Relative importance of direct and trophic uranium exposures in the crayfish Orconectes limosus: Implication for predicting uranium bioaccumulation and its associated toxicity

Abstract

Abstract-Pollutants that occur at sublethal concentrations in the environment may lead to chronic exposure in aquatic organisms. If these pollutants bioaccumulate, then organisms higher in the food chain may also be at risk. Increased attention has thus been focused on the relative importance of dietary uptake, but additional knowledge of the cellular distribution of metals after dietary exposure is required to assess the potential toxicity. The authors address concerns relating to increasing uranium (U) concentrations (from 12 mg/L to 2 mg/L) in the freshwater ecosystem caused by anthropogenic activities. The objective of the present study is to compare uranium bioaccumulation levels in tissues and in the subcellular environment. The authors focused on the cytosol fraction and its microlocalization (TEM-EDX) in the gills and the hepatopancreas (HP) of the crayfish Orconectes limosus after 10 d of direct exposure (at concentrations of 20, 100, and 500 mg/L) and five trophic exposure treatments (at concentrations from 1 to 20 mg/g). Results indicated that adsorption of uranium on the cuticle represents the main contribution of total uranium accumulation to the animal. Accumulation in the gills should be considered only as a marker of waterborne uranium exposure. Accumulation in the HP after trophic environmental exposure conditions was higher (18.9 AE 3.8 mg/g) than after direct exposure. Moreover, no significant difference in the subcellular distribution of uranium (50%) in HP was observed between animals that had been exposed to both types of treatment. A potential toxic effect after uranium accumulation could therefore exist after trophic exposure. This confirms the need to focus further studies on the metal (uranium) risk assessment. Environ. Toxicol. Chem. 2013;32:410-416. # 2012 SETAC

Subcellular fractionation and chemical speciation of uranium to elucidate its fate in gills and hepatopancreas of crayfish Procambarus clarkii

“…The cytosol fraction in gills represented between 13% and 30% of the total amount accumulated in the four subcellular fractions that is concordant with the suspected high fraction of adsorbed U on gill cuticle and also with the values found by Simon et al (2012) in their direct exposure study.…”

“…The pattern of U subcellular relative partitioning in hepatopancreas appears similar between the control and contaminated organisms, with a strong contribution of the cytosol fraction and a small contribution of the MRG fraction as shown by Simon et al (2012) in similar conditions of direct exposure. However, the influence of time duration on U distribution pattern within subcellular fractions between 30, 600 and 4000 lg L À1 groups can be due to the set-up of detoxification mechanisms more efficient at environmental levels than at high level of U exposure.…”

How toxic is the depleted uranium to crayfish Procambarus clarkii compared with cadmium?

“…In the chronic experiment gills also accumulated more U than Cd possibly for the same reasons stated above. Recently, Simon et al () demonstrated that only 12% of total U accumulation in gills of crayfish O rconectes limosus after waterborne exposure was measured in the cytosol fraction which is considered as the potential toxic fraction. Authors stated that adsorption of U on the gills cuticle of O. limosus represented the main contribution of U accumulation.…”

Effects of trophic exposure to diclofenac and dexamethasone on hematological parameters and immune response in freshwater fish

“…Many standard toxicology tests do not take trophic exposure into account, even though in controlled conditions it is easy to reproduce and interpret as a direct exposure standardized test [10]. Many standard toxicology tests do not take trophic exposure into account, even though in controlled conditions it is easy to reproduce and interpret as a direct exposure standardized test [10].…”

“…Trophic exposure was also selected because ecological risk assessments often focus on the relationship between direct exposure and the associated effects. Many standard toxicology tests do not take trophic exposure into account, even though in controlled conditions it is easy to reproduce and interpret as a direct exposure standardized test [10].…”