Transfer of cadmium from ants to ant-lions

摘要

Ants have been found to bear exceptionally high loads of Cd and other metals, but are in general quite resistant to the toxic effects of Cd. Possible harmful effects caused to their predators by high Cd content have not been studied. Detection of a sparse population of ant-lions on a beach at Padva in Bromarv, offered the possibility to make some preliminary observations of such harmfull effects. AAS-analyses showed that free-living ant-lion larvae bear a Cd load of 4.5 ppm/dwt in young larvae, 8.5 ppm in old ones. This corresponded approximately to the level occurring in their most important food items in Padva (4.5 ppm mean for workers of Formica rufibarbis Fabricius and 6.1 ppm for foragers of F. fusca Linnaeus). The level of Cd in the single ant-lion imago caught (0.5 ppm) was clearly lower than in larvae. Among the Cd-antagonistic metals, Cu showed levels in ant-lions two- or three-fold those found in ants, whereas no parallel difference existed for Zn levels. During larval development the level of the essential Cu diminished to half whereas the level of Zn increased two-fold. The fate of surplus cadmium in the food chain was followed experimentally by feeding a forest-living colony of Formica aquilonia Yarrow with 0.5 kg honey containing 600 mg CdCl_2. This elevated the Cd content of surface workers up to a level 10-fold that considered normal, 90-100 ppm (n = 4), and of the inside workers up to 5-fold, 36-61 ppm (n = 6). When surface workers were fed to ant-lion larvae ad libidum, larval Cd content rose in one week to the level of the food (87 ppm). When the feeding of ant-lion larvae was continued by feeding them inside workers for additional 4 weeks, these larvae showed a Cd level (49 ppm), similar to that of their food; then when the feeding had continued for 8 weeks, the level, however, rose to 120 ppm. All ant-lion larvae, including those with the highest Cd content, were fully active and showed no symptoms of disease. Artificial Cd-feeding had no clear effect on the Cu-levels in ants or ant-lions, but Zn responded by an increase from the natural level of 501-603 ppm to 560-1 200 ppm.