With the expanding of economy, the environment protection has become more and more critical especially in developing countries. China is the 2^nd economic entity in the world and faces even more challenge. Heavy metals are naturally found in soils and rock formations but may also occur in fertilizers and pesticides, as a result of which may cause heavy-metal contamination. The global rate of heavy metal pollution is rapidly increasing in various habitats, heavy metals such as Cadmium (Cd) are one of the most fundamental causes of soil and water pollution in industrialized and developing countries. Metal pollution is a serious environmental problem worldwide, and severely threatens biological diversity and human health. Cadmium (Cd) is a heavy metal that accumulates in the environment and causes pollution as well as intoxication of both vertebrates and invertebrates. Cd biomagnification in the terrestrial food chain appears to be dependent on the physiological properties of the organisms rather than on their trophic level. Although high Cd body burdens in spiders from the field have been reported many times, experimental verification of the key factors that determine the rate of cadmium accumulation is lacking. Metals can accumulate in plants, and via food webs can cause harmful effects to herbivorous and pollinating insects and their predators, among other members of the biota. Biological indicator species are species that can be measured as surrogates for environmental health and levels of pollution before adverse environmental impacts become obvious.
spiders are exposed to environmental pollutants, growth and reproduction can be sharply reduced due to an increased detoxification effort. Spiders, at the individual level, have great potential as biological indicators of metal contamination in soil, because of their position in the food web and consequent biological magnification. Spiders occupy an important part of the predatory arthropod fauna in terrestrial ecosystems. They also play a large role in the regulation of pest species in agriculture. Wolf spiders are generalist predators of other terrestrial invertebrates. The wolf spider Pirata subpiraticus (Araneae,Lycosidae) is a common, surface-active wolf spider that inhabits very wet places and can be used as a very important bio-indicator for heavy metals pollution. Here, we investigated the cadmium assimilation rate in the common wolf spider Pirata subpiraticus for three generations fed by Drosophila melanogaster reared on artificial diets with 20 mg/kg. In addition, biological response traits of P. subpiraticus to adapt to heavy metal polluted diets was tested experimentally. It was demonstrated that a high cadmium assimilation (65.4%,68.5% and 69.1%) and an excretion rate approaching zero resulted in high Cd concentration factors in P. subpiraticus for three generations. Cd biomagnification fators were 1.71, 2.12 and 2.17, respectively. The results indicate the importance of spiders in cadmium biomagnification along critical pathways. Furthermore, Our results illustrate that P. subpiraticus responds behaviorally to the presence of high concentrations of heavy metals in food. The results also indicate the metal-selected P. subpiraticus have a significantly lower width of carapace, survival rate, cocoon weight and egg number. And P. subpiraticus also exhibit behaviors resulting in extended total duration, increased egg volume and decreased tolerance starvation life span. Our results suggest that although P. subpiraticus displays the potential to develop tolerance to heavy metals, particularly Cadmium, this may occur at a significant biological cost, which can adversely affect its ecological fitness. From these observations, we speculate that P. subpiraticus avoidance behavior towards high concentrations of heavy metals may have a positive effect on their survival and reproductive success in nature, particularly in the presence of metal-contaminated food sources. P. subpiraticus can be employed as a specific indicator for metal exposure, and also for the evaluation of chronic effects of metals in foodchains after long-term exposure. The results might provide more adequate theoretical basis insight into Cd along the soil-insects-predators transmission, biomagnification and physiological tolerance.