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<p>Direct uptake of an element from water by an aquatic organism and its retention, leading to a higher concentration than in its surrounding water, is an environmental concern known as bioconcentration. It occurs when an organism absorbs a substance faster than it is eliminated by various metabolic processes, such as catabolism and excretion. A bioassay experiment was performed to determine the 96-hour LC<sub>50</sub> of cadmium chloride (CdCl<sub>2</sub>), a heavy-metal salt. For experimentation, pre-acclimated <i>Limnodrilus hoffmeisteri</i> worms were divided into eleven treatment groups (T<sub>1</sub> through T<sub>11</sub>) and a control group (C), each of 50 number of individuals and were exposed to 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0, 2.25, 2.5, 2.75 and 3.0&#xa0;mg/L cadmium concentrations respectively for 96&#xa0;h under semi-static condition in a closed-circuit flow-through system with complete renewal of water with the respective relevant cadmium concentration after 48&#xa0;h. Post-exposure cadmium content per unit amount of tissue samples and of residual water samples was measured with atomic absorption spectrophotometry (AAS). Probit analysis revealed the 96-hour LC<sub>50</sub> value of cadmium against <i>L. hoffmeisteri</i> as 1.002&#xa0;mg/L. The outcome of this study established a low BCF for the experimental species for cadmium, indicating a positive correlation between BCF and exposure concentration and demonstrating the inherent bioconcentration nature of cadmium in <i>L. hoffmeisteri</i>. A gradual declining trend in cadmium content of the whole body was observed at exposure to a cadmium concentration higher than 2.0&#xa0;mg/L. Concurrent autotomy of the caudal part of the organism has also been observed at this exposure level. Cadmium content of the autotomized tail has been estimated significantly (<i>P</i> &lt; 0.05) higher. It is concluded that autotomization is a defensive mechanism evolved by <i>L. hoffmeisteri</i> to reduce the body’s heavy metal load and, hence, toxicity, thereby serving as an indicator species.</p>

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Cadmium bioconcentration in an aquatic oligochaete Limnodrilus hoffmeisteri: a semistatic bioassay evaluation

  • 期刊论文

  • 发表日期：

    2026年7月3日

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  • Pritam Paul,
  • Samar Kumar Saha

摘要

Direct uptake of an element from water by an aquatic organism and its retention, leading to a higher concentration than in its surrounding water, is an environmental concern known as bioconcentration. It occurs when an organism absorbs a substance faster than it is eliminated by various metabolic processes, such as catabolism and excretion. A bioassay experiment was performed to determine the 96-hour LC50 of cadmium chloride (CdCl2), a heavy-metal salt. For experimentation, pre-acclimated Limnodrilus hoffmeisteri worms were divided into eleven treatment groups (T1 through T11) and a control group (C), each of 50 number of individuals and were exposed to 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0, 2.25, 2.5, 2.75 and 3.0 mg/L cadmium concentrations respectively for 96 h under semi-static condition in a closed-circuit flow-through system with complete renewal of water with the respective relevant cadmium concentration after 48 h. Post-exposure cadmium content per unit amount of tissue samples and of residual water samples was measured with atomic absorption spectrophotometry (AAS). Probit analysis revealed the 96-hour LC50 value of cadmium against L. hoffmeisteri as 1.002 mg/L. The outcome of this study established a low BCF for the experimental species for cadmium, indicating a positive correlation between BCF and exposure concentration and demonstrating the inherent bioconcentration nature of cadmium in L. hoffmeisteri. A gradual declining trend in cadmium content of the whole body was observed at exposure to a cadmium concentration higher than 2.0 mg/L. Concurrent autotomy of the caudal part of the organism has also been observed at this exposure level. Cadmium content of the autotomized tail has been estimated significantly (P < 0.05) higher. It is concluded that autotomization is a defensive mechanism evolved by L. hoffmeisteri to reduce the body’s heavy metal load and, hence, toxicity, thereby serving as an indicator species.