Effects of cadmium, mercury and lead on the survival and instantaneous rate of increase of Paronychiurus kimi (Lee) (Collembola)

The invertebrate springtail species Paronychiurus kimi (Lee) was selected for use in toxicity testing because it is more ecologically relevant to Korean soils than Folsomia candida Willem, which is the standard animal for toxicity tests. Responses of P. kimi to cadmium, mercury and lead were evaluated in artificial soils following the standardized ISO protocol. Although, reproduction of P. kimi was not as high as that of F. candida, 30 adults produced at least 200 juveniles over 28 days. For each of the three heavy metals, LC50 and EC50 for reproduction and NOEC and LOEC for the effect on reproduction and instantaneous rate of population increase (ri) were also estimated. The 7 days LC50 was 532, 3.9 and 1322 mg/kg dry soil for cadmium, mercury and lead, respectively. As exposure time increased from 7 to 28 days, the LC50 values decreased for cadmium but not or only slightly for mercury and lead. The 28 days EC50 was 60.0 for cadmium, 0.23 for mercury and 428 mg/kg for lead. Significant changes in ri of P. kimi were closely followed by the changes in the sublethal endpoint measured (reproduction) and populations were heading toward extinction (ri = 0) at concentration of 129, 2.0 and 1312 mg/kg dry soil for cadmium, mercury and lead, respectively. P. kimi was found to be more sensitive to all heavy metals tested than F. candida, confirming its suitability as a bioindicator species for soil toxicological testing in Korea.