International audience | Community structure and microcystin accumulation of freshwater molluscs were studied before and after cyanobacterial proliferations, in order to assess the impact of toxic blooms on molluscs and the risk of microcystin transfer in food web. Observed decrease in mollusc abundance and changes in species richness in highly contaminated waters were not significant; however, relative abundances of taxa (prosobranchs, pulmonates, bivalves) were significantly different before and after cyanobacterial bloom. Pulmonates constituted the dominant taxon, and bivalves never occurred after bloom. Microcystin accumulation was significantly higher in molluscs from highly (versus lowly) contaminated waters, in adults (versus juveniles) and in pulmonates (versus prosobranchs and bivalves). Results are discussed according to the ecology of molluscs, their sensitivity and their ability to detoxify.

Community structure and microcystin accumulation of freshwater molluscs were studied before and after cyanobacterial proliferations, in order to assess the impact of toxic blooms on molluscs and the risk of microcystin transfer in food web. Observed decrease in mollusc abundance and changes in species richness in highly contaminated waters were not significant; however, relative abundances of taxa (prosobranchs, pulmonates, bivalves) were significantly different before and after cyanobacterial bloom. Pulmonates constituted the dominant taxon, and bivalves never occurred after bloom. Microcystin accumulation was significantly higher in molluscs from highly (versus lowly) contaminated waters, in adults (versus juveniles) and in pulmonates (versus prosobranchs and bivalves). Results are discussed according to the ecology of molluscs, their sensitivity and their ability to detoxify.

Effects of contamination on aquatic organisms have been investigated and employed as biomarkers in environmental quality assessment for years. A commonly referenced aquatic organism, mollusks represent a group of major interest in toxicological studies. Both gastropods and bivalves have external mineral shells that protects their soft tissue from predation and desiccation. These structures are composed of an organic matrix and an inorganic matrix, both of which are affected by environmental changes, including exposure to hazardous chemicals. This literature review evaluates studies that propose mollusk shell alterations as biomarkers of aquatic system quality. The studies included herein show that changes to natural variables such as salinity, temperature, food availability, hydrodynamics, desiccation, predatory pressure, and substrate type may influence the form, structure, and composition of mollusk shells. However, in the spatial and temporal studies performed in coastal waters around the world, shells of organisms sampled from multi-impacted areas were found to differ in the form and composition of both organic and inorganic matrices relative to shells from less contaminated areas. Though these findings are useful, the toxicological studies were often performed in the field and were not able to attribute shell alterations to a specific molecule. It is known that the organic matrix of shells regulates the biomineralization process; proteomic analyses of shells may therefore elucidate how different contaminants affect shell biomineralization. Further research using approaches that allow a clearer distinction between shell alterations caused by natural variations and those caused by anthropogenic influence, as well as studies to identify which molecule is responsible for such alterations or to determine the ecological implications of shell alterations, are needed before any responses can be applied universally.

Effects of contamination on aquatic organisms have been investigated and employed as biomarkers in environmental quality assessment for years. A commonly referenced aquatic organism, mollusks represent a group of major interest in toxicological studies. Both gastropods and bivalves have external mineral shells that protects their soft tissue from predation and desiccation. These structures are composed of an organic matrix and an inorganic matrix, both of which are affected by environmental changes, including exposure to hazardous chemicals. This literature review evaluates studies that propose mollusk shell alterations as biomarkers of aquatic system quality. The studies included herein show that changes to natural variables such as salinity, temperature, food availability, hydrodynamics, desiccation, predatory pressure, and substrate type may influence the form, structure, and composition of mollusk shells. However, in the spatial and temporal studies performed in coastal waters around the world, shells of organisms sampled from multi-impacted areas were found to differ in the form and composition of both organic and inorganic matrices relative to shells from less contaminated areas. Though these findings are useful, the toxicological studies were often performed in the field and were not able to attribute shell alterations to a specific molecule. It is known that the organic matrix of shells regulates the biomineralization process; proteomic analyses of shells may therefore elucidate how different contaminants affect shell biomineralization. Further research using approaches that allow a clearer distinction between shell alterations caused by natural variations and those caused by anthropogenic influence, as well as studies to identify which molecule is responsible for such alterations or to determine the ecological implications of shell alterations, are needed before any responses can be applied universally. | Fil: Yokota Harayashiki, Cyntia Ayumi. Universidade Federal de Sao Paulo.; Brasil | Fil: Marquez, Federico. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina | Fil: Cariou, Elsa. Universite de Nantes; Francia | Fil: Castro, Ítalo Braga. Universidade Federal de Sao Paulo.; Brasil

Imposex is a disorder caused by organotins, mainly tributyltin, which results in the appearance of male sexual characteristics in females of gastropod mollusks. The main objective of this work was to make a critical analysis of the relationship between imposex and butyltin body burdens in Nucella lapillus and Nassarius reticulatus. Specifically, this study evaluates possible additive effects among butyltins, proposes scales of effects based on robust statistical criteria as alternatives to existing ones and defines the body burdens of TBT in N. lapillus and N. reticulatus corresponding to the assessment classes (ACs) of the Vas Deferens Sequence Index (VDSI) established by OSPAR. Data of organotin body burdens and biological effects was retrieved from the ICES Dataset and from scientific literature. All responses, except the percentage of females displaying Imposex (IMPF) in Nucella lapillus, showed a sigmoidal profile regarding to the body burden of mono- (MBT), di- (DBT) and tributyltin and sum of butyltins (SumBTs). TBT and the SumBTs were better indicators of the VDSI or Relative Penis Size Index/Relative Penis Length Index (RPSI/RPLI) responses than MBT or DBT in most cases. From a statistical point of view, RPSI/RPLI and VDSI were better indicators of contamination by TBT than IMPF, although both RPSI and RPLI showed lower sensitivity than VDSI. The model used for describing the joint effect of butyltins provided a statistically significant fitting to the data assuming a null effect for both MBT and DBT for N. lapillus, and a lower toxic contribution of MBT and DBT with respect to TBT for N. reticulatus. RPSI or RPLI values, equivalent to the ACs for VDSI, were proposed as alternative criteria when measuring moderate to high levels of imposex. TBT concentrations in N. reticulatus and N. lapillus tissues, corresponding to the ACs were calculated and provided valuable information for cross-species comparisons.

Imposex is a disorder caused by organotins, mainly tributyltin, which results in the appearance of male sexual characteristics in females of gastropod mollusks. The main objective of this work was to make a critical analysis of the relationship between imposex and butyltin body burdens in Nucella lapillus and Nassarius reticulatus. Specifically, this study evaluates possible additive effects among butyltins, proposes scales of effects based on robust statistical criteria as alternatives to existing ones and defines the body burdens of TBT in N. lapillus and N. reticulatus corresponding to the assessment classes (ACs) of the Vas Deferens Sequence Index (VDSI) established by OSPAR. Data of organotin body burdens and biological effects was retrieved from the ICES Dataset and from scientific literature. All responses, except the percentage of females displaying Imposex (IMPF) in Nucella lapillus, showed a sigmoidal profile regarding to the body burden of mono- (MBT), di- (DBT) and tributyltin and sum of butyltins (SumBTs). TBT and the SumBTs were better indicators of the VDSI or Relative Penis Size Index/Relative Penis Length Index (RPSI/ RPLI) responses than MBT or DBT in most cases. From a statistical point of view, RPSI/RPLI and VDSI were better indicators of contamination by TBT than IMPF, although both RPSI and RPLI showed lower sensitivity than VDSI. The model used for describing the joint effect of butyltins provided a statistically significant fitting to the data assuming a null effect for both MBT and DBT for N. lapillus, and a lower toxic contribution of MBT and DBT with respect to TBT for N. reticulatus. RPSI or RPLI values, equivalent to the ACs for VDSI, were proposed as alternative criteria when measuring moderate to high levels of imposex. TBT concentrations in N. reticulatus and N. lapillus tissues, corresponding to the ACs were calculated and provided valuable information for cross-species comparisons. | Sí