Organotin compounds are an useful class of tin chemicals, a number of which have found commercial applications and are industrially synthesized in large amounts. Their uncontrolled use may cause profound effects on the fate and long-term environmental impact in natural aquatic environments. Butyltin compounds (TBT and its degradation products, i.e. DBT and MBT) are leached out from antifouling paints; triphenyltin (TPT) and tricyclohexyltin (TCHT) compounds have source in the run off waters of treated plants on which they are use as pesticides. There is much concern about their hurtful effects on marine life, especially fish and molluscs. The lagoon of Venice is a particular coastal area with shallow and incompletely turnovering waters, in which the resident benthonic population suffers the negative impact of organotins for bioaccumulation. In order to clarify the interaction mechanism, we studied the toxic effects of organotins on a benthonic filter-feeding ascidian. We followed the embryonic development of the ascidian Styela plicata with two different approaches: i) in vivo observations on different stages of ascidian development from fertilized egg to larval stages by incubation with 0.1, 1, 10 µM organotins for various exposure times; ii) ultrastructural observations on the early embryonic stages (2-4 cells, morula, gastrula) incubated with 10 µM TBT or TPT for 1 hour. Our results show that organotins significantly affect all stages of ascidian development in a dose- and time-dependent manner and the most sensitive stages are gastrula and neurula. These compounds are able to block the development giving rise to anomalous embryos with irreversible effects. The order of inhibition appears strongly dependent on the organotin liposolubility: TBT>DBT>MBT and TPT>TCHT. The mitosis block of blastomers in the early stages may be related to an inhibition of the microtubule polymerization. Observations with light and electron microscopes reveal globe-shaped blastomers with large intercellular spaces in morula and gastrula stages, suggesting a toxic damage on aggregation of microfilaments. Moreover the occurrence of electron-dense precipitates of organotins in the inner membrane of mitochondria and morphological changes of their cristae suggests an inhibition of mitochondrial oxidative phosphorylation which is important in the gastrula stage. In this stage, these electron-dense aggregates grow from 50-70 nm to 110-170 nm and the alteration of the cristae increases.

Toxicity of organotin compounds on embryos of a marine invertebrate (Styela plicata; Tunicata)

CIMA, FRANCESCA;BALLARIN, LORIANO;
1995

Abstract

Organotin compounds are an useful class of tin chemicals, a number of which have found commercial applications and are industrially synthesized in large amounts. Their uncontrolled use may cause profound effects on the fate and long-term environmental impact in natural aquatic environments. Butyltin compounds (TBT and its degradation products, i.e. DBT and MBT) are leached out from antifouling paints; triphenyltin (TPT) and tricyclohexyltin (TCHT) compounds have source in the run off waters of treated plants on which they are use as pesticides. There is much concern about their hurtful effects on marine life, especially fish and molluscs. The lagoon of Venice is a particular coastal area with shallow and incompletely turnovering waters, in which the resident benthonic population suffers the negative impact of organotins for bioaccumulation. In order to clarify the interaction mechanism, we studied the toxic effects of organotins on a benthonic filter-feeding ascidian. We followed the embryonic development of the ascidian Styela plicata with two different approaches: i) in vivo observations on different stages of ascidian development from fertilized egg to larval stages by incubation with 0.1, 1, 10 µM organotins for various exposure times; ii) ultrastructural observations on the early embryonic stages (2-4 cells, morula, gastrula) incubated with 10 µM TBT or TPT for 1 hour. Our results show that organotins significantly affect all stages of ascidian development in a dose- and time-dependent manner and the most sensitive stages are gastrula and neurula. These compounds are able to block the development giving rise to anomalous embryos with irreversible effects. The order of inhibition appears strongly dependent on the organotin liposolubility: TBT>DBT>MBT and TPT>TCHT. The mitosis block of blastomers in the early stages may be related to an inhibition of the microtubule polymerization. Observations with light and electron microscopes reveal globe-shaped blastomers with large intercellular spaces in morula and gastrula stages, suggesting a toxic damage on aggregation of microfilaments. Moreover the occurrence of electron-dense precipitates of organotins in the inner membrane of mitochondria and morphological changes of their cristae suggests an inhibition of mitochondrial oxidative phosphorylation which is important in the gastrula stage. In this stage, these electron-dense aggregates grow from 50-70 nm to 110-170 nm and the alteration of the cristae increases.
1995
Abstract book of the 8th International Symposium on Environmental Pollution and its Impact on Life in the Mediterranean Region
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2462367
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