MOLLUSCS (SLUGS, SNAILS AND CLAMS)

After rain the pathways of the Lobau are sometimes covered with slugs whereas during hot dry periods you notice the snails more. They creep up stems of plants and stick themselves there, closing the opening to their shell and going into a kind of dormant state (aestivation).

Some basic biology – short and simple!

These animals have soft bodies, the skin protected by mucus (slime), a muscular ‘foot’ and a cavity surrounded by a thinner mantle. This mantle may form a hard protective shell (snails), two shells that hinge and can open and close (clams) or a layer of thick slime (slugs). (Other members of the mollusc phylum such as squids, octopus and cuttlefish are restricted to the marine environment).

Snails and slugs are hermaphrodite (possessing both male and female organs) and when they mate they exchange sperm, both partners then laying eggs in moist soil. They mate regularly during their lifetime, producing large numbers of eggs, relatively few of which survive.

As the snail grows, the shell grows with it (unlike crustaceans that moult).

Bivalve molluscs (clams) are usually either male or female, fertilization is external, sperm and eggs being released into the water simultaneously and the eggs then developing into minute larval forms.