Depuration kinetics and persistence of the cyanobacterial toxin microcystin‐LR in the freshwater bivalve Unio douglasiae

Abstract

We carried out uptake and depuration experiments in the laboratory to investigate the effects of temperature (15 degrees C and 25 degrees C) on the depuration kinetics and persistence of a cyanobacterial toxin, microcystin-LR (MCYST-LR), in a freshwater bivalve, Unio douglasiae. Bivalves were fed toxic Microcystis cells in the 15-day uptake experiment and nontoxic diatoms in the following 15-day depuration experiment. Each bivalve's hepatopancreas was lyophilized and extracted with a butanol:methanol:water solution for analysis of MCYST-LR by high-performance liquid chromatography. The toxin in the organ accumulated rapidly after the beginning of the uptake experiment and reached approximately steady-state conditions on day 5 at concentrations of 130 +/- 11 microg g(-1) dry weight at 15 degrees C and 250 +/- 40 microg g(-1) at 25 degrees C. In the depuration experiments MCYST-LR was eliminated asymptotically from the tissue. The values of the depuration rate constant (k(d)), calculated with a first-order one-compartment model, were found to be 0.142 +/- 0.044 day(-1) at 15 degrees C and 0.226 +/- 0.046 day(-1) at 25 degrees C. The depuration Q(10) value from 15 degrees C to 25 degrees C equaled 1.6. This study was the first to reveal the kinetics of depuration for MCYST-LR in a bivalve. The results show that MCYST-LR may be eliminated slowly in autumn and winter and persist in the tissue until spring. Thus, in terms of toxicokinetics, the risk to people of being poisoned by bivalves would increase if toxic blooms occur in autumn.

Spatial and temporal variations of microcystins in hepatopancreas of a freshwater snail from Lake Taihu

“…In the present study, temperature had close correlations both with intracellular toxin content, and with MCs content in snail hepatopancreas, suggesting the importance of water temperature on the MCs accumulation in snail hepatopancreas. Yokoyama and Park (2003) reported that Unio douglasiae accumulated much higher concentration (250740 mg/g DW) at 25 1C than that at 15 1C (130711 mg/g DW).…”

Accumulation of nodularin in sediments, mussels, and fish from the Gulf of Gdańsk, southern Baltic Sea

“…Metabolic processes in living organisms, including biotransformation and detoxication, are strongly temperature dependent. Yokoyama and Park (2003) studied the kinetics of microcystin-LR depuration in freshwater bivalves. They revealed that significantly less toxin was eliminated from an organism incubated at 158C than at 258C, which indicated slower depuration rate of the toxin in winter.…”

Temporal and Spatial Effects on Some Physiological Parameters of the Bivalve <i>Lithophaga lithophaga</i> (Linnaeus, 1758) from Coastal Regions of Alexandria, Egypt

“…Pollution in marine bivalve mollusks can induce effects on the immune system and thus diseases susceptibility can be enhanced [62]. [63] studied the expression of Glutathione peroxidase (GPx) that is known to be directly involved in oxidative metabolism and reported that, oxygen is at the basis of oxidative metabolism, genes encoding enzymes involved in the cellular regulation of oxidative stress such as antioxidants are consequently expected to be regulated by hypoxia.…”