The Effect of Metals on the Mortality of Parnassius Apollo Larvae (Lepidoptera: Papilionidae)

Abstract

The population sizes and range of Parnassius apollo started to decline in Finland in the 1930s and resulted in complete extinction in many parts of its former range 30 years later. It has been suggested that metal pollution is one potentially very important reason for the decline. Recently, a recovery of P. apollo and widening of its range has started in the southwestern Finland, simultaneously with a decline in metal fallout from air. Metal analyses were performed with larval and host plant samples collected from an area where P. apollo is recolonising its former range (the archipelago between the island of Kemio and the Hankoniemi peninsula). In the host plants (Sedum telephium), the level of Fe was significantly lower and the levels of Cd and Zn suggestively lower in the current range (nD 35) of P. apollo than in the former range (nD 12). Analyses on larvae of P. apollo (nD 29) showed lower levels of Cd, Fe and Mn than in the host plant leaves. The excretion of these metals, as well as Zn, via the faeces was effective. The level of the Cd-antagonist Cu was considerably higher in caterpillars than in the food. When caterpillars were fed with metal-polluted food from Helsinki city (4.35 ppm Cd/dwt;nD 5) they died, whereas control individuals fed with food from the archipelago (2.49 ppm Cd/dwt;nD 5) survived. These results indicate that metals may play an important role in the large-scale decline and partial recovery of P. apollo in the western Europe.