The four main types of earthworms include nightcrawlers, garden worms, manure worms, and red worms. There would be a great deal of difference between a garden without earthworms and the one which houses them. This is due to the fact that these creatures present several benefits for the healthy growth of the plants and vegetables in a garden. The soil being their main habitat, it gets tilled when they tunnel their way through it. This in turn gives way for air and moisture to pass easily through the soil, creating a favorable habitat for plants.
The tunnels which have been created in the soil serve as reservoirs of water which plants can make use of. They also hold air, which aids bacteria to break down organic matter within the soil. The castings which the earthworms leave behind serve as natural manures and soil conditioning materials. These castings favor moisture retention and improve the porosity of the soil, thus adding to plant growth and preventing infestation of pests and many plant diseases.
Adaptation of Earthworms
Moist soil is the main habitat of earthworms, while mud such as that found along the shore of lakes and swamps is preferred by some species. Fresh or salt water bodies have soil which is favorable for earthworms, so they are also found in abundance in such places. Backyard soil and soil which is found in tree branches are also some of the common places which serve as habitats of earthworms. During winter months, earthworms remain coiled up in enlarged soil chambers which lie below the frost line. In general, earthworm habitat includes dark and damp places such as moist soil under rocks, fallen logs, dead vegetation, etc.
The habitat of earthworms differs according to the species. The different species inhabit separate layers of the soil. Epigeic earthworms live on the soil surface or just below it. Endogeic earthworms are inhabitants of the topsoil layer. They live 20 to 25 cm below the soil surface. Anecic earthworms inhabit the subsoil layer. They can be found at depths of up to 3 meters below the soil surface. There are also some earthworm species that are aquatic, and some species that are arboreal, which means that they live on trees. Thus, there are variations in the habitat of earthworms depending on their species. Accordingly, their diet also differs from each other.
- Earthworms do not have eyes. They detect light with their light-sensitive organs and other vibrations through organs which are touch-sensitive.
- The reason why the habitat of earthworms consists of a moist environment is that they respire through their skin. So, they require humid conditions in order to prevent themselves from drying out. The dissolved oxygen makes its way into the bloodstream with the help of their skin which is coated with mucus.
- Earthworms have no teeth and they digest their food through a type of gizzard (thick-walled muscular pouch below the crop, present in many birds and reptiles for grinding food).
- Earthworms have no hearts, but have organs with a similar function. These are known as aortic arches, and earthworms have 5 of these.
- Studies have revealed that earthworms are an excellent source of protein. They are also high in Omega 3 essential oil, which helps in lowering the level of 'bad' cholesterol in the body.
- These creatures can move stones 60 times their body weight. Some species, in an ideal habitat (no predators, etc.), have a life span of about 10 years. Some species live for 4 years or so and some up to 6 years.
- Several forms of organic matter in soil, decaying roots and leaves, and living organisms such as nematodes, protozoans, rotifers, bacteria, and fungi are a part of the nutrition of earthworms.
- Earthworms are hermaphroditic; they contain organs of both sexes. The mating pair overlaps their front ends ventrally and each exchanges sperm with the other.
- Earthworms are commonly preyed upon by snakes, birds, moles, toads, and even foxes. Beetles, centipedes, leeches, slugs, and flatworms are also known to include these creatures in their diet.
- Earthworms are capable of regeneration. However, it depends upon the type of species and the severity of the damage caused.
- Favorable conditions pertaining to the habitat of earthworms, their diet, and their age govern the size of these animals. Giant Gipsland earthworms are known to attain an average length of about 1 meter. The South African giant specimen (Microchaetus rappi), about 7 meters in length, was recorded to be the longest of all.
A lesser known fact about earthworms is that they are the recycling machines of nature. They work as hard as a farmer, and without any summer or winter break.