used by the North American Indian.

Many dead, vacant gastropod shells become mobile homes for hermit crabs. As the crab grows larger, it discards it's shell and moves into a larger vacant shell. Bivalve Facts: (Giant Bittersweet Clam) Covering their soft body is a thin membrane called the mantle (like a thick piece of skin). The mantle takes lime and calcium out of the water and turns it into a two-piece shell Bivalves all have this two-part shell which is hinged together. These two shell parts are called valves. They open and close these valves by using strong adductor muscles and ligaments much like you bend your elbow or knee. Many bivalves anchor themself to hard rocks, or other objects by very fine yet very strong byssal threads which they produce. They have an input siphon (like a short, fat drinking straw that feels like rubber) which they use to pull in water and tiny animals that live in the water. They extract both oxygen and their nutrients from this inflow of water. Oxygen is filtered out in the gill then the food particles are coated with mucous like substance and then fine hair like cilia sweep this food into their digestive systems where they are digested.

A second siphon the output syphon then returns the filtered water back out. If a foreign object such as a piece of sand gets into their soft mantle, it HURTS, so they take the same smooth shelly material that we put on the inside of their shell and cover the offending object up and guess what! They just made a pearl. Most bivalves reproduce by laying millions of eggs into the water surrounding us. The male bivalves then release their sperm into the same water. If the eggs and sperm meet, a new baby bivalve is born. However, some species hold their eggs in a space called the mantle cavity in their body. The males still spurt their sperm into the water and when she pulls this water in through her siphon, the eggs are fertilized. These are then brooded inside her body until she knows they are big enough to live in the water. She then releases them into the water. All baby bivalves start life as tiny specks, (larval stage of growth) swimming in the water. When these larva become big enough, they start to settle onto their new homes. When they are still young, yet settled, they are called "spat".

Some molluscs, such as the oysters, change sex. Some like oysters even alternate their gender. Male one year, female the next! Some bivalves like to live attached to hard objects such as rocks or manmade objects. Some live all their lives buried beneath the sandy or muddy ocean, lake or stream bottoms. Some actually live inside wood. These bivalves (known as ship worms) have caused man a lot of trouble when he used to sail in wooden ships. HE ATE HOLES IN THE SHIP and it often SANK. They still attack wharfs and other wooden man made structures causing a lot of damage. Some of my other species are parasites, meaning that they live inside a living host, such as a fish, and survive by eating part of the host. Some bivalves swim as well. They do this by flapping their shell valves together rapidly forces water out. This sort of like a bit of jet propulsion!valves Bivalves can be very long-lived. The ocean quahog (Arctica islandica Linne,1758), can live to be 220 years old.

The largest known bivalve harvested was a Tridacna gigas(Linne, 1758), which weighed 330kg (734 pounds), and was 1.4m (nearly four feet) in length! Bivalves are a very important food source today. Many are actually farmed for their meat and some for their valuable pearls. Marine snail farming is called Aquaculture of mariculture. Cephalopod Facts Giant Pacific Octopus Cephalopods reach the largest size of any invertebrate. The giant squid, Architeuthis, which lives in the North Atlantic, may reach 17 m (56 ft) in length and weigh three tons. This length includes the tentacles, which may measure 6 m (2 0 ft). In an animal this size, the eye is 30 cm (1 ft) across. All cephalopods are all carnivorous predators (catch live food) eating such things as other molluscs, fish and other marine invertebrates. They crush their food in a hard beak (looks very much like a parrot's beak).

Once the beak has pierced the prey, a poison glad will inject a nasty substance into its body. The poison paralyzes the prey and softens the meat so that the octopus can suck all of the e flesh into its small mouth. In this way, it devours everything but the shell. Often, a diver can locate an octopus den by looking for a pile of empty shells that have been tossed out after feeding. The cephalopods are unusual invertebrates because most lack a hard shell. The chambered nautilus is the only type that has a complete shell. The squid and cuttlefish have small shells that are located inside of the body, rather than outside. The octopus, on the other hand, has lost its shell completely. Cephalopods can see images, an ability that is not found in other mollusks or any other invertebrates. They have two large complex eyes and use them to see almost as we humans do. The eye of the giant squid may measure up to 30 cm (1 ft) across. Cephalopods have cells in their skin, called chromataphores, which enable them to rapidly change skin color and pattern whenever they want to.

They can to change the color of their skin so that it blends in with the surroundings or when registering emotions such as; fear, pain, sorrow, etc. All cephalopods breath through gills Most cephalopods are fast swimmers. They are also known for their ability to squirt a potential predator with "ink" and escape backwards by forcing water from a siphon near the head. This is called jet propulsion! When threatened, cephalopod may use three deferent escape maneuvers to escape: It can sink to the bottom, rapidly pump water out through the siphon and then bury itself in the disturbed sand. It can pump water out of the siphon and propel itself backwards. It can pump a protein-based sepia ink out of the siphon and escape during the confusion. The sepia ink may be produced as a mucus-bound blob or as a large cloud. Most cephalopods have separate sexes and fertilization is internal. The males produce a "sperm packet" which he places inside the females body using one of his tentacles. Sometime later, the female then lays eggs. Many cephalopods are good mothers and stay with their eggs until they hatch.

They keep clean, fresh water flowing over the eggs and caress them to keep them clean of derbies. The young hatch out as perfect small copies of their parents. Most cephalopods are eaten by man. We have also used their ink (called sepia) in our art. This is not used as much today as since natural sepia fades in time and man has developed superior and much less expensive inks and dyes. OCTOPUS Octopus are very intelligent and can even learn to solve complex problems such as seeking out food in a maze Octopus range in size from a few inches to 3.5 m (12 ft). Octopus have three hearts Octopus have 8 tentacles or legs. The arms may have as many as 240 suction cups on the underside, in two rows. These suckers make it almost impossible to remove an octopus once it has attached to an object. If an arm is bitten off by a predator, it will grow back over time. Octopus usually remains inside of its lair unless it is searching for food.

Most such as octopus are highly intelligent as compared to other molluscs and have large heads and very complex brains After mating, a female octopus may lay as many as 45,000 eggs, which she attaches to the roof of her den. She will take care of the eggs during the development period which lasts 1-2 months. She uses her arms to remove any particles that might settle down on the eggs and even squirts water from a siphon if necessary. This is known as brood care. She never leaves the eggs, not even to look for food. Unfortunately, soon after the eggs hatch and release hundreds of tiny octopuses, the mother will die. Octopus can squeeze their bodies through remarkably small openings. A large octopus could easily crawl through a pop can that had been opened at both ends. SQUIDS: While octopuses are known for their intelligence, squids are known for their speed and agility. They swim, usually backwards, using water jets. They have been known to move as fast as 20 knots (23 mph). Unlike the octopus who is solitary creature, squid swim in schools and will frequently follow the schools of fish on which they feed.

Squids have ten arms, two of which are called tentacles. The tentacles are longer than the arms and have flattened ends like a spatula. Suckers are on the underside of all the arms and only on the flattened ends of the tentacles. The tentacles are used for feeding. The suckers, which may have hooks, help capture small fish and shrimp, which are quickly torn apart by the beak. . Squid have an internal shell, called a pen, gives support to the muscular mantle. Some squid do have a small, fragile, coiled shell inside of their body. These tiny white coils often wash up on beaches. Argonauts do have a shell, but they do have a shelly nursery in which they deposit their eggs and where they are incubated. This is not a true shell. Squids can cruise along at constant speeds or dart about in quick jerky movements. Some have been know to jet 3 1/2 m (12 ft) out of the water and land on boat decks. For protection against predators, squid use the same methods as other cephalopods: camouflage coloring, ink clouds and speed.

Some squid have special light organs which not only frighten away predators but also help to attract food or a mate in the permanent darkness of the deep sea. They are luminous CUTTLEFISH Large specimens may reach 60 cm (2 ft), while the common cuttlefish has a maximum size of 30 cm (12 in). Cuttlefish remain hidden during the day, like the octopus, and move about to feed at night. Most only live about 18 months. Cuttlefish eyes have a "W" shaped pupil and are set far apart on the face. These animals probably have the same image forming ability as the other cephalopods. In front of the eyes are eight arms and two tentacles, as in the squid. However, the cuttlefish keeps its tentacles withdrawn in a pouch beneath the eyes. When extended, they are long and thin with suckers on the flattened end only. The arms have suckers all along the underside. Some cuttlefish feed by hiding in the sand or seaweed with its tentacles extended, wiggling like fat little worms. It is so well camouflaged that other animals will not notice it.

When a small fish comes closer to investigate the "worms," the cuttle will jet forward and grab the fish with its arms. Other cuttlefish simply swim along, using their fins, until they see a crab or shrimp. Then it will sneak up from behind and nab the crustacean with its suckered tentacles. The prey is quickly carried to the arms and directed to the hard beak. Besides its beak, the cuttle has another hard body structure. Like the squid, it has a shell inside its mantle. This is the cuttlebone. When cuttlefish die, the cuttlebones rise to the surface and wash up on beaches. These shells, sometimes called "sea biscuits," have been used as a source of calcium and as beak sharpeners for pet birds. Cuttlebone has also been used to relieve earaches, stomach acid and skin diseases, among other things. Cuttlefish do not produce as many eggs as the octopus and squid. Females produce about 500 tiny eggs which look like grains of rice. The eggs are laid one at a time and attached to corals or seaweed. The females do not care for the eggs and die soon after they spawn.

Nautilus: Nautilus are the only cephalopod which produces and external shell The nautilus possess approximately 94 tentacles that arise from lobes that are arranged in both the inner and outer circle around their head. These tentacles lack sucker or adhesive discs. They are instead annulated and can be drawn into a sheath. Located above the head and tentacles is a leathery hood which can be pulled over the vulnerable soft body parts, which the animal pulls into its shell when, threatened. Nautilus can swim with surprising speed. The process for this action is the same as that in the squid; however, the ejection of the water is produced when their body and funnel muscles contract rather than those of the mantle. Nautilus often rest on the bottom with their tentacles forming a stabilizing platform. Whether swimming or resting, their gas filled chambers keep their shell upright at all times. Scientists have yet to discover just how the nautilus regulates this gas production Nautilus do not have chromatophores in their skin as do the other cephalopods The Argonauts: ( called paper nautilus) have two dorsal arms of the female are greatly expanded at their tip to form a membrane.

The expanded portion of each arm secretes one half of a beautiful calcareous bivalved shell. She then deposits her eggs directly into this case. The shell acts as both a brood chamber and a retreat for the female. The posterior of the female usually remains in this shell. The male, which is much smaller than the female, does not have such a shell and is often found in cohabitation within the same shell, more or less as a freeloader! The following Three Classes are for the more senior level of students: Polyplacophora: They're also called chitons or coat-of-mail shells They range in size from 2 millimeters to 40 centimeters (1/16 inch to 16 inches), Their shells are made out of eight separate, but overlapping, plates or valves held together by a fleshy "girdle" or skirt By having several valves that can be moved separately, they are able to change the shape of their bodies to fit onto the uneven hard rocky places they live on. Their broad, fleshy foot holds them to the rocks so tightly that neither the violent ocean waves nor an enemy can dislodge them easily.

You would have to take a sharp object, like a knife, to pry them off the rock and even if you did succeed in getting them off, they would curl up into a ball. Their hard plates would be on the outside of this ball and their soft, vulnerable body parts are then protected on the inside of the ball. They are only found on the ocean where they generally are found clinging tightly onto the rocks in the intertidal zone; however, a few live at depths of more than 5,000 meters Most of the chitons are herbivores They breathe in oxygen from the water through six to eighty-eight pairs of gills. In some species (Most chitons) both the male and females release their eggs and sperm directly into the water. If these eggs and sperm meet by chance, new baby monoplacophora are born. Other times, when females draw in water to breathe, they also draw in the sperm and thus fertilize their eggs internally . They then give live birth to their young, all ready to fend for themselves in the sea! Aplacophoras: This is a very ancient and quite atypical class of molluscs.

They are never seen in large numbers although they are widely distributed in the oceans depths ( usually over 9,000 meter deep) Man scientists feel that they are a very specialized mollusc They closely resemble an unsegmened worm and are somewhat kidney-bean shaped/ In some species the foot is totally absent while in other species this foot is visible as a ventral fold Aplacophoran heads are very poorly defined Apacohorans appear to eat only coelenterates (jellyfish, sponge, hydra, sea anemones, and corals) Monoplacophoras: This is a predominantly fossil group with only a few living species All are marine species and live at depths exceeding 2,00 meters. In 1952, while on the Danish "Galathea" expedition, scientists discovered ten living specimens of Neopilina. Until that time this class was considered extinct! They possess a single symmetrical shell about 1.0 to 3.5 centimeters long and is shaped like a cap They crawl around the ocean bottom by means of a large, round, flat foot.

Inside their body, the organs are in pairs almost like those of the earthworm; however, they are not segmented like a worm. They have several paired gills (one per section) through which they breathe and one heart and kidney per body section Females release their eggs directly into the surrounding water in great clouds. The males also release their sperm into the same water. If these eggs and sperm meet by chance, new baby monoplacophora are born. Closure Have students examine the shells that have been collected for this lesson plan. With the use of books or Internet resources (like the visual identification kit) see if students can identify their finds. Have each student choose a shell to take back to his or her desk to draw. Encourage them to use colour. Students should write up a report on a selected mollusc or molluscs. This should containe both a drwned picture and written facts. Collect these molluscan reports, dreawings and worksheets to mark. This will also let you know what points they have learned and it will also help you to prepare fpr future classes Students can also make and cut out drawings once they are completed.

Students can arrange these cut-out shell drawings g;ue them on to the large poster board provided.Shells can be labeled and poster displayed in class. Sample title for this is "Molluscs We Have Found." Provide students with colouring sheets to colour in class, or to take home, if there's not time in class. Discuss what colours the molluscs in the pictures would likely be (camouflage). Continue on with any additional activities that you wish to add to the unit. If time and space permits, keep the snails in their terrarium of aquariums in the classroom for several weeks. Actually, this could become a very interesting yearly class project. Have the students help in feeding them and keeping their home clean. Have them observe the lifecycles of their snails. Further report or notes and pictures should be encouraged. observations in the form of a small report about their lifecycle could be a great long-term project OPTIONAL: Man and Mollusc has a children's art and story page set up online where children may have their works of art, stories, limericks, poems etc. placed. These can be viewed fro the Children's Zone at: /kid_zone.html .

To have items placed on these pages, contact Avril Bourquin and arrange for this Evaluation Procedures Evaluate what the students have learned (glean whether or not students are comprehending and absorbing the information you are presenting). This can be done by discussing and brainstorming about molluscs with students. Mark the snail and shell drawings, and written reports to see what each student has been able to observe, learn, and record about snails, and molluscs in general from this lesson. Consider the contribution each student made to the brainstorm/discussion on molluscs, as well. Consider the ability of each student, the accuracy of their observations, and the time they each spent on these class projects. Did your students enjoy this lesson? If not ask them how or what they would suggest you change. So much can be learned from children. Never under estimate their contributions! Optional:If you have chosen to keep the snails in the classroom and have asked the students to do a follow-up report on the lifecycle of the snails, make sure to collect these and mark them based on the accuracy of their observations and the time they've put into their project.

References Man and Mollusc web site: by Avril Bourquin "Sammy 's Adventure" story by Robynn Honeychurch, Anna Palumbo and Avril Bourquin Additional Resources

Question: What name is shared by a violet-coloured flower and a gastropod mollusc?
Answer: PERIWINKLE