REGENERATION CAPACITY OF EARTHWORM
Regeneration is the power of producing the lost body parts. Earthworms have remarkable power of regeneration. They can regenerate segments lost by accident. If a worm is cut into two parts, the anterior part will regenerate the entire posterior part but the posterior part cannot develop the anterior part, though it can produce a limited number of segments at the anterior end. It is important to note that the reproductive organs are not regenerated.
ADAPTATIONS OF EARTHWORM
Earthworms are well adapted for a subterranean or fossorial mode of life. The following are the adaptations which help earthworm to lead its life,
- Elongated, slender and streamlined body which is much helpful in burrowing habitat
- Presence of setae and musculature which help it in locomotion and also for anchorage
- Secretion of mucous to plaster the internal walls of the burrow
- Coelomic fluid oozing through dorsal pores keeps skin moist.
- And this moist skin is also helpful in gaseous exchange in the absence of specialized respiratory organs
- Amoebocytes of the coelomic fluid kill harmful bacteria and other parasites. Thus protecting the worm
- The nocturnal and burrowing habits of the earthworms also protect them from predators.
- Due to its fossorial mode of life special sensory organs like eyes and ears are absent
- Hermaphroditism and regeneration capability ensures continuity of species against all odds of the life
- Copulation followed by the formation of cocoon for fertilization and development are adaptations for reproduction on dry land.
ECONOMIC IMPORTANCE OF EARTHWORM
Earthworms are of great economic importance to man. They play an important role in agriculture and are the best friends of farmers as they are continuously ploughing and manuring the soil. However, a few species of earthworms are harmful.
Earthworms in Agriculture: Earthworms make burrows and hence aerate the soil. They continually bring the lower soil and deposit it on the surface. It is said that in a time of ten years, they can fill the whole surface of earth up to 5 cm. The earth worms have been ploughing the land long before man. Their habit of burrowing and soil feeding makes the soil loose and porous. Their burrows permit the penetration of air and moisture in the porous soil, improve drainage and make the downward growth of roots easier.
The faeces of the worms make good manure. By burying the dead and decayed matter, they enrich the soil. The excretory wastes and other secretions of the worms also enrich the soil by adding nitrogenous matters that form important plant food. The faeces of earthworm contain nitrate, calcium, phosphorus, potassium and magnesium which constitute an important component of the humus essential for plant growth. They also reduce the alkalinity and acidity of the soil.
Earthworm as Bait and Food: Earthworms are used as baits for fishing in many parts of the world. They are used as food by large number of animals like frogs, moles, lizards, small snakes, centipedes and also some birds. In many parts of the world uncivilized people use the earthworms as food. The earthworms make the best food of fish aquarium and small animals in laboratory.
Earthworms in Medicines: Ayurveda and Unani system of therapy suggests that earthworms are used for reducing the size and finally removing bladder stones, jaundice, piles, diarrhea, weakness after pregnancy, sexual impotency and gout. Today they are used in India, China and Japan in various fancy medicines.
Earthworms in laboratories: Earthworms are universally used for dissection in zoological laboratories, as they are easily obtained.
Harmful Earthworms: A few species of earthworms may cause harm to man in various ways:
Their burrows may cause loss of water by seepage from ditches, canals and irrigated lands. Their casting on sloppy lands easily gets washed away by rain and thus contributes to soil erosion.
Some species bury in the carcasses of animals, and bring disease germs to the surface, which infect others. While a few species live as ectoparasite on frogs and man. They also act as intermediate host of some parasites like the tapeworm (Amoebotaenia sphenoides) of chicken and the lung nematode (Metastrongylus elongatus) of pig. Pheretima elongata damages the roots of betel vine, Malabaria podudicola and Aphanascus oryzivorus damage roots of paddy.
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