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Life Science Research and Sustainable Development ISBN: 978-98-84663-33-9

having significant risk factors for cancer when exposed to contaminated environment Shefali and
Yadav (2018). Earthworms are an essential part of the soil fauna in most global soils, represent a
significant proportion of the soil biomass and are regarded as a useful indicator of soil health and
quality. It is their important role in the decomposition of organic matter and subsequent cycling
of nutrients that has led to their use as an indicator organism for the biological impact of soil
pollutants and this in turn has lead to a large body of work on earthworm ecotoxicology.
Earthworms are also often the subject of inoculation programmes during the restoration of
degraded lands and inoculation of earthworms to metal-contaminated soils has been suggested
largely due to the role earthworms are known to play in soil formation at such sites Sizmur and
Hodson (2009). Heavy metals are present in soils as natural components or as a result of human
activities. Industrial, mining and agricultural activities have in some cases produced considerable
metal pollution of soils, which is increasingly becoming a serious environmental problem.
Previous studies have shown that the presence of excess heavy metals in the soil, is
leading to increased mortality of the worms Mostafaii et al., (2016). Mortality is a parameter used
to evaluate the LC50, i.e. the concentration which proves lethal for 50% of exposed individuals.
In the literature review, the median lethal concentration was assessed for various metals using
various earthworm species and substrates at different time periods from 24 h to 56 days
Sivakumar (2015). The effects of metals on the growth and reproduction of earthworms, as well
as their behavioural and morphological symptoms and their avoidance behaviour due to metal
exposure. Statistical analysis is an essential tool for the interpretation of ecotoxicity test results.
Estimations of the ecotoxicological impact of pollutants are usually expressed either as a
concentration causing 50 % mortality (lethal concentration, LC50) and effects on the growth and
reproduction of the tested organisms (effective concentration, EC50) or as the highest
concentration tested not showing any effects on growth and reproduction compared to controls
(no observed effective concentration, NOEC).
The earthworm Perionyx excavatus is an indigenous, epigeic earthworm widely recognized
as a model test organism for ecotoxicological risk assessment of polluted soil. The term epigeic in
Greek stands for "upon the earth." These compost worms don't create permanent burrows
underground and spend most of the time above at upper soil surface. They are phytophagous
worms and are efficient bio-degraders.
The LC50 test using the earthworm Perionyx excavatus has been important for risk
assessment and regulation of new and existing chemicals (Becker et a/., 1992). The end point of
the 'earthworm acute toxicity test' is mortality. However, mortality is unlikely to be either the
most sensitive or ecologically relevant parameter for predicting effects on field populations. The
standard earthworm acute toxicity test (OECD, 1984) has been used to determine the
concentrations of mercuric chloride, copper sulphate and zinc sulphate that cause specific lethal and
sub-lethal effects in the earthworm Perionyx excavatus.
Material and methods:
The megascolecid earthworm Perionyx excavatus having approximately equal size (10 cm
in length) and weight (3 g) were exposed for 5 days separately to lower and higher sublethal
concentrations of heavy metals. Soil was collected from an upland non-irrigated field, which had
no record of input of agrochemicals (fertilizers and pesticides). The soil had the following
characteristics: Laterite type, sandy loam texture, pH-6.8, organic matter 2.7 g%, nitrogen 0.22 g%
and a C/N ratio of 12.27. The soil was air dried and sieved before use. The earthworms were also
collected from the above characterized field. They were cultured in their habitat soil and
acclimated for one month with adequate provision of food (10% organic matter, cow dung+leaf

https://jesjalna.org/Zoology-Publications/index.html 124 Department of Zoology, J. E. S. College, Jalna