Mercury Content in Anguillicola crassus (Nematoda) and its Host Anguilla anguilla

Palíková M., V. Baru‰: Mercury Content in Anguillicola crassus (Nematoda) and its Host Anguilla anguilla. Acta Vet. Brno 2003, 72: 289-294. Mercury content in parasite-host system (Anguillicola crassus and Anguilla anguilla) was studied in the Koryãany Reservoir (Czech Republic). The swimbladder nematode contained the lowest mercury levels (0.050 0.183mg kg-1 wet weight), (p<0.05), compared to muscles (0.162 0.827) and the liver (0.175 1.430) of the fish definitive host. The mercury concentrations in the definitive host were higher in the liver, but not significantly different from muscle concentrations. Regression analysis indicated a positive ratio between mercury concentrations in the liver and the total body length of the fish. In eels from the reservoir under study the mercury content in fish muscles exceeded the hygienic limit in one fish specimen only. Muscle, liver, parasite-host system There is a developing body of literature analysing different amounts of heavy metals in fish and their organs and tissues (survey in Jezierska and Witesca 2001). The same tendency is manifested in comparative quantitative studies of various fish-parasite host systems (survey in Sures et al. 1999; Tenora et al. 2000; Turãeková et al. 2002). The parasite-host system of the nematode Anguillicola crassus Kuwahara, Niimi et Itagaki, 1974 and its definitive host the European eel, Anguilla anguilla L. was studied relatively frequently. Sures et al. (1994) analysed the lead content in this nematode and its host from nature only, while Zimmermann et al. (1999) did it experimentally. More heavy metal burdens (lead, cadmium, chromium and nickel) in these parasite-host systems were reported by Tenora et al. (1999). The content of selected microelements in males and females of A. crassus were studied by Baru‰ et al. (1999). Data on concentrations of mercury in this parasite-host system were still lacking. In this study, therefore, we deal with the first assessment of mercury concentrations in eels and its specific parasite A. crassus. Materials and Methods The eels used in this study were caught on March 13, 2001 in the Koryãany reservoir in South Moravia (Czech Republic) by electrofishing. The Koryãany reservoir has 35.15 hectares and 20 metres in maximum depth. The description of the locality and occurrence of A. crassus was published in Pal íková and Navrát i l (2001) or in Navrát i l et al. (1999). All fish specimens were placed in aerated aquaria filled with water from the collection site, and immediately transferred to the laboratory. In the laboratory, specimens were killed after three days and examined for metazoan parasites using standard procedures. The examination was aimed at the infection by the swimbladder nematode A. crassus, in particular. Total length (Tl in mm), weight (w in g) and infection intensity by A. crassus were measured in individual fish specimens (Table 1). Samples of muscles, liver of all eels (n = 10) and collective samples of nematodes from infected eels (n = 7) were stored at a temperature of -18 °C. Samples were digested using HNO3 for the determination of mercury in closed system. Mercury was determined using ColdVapour Atomic Absorption Spectrometry (CV-AAS). The reproducibility precision as a relative standard deviation, limit of detection and limit of determination are in Table 2. Parallel duplicate analysis of each sample ACTA VET. BRNO 2003, 72: 289–294 Address for correspondence: MVDr. M. Palíková, PhD. Department of Biology and Wildlife Diseases University of Veterinary and Pharmaceutical Sciences Palackého 1-3, 612 42 Brno, Czech Republic Phone: +420 541 562 821 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm