The effects of sediment-associated triorganotin compounds on the gills of the European flounder, Platichthys flesus (L.)

Effects of cumulative stress on fish health near freshwater outlet sluices into the sea: a case study (1988-2005) with evidence for a contributing role of chemical contaminants

Epizootic skin diseases in euryhaline flounder (Platichthys flesus) in the Dutch Wadden Sea were first reported in 1988. Particularly high prevalences of skin ulcers (up to one-third of individual fish being affected) were encountered in the vicinity of sluices draining freshwater from IJsselmeer Lake, in contrast with much lower levels in the freshwater bodies behind the sluices and open sea areas (<2%). It was proposed that salinity stress, high bacterial loads, nutritional deficiencies, and obstruction to fish migration by the sluices could all be involved in disease causation. Results of follow-up surveys at these outlet sluices from 1994 to 2005 further substantiate our preliminary findings. The follow-up data also show a general reduction in disease and improved condition factor during this period, which can be explained by improved habitat conditions for the flounder, partly due to effective sluice gate management. Furthermore, statistical correlations (p<0.05) were demonstrated between flounder ulcer occurrence and chemical contaminant concentrations in liver (Hg, Cd, Cu, Zn) and bile (the metabolite 1-OH pyrene as an indicator of chronic polycyclic aromatic hydrocarbon exposure), and histological liver lesions generally indicative of contaminant exposure (hydropic vacuolization of biliary duct epithelial cells). The findings suggest that a combination of osmotic and contaminant-induced stress also contributed to the observed disease patterns.

Histopathological effects of chronic aqueous exposure to bis(tri-n-butyltin)oxide (TBTO) to environmentally relevant concentrations reveal thymus atrophy in European flounder (Platichthys flesus)

Although the use of tributyltin in antifouling paints has been banned, this compound is still a serious pollutant of the marine environment. This paper describes a unique study in which European flounder (Platichthys flesus) were chronically (8 months) exposed to bis(tri-n-butyltin)oxide (TBTO) in the water under controlled laboratory conditions. Residue levels in selected tissues (liver, muscle) and general health status indices were measured and the effects on several organs (gills, liver, mesonephros, ovary/testis, spleen, and gastrointestinal tract) were examined histopathologically. Additionally, morphometric analysis of the thymus was performed. The major finding is that exposure of flounder to 5 microg TBTO/l over a period of 8 months, resulting in body burdens comparable to high field levels, induced significant reduction of thymus volume, possibly affecting immunocompetence of the animals. Chronic exposure of European flounder to tributyltin is therefore likely to affect the general health status of this species in heavily polluted aquatic environments.

Response to alkyltins of two Na+-dependent ATPase activities in Tapes philippinarum and Mytilus galloprovincialis

Organotin effects on the Na-dependent ATPases involved in ionic regulation of aquatic animals are poorly known, in spite of the largely documented contamination of seafood, especially bivalve molluscs. This study deals with the in vitro effect of TBT on the Na,K-ATPase and the ouabain-insensitive Na-ATPase in gill and mantle microsomes from the cultured bivalve molluscs Tapes philippinarum and Mytilus galloprovincialis. In the mussel also MBT, DBT and TeET were tested. While in both species the Na-ATPase showed an overall refractoriness to organotins, the Na,K-ATPase was progressively inhibited by increasing TBT concentrations (0-34 microM). In both species the Na,K-ATPase activity was more strongly inhibited in the gills than in the mantle. At the maximal TBT concentration tested (34.4 microM), while gill Na,K-ATPase activity was abolished, mantle enzyme activity was, respectively, reduced to 20% in T. philippinarum and to 50% in M. galloprovincialis. Mussel Na,K-ATPase was differently susceptive to the organotins tested and in both tissues showed an inhibition efficiency order TBT>DBT>>MBT=TeET (no effect), tentatively related to the different organotin polarity and to a possible interaction with membrane-bound enzyme complexes. The different response of the two ATPases to organotins is consistent with the known different susceptivity of the two enzyme activities to environmental contaminants, assay conditions and endogenous factors.