Potassium Dichromate as a Reference Substance for Embryonic Tests of Toxicity in the Common Carp (Cyprinus carpio L.)

Potassium dichromate (K2Cr2O7) has already been used as a reference substance in tests of toxicity with aquatic animals. The aim of this study was to determine and compare values of LC50 for potassium dichromate during the whole period of embryonic development (i.e., 120 h) and 48 h after hatching of embryos in the common carp (Cyprinus carpio L.). Fish eggs and embryos were exposed to 5 different concentrations of potassium dichromate (i.e., 372, 409, 450, 495, 545 mg l-1) during two experiments. Such characteristics as the cumulative mortality, the start and the end of hatching, the number of deformities, body length, and body mass of surviving individuals were studied during the tests. The highest mortality was found in the hatched embryos. Mortality and frequency of deformities increased with the growing concentration of potassium dichromate. The value of 120 LC50 for potassium dichromate was 464.91 ± 23.83 mg l-1 and the value of 48 LC50 was 458.94 ± 4.14 mg l-1 (mean ± SD). No statistically significant difference between values 120 LC50 a 48 LC50 was found. This is why reduction of the exposure period to only 48 h after hatching seems a reasonable method to study the control of susceptibility using potassium dichromate in embryonic tests of toxicity

Chromosomal Aberrations in Early Embryos of Weatherfish (Misgurnus fossilis L.) Exposed to Crude Cyanobacterial Extract and Semipurified Compound of Microcystins - a Pilot Study

The genotoxicity of semipurified compound of microcystins and crude extract of cyanobacteria was analyzed and assessed using detection of chromosomal aberrations in early life stages of weatherfish. For 96 hours, weatherfish eggs at an eye spot stage were exposed to semipurified compound of microcystins (MC-LR: ΣMC= 1: 2.6) and crude cyanobacterial extract (MC-LR: ΣMC= 1: 2.1) both at doses of 130, 50 and 13 μg l-1. Hatching time in individual groups and aberrations in the behaviour of hatched specimens were recorded. Cumulative mortality and the proportion of deformed specimens were determined; materials for histological and cytogenetic screening were simultaneously sampled. Cumulative mortality (28 and 26%, respectively) increased after the application of higher doses (130 and 50 μg l-1) of crude cyanobacterial extract (p ⪬ 0.05). In these groups, hatched embryos showed reduced agility and stayed in clusters and in the group with the highest dose of crude cyanobacterial extract white spots on yolk sacks appeared. Cytogenetic screening revealed both chromatid (gaps) and chromosomal aberrations (rings, dicentrics), percentage of which increased with the increased concentration of microcystins and the higher doses of crude cyanobacterial extract. The highest number of aberrant metaphases was recorded after the application of the highest concentrations of cyanobacterial extract and microcystin (p ⪬ 0.05). Embryo mortality was affected especially by crude cyanobacterial extract, therefore other toxic elements than microcystins present in the extract were probably involved

IMPACTS OF DIETARY CYANOBACTERIA ON FISH

Abstract ZIKOVÁ, A., PALÍKOVÁ, M., MAREŠ, J., NAVRÁTIL, S., KOPP, R.: Impacts of dietary cyanobacteria on fi sh. Acta univ. agric. et silvic. Mendel. Brun., 2010, LVIII, No. 4, pp. 277-284 Development of cyanobacterial water bloom became a common issue all over the world. Cyanobacteria are the most important primary producers in aquatic ecosystems but in some abundant species their secondary metabolites called cyanotoxins seem to be harmful for many animal groups especially mammals but also fi sh. In fi shes, adverse eff ects have been demonstrated in several studies applying cyanotoxins by unnatural injection. However, cyanobacteria and fi sh coevolved during ages and therefore the question arises whether cyanobacteria might be even used for fi sh via oral application (fi sh diet). The use of cyanobacteria for fi sh diets is varying including applications of pure cyanobacteria biomass as well as incorporation of cyanotoxin containing cyanobacteria biomass into commercial fi sh diet. The impacts of cyanobacteria in fi sh diets administered via the oral route revealed contradictory fi ndings ranging from moderate negative to growth promoting impacts and it seems that any bioaccumulation of microcystins can become depurated by rearing fi sh in clean water for a short period. According to the results obtained from various experiments, cyanobacteria as primary producers might be used as a component of fi sh diets especially concerning partial replacement of fi sh meal. However, the determination of nutrition value and the bioavailibility of nutrients present in cyanobacteria for diff erent fi sh species needs to be determined. Furthermore thorough research is needed to exclude any harmful problem for the fi nal consumers -humans. blue-green algae; fi sh diet; cyanotoxins Cyanobacteria development became recently the most discussed topic all over the worl