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National Repository of Grey Literature 2 records found  Search took 0.01 seconds. 
Relationship between the age of freshwater pearl mussel and the number of increments in shell section
 TOMAN, Jan
The aim of this thesis was to determine the relationship between the age of dead individuals of the freshwater pearl mussel (Margaritifera margaritifera) and the number of incremental lines on the shell section. A total of 124 pearl mussel shells of known age were collected from several Czech, German and Finnish localities. There was a statistically significant difference between the actual age and the age according to the number of incremental lines on shell section. On average, the age determined by increment lines was higher than the actual age by 2.6 years, which is 42 ? 25% (? S.D.). Thus, the increment lines on the section of the pearl mussel shell do not correspond to the annual increments. It was confirmed that increment lines count on the shell surface or estimating age from shell size are less reliable approaches to determine the true age of individuals.
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Morphology and reproduction parameters of Achatinidae (Gastropoda)
 BUNDOVÁ, Michaela
The bachelor thesis deals with aspects of breeding of gastropods of the family Achatinidae. The thesis contains basic information about the family Achatinidae and the overview of the gastropods of the family Achatinidae in the Czech Republic. There is a problem of reproduction of terrestrial gastropod mollusks and Achatinidae land snail. In the practical part, data were collected from the breeders of these gastropods. There was the determination of the basic morphological parameters of the sexually mature land snail and the size of the clutches, which were compared among the specified species. The processed results show that the larger the individual's shell, the greater the number and the volume of the eggs in the clutch. With the increasing number of eggs in the clutch, the volume of eggs decreased.
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