HSP70 expression in Biomphalaria glabrata snails exposed to cadmium.

In this study, the effects of the heavy metal cadmium on the stress protein HSP70 are investigated in freshwater mollusks Biomphalaria glabrata. Adult snails were exposed for 96h to CdCl2 at concentrations ranging from 0.09 to 0.7mgL-1 (LC50/96h=0.34 (0.30-0.37). Time and concentration-dependent increases in the expression of HSP70 were observed at sub-lethal levels in the immunoblotting assay. Further, an increased survival to a lethal heat shock was observed in animals pre-exposed to a nonlethal concentration of cadmium, evidencing the induction of acquired tolerance. The present study demonstrated the inducibility of B. glabrata HSP70 by cadmium, a relevant environmental contaminant, at non-lethal levels, providing evidences that the assessment of HSP70 in B. glabrata can be regarded as a suitable biomarker for ecotoxicological studies.

da Silva Cantinha R ，Borrely SI ，Oguiura N ，de Bragança Pereira CA ，Rigolon MM ，Nakano E ... -  《-》

Biomphalaria alexandrina as a bioindicator of metal toxicity.

Heavy metals are common environmental pollutants to the aquatic ecosystems. Several aquatic species have been used as bioindicators and biomonitoring subjects for heavy metals pollution. In the present study, the effects of cadmium (Cd) and manganese (Mn) on the survival, attachment, locomotion, and feeding behaviours of the gastropod snail Biomphalaria alexandrina were determined. The short-term (96 h) LC50 for Cd and Mn were found to be 0.219 and 154.2 mg/l, respectively. Long-term exposures (16-20 days) to ascending concentrations of Cd (0.01-1 mg/l) and Mn (50-500 mg/l) also caused gradual decreases in the survival rate of B. alexandrina in a dose-dependent manner. Attachment, locomotion and feeding behaviours of snails exposed to lethal and sublethal concentrations of Cd and Mn at acute (96 h) and chronic exposure (24 days) intervals, respectively, were also recorded. Compared to controls, a significant decrease (p ≤ 0.05) was recorded in the different behaviours of exposed snails. These changes in behaviour would potentially impact the snail's ability to survive in the wild. Although Cd caused a more severe decline in snail survivorship than Mn, the behavioural effects of Mn were much more severe than Cd when the metals were roughly matched for lethality. In sum, the present study demonstrates B. alexandrina to be a sensitive bioindicator and model organism to assess heavy metals risk factors for severe toxicity in freshwater ecosystems.

Habib MR ，Mohamed AH ，Osman GY ，Mossalem HS ，Sharaf El-Din AT ，Croll RP ... -  《-》

Effect of cadmium, lead and arsenic on the oviposition, hatching and embryonic survival of Biomphalaria glabrata.

Ansaldo M ，Nahabedian DE ，Di Fonzo C ，Wider EA ... -  《SCIENCE OF THE TOTAL ENVIRONMENT》

Metallothionein and Hsp70 trade-off against one another in Daphnia magna cross-tolerance to cadmium and heat stress.

The association between the insensitivity of adapted ecotypes of invertebrates to environmental stress, such as heavy metal pollution, and overall low Hsp levels characterizing these organisms has been attracting attention in various studies. The present study seeks to induce and examine this phenomenon in Daphnia magna by multigenerational acclimation to cadmium in a controlled laboratory setting. In this experiment, interclonal variation was examined: two clones of D. magna that have previously been characterized to diverge regarding their cadmium resistance and levels of the stress protein Hsp70, were continuously exposed to a sublethal concentration of Cd over four generations to study the effects of acclimation on Hsp70, metallothionein (MT), reproduction and cross-tolerance to heat stress. The two clones differed in all the measured parameters in a characteristic way, clone T displaying Cd and heat resistance, lower Hsp70 levels and offspring numbers on the one hand and higher MT expression on the other hand, clone S the opposite for all these parameters. We observed only slight acclimation-induced changes in constitutive Hsp70 levels and reproductive output. The differences in MT expression between clones as well as between acclimated organisms and controls give evidence for MT accounting for the higher Cd tolerance of clone T. Overall high Hsp70 levels of clone S did not confer cross tolerance to heat stress, contrary to common expectations. Our results suggest a trade-off between the efforts to limit the proteotoxic symptoms of Cd toxicity by Hsp70 induction and those to sequester and detoxify Cd by means of MT.

Haap T ，Schwarz S ，Köhler HR 《-》

Cadmium in vivo exposure alters stress response and endocrine-related genes in the freshwater snail Physa acuta. New biomarker genes in a new model organism.

The freshwater snail Physa acuta is a sensitive organism to xenobiotics that is appropriate for toxicity testing. Cadmium (Cd) is a heavy metal with known toxic effects on several organisms, which include endocrine disruption and activation of the cellular stress responses. There is scarce genomic information on P. acuta; hence, in this work, we identify several genes related to the hormonal system, the stress response and the detoxification system to evaluate the effects of Cd. The transcriptional activity of the endocrine-related genes oestrogen receptor (ER), oestrogen-related receptor (ERR), and retinoid X receptor (RXR), the heat shock proteins genes hsp70 and hsp90 and a metallothionein (MT) gene was analysed in P. acuta exposed to Cd. In addition, the hsp70 and hsp90 genes were also evaluated after heat shock treatment. Real-time reverse transcriptase-polymerase chain reaction (qRT-PCR) analysis showed that Cd presence induced a significant increase in the mRNA levels of ER, ERR and RXR, suggesting a putative mode of action that could explain the endocrine disruptor activity of this heavy metal at the molecular level on Gastropoda. Moreover, the hsp70 gene was upregulated after 24-h Cd treatment, but the hsp90 gene expression was not affected. In contrast, the hsp70 and hsp90 genes were strongly upregulated during heat shock response. Finally, the MT gene expression showed a non-significant variability after Cd exposure. In conclusion, this study provides, for the first time, information about the effects of Cd on the endocrine system of Gastropoda at the molecular level and offers new putative biomarker genes that could be useful in ecotoxicological studies, risk assessment and bioremediation.

Martínez-Paz P ，Morales M ，Sánchez-Argüello P ，Morcillo G ，Martínez-Guitarte JL ... -  《-》