General Introduction to Earthworms, Their Classifications, and Biology

Abstract

Charles Darwin described earthworms as the ‘unheralded soldiers of mankind’, and Aristotle called them as the ‘intestine of earth’, as they could digest a wide variety of organic materials (Darwin (1881) The formation of vegetable mould through the action of worms, with observations on their habitats. Murray, London, p 326). Before Darwin’s book was published, earthworms were commonly considered soil-inhabiting crop pests. His views on the beneficial aspects of earthworms were supported and expanded subsequently by other contemporary scientists such as (Muller (1878) Tidsskrift Skogbruk 3:124; Urquhart (1887) Trans NZ Inst 19:119–123), and many others. Earthworms are an important link in the food chain of many invertebrate and vertebrate animals (Macdonald (1983) Predation on earthworms by terrestrial vertebrates. In: Satchell JE (ed) Earthworm ecology from Darwin to vermiculture. Chapman & Hall, London, pp 393–414). Early humans used earthworms both as food and as baits in hunting and fishing. Research on potential of earthworms in processing organic wastes began in Germany (Graff and Makeshin (1980) Crop yield of ryegrass influenced by the excretions of three earthworm species. Pedobiologia 20:176–180) and continued in United States. Appelhof (Appelhof (1982) Worms eat my garbage. Flower Press, Kalamazoo) summarized the extensive research into the breakdown of sewage bio-solids by earthworms and the overall commercial potential of vermiculture up to that date. Research on using earthworms to break down animal and vegetable wastes and also to produce earthworm protein that could be used in fish farming for animal feeds began in 1980s (Edwards et al. (1985) The use of earthworms for composting farm wastes. In: Gasser JKR (ed) Composting of agricultural and other wastes. Elsevier, Amsterdam, pp 229–242; Edwards (1998) The use of earthworms in the breakdown and management of organic wastes. In: Edwards CA (ed) Earthworm ecology. CRC Press, Boca Raton, pp 327–354). Various researchers have examined the potential utilization of earthworm-processed wastes, commonly referred to as vermicomposts, in the horticultural and agricultural industries. Whether used as soil additives or as components of horticultural media, vermicomposts usually enhanced seedling growth and development, and increased productivity of a wide variety of crops. Enhancement in plant growth and productivity has been attributed to the physical and chemical characteristics of the processed materials. Several epigeic earthworms, e.g., Eisenia fetida (Savigny), Perionyx excavatus (Perrier), Perionyx sansibaricus (Perrier), and Eudrilus eugeniae Kinberg have been identified as detritus feeders and can be used potentially to minimize the anthropogenic wastes from different sources. The potential of composting earthworms, i.e., Eisenia fetida (Savigny), to manage organic waste resources is well established. It is considered as a key organism of vermicomposting industries in many parts of the world. Several workers had reported the vermicomposting potential of E. fetida by using a variety of waste materials such as cattle dung (Kale. Earthworms: nature’s gift for utilization of organic wastes. In: Edwards CA (ed) Earthworm ecology. Soil and Water Conservation Society/St. Lucie Press, Ankeny/New York, pp 355–373, 1998; Garg et al. Biores Technol 97:391–395, 2006; Reinecke et al. Soil Biol Biochem 24:1295–1307, 1992), household waste (Kale. Earthworms: nature’s gift for utilization of organic wastes. In: Edwards CA (ed) Earthworm ecology. Soil and Water Conservation Society/St. Lucie Press, Ankeny/New York, pp 355–373, 1998), sewage sludge (Gupta and Garg. J Hazard Mater 153:1023–1030, 2008; Suthar. Int J Environ Waste Manage 2:84–101, 2008), industrial waste (Suthar. Environmentalist 27:329–335, 2007; Garg and Kaushik. Biores Technol 96:1063–1071, 2005), etc. (Suthar. Environmentalist 27:329–335, 2007) worked on the influence of different food sources on growth and reproduction performance of composting epigeic: Eudrilus eugeniae, P. excavatus and P. sansbaricus.