microcystin and Body-Weight

The microcystin-producing cyanobacterium Planktothrix is one of the most widespread genera amongst toxin producing cyanobacteria in European lakes. In particular, the metalimnic blooms of Planktothrix rubescens have been associated with growing problems in the professional freshwater fishery as a decrease in yearly yields in the important coregonids fishery often coincides with the appearance of P. rubescens. P. rubescens is a cyanobacterial species known to produce toxic compounds, e.g. microcystins. Although microcystins have been reported to affect fish health, behaviour, development and growth and have also been associated with feral fish kills, there is currently no specific information on the effects of toxic Planktothrix filaments in fish and especially coregonids. Therefore, the aim of this study was to investigate the effects of an environmentally relevant dose of P. rubescens filaments orally applied to coregonids and to discuss the findings in the context of microcystin toxicity previously reported in carp and trout. A single dose of P. rubescens culture, at a density of 80,000 cells per 120 microl, was applied to coregonids thus corresponding to 0.6-0.9 microg microcystin-LR(equiv.)/kg body weight. Behavioural changes and opercular beat rates, growth, hepatosomatic index, condition and plasma glucose were determined. Liver, kidney, gill and the gastrointestinal tract were assessed histopathologically and immunohistologically. Exposed fish showed behavioural changes, increased opercular beat rates and elevated plasma glucose levels, possibly representing a physiological stress response. Histopathological alterations in liver, gastrointestinal tract and kidney, also immunopositive for microcystin suggested causality of tissue damage and the in situ presence of microcystins. The observed combination of stress and organ damage may explain the frequently reduced weight and thus the fitness noted in coregonids subjected to regular occurrences of stratified and dispersed P. rubescens blooms, e.g. in lake Ammersee, Bavaria, Germany.

Topics: Administration, Oral; Animals; Antibodies; Behavior, Animal; Blood Glucose; Body Weight; Cyanobacteria; Environmental Exposure; Gastrointestinal Tract; Gills; Immunohistochemistry; Kidney; Liver; Microcystins; Salmonidae; Time Factors

Among the Cyanoprokaryota (blue-green algae), the genus Phormidium has thus far rarely been studied with respect to toxin production and potentially resulting human and environmental health effects. We here show that five previously unexplored freshwater species of this genus (Ph. bijugatum, Ph. molle, Ph. papyraceum, Ph. uncinatum, Ph. autumnale) are indeed capable of producing bioactive compounds. Phormidium extracts caused weight loss as well as neuro/hepatotoxic symptoms in mice, and in the case of Ph. bijugatum even death. Very low levels of saxitoxins and microcystins, as confirmed by ELISA, were insufficient to explain this toxicity and the differing toxic potencies of the Phormidium species. Qualitative HPLC analyses confirmed different substance patterns and in the future could aid in the separation of fractions for more detailed substance characterisation. The results in vivo were confirmed in vitro using cells of human, mouse and fish. The fish cells responded least sensitive but proved useful in studying the temperature dependence of the toxicity by the Phormidium samples. Further, the human cells were more sensitive than the mouse cells thus suggesting that the former may be a more appropriate choice for studying the impact of Phormidium to man. Among the human cells, two cancer cell lines were more responsive to one of the samples than a normal cell line, thereby indicating a potential anti-tumour activity. Thus, the five freshwater Phormidium species should be considered in environmental risk assessment but as well, as a source of therapeutic agents.

Topics: Animals; Bacterial Toxins; Body Weight; Cell Survival; Cells, Cultured; Chromatography, High Pressure Liquid; Cyanobacteria; Enzyme-Linked Immunosorbent Assay; Fishes; Fluorescent Dyes; Formazans; Humans; Liver; Male; Mice; Microcystins; Peptides, Cyclic; Saxitoxin; Species Specificity; Statistics, Nonparametric; Tetrazolium Salts

With direct exposure to phytoplanktivorous fish (Hypophthalmichthys molitrix), increased mass-specific microcystin production occurred in three monoclonal Microcystis aeruginosa strains (NIES 44, 88 and 99). Total mass-specific microcystin content of NIES 44 exposed to H. molitrix was over 50 times higher than controls (a mean value of 16.2 microgg(-1)-dry cell in controls versus 878.6 microgg(-1)-dry cell in treatments). Up to nine times higher microcystin levels were detected in NIES 88 exposed to H. molitrix compared to controls (a mean value of 553 in controls versus 5145 microgg(-1)-dry cell in treatments). The microcystin levels of all strains were significantly different between controls and H. molitrix treatments (P < 0.01 for NIES 44 and 88; P < 0.05 for NIES 99). The microcystin response to the omnivorous Carassius gibelio langsdorfi was weaker than that of H. molitrix, though the levels in all strains exposed to the fish were higher than in controls and a significant difference in microcystin production between controls and omnivorous fish treatments occurred for NIES 44 (a mean value of 6.9 in controls versus 41.5 microgg(-1)-dry cell in treatments; P < 0.01) and NIES 88 (a mean value of 359.8 versus 480.4 microgg(-1)-dry cell; P < 0.05). Microcystis cells were observed in the both fish faeces and gut contents, and microcystin was also detected in the body tissues (from 0.6 to 2.5 microgg(-1)-dry weight) and faeces of both fish species on the final day of experiment, although 98% of fish in three strains of Microcystis cultures had lost weight (mean +/- S.E. fish growth rate with M. aeruginosa; -0.90 +/- 0.06% per day, n = 96). This study showed that several M. aeruginosa strains increased toxin production when exposed to fish, especially phytoplanktivorous species, even though fish appeared not to feed vigorously on toxic Microcystis, and supports the hypothesis that this response is a fish-induced defence mediated by physical contact associated with feeding or by chemical cues (e.g. kairomones).

Topics: Analysis of Variance; Animals; Bacterial Toxins; Body Weight; Carps; Chromatography, High Pressure Liquid; Ecosystem; Feces; Microcystins; Microcystis; Peptides, Cyclic; Predatory Behavior

There is only limited information about the accumulation of algal toxins in aquatic organisms in the Baltic Sea. In this study we measured total cyanobacterial hepatotoxin levels in blue mussel (Mytilus edulis) and flounderi (Platichthys flesus) tissues. Flounder were caught with gillnets from the western Gulf of Finland during July and August 1999. Blue mussels were collected from an enclosure at 3 m depth and from an artificial reef (wreck, 25-35 m depth) in the western Gulf of Finland between June and September 1999. Flounder liver and muscle samples and soft tissues of mussels were analyzed for the cyanobacterial hepatotoxins (nodularin, NODLN and/or microcystins, MCs) using an enzyme-linked immunosorbent assay (ELISA). Results showed a time-dependent accumulation of hepatotoxins in flounder and mussels. In flounder, the maximum concentration 399 +/- 5 (sd) ng NODLN or MC/g dry weight (dw) was found in the liver of specimens caught on 21 August 1999. No hepatotoxins were detected in muscle samples. The maximum concentration of 2150 ng +/- 60 (sd) ng hepatotoxin/g dw was found in the mussel soft tissues collected on 20 August 1999. Temporal NODLN or MC trends indicated depuration of cyanobacterial hepatotoxin from mussels at surface level and an increase in NODLN or MC concentrations in those from the sea bed. These studies showed that despite the low cyanobacteria cell numbers the cyanobacterial hepatotoxins can accumulate in flounder and mussels. This may allow the further transfer of cyanobacterial hepatotoxins in the food web.

Topics: Animals; Bivalvia; Body Weight; Cyanobacteria; Enzyme-Linked Immunosorbent Assay; Flounder; Kinetics; Liver; Microcystins; Muscle, Skeletal; Peptides, Cyclic; Seasons; Tissue Distribution

The growth and toxicity of various Microcystis aeruginosa strains were tested. Six of 14 strains were lethal to mice, five of which produced microcystin. Of these, M. aeruginosa PCC 7806 produced the most toxin per biomass and was thus used to examine the influence of various trace metals on exponential growth rate and production of microcystin. Zinc was shown to be required for optimal growth as well as toxin production. Al, Cd, Cr, Cu, Mn, Ni, and Sn did not significantly affect toxin yield at non-toxic concentrations of the metals. In contrast, iron had a pronounced effect on growth rate and toxin yield. In the absence and at low concentrations of Fe (< or = 2.5 microM), the cells grew much more slowly, but produced 20-40% more toxin. This is in agreement with the hypothesis that production of microcystins may be a response to specific environmental stress conditions.

Topics: Animals; Body Weight; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Mice; Mice, Inbred BALB C; Microcystins; Microcystis; Organ Size; Peptides, Cyclic; Phosphoprotein Phosphatases; Species Specificity; Spectrophotometry, Ultraviolet; Trace Elements