slugs & Snails

by Ginny (P7) 18/05/2011

What are they ?

• Snails and slugs belong to the animal group - molluscs.

• This group includes squids & octopus (and all the aquatic bivalves, i.e. cockles & mussels), as well as snails & slugs.

• Molluscs are soft-bodied animals, without internal skeletons, but the majority of them have some sort of shell which both supports and protects the body.

• Snails and slugs belong to a sub-group called the gastropods (within the group of molluscs.)

• Gastropod means 'belly feet' and refers to the way the animals creep about on their bellies.

• Slugs have descended from various groups of snails through the reduction or complete loss of the shell.

Snails • Snails have soft, un-segmented

bodies which are protected by a hard shell.

• The scientific name for the garden snail is Helix aspersa.

• When a snail is disturbed, retreats into its shell.

• It also retreats into its shell & seals the entrance, in dry weather, to protect its body from drying up.

• A snail is most active at night & cloudy days. It does not like the sunshine very much.

• During very cold weather or winter, snails hibernate in the ground.

Source:http://qspace.library.queensu.ca/html/1974/136/images/snail01.gif http://www.kiddyhouse.com/Snails/

snails (on the outside )

Source: http://cnx.org/content/m19897/latest/snail.png

shell

eye

feeler

mouth

Breathing hole

Muscular foot

snails (on the inside)

Source: http://www.gireaud.net/images/snail_biology.jpg

Snails 2

• The eye of a snail is on the tip of the tentacle, a 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 of tentacles is used for smelling and feeling its way around.

• A snail moves by creeping on a flat foot underneath the body.

• The band of muscles in the foot contract and expand and this create a kind of rippling movement that pushes the snail forward.

Source: http://www.kiddyhouse.com/Snails/

Snails 4

A snail is even able to move on very sharp pointed needles, knife, razors and vines without being injured because the slime helps to protect its body.

Source: http://www.odivinorum.com/11-strength.html

snailS eat…• Snails have a radula for grinding up

food.

• A radula is like a rough tongue / file with rows of tiny teeth that it uses to consume leaves and flowers.

• Snails can cause serious damage to crops.

• They eat living plants as well as decaying plants. They also chew on fruits & young juicy plant barks.

• The pond snail feeds mainly on plants like algae and microscopic creatures that are found on the surface of water weeds.

Source: http://www.pirx.com/gallery/albums/mollusks/radula.jpg http://www.kiddyhouse.com/Snails/

Eggs to Babies• Snails are hermaphrodites (both male &

female).

• Snails take approx. 2 years to become adults.

• After mating, each snail will search for soft ground to lay its eggs.

• Snails lay their eggs in a nest in the soil. (2.5cm - 4cm’s in size).

• Snails can lay an average of 85 eggs & they hatch in 2 to 4 weeks, depending on the temperature and moisture of the soil.

• Snails are most active in the months from February - October.

• The first thing a newly hatched snail does is find food. They will eat what is left of their eggshell & will also eat any eggs that have not hatched yet.

Source: http://farm4.static.flickr.com/3170/2894307647_826cbff41a.jpg http://www.kiddyhouse.com/Snails/ http://www.kiddyhouse.com/Snails/

Pond Snails• 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.

• These snails will live on the surface so that they can come up to breathe easily.

• The pond snail reproduces just like the garden snail.

• The only difference is that, the pond snail carries its fertilized eggs with it and the baby snail will only leave its mother when it is hatched.

Source http://www.kiddyhouse.com/Snails/

Snails

• Some snails are edible you can buy pond snails from a fish monger in the city.

• The flesh of the snail is supposedly very delicious.

Source http://www.kiddyhouse.com/Snails/ , http://www.kidsrecipe.co/category/whats-groser-than-gross/

why would people eat snails?

Probably in years of war / famine people were forced to eat things they would not usually eat, due to lack of food. 

People in the countryside were so poor / hungry that they probably decided to eat snails .

Popularity over the centuries has varied but people kept on eating them because they are quite tasty if prepared well i.e. with garlic and butter.

According to the ‘Larousse Gastronomique’, snails have been popular since Roman times. They were also included in a famous 14c. cookbook. the ‘Menagier de Paris’,

The most common kind of snail eaten, apparently used to be one’s on vines and they would have been readily available in wine country.

There lot of countries where snails are a traditional meal e.g. France (Escargot), some regions in Spain, Italy, Greece, England, Asia (they put snails in the soup), Africa (there are giant snails). 

Source http://www.kiddyhouse.com/Snails/ http://wiki.answers.com/Q/Why_do_the_french_eat_snails

A super,A super, big guy big guy

• One of the largest species of land snail is the Giant African Snail which can grow to be 38 cm from snout to tail, and weigh 1 kg.

Source:http://4.bp.blogspot.com/_8DfUOJtGfL8/S9_PdTC1CnI/AAAAAAAAEDc/hPu5vfD7YCE/s1600/giant-african-snail-1.jpg http://www.papuaweb.org/gb/foto/muller/ecology/09/05.jpg

Slugs• Most slugs prefer to eat decaying plant matter. Slugs don’t actually do much damage.

• Slugs have also lost their visceral humps (the part of the snail which is inside the shell).

• This means that the digestive system and other internal organs have to be packed into the head-foot.

• The mantle still covers part of the body and, as in snails, it encloses the lung.

• A few slugs retain a small shell at the hind end like the Testacella baliotidea, but the shell has been reduced in most species to a very thin plate or just a few chalky granules embedded in the mantle.

• Slugs evolved from aquatic animals.

• All land slugs and snails have adapted to breathing air by developing a hole on their side which expands and contracts to take in oxygen.

• The hole was formed, as their prehistoric gills disappeared to make way for a set of new, lungs.

Image + Text source: http://www.jaxshells.org/aba.jpg http://www.the-piedpiper.co.uk/th11a.htm

A Baby Slug

Slugs (from The outside )

FOOT SKIRT Anus(Under the mantle)

trunkkeel

mantle

head

Pneumostome(Respiratory pore)

Optic tentacles(eyes at tips)

Genital Opening

Pedal Slime guard

Mouth(Radula)

Sensory tenacles

Slugs (From The Inside)

Source;http://snailstales.blogspot.com/2006/04/tiny-slugs-last-meal.html

Stomach

BuccalMass

Salivarygland

Rectum

Anus

Slugs

• Water is quickly lost from the slug's soft, moist and unprotected body so it has to live in damp places in the soil and among debris.

• It emerges only at night or on wet days. A slug's organs of smell are in its tentacles and enable it to detect food several feet away.

• With no portable home into which they can withdraw, the slugs are more susceptible to drought and to enemies than the snails, although they protect themselves to some extent with various kinds of mucus.

Source: http://www.the-piedpiper.co.uk/th11a(5).htm http://i.telegraph.co.uk/multimedia/archive/01627/slug_1627430c.jpg

Slugs

Source: http://www.the-piedpiper.co.uk/th11a(5).htm http://i.telegraph.co.uk/multimedia/archive/01627/slug_1627430c.jpg

• Many species are active all through the year as long as the weather remains kind.

• During very dry/cold weather they tunnel deep down into the soil.

• Some slugs live most of their lives in the soil, but most of them are surface feeders & they come out to feed at night or when the air is damp after rain.

• Slugs dislike rain falling on them, but often emerge in their thousands as soon as it stops.

• If you look closely at a keeled slug you can often see lots of tiny animals running all over their bodies.

• These tiny animals are mites and you will see them on the keeled slugs.

• The slugs don’t mind their tiny mites and don't even cough when these passengers scuttle in and out of their breathing pores.

• Although slugs have descended from snails, they have not all descended from one group of snails i.e they are not all closely related.

Slugs

Source: http://www.the-piedpiper.co.uk/th11a(5).htm http://i.telegraph.co.uk/multimedia/archive/01627/slug_1627430c.jpg

British slugs belong to 3 distinct groups:

• shelled slugs,

• keeled slugs

• round backed slugs.

There are approx. 24 British species of slugs. Half of these turn up in the garden over time.

Thanks for watching

Background image source: http://wallpaper-s.org/11__Raindrops_on_a_Leaf.htm