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Individual marking of small insects and its usage in describing societies and migration of semiaquatic bugs (Heteroptera: Gerromorpha) in lentic and lotic habitats of Novohradské Mountains.
VOJÍŘOVÁ, Eva
Experiments based on the method of mark-recapture can be used for estimation of the abundance of natural populations, for monitoring dispersion of groups or individual specimens within a population using group or individual marking. Semiaquatic bugs (Heteroptera: Gerromorpha) were marked and recaptured many times in the field during research, individual marking was much less used since marking of small insects is difficult. The aim of this work is to develop a method of individual marking of semiaquatic bugs so that it would meet conditions such as durability, legibility and non affecting health of the marked specimen. Semiaquatic bugs of Aquarius paludum, Gerris lacustris, Limnoporus rufoscutellatus (Gerridae) and Velia caprai (Veliidae) species were selected as experimental organisms. Partial aims of this thesis were to try using this method to describe the abundance of the monitored population and to monitor dispersion of the selected species, both at lotic (V. caprai) and lentic habitats (water striders, family Gerridae). A new method of individual marking of semiaquatic bugs was developed on the basis of modifications of the commonly used methods. After a series of tests and in-field research, this method proved to be suitable as it met the essential conditions for marking insects. The abundance of the monitored population was estimated and dispersion of the selected species (V. caprai) in running water was described by using this method. The partial aims of this thesis were met, too. It was confirmed that individuals of the V. caprai species move between the monitored areas along the water course. This inclination to move is greater than tendency to remain in the place of release. The gained data also show conclusively higher rate of movement of V. caprai specimens in the upstream direction, compared to the downstream. The tendency of V. caprai to travel larger distance upstream than downstream, is significant too. No statistically relevant difference in either direction of the water course (up or down) in the surpassed altitude difference was confirmed. The differences in the monitored phenomena between the sexes and generations were compared as well. The differences, however, were not significant. A movement of the adults of the water cricket Velia caprai thus can be characterized as an upstream migration, common in insects of lotic habtitats. A part of the study taking place in still waters showed, that G. lacustris specimens move on the surface of the pond, but not to a larger degree than they remain in place. On the other hand, A. paludum specimens were proved to move away from the place of release rather than remaining in that place. These also overcome greater distance than G. lacustris specimens.
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