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Novel combinations of mitochondrial DNA (CO1) and internal transcribed spacers of nuclear ribosomal DNA (ITS) were detected among Gyrodactylus parasites on brown trout (Salmo trutta L.), rainbow trout (Oncorhynchus mykiss (Walbaum)), and Ohrid trout (Salmo letnica (Karaman)) from salmonid farms in Poland and Macedonia. Some clones differed from standard ITS only by ≤ 4 nucleotides, but they belonged to a mtDNA clade that differed from the Northern European lineages of G. salaris by d MCL = 0.266 ± 0.108 (maximum composite likelihood distance). The divergence of d MCL = 0.013 ± 0.005 within the alien mtDNA clade suggested introgression from an unknown maternal ancestor into the G. salaris Malmberg genome 137 to 57 kyr ago (or, less probably, repeated introgression). A comparable modern hybrid was detected based on permanently heterozygous ITS (28 bp/1264 = 2.2%) in a clone that is widespread throughout Finnish rainbow trout farms. This was a F1 hybrid of maternal G. pomeraniae Kuusela, Ziętara et Lumme (on roach, Rutilus rutilus (L.)) and G. lavareti Malmberg (on whitefish, Coregonus lavaretus (L.)). The mtDNA of the parental species differed by d MCL = 0.290 ± 0.130. The observations emphasize that both nuclear and maternally-inherited DNA markers are necessary to characterize sexually-produced lineages or clones of Gyrodactylus. The hybridization events demonstrated predict incongruence of mitochondrial vs. nuclear gene trees, i.e., reticulate evolution in species trees.
The Gyrodactylus fauna of 274 fish taken from ten salmonid farms in Poland was sampled in 2006. Four fish species were investigated: rainbow trout Oncorhynchus mykiss, brown trout Salmo trutta (morphs fario, lacustris, and trutta), grayling Thymallus thymallus and huchen Hucho hucho. No parasites were observed on huchen. No indications of gyrodactylosis were observed, but an unexpected parasite species diversity was found. A molecular species identification by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) of ITS1 + 5.8S + ITS2 was utilized, with addition of morphometric methods. The most frequent parasite was a new record in Poland, G. teuchis. It was present in two molecular forms on brown trout and rainbow trout, which also carried G. derjavinoides and G. truttae. Three molecular forms of G. salaris/G. thymalli were found, the standard type ITS only on grayling. A heterozygous (or heterogenic) G. salaris type described earlier in Denmark was found in seven farms on rainbow trout, and a complementary homozygous clone which differs from the standard by three nucleotides, in two farms. This homozygous form has not been recorded earlier. The PCR-RFLP results were confirmed by sequencing ITS segment from representative specimens of each type and comparing them with all available salmonid-specific Gyrodactylus sequences in GenBank. The Polish fauna with seven different Gyrodactylus clones separated by PCR-RFLP was the most diverse reported in fish farms in any country so far.
Providing the optimal temperature is a means of increasing the effectiveness of methane fermentation processes. The use of an electromagnetic microwave field enables energy to be directed to a mixture of anaerobic sludge and processed biomass this reduces energy losses. The aim of this study was to determine the effect of electromagnetic microwave radiation in stimulating thermal conditions in anaerobic reactors, on the effectiveness of methane fermentation process of microalgae biomass and on the qualitative composition of biogas produced. The quantity of gaseous metabolites of anaerobic bacteria produced in both experimental variants (convective and microwave heating) averaged approximat’s 450 cm³ g⁻¹ VS. The electromagnetic microwave radiation proved to have an immediate impact on the improvement in the qualitative composition of biogas produced. The stimulation of thermal conditions using electric heaters resulted in a methane contetnt of 65% in biogas, whereas the use of microwaves assured ca. 69% in sewage gas.
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