Why is salt deadly to snails?

Although every gardener wants to save their plants from being munched on by these hungry pests, salt is not the most humane solution.

By   |  Published: 24th Sep 2020  7:10 pm

The rainy season brings with it a plenty of unwelcome pests, primarily snails and slugs! They (snails and slugs) are every gardener’s nightmare, creeping around the crops, munching on leaves and roots as they go. Their ravenous appetites enable them to eat several times their own body weight every single day.

Both snails and slugs belong to the phylum Mollusca and class Gastropoda. Their slimy, squishy bodies are essentially one giant stomach on a single foot. They travel by scooting on this muscular ‘foot’. This muscle continuously secretes mucus that facilitates their motion. The mucus prevents their cells from losing moisture to the surrounding dry soil. This also saves them from being sliced open by sharp articles in the earth.

Salt prevents these slimy crawlers from damaging plants.

Snail and slugs have a foot composed of cells, which can be thought of as bags of organelles inside an aqueous medium surrounded by a cell membrane. The cell membrane is a semi-permeable phospholipid bilayer. The semi-permeability allows for the selective passage of molecules. Thus, smaller molecules can pass through with ease, while larger ones are prevented from crossing the membrane.

Osmosis can occur due to the presence of the semi-permeable membrane. Osmosis is a process in which solvent molecules migrate from a solution of lower concentration to a higher one through a semi-permeable membrane. The difference in concentration on the two sides of the membrane leads to the build-up of osmotic pressure. This pressure is responsible for the movement of the solvent molecules.

Now, animal cells are not composed of water alone. They also contain several ions, including Na+ and Cl-, which form common salt. When salt is sprinkled on them, the salt crystals bind to the moisture on their skin. This creates a highly concentrated NaCl solution, leading to the development of osmotic pressure.

A solution with high salt concentration is called a hypertonic solution. When a hypertonic solution surrounds animal cells, they tend to shrivel up due to heavy water loss. Water rapidly travels out of the cell to dilute the salt solution outside.

Water loss triggers the production of a slimy secretion to prevent the skin from drying up. Bubbling occurs as air is driven out of the critter’s body while it shrivels up. Enough salt can cause the slimy being to die fairly easily from dehydration, which is incredibly painful and gruesome.

Although every gardener wants to save their plants from being munched on by these hungry pests, salt is not the most humane solution. Scientists suggests that earthworms are a preferable solution to this problem.

Earthworms’ not only improve soil fertility, but also decrease slug-induced damage by a whopping 60%. The 18% increase in nitrogen in the soil helps the plants better protect themselves. Unable to gorge in peace, the snails and slugs migrate to ‘greener’ pastures.

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