Nottingham Post - - WILD LIFE -

WHILST snails and slugs are of­ten the bane of gar­den­ers and hor­ti­cul­tur­al­ists alike due to their propen­sity for feed­ing on crops and or­na­men­tal plants, and are con­sid­ered as pests, it should be re­mem­bered that not all species cause dam­age and they are also an im­por­tant food source for a num­ber of nat­u­ral preda­tors. Con­trol­ling slugs and snails in your gar­den can have a se­vere im­pact on this im­por­tant food source for other an­i­mals such as hedge­hogs and birds such as the song thrush whose num­bers are al­ready threat­ened by many other habi­tat, cli­mate and hu­man chal­lenges.

In the UK there are ap­prox­i­mately 100 species of land snail and ap­prox­i­mately 40 species of slug. Land snails and slugs are mol­luscs and gas­tropods- gas­tro­pod lit­er­ally means an “eat­ing foot”. All land slugs have evolved from land snails with the most ob­vi­ous vis­ual dif­fer­ence be­ing the lack of a shell al­though slugs still have the rem­nants of a shell, known as a “ves­ti­gial shell”.

This ves­ti­gial shell is found ex­ter­nally in a small num­ber of UK species, how­ever in the ma­jor­ity it is now lo­cated in­ter­nally. They have nearly 30,000 teeth and both se­crete mu­cus which helps them glide over a sur­face; this slimy mu­cus also acts as a de­ter­rent to would be preda­tors.

A bird can some­times be ob­served to wipe away this mu­cus on grass and plants prior to in­ges­tion. Land snails have no hear­ing or­gans but have both sight and ol­fac­tory (smell) or­gans. It is their good sense of smell that helps them find food.

Snail shells es­sen­tially con­sist of cal­cium car­bon­ate. Snails are born with colour­less soft cells known as a “pro­to­conch” and they need to con­sume a lot of cal­cium to help the shell to har­den. The shell con­tin­ues to grow as the snail grows; the num­ber of whorls or spi­rals in the shell in­creases and the pro­to­conch ends up in the cen­tre of the spi­ral of the snails shell. Sim­i­lar to tree rings these rings can be used to es­ti­mate the age of the snail.

Most snails are hermaphrodites, mean­ing that they have both male and fe­male re­pro­duc­tive or­gans but mate with a part­ner as they do not fer­til­ize their own eggs. Fol­low­ing mat­ing both snails lay eggs thus in­creas­ing the over­all chances of sur­vival. The re­sult­ing eggs are tiny and are dropped into moist soil and take up to four weeks for to hatch.

One of the most com­mon species en­coun­tered in our gar­dens is the gar­den (com­mon) snail, Cornu as­persa. The body is grey­ish and the adult shells are 25–40 mm in di­am­e­ter and 25–35 mm high, brown in colour with darker brown mark­ings with a white lip. They have two long ten­ta­cles, each with an eye at the tip. Be­low these eye stalks are two shorter ten­ta­cles which help the snail to feel where it is go­ing. The mouth is sit­u­ated be­tween these two lower ten­ta­cles. They are pri­mar­ily her­bi­vores feed­ing on veg­etable crops, ce­re­als, fruit trees and gar­den flowers, but will scav­enge on rot­ting plant ma­te­rial and oc­ca­sion­ally on an­i­mal mat­ter, such as crushed snails and worms.

In late au­tumn they start to search out places in which to hi­ber­nate where they will of­ten form large groups in tree crevices and un­der rocks and stones. Once a se­cure place has been found they seal them­selves into their shells.


Gar­den snail

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