Cepaea hortensis is a widespread terrestrial pulmonate, contributing significantly to element fluxes in soil ecosystems. Due to its capacity of accumulating certain trace elements in its tissues, Cepaea hortensis can serve as a biological indicator of metal accumulation in contaminated areas. In response to Cd exposure this species and related helicid pulmonates are also able to synthesize an inducible, Cd-binding metallothionein (MT) isoform specifically serving in binding and detoxification of this metal. As shown by field-collected garden-snails from a metal-contaminated site near a zinc smelting works in Avonmouth (UK) and an unpolluted reference site in Reutte (Tyrol, Austria), Cd and Cd MT concentrations in midgut gland of C. hortensis from these sites increased with rising Cd concentrations in the soil substrate from the same contaminated sites. By combining the results of these field data with laboratory experiments it appears that midgut gland Cd-MT of Cepaea hortensis seems to fulfil the criteria of a successful biomarker in many respects. First, the synthesis of the protein can rapidly be induced by Cd exposure. Second, the level of Cd MT induction in C. hortensis directly reflects the intensity of metal exposure. Third, the induced signal of increased Cd-MT concentration in C. hortensis is persistent over extended periods of time. Fourth, the Cd-MT signal in C. hortensis seems to be very specific for Cd exposure. Regression analyses demonstrate that tissue levels of Cd and Cd MT in C. hortensis depend on Cd concentrations in the substrate which is represented by either soil or plant material on which snails normally feed. In both cases the best fit for this dependence is exhibited by a semi-logarithmic relationship, with substrate (soil or plant feed) concentrations expressed on a logarithmic scale. It is concluded that C. hortensis and other related pulmonates can successfully be used either as biological indicators of Cd accumulation, or as key species in biomonitoring studies focusing on Cd-MT induction as a biomarker for Cd exposure.
The two function-specific metallothionein (MT) isoforms characterized from the midgut gland and mantle tissue of Helix pomatia differ substantially in their metal-binding preferences, as well as molecular and biochemical features. These differences make them potential candidates for biomarker studies based on a differential, isoform-specific approach. To prove this hypothesis, induction experiments with two metals (Cd and Cu) that are normally bound by the two isoforms were compared with a range of organic chemicals and physical stressors under laboratory conditions to test the responsiveness of the two isoforms to the stressors applied. In addition, field studies were conducted with Roman snails and substrate samples collected from different metal-contaminated sites in Austria to test the suitability of the two isoforms as biomarkers under field conditions. The results of these combined laboratory and field studies confirmed the validity of the biomarker approach with the two metal- and tissue-specific isoforms. It is demonstrated that the Cd-binding MT specifically and exclusively responds to Cd exposure by increasing concentrations, whereas the Cu-binding MT isoform decreases in its concentration upon exposure to physical stress (X-ray irradiation and cold). This suggests researchers should adopt, under certain preconditions, a dual biomarker approach by combining the simultaneous quantification of Cd-MT concentrations in the midgut gland as a biomarker for Cd pollution and of Cu-MT concentration in the mantle as a biomarker for the impairment of snails by additional physical stressors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.