Earth Worms

Earthworms are the largest members of Oligochaeta in phylum Annelida. They are also called as megadriles which means big worms. The megadriles are characterized by having a distinct clitellium and a vascular system with true capillaries.

Anatomy

Earthworm has tubular body shape. Its outer body is muscular slimy and moist. Its body is annular and consists of segments that are more concentrated in the anterior part. They have a simple closed circulatory system. It consists of two main blood vessels which extend through the length of their body. A ventral body vessel which leads blood to the posterior end and a dorsal blood vessel that leads to anterior end.

Reproduction

Earthworms are hermaphrodites. It means, each earthworm has male parts that produce sperm and female parts that produce eggs. All earthworms lay eggs. They have two pairs of testes surrounded by two pairs of testes sacs. There are two to four pairs of seminal vesicles which produce, store and release the sperm through male spores. The mating pair overlaps each other from front ends and exchanges sperm with each other.

Regeneration

Earthworms have the ability to restore its lost segments, but this ability varies between species and depends on the extent of damage.

Behavior

Earthworms can sometimes be found on ground surface flowing with heavy rain storms. They are also found on hard and rocky surfaces. On these surfaces earthworms get trapped and suffer from injury or death. This is caused due to excessive heat, exposure and dehydration on the rocky surfaces. There are certain species that survive in water for several days if it is sufficiently oxygenated.

Locomotion and importance to soil

Earthworms travel underground by means of waves of muscular contractions which alternately shorten and lengthen their body. In all body segments except first, last and the clitellium, there is a ring of S shaped setae in the epidermal pit of each segment.

The whole burrowing process is aided by secretion of lubricating mucus. Worms make gurgling sound underground when they are disturbed. They also act as biological pistons forcing air through tunnels as they move.

A large wooden box full of garden soil, which has been sterilized in the oven at 200°C (400°F) for 30 minutes with a layer of dead leaves on the top is a good place to breed earthworms. The soil should always be slightly moist and a piece of sacking, cut to the size of the container, laid on top of the dead leaves will help to cut down water loss; but do not let the thing get too wet. When you have set up their home, go and catch your earthworms and put them in a bucket of cut grass overnight. In the morning discard any dead or injured worms and put the rest in your vermicarium. Worms do not appreciate being overcrowded so you should not introduce more than about 40 of them per .03 cu m (1 cu ft). They like to be cool and a temperature of 16°C (60°F) will kill them. It is quite a good idea to breed earthworms if you have animals that will eat them since wild specimens are virtually unobtainable during the winter, and in captivity you can sterilize the soil in which they live, which could be important, because there have been stories of wild worms causing the death of the animals to which they were fed due to nasty things that they had picked up along the way.

Benefits

Earthworm’s activities help in soil fertilization. It can be summarized as:

• Biological In many soils, earthworm plays a major role in converting large pieces of organic matter. For example, dead leaves are turned into rich humus and thus improve soil fertility. This is gained by worm’s action of pulling down the organic matter on the dried dirt. Dried dirt can be leaf fall or manure which is pulled in for either food or when earthworms need to plug its burrow. In the burrow, worm shreds the leaf and partially digest it and then mingles it with earth by saturating it with intestinal secretions.
• Chemical Apart from dead organic matter, earthworm also ingests other soil particles that are small which includes stones up to 1.25mm. These fragments are then made into a fine paste by the gizzard which is then digested in the intestine. When the worm excretes this in form of casts they are deposited on the soil surface or deeper in the soil. These excreta are rich in minerals and serves as a plant nutrient.
• Physical By its burrowing actions, earthworm helps in keeping the soil structure open. This creates a multitude of channels which allow the processes of both aeration and drainage. Earthworms are best friends of farmers as they help in making soil healthy.