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The influence of 3-methylcholanthrene to zebra mussel (Dreissena polymorpha) larvae was studied. The artificial spawning of zebra mussels was used for obtaining larvae. Two different concentrations of 3-methylcholanthrene were used. The chromosome analysis showed a significant increase in chromosome aberrations (CA) at the higher concentration of the compound. The resistance of zebra mussel larvae to the lower concentration of 3-methylcholanthrene indicated that zebra mussel larvae are probably not sensitive enough for the study of genotoxicity of the compounds from the PAH group.
Mitochondrial genomes are frequently used to infer phylogenetic relationships. Some taxa are, however, poorly represented. To facilitate better understanding of the potential of mitochondrial genome data in freshwater mussels, we present here, for the first time, the mitochondrial sequences of 4 complete F-type mitochondrial genomes from the European freshwater bivalve Unio pictorum (Unionidae). These genomes are very compact (15 761 bp) but have atypical gene complement for bilaterian mitochondrial genomes and a very similar organization to other unionid genomes available in databases. Very low nucleotide diversity within the species suggests a small effective population size of Polish U. pictorum, a phenomenon of potential importance for environmental management policies.
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.
This paper presents populations of Anodonta cygnaea (L.), Anodonta anatina (L.) and Unio pictorum (L.) inhabiting an artificial pond (area 0.3 ha, depth 4 m) formed at a peat excavation site 13 years prior to the collection of the data. The mussels probably colonized the pond as glochidia attached to host fish introduced for angling or migrating with flood waters. The mussel populations were characterized by high densities, high average and maximum shell lengths and high proportions of young individuals. Our study shows that man-made ponds can become favorable habitats for freshwater mussels, and that relatively short time is needed to establish their viable populations. Active conservation of unionid mussels in man-made habitats may require human help at the dispersal stage.
Mollusc shells from archaeological excavations are often well preserved and allow for species identification and measurements. Large shell assemblages can provide information for environmental reconstruction and investigation of anthropogenic impacts. In this study we compare freshwater mussel shells from a shell midden excavated on a lake island in northern Poland, dated 2,700–2,600 BP, with contemporary populations from that lake. No changes in species composition occurred, with only Unio tumidus and Anodonta sp. present in the prehistoric sample, and Unio tumidus and Anodonta anatina in the contemporary one. In both the archaeological and contemporary samples, shells of Unio tumidus were relatively small (mean shell length 49.3 } 5.2 mm, max 64 mm, and 46.0 } 5.9 mm, max 61 mm, respectively). However, the values of all measured characteristics (length, height, mass, and thickness) were significantly lower in the contemporary compared to prehistoric shells. In modern times, in the region of the study largescale forest clearing and conversion of land into agricultural areas occurred; presently areas of intensive agriculture directly adjoin the lake. Dwarfing of the shells likely results from anthropogenic deterioration of mussel habitat.
Two types of metacercariae with 37 and 43 collar spines were obtained from Diplodon chilensis (Unionacea, Pelecypoda). They were fed to chicken and mice and mature adults with eggs were only obtained from the latter. These are described as a new species, Echinoparyphium megacirrus sp. n.
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