Validation ofhsp70stress gene expression as a marker of metal effects inDeroceras reticulatum(pulmonata): Correlation with demographic parameters

Abstract

The presence of a stress gene comprising a motif homologous to the hsp70 consensus sequence was proven for the grey garden slug, Deroceras reticulatum (Müller). The induction of stress gene transcription (including mRNA stability) and the accumulation of the corresponding stress protein, Hsp70, was quantified in slugs exposed to cadmium‐ or zinc‐enriched food for 2 to 3 weeks. To validate the suitability of these two aspects of the cellular stress reponse to act as early‐warning markers for metal effects on life‐history parameters, fecundity, offspring number, longevity, and mortality of slugs were recorded in life‐cycle experiments. Quantitative reverse transcription‐polymerase chain reaction and a standardized immunoblotting technique revealed higher sensitivity of changes in hsp70 transcription than stress protein accumulation in response to both metals. The elevation of the hsp70‐mRNA level caused by short‐term (14 d) metal exposure coincided with both diminished fecundity and reduced offspring production due to chronic metal exposure in terms of threshold concentrations for cadmium (˜0.2 mg/kg) and zinc (˜200 mg/kg) effects. As well, accumulation of Hsp70 after 3 weeks of exposure can be considered an early‐warning signal for increased mortality when cadmium (threshold concentration ˜0.3‐2 mg/kg) or zinc exposure (threshold concentration ˜0.4‐2 g/kg) is throughout the entire lifetime of the slugs.