Earthworm

Earthworm are typical annelids, ie, true segmented coelomate invertebrate worms that live in moist soil environments under three broad habitats, epigeic (litter dwelling), endogeic (soil-dwelling), and anecic (deep burrowing). They are nocturnal, and thus people cannot see them during day time. The naming of earthworms is due to their common occurrences in unpolluted cultivated lands where piles of fecal casting can be seen at the mouth of a tunnel they live in. This nature of tunnel-digging is related to their feeding habits. They feed on organic matters, dead animals, eggs, etc, by ingesting soil and releasing paste-like fecal materials called ‘casting’ at the tunnel top. The tunnel could be a few centimeters from the soil surface to even three meters below. They are also called 'natural-plow' as they act as a ‘soil-conditioner’ by mixing the topsoil with the bottom soil due to the activities. More than 7000 species of earthworm are distributed in most temperate to tropical soils of the world. However, in Bangladesh, this is the least studied group. So far, 42 species have been identified under 3 families. They are hermaphrodites, ie, each animal bears both male and female reproductive organs. After mating, eggs are released in a cocoon. A juvenile comes out of the cascades. They are seldomly used as lab animals in biology and zoology lab classes in Bangladesh. Live or minced earthworm sometime be used for traditional fish baits and animal feed as protein sources. A few species are being used for producing quality vermicompost in Bangladesh. [Md. Niamul Naser]