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Vulnerable benthic water bug species \kur{Aphelocheirus aestivalis }(Fabricius, 1794) (Heteroptera: Aphelocheiridae): distribution and habitat preference in the Czech-Austrian border area of the Lužnice river basin
BAUER, Martin
The occurence, ditribution, habitat preference of benthic water bug Aphelocheirus aestivalis, and structure of macroinvertebrate benthic communities were studied in the upper Lužnice River basin. A. aestivalis is distributed only in a lower part of the upper Lužnice river basin. It inhabites stony biotopes of Dračice river (= Reissbach in the Austrian side), Lužnice river downstream from Suchdol nad Lužnicí, Old part of Lužnice river, Nová řeka river, and Nežárka river. This species occurs only in the rocky and sandy bottom where current speds and dissolved oxygen are both high in the investigated area. Prefered microhabitats are represented by sand and coarse gravel, that overline the larger boulders, rocks, dead woods or rootlets of trees growing in banks and sandy places with submerged plants. Though the Lužnice river has numerous sites of character of prefered habitats and microhabitats also upstream from Suchdol nad Lužnicí, any specimens of A. aestivalis were never found upstream from this small city and in the Koštěnický potok brook (mouth of this right side tributary into Lužnice river is located dovnstream from Suchdol nad Lužnicí). The macroinvertebrate benthic communities in the sites with occurence of A. aestivalis include larvae of following species of water insects: Cloeön dipterum, Baetis vernus, Ephemera danica, Ephemerella ignita, Heptagenia sulphurea (Ephemeroptera); Isoperla cf. rivulorum, Leuctra cf. albida (Plecoptera); Hydropsyche pellucida or incognita, H. angustipennis, Limnephilus sp., Molanna angustata, Polycentropus flavomaculatus, Potamophylax sp. (Trichoptera). Dominant and most abundant insects were Hydropsyche larvae. It is possible to suppose that the larvae of Baetis, Ephemerella (Ephemeroptera) and Hydropsyche (Trichoptera) larvae are prefered prey of A. aestivalis in the investigated area. The Lužnice river is characteristic by often floods including the destructive ones. Chemical parameters of water change espec
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