This work illustrates the toxicological impact
of pesticide methyl parathion (MP) (dust—2 % active
ingredient, a.i.) on growth and reproduction performance in
tropical earthworms:
Metaphire posthuma
(endogeic),
Lampito mauritii
(anecic) and
Allolobophora parva
(epigeic).
A total of three concentrations (a.i. g kg
-1 dry test
soil), 1.00 (
T1), 1.125 (
T2) and 2.25 (
T3) of MP, were
applied in test substrate to examine the impact on mortality,
individual live weight changes and reproduction patterns
in test species over 60 days under laboratory
conditions. MP caused significant mortality in all tested
species, and median lethal dose (LD
50) for
L. mauritii,
M.
posthuma and
A. parva was 24.85, 23.64 and 22.67 mg a.i.,
respectively. The individual live weight loss was
27.0–37.0 % in
L. mauritii, 36.0–57.1 % in
M. posthuma
and 1.2–11.0 % in
A. parva in different test concentrations.
The pesticide-exposed worms produced less cocoons than
control, but in
L. mauritii, an unusual reproduction (hormesis)
was recorded. Results suggested the species-specific
toxicity of MP against tropical earthworms.
