Miroslava Palíková

MICROCYSTIN KINETICS (BIOACCUMULATION AND ELIMINATION) AND BIOCHEMICAL RESPONSES IN COMMON CARP (CYPRINUS CARPIO) AND SILVER CARP (HYPOPHTHALMICHTHYS MOLITRIX) EXPOSED TO TOXIC CYANOBACTERIAL BLOOMS

Two species of common edible fish, common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix), were exposed to a Microcystis spp.-dominated natural cyanobacterial water bloom for two months (concentrations of cyanobacterial toxin microcystin, 182-539 microg/g biomass dry wt). Toxins accumulated up to 1.4 to 29 ng/g fresh weight and 3.3 to 19 ng/g in the muscle of silver carp and common carp, respectively, as determined by enzyme-linked immunosorbent immunoassay. Concentrations an order of magnitude higher were detected in hepatopancreas (up to 226 ng/g in silver carp), with a peak after the initial four weeks. Calculated bioconcentration factors ranged from 0.6 to 1.7 for muscle and from 7.3 to 13.3 for hepatopancreas. Microcystins were completely eliminated within one to two weeks from both muscle and hepatopancreas after the transfer of fish with accumulated toxins to clean water. Mean estimated elimination half-lives ranged from 0.7 d in silver carp muscle to 8.4 d in common carp liver. The present study also showed significant modulations of several biochemical markers in hepatopancreas of fish exposed to cyanobacteria. Levels of glutathione and catalytic activities of glutathione S-transferase and glutathione reductase were induced in both species, indicating oxidative stress and enhanced detoxification processes. Calculation of hazard indexes using conservative U.S. Environmental Protection Agency methodology indicated rather low risks of microcystins accumulated in edible fish, but several uncertainties should be explored.

Seasonal changes of immunocompetence and parasitism in chub (Leuciscus cephalus), a freshwater cyprinid fish

Seasonal variation of water characteristics, predominantly temperature, is considered to strongly affect fish physiology and immunology. In nature, this variation directly influences the life cycle especially in fish parasites, but the infection of parasites is also altered by the host immune response. This study is aimed to analyze the seasonal changes in selected physiological and immunological parameters, the latter a potential measure of fish immunocompetence. Moreover, the seasonal changes in metazoan parasite infection were investigated, and the potential associations between fish physiology, immunocompetence, and parasitism were estimated. No differences in gender were recognized for immunological parameters. The significant differences in the spleen–somatic index were found among fish samples of different seasons indicating higher investment in spleen size in April (after winterizing) and August (post-breeding with low gonado-somatic index [GSI]). The significant seasonal differences in erythrocyte and leukocyte cell counts, as well as in phagocyte count affecting respiratory burst, were recorded. The general trend of leukocyte composition was similar in all seasons investigated; however, the changes in proportion of different neutrophilic cells were reported. The parasite diversity and the infection parameters in parasite communities were highest in spring and early summer. When comparing parasite abundance in infracommunities among seasons, the statistically highest values were observed in April and June for Monogenea, in April and November for Acanthocephala, and in April for Cestoda. The positive correlations between GSI and the parasite abundance of groups with higher infection parameters were found in males. Moreover, the positive association between Monogenea as the dominant parasite group and respiratory burst was observed. The higher investment in condition and the seasonal variation in GSI were associated with a decrease immune function measured by spleen size or leukocyte cell count especially for males suggesting the seasonal energy allocation between immune function and somatic or reproductive investment.

Microcystin kinetics (bioaccumulation, elimination) and biochemical responses in common carp and silver carp exposed to toxic cyanobacterial blooms

The study investigating microcystin kinetics (bioaccumulation, elimination) and biochemical responses in common carp and silver carp exposed to toxic cyanobacterial blooms

Effect of T-2 toxin-contaminated diet on common carp (Cyprinus carpio L.).

ABSTRACT The T‐2 toxin, a fungal metabolite produced by Fusarium molds, occurs in a range of agriculture products. Reduced availability of fish meal has led to increasing use of cereals as a source of protein in commercial aquaculture feeds, which has increased the potential for mycotoxin contamination. The purpose of this study was to investigate toxicity of T‐2 toxin intake in common carp (Cyprinus carpio L.) using haematological, biochemical and immunological parameters and oxidative stress indices. In a four‐week feeding trial, fish were fed a commercial diet with 5.3 mg/kg T‐2 toxin added. Ingestion of contaminated diet did not lead to mortality of fish, probably due to lower feed intake. On the other hand, it significantly affected haematological variables such as haematocrit, haemoglobin, red blood cell counts leading to anemia and white blood cell counts leading to leukopenia due to lymphopenia. Plasma glucose concentration and alanine amino transferase activity showed a significant increase while triglycerides concentration decreased. Activity of ceruloplasmin was significantly decreased in plasma. Further, liver glutathione S‐transferase activity was significantly increased and catalase activity decreased, in parallel with a significant increase in caudal kidney catalase activity and a decrease in glutathione peroxidase activity. Finally, lipid peroxidation (detected as malondialdehyde) was significantly increased in the liver and caudal kidney. Changes in non‐specific immune response and cytokine levels in head kidney indicated immune system sensitivity to T‐2 toxin. Overall, the results demonstrate that this feed‐borne mycotoxin is able to induce anaemia and oxidative stress and cause changes in the immune response of common carp. HIGHLIGHTSThe aim of the study was to investigate toxicity of T‐2 toxin intake in common carp.Feeding trial led to changes in haematological and biochemical parameter.Lipid peroxidation was significantly increased in the liver and caudal kidney.Exposition to T2 led to changes in non‐specific immune response.Exposition to T2 led to changes in mRNA expression for selected cytokines.

Haematological indices are modulated in juvenile carp, Cyprinus carpio L., exposed to microcystins produced by cyanobacterial water bloom

This study evaluated the influence of toxic cyanobacterial water blooms on the blood indices of the common carp, Cyprinus carpio L. Experimental fish were exposed to a natural population of cyanobacterial water blooms (mainly Microcystis aeruginosa and M. ichthyoblabe), which contained microcystins [total concentration 133-284 μg g⁻¹ (DW), concentration in water 2.8-7.4 μg L⁻¹]. Haematological indices showed marked changes in fish exposed to the cyanobacterial population in comparison with the control group. Statistical evaluation of the influence of cyanobacterial water blooms on biochemical indices of the juvenile carp showed a distinct decrease in albumin, alanine aminotransferase, total bilirubin, calcium, cholesterol, glucose, phosphorus and iron when compared to controls. Values of red blood counts [haemoglobin, haematocrit (PCV), mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration] and lactate were significantly increased compared to controls. After exposure to cyanobacterial water bloom, the carp were kept in clean water to monitor the persistence of biochemical indices. The influence of cyanobacterial populations on calcium, cholesterol, glucose, lactate, phosphorus and PCV persisted up to 28 days after conclusion of the experiment. Duration of exposure, toxicity and density of cyanobacterial water blooms had an important impact on individual haematological indices.

Proliferative kidney disease in rainbow trout ( Oncorhynchus mykiss ) under intensive breeding conditions: Pathogenesis and haematological and immune parameters

Proliferative kidney disease (PKD) is an endoparasitic disease of salmonid fish caused by Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea). This study presents a comprehensive view on PKD development in rainbow trout (Oncorhynchus mykiss) reared at an intensive fish breeding facility, with focus on mortality, pathology/histopathology, haematological findings and immune functions. Diseased and reference fish were sampled monthly and time course of natural infection was followed up from the onset of clinical signs (September 2014) to full recovery (January 2015). PKD- associated cumulative mortality was 30% with a peak value in October, while immunohistochemical testing indicated a continuous significant decrease in T. bryosalmonae numbers from September to December; with no parasites detected in January. During peak clinical infection, a significant decrease in red blood cell counts, haematocrit values, haemoglobin concentration, along with a reduction in lymphocytes and a significant phagocyte elevation corresponding with an increase in phagocyte oxidative burst were measured in comparison to control animals. Complement activity and total immunoglobulin plasma concentrations were also elevated, though only during the initial monitoring period (September). Individuals surviving PKD, recovered and were able to fully regenerate both renal structure and haematopoietic parameters to normal levels. Changes in the red blood cell parameters indicate anaemia and a decreased oxygen transportation capacity during the clinical disease phase. Together with an increased oxygen demand at higher temperatures and decreased oxygen solubility this could lead to decompensation and elevated mortality. The stimulation of immune parameters, and especially oxidative phagocytic burst, is likely to have had a strong effect on both, regeneration and elimination of the pathogenic agent.

Effect of oxalic acid on the mite Varroa destructor and its host the honey bee Apis mellifera

Here, we study the effect of oxalic acid on isolated varroa mites and on varroa mites parasitizing caged honey bees treated with oxalic acid per os or topically (by trickling or by sublimation). We also study the effect of oxalic acid (trickling and sublimation) on individual bees, focusing on their lifespan, midgut morphology and function, and Malpighian tubule morphology. Effect on mites: contact of isolated mites with oxalic acid coated surface (Petri dishes treated by sublimation) significantly decreased mite viability. In an experiment on varroa mites parasitizing caged bees treated with oxalic acid, the strongest acaricidal effect was observed following oral application and the lowest when oxalic acid was applied through sublimation. Effect on bees: oxalic acid applied by sublimation did not decrease bee lifespan over the 21 days of observation contrary to trickling, where a nonsignificant lifespan decrease was observed. Topical application of oxalic acid increased the rate of midgut cell apoptosis, with a stronger statistically significant effect seen in the group treated by trickling. However, neither trickling nor sublimation caused epithelial destruction in the midgut and Malpighian tubules or loss of digestive tract function.

Seasonal changes in immune parameters of rainbow trout (Oncorhynchus mykiss), brook trout (Salvelinus fontinalis) and brook trout × Arctic charr hybrids (Salvelinus fontinalis × Salvelinus alpinus alpinus).

Despite the high number of studies concerning seasonality of immune response in fish, information for some fish species is still scarce. Here, we assess seasonal changes in leukocyte counts and several immune parameters in three groups of farmed salmonids, i.e. brook trout (Salvelinus fontinalis), brook trout x Arctic charr hybrids (Salvelinus fontinalis x Salvelinus alpinus alpinus) and rainbow trout (Oncorhynchus mykiss) reared under the same conditions and fed with the same feed. Fish were sampled in five periods of the year (late April, early July, late August, early November and early February) and leukocyte counts, respiratory burst of blood phagocytes, lysozyme concentration in skin mucus and total complement activity were measured. Generalized linear models using fish body length as a continuous predictor and sampling period and fish species as categorical predictors, were significant for each of the parameters analysed. The highest seasonal variations in measured parameters were found in rainbow trout and lowest in hybrids. Our results confirm that measures of innate and adaptive immunity are strongly affected by season in all three groups of salmonids. The results will contribute to the improved assessment of immunocompetence in farmed fishes, essential for future sustainable development in aquaculture.