Earthworms are tiny invertebrate organisms that live in the soil, as they are susceptible to pH, waterlogging, compaction, rotation, tillage, and organic matter, which are considered good biological indicators of soil health. The numbers and distribution of Earthworms in a field indicate what is happening under the surface. In nearly all types of soils in the world, Earthworms are present wherever the conditions are suitable according to them, i.e. the moisture and organic content are sufficient to support them.
Classification of Earthworms
The scientific name for Earthworms is Lumbricina.
There are more than 1,800 species of the Oligochaeta class of terrestrial worms present in the world. The most common species of Earthworm found in the environment is Lumbricus terrestris.
Currently, according to the species name database, there are over 6,000 terrestrial Earthworm species and just about 150 species are widely distributed around the world, out of a total of around 6,000 species. These are Earthworms, either peregrine or cosmopolitan in nature.
Morphology of Earthworm
Earthworms are extremely important for the environment and there is an essential need to preserve and understand the Earthworms. Some key details about the shape and size of an Earthworm are:
Earthworms are generally broad, small, cylindrically elongated with points at the front, blunt behind, and thickest slightly behind the anterior end.
Some key features about the anatomy of an Earthworm are given below:
There are 4 pairs of small ventrolateral spermathecal pores which lie intersegmental between the grooves of 5/6, 6/7, 7/8, and 8/9 segments.
Dorsal pores of minute apertures of coelomic chambers are present behind the 12th segment which is located mid-dorsally, one in each intersegmental groove, except the last groove. Through these pores, coelom communicates with the exterior.
The excretory system includes a pair of nephridia in every section, except for the first three and the last ones. Integumentary, septal, and pharyngeal are the three forms of nephridia.
Earthworms do not have any separate breathing organs. Gases are exchanged through the wet skin and capillaries, where the haemoglobin dissolved in the blood plasma takes up oxygen and releases carbon dioxide. Water can also be transferred through the skin through active transport, as well as salts.
The musculature (a combined effect of contraction and relaxation of both the muscle layer) of the body wall and seta and the hydrostatic pressure produced by the coelomic fluid is involved in Earthworm movements. For forward locomotion, the increase in the hydrostatic pressure of the anterior segments of the body (usually 9 segments) is responsible.
Types of Earthworms
There are three types of Earthworms and all these three can be defined by the part of the ecosystem that the worms primarily inhabit. These are: