Radovan Erben

Application of the micronucleus and comet assays to mussel Dreissena polymorpha haemocytes for genotoxicity monitoring of freshwater environments

Assessment of DNA damage is of primary concern when determining the pollution-related stress in living organisms. To monitor genotoxicity of the freshwater environments we used micronucleus (MN) and comet assay on Dreissena polymorpha haemocytes. Caged mussels, collected from the river Drava, were transplanted to four monitoring sites of different pollution intensity in the river Sava. Exposition lasted for a month. The baseline level of MN frequencies in the haemocytes of mussels from reference site (river Drava) was 0.5 per thousand. No increase in MN frequency was found in mussels from the medium-polluted site (Zagreb) in the river Sava while other, more polluted sites showed higher MN frequencies ranging from 2.7 per thousand (Lukavec) and 3.1 per thousand (Oborovo) to 5.2 per thousand (Sisak). Results from comet assay showed concordance with MN assay in indicating intensity of DNA damage. The use of haemocytes from caged, non-indigenous mussels in MN and comet assay proved to be a sensitive tool for the freshwater genotoxicity monitoring.

Detection of DNA damage in haemocytes of zebra mussel using comet assay

The aim of the study was to use the comet assay on haemocytes of freshwater mussel, Dreissena polymorpha Pallas, for detection of possible DNA damage after exposure to pentachlorophenol (PCP) and to evaluate the potential application of the comet assay on mussel haemocytes for genotoxicity monitoring of freshwater environment. Zebra mussels were exposed for seven days to different concentrations (10, 80, 100, 150 microg/l) of PCP and in the river Sava downstream from Zagreb municipal wastewater outlet. Significant increase in DNA damage was observed after exposure to PCP at doses of 80 microg/l and higher and after in situ exposure in the river Sava as well. This study confirmed that the comet assay applied on zebra mussel haemocytes may be a useful tool in determining the potential genotoxicity of water pollutants.

DETECTION OF MICRONUCLEI IN HAEMOCYTES OF ZEBRA MUSSEL AND GREAT RAMSHORN SNAIL EXPOSED TO PENTACHLOROPHENOL

The frequency of micronuclei (MN) induced by pentachlorophenol (PCP) in haemocytes of zebra mussel, Dreissena polymorpha Pall. and great ramshorn snail, Planorbarius corneus L. was determined over a 14 days of exposure (sampling after 4, 7 and 14 days) under laboratory conditions. PCP doses for zebra mussel ranged from 10 to 150 microg/l, and for ramshorn snail from 10 to 450 microg/l. Micronuclei were detected after bisbenzimide fluorescent staining. Positive responses were observed in both species. The mean MN frequencies in treated mussels ranged between 0.69 and 7.50 per thousand, and between 2.07 and 13.80 per thousand in treated snails. The spontaneous MN levels in mussels averaged from 0.5 to 2.75 per thousand, and in snails from 1.56 to 2.00 per thousand. Our results suggest that haemolymph of both species represent an appropriate test tissue in environmental genotoxicity assessment.

The effects of the trematode Bucephalus polymorphus on the reproductive cycle of the zebra mussel Dreissena polymorpha in the Drava River

The effects of the trematode Bucephalus polymorphus on the reproductive cycle of the zebra mussel Dreissena polymorpha were examined in mussel populations from the Drava River. The reproductive cycle was studied by histological examination of the gonads and quantified by an image analysing system to determine changes in volume of the entire visceral mass, gonads, digestive glands and in particular the volume of trematodes. Results confirmed that (1) gonads of D. polymorpha were affected by B. polymorphus infection more than any other organ and (2) development of cercariae in sporocysts of B. polymorphus coincides with host gonad maturation. This is the first study in which the image analysing system was used to determine the effect of trematodes on the reproductive cycle of D. polymorpha. Also, this is the first record of sporocysts of B. polymorphus in D. polymorpha in this part of Europe.

Trophic role of rotifers in the plankton of lake Kozjak (Plitvice Lakes)

The trophic role of rotifers in the zooplankton community of dimictic, oligotrophic lake Kozjak, the largest lake of the Plitvice Lakes, NW Dinarid Mountains, is analyzed. Their spatial and temporal biomass distribution in relation to that of protozoans, cladocerans and copepods shows that they form a significant part of the non-predatory zooplankton of this karstic standing water.

Seasonal changes of the condition indices and haemocyte counts of the Austropotamobius torrentium population in Kraljevec Stream, Croatia

The stone crayfish, Austropotamobius torrentium (Schrank, 1803) is one of the four native European crayfish living in Croatian freshwaters. Kraljevec Stream is situated on the southern slopes of Medvednica Mountain (north-west Croatia) at 400 m above sea level. Our research was carried out for one year, from May 2003 to April 2004. During the study period water temperature varied between 2 to 17.2°C, alkalinity between 100 and 200 mg CaCO 3 /L, the mean oxygen concentration and pH was 12.1 mg/L and 8.3, respectively. Crayfish were trapped by baited hand made traps, which were secured in a stream current with the stones and roots of the surrounding trees. We caught 100 crayfishes, 68 males and 32 females. Hemolymph was sampled 10 to 15 min after the catch. EDTA anticoagulant was used to prevent hemolymph coagulation and 10% formalin was used to fix haemocyte for differential counts. Each month five or six specimens of each sex, if possible, were sacrificed and hepatosomatic, gonadosomatic and muscle indices were measured. We found statistically significant differences in hepatosomatic and gonadosomatic indices between months and between sexes. Muscle indices were significantly different between males and females. The average total haemocyte counts were 7.6 · 10 5 cells/ ml and 6.5 · 10 5 cells/ml hemolymph for males and females, respectively. The average hyalinocyte, granulocyte and semigranulocyte ratio was 77: 14.5: 8.5%. There were no statistically significant differences in total haemocyte counts between months and between sexes.

Rotifer fauna in the periphyton of Karst rivers in Croatia, Yugoslavia

Rotifers from periphyton communities of rivers in the Karst area of western Yugoslavia were examined. Thirty-two species, belonging to 10 families, were found. Rotifers were absent from locations without periphyton. Low densities of animals were noted at stations near urban centres and in the estuaries of the Mirna, Rasa, Rjecina and Krka rivers. Several species were found in all of the rivers studied, but always in low numbers. Most of these species are generally considered to be euryvalent and cosmopolitan.

Seasonal distribution of the zebra mussel larvae in the dam reservoirs Dubrava, Čakovec, and Varaždin, Croatia

Rad se bavi problematikom vertikalne i horizontalne stratifikacije licinki skoljkasa Dreissena polymorpha u akumulacijskim jezerima hidroelektrana Dubrava, Cakovec i Varaždin. Prikazana je distribucija i gustoca licinki D. polymorpha ovisno o koncentraciji klorofila i temperaturi vode.

Zooplankton in the dam reservoirs Hazna and Vidara, Bosnia and Herzegovina

Dam reservoirs Hazna and Vidara were constructed in 1967 with the purpose of preventing flooding of the lowlands in the Gradasnica river basin, and the communities and industrial zone around the town of Gradacac. They were the result of conversion of the streams Hazna and Vidara. The average lenght of the reservoir Hazna is about 1000 m, and its width is approximately 200 m. Total volume is about 630 000 m3. The maximum depth of the reservoir is 17 m, while the average depth is 3 m. The size of the Hazna basin area is about 10 km2. The dam reservoir Vidara is 2 km far from Hazna. The average lengh is 1500 m, its width is 350 m. The reservoir volume is 3 440 000 m3. The maximum depth of the reservoir is 17 m, while the average depth 6.7 m. The basin area is over 20 km2. Water quality was investigated to determine whether the water of the reservoirs could be used for drinking. The biological and bacteriological quality of the water and its physico-chemical characteristics were studied. This paper mainly deals with zooplankton community which is an important group for the trophic degree estimation.

Rotifer fauna in Modrac reservoir (Bosnia and Herzegovina)

Research on the dam reservoir Modrac, relating to the appearance of mollusk Dreissena polymorpha, as well as water supply needs of Tuzla, included analyses of the plankton community, benthos and physico-chemical parameters. twenty-five species of Rotatoria were found, the majority of which belong to nanophytoplankton filtrators and some to sedimentary microfiltrators. The abundance of rotifer was below the tipical abundance for mesotrophic lakes of polymictic type, such as Modrac lake.