Clinical Symptoms and Histological Changes in Poecilia reticulata following Gamma-Rays Irradiation

BeÀová K. , V. Cigánková, M. Fal is , B. ·majda: Clinical Symptoms and Histological Changes in Poecilia reticulata following Gamma-Rays Irradiation. Acta vet. Brno 2006, 75: 557-560. Lethality, food intake, clinical symptoms and terminal histological changes were followed after gamma-irradiation with doses of 10, 20, 30, 35 and 40 Gy in guppy, Poecilia reticulata. Clinical symptoms, food intake and longevity were also monitored in the progeny of fish irradiated with a dose of 10 Gy. In the first days after irradiation timidity and lethargy were observed. After doses of 30, 35 and 40 Gy, these symptoms were accompanied with anorexia. The most prominent clinical symptoms observed were emaciation, hampered breathing, exophthalmia and haemorrhages. Histological findings corresponded with these symptoms. In the fish irradiated with 10 or 20 Gy the progeny survived, after a dose of 30 Gy the progeny died within 24 hours after birth and after doses of 35 and 40 Gy dead progeny was born. The survival data provide an estimate of LD50/30 equal to 29 Gy. Higher relative mortality and more severe clinical symptoms were observed in females. The progeny of irradiated parent fish grew and survived for 3 months maximum. Guppy, gamma irradiation, lethality, clinical symptoms, morphological changes Ionizing radiation represents one of the universal components of the environment. Humans and animals are permanently exposed to ionizing radiation from external and internal sources (Dvofiák et al. 2005). During hundreds of millions years of phylogenesis animals developed adaptive mechanisms enabling them to survive in an environment with a radiation background. In approximate estimate it may be said that the lower the phylogenetic stage of a species, the higher is its resistance to harmful effects of radiation (BeÀová et al. 2001; Dvofiák and BeÀová 2002; ·kardová et al. 1994). In the past, the prevailing part of the radiobiological research was done on mammals and birds; the radiation effects on fish were not studied in a comparable extent. Recently, some alternative biomedical models have been used in the study of radiation effects on animals (Dvofiák and ·ucman 1996; Dvofiák and BeÀová 2002). Guppies (Poecilia reticulata) and the species Danio rerio, often bred in home aquaria as undemanding species have found broad application as experimental animals, too (Le‰ník and Jurãina 1994). Materials and Methods In the experiments guppies (Poecilia reticulata) were used from a laboratory breed established two years before from fish bred specially for laboratory purposes. The breed had been kept under constant conditions: water temperature of 24 oC, Ca + Mg concentration of 0.7 mmol/l, pH = 7.04, artificial aeration, water filtration, light regimen LD 12:12 hours (Procházka and Dvofiák 2002). The fish were fed with live, flocked or granulated food. Experimental fish picked at random and divided into experimental groups were kept under the same conditions as described above. There were 16 fish in each experimental group (8 males and 8 females), living in an aquarium with a volume of 10 litres. During the experiment the fish were fed a flocked food mixture (AQUA EXOTIC, Kapu‰any, Slovakia). ACTA VET. BRNO 2006, 75: 557–560; doi:10.2754/avb200675040557 Address for correspondence: MVDr. Katarína BeÀová, PhD. University of Veterinary Medicine Komenského 73 041 81 Ko‰ice, Slovakia E-mail:benova@uvm.sk http://w ww.vfu. cz/acta-vet/actavet.htm During 30 days after irradiation the changes of behaviour and other possible pathological symptoms, mainly changes on the body surface observable by naked eye, and lethality were recorded (Dvofiák 2004). The results were compared with the control group. Lethal concentrations were calculated by means of the ML method of probit analysis, which enables to calculate the confidence interval for 95% probaility (Litchfield and Wilcoxon 1949). The results were completed with histological analyses. The guppies were irradiated with doses of 10, 20, 30 and 40 Gy of gamma-rays from a 60Co source (CHISOSTAT apparatus, Chirana, Prague, Czech Republic) with a dose rate of 11.36 Gy/min. In contrast to claims of OECD, gravid females were irradiated, too. The fish were irradiated in Petri dishes (∅ 9cm) filled with aquarium water to 1 cm of the water column. The controls were sham-irradiated. Samples for histological analysis were processed by commonly used methods. Whole fish were fixed in a 3% of neutral formaline solution and mounted in paraffin. Histological slices of 7 mm thickness were stained with hematoxylin-eosin and microscopically evaluated. The progeny of fish irradiated with 10 Gy was displaced after finishing the 30-day period after irradiation into an aquarium with a volume of 50 l, where the clinical symptoms, food intake and longevity were observed. They were compared with age-matched controls. The whole experiment was repeated two times.