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Bryozoans are widely distributed benthic invertebrates which form colonies both in running and stagnant waters. There are 19 freshwater species of Bryozoa in Europe, and only three have been recorded in Serbia so far. Statoblasts (the dormant stages of these colonial animals) are relatively frequently found in the gut contents of fish, but those of the Hyalinella punctata species (Phylactolaemata) have not been registered. Statoblasts of H. punctata were determined for the first time in the gut content of chub Leuciscus cephalus sampled from the Zapadna Morava River (West Serbia, Danube River basin) in late summer and autumn. The intactness in form supports their viability after the passage through intestines, implying that the fish may be a vector of the dispersal of H. punctata in new aquatic habitats, as well as a risk factor in the transmission of certain salmonid fish disease agents into fish farms and natural habitats.
The relationships of Hildenbrandia rivularis (Rhodophyta), the species composition of its surroundings detailed environmental variables (water chemistry and hydrological, morphological and bottom features) in a lowland river (Wełna river, Western Poland) was investigated. H. rivularis from 40 stands was tested together with 25 environmental variables and vegetation. Detrended correspondence analysis (DCA) and redundancy analysis (RDA) were used to describe the relations between the species composition and the selected variables. The uniqueness of this protected species is an ability of formation incrustation on rocks but also coexistence with two groups of species: other algae and vascular plants. In study twenty-two plant taxa were recorded in 40 vegetation plots, including 4 macroscopic algae, 2 mosses and 16 vascular plants. The most common H. rivularis co-occurred with Leptodictyum riparium, Fontinalis antipyretica and Nuphar lutea. Most of the studied plots with red algae were characterised by shallow water and strong water velocity. H. rivularis prefers alkaline water with high conductivity. The results of the RDA, after forward selection, demonstrated that pH gradient, optical features such as dissolved organic matter and water colour – control the variation in the floristic communities with H. rivularis.
In 1992 and 1993 six freshwater species formed 96% of the assemblage. In number Acanthobrama marmid Heckel was dominant (70.8%), while Liza abu Heckel, Aphanius dispar (Ruppell), Alburnus mossulensis Heckel, Barbus luteus (Heckel), and Garra rufa (Heckel) constituted 7.5, 5.2, 4.4, 4.3, and 4.1% respectively of the total fish captured. Seven marine species constituted 2.1% of this assemblage.
Background. Thirty species were previously recorded for unstructured habitats (unvegetated soft substrates: USS) in Pantanos de Centla. However, a lack of information on the tropical ichthyofauna of the structured habitats such as marginal vegetation (MV), submerged macrophytes (SM) and coarse woody debris (CWD) emphasizes the importance of the aim of this paper that is the updating the records of the species distributed in these habitats, as they have been frequently reported as high biodiversity sites that are currently threatened by anthropogenic activities. Materials and methods. Sampling was carried out in 30 shallow sites, each with unstructured habitats and the three structured habitats, in Pantanos de Centla, a Ramsar wetland, over a period of three years. Fish were collected with a dip net, a drop net and a Renfro beam net. Results. A total of 6506 fish of 37 genera and 44 species were collected. Eleven species are new records for Pantanos de Centla, and the scientific name of 11 species was updated. The Poeciliidae and Cichlidae families are dominant with 10 and 13 species, respectively. Nine species of the genus Cichlasoma sensu lato were placed in six genera. Three species are new records for the Usumacinta Province. Ctenogobius claytoni, Gobionellus oceanicus, and Rhamdia quelen proved to be synonyms. Of all species, 84% were collected from USS, however, the number of species distributed in USS, MV, and SM was similar (CCj 0.4736-0.5813). Conclusion. Most of the species that were added to the previously recorded species list of Pantanos de Centla, inhabit structured habitats. This confirms the importance of including these habitats in surveys aimed at generating checklists, and of analysing the distribution of fish species in shallow tropical ecosystems.
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