Life Story Of A Snail (1963)

this is a freshwater snail snails are part of a large grou group of animals called mollusks mollusks are invertebrates this means that they do not have a backbone like you do snails can be found almost everywhere in the world they live in the oceans they live in freshwater rivers lakes and ponds and they live on land to photograph the life of the snail we will use an aquarium as a pond in an aquarium it is easy to observe the habits and characteristics of snails the most striking part of the animal's appearance is the spiral shape of its protective shell inside the animal's body twists in the same spiral pattern of the shell some snail shells are both cone-like and spiral the they are also of many sizes and colors the shell has an opening through which the animal extends or pulls in its body here the body is coming out of the shell when fully extended the body is partly outside and partly inside the shell outside is a large flat muscular foot on which the snail moves at the front of the foot is a head which has a brain tentacles eyes and a mouth the tentacles and foot are especially sensitive to touch 2 to 3 in per minute is about the fastest a large snail can move most snails move more slowly movement is caused by a wavelike Rippling of the muscles on the underside of the foot here another kind of snail moves along a special gland in the snail's foot secretes a slimy track on which the animal Glides the track dries and can usually be seen after a snail has passed notice the wav likee forms in the dried track on top of the foot and behind the shell is a hard plate-like form when the snail withdraws into its shell this part of the foot seals the opening like a door and protects the animals soft body most snails are vegetarians and eat nothing but plants some are scavengers that eat dead and decaying material why would this make them useful in your aquarium living algae or Pond scum found on nearly all underwater surfaces are the main source of food for snails when eating the snail uses a filik tongue called the radula hundreds of hard sharp teeth on the surface of the radula tear the food into small bits here is the rajula of a different kind of snail these are marks left by the radula on the slimy surface of the glass after a snail has eaten this radula has been removed from a snail so that you can see the ribbon of tiny teeth now let's look on the inside of the snail shell here you will find most of the body organs the mouth stomach and intestines of the digestive system the heart for circulation of the blood the gills for breathing and the anal and kidney outlets for the removal of waste products from the body land snails have a single lung instead of a gill for breathing all of the body within the shell is enclosed in a sacklike covering of flesh called the mantle the mantle also produces the shell the shell grows only around the edge of the opening this is the only place where the mantle is attached to the Shell a lime solution secreted by the mantle hardens and forms the new parts of the shell here are the lines that Mark the rings of new shell growth up under the shell and just behind the head is a kind of pocket called the mantle cavity water which flows into this pocket brings oxygen to the gills and flushes away the waste products of digestion here you can see waste products being flushed from the mantle cavity most snails have both male and female reproductive organs therefore each snail can produce eggs from which new snails can develop before reproduction can begin however two snails must make bodily contact and fertilize each other's eggs the pond snail attaches its eggs to water plants rocks or other underwater surfaces the eggs are deposited in a jelly-like mess these are attached to the side of the aquarium each egg develops a snail if it is warm young snails will hatch in as little as 5 days as soon as a snail hatches it begins to feed the snail grows rather rapidly soon the shell hardens and darkens like the adult by eating algae and other plants snails help to control the amount of plant life in their water Community snails likewise are kept from becoming too numerous by being eaten by fish or other animals thus no one organism becomes so abundant as to endanger the lives of any of the others we call this the balance of nature as cold weather approaches the snail's body processes slow down and the animal prepares to hibernate it crawls into a hole in the bottom of the pond withdraws into its shell and becomes inactive during hibernation the snail's heartbeat and breathing are carried on more slowly there are over 880,000 kinds of snails land snails are common in tropical climates or in other moist areas the slug is a close relative of the last snail you saw it is also a land dweller the greatest number and variety of snails live in the oceans slugs also dwell in the oceans the oceans also contain a great many other relatives of the snail how do each of the mollusks that follow differ from the snail the oyster and the clam the squid which sometimes grows to 50 ft or more and the o us with its long arm-like tentacles although all these animals differ widely in outward appearance from one another and from the snail whose life story you have just seen they are all mollusks because their internal body plan is fundamentally the same