Chironomidae in shallow water bodies of a protected lowland freshwater floodplain ecosystem.

Lowland floodplains are complex ecosystems comprised of standing and flowing waters interacting with terrestrial habitats, and the main force creating, shaping and influencing, both habitats and biotic communities, is a hydrological regime and water supply from the parent river. In areas not much altered by anthropogenic influence, the Danube creates such floodplain areas, and temporary shallow water bodies within represent biodiversity important habitats. In the Kopacki Rit Nature Park floodplain in Croatia, diversity based on Chironomidae (Diptera) in both benthic and epiphytic communities was studied in eight ponds (temporary shallow water body) and at two channel locations (permanent shallow water body). At each location samples of sediment and macrophytes were taken at three sites. The benthic chironomid community was comprised of 29 taxa, most abundant being representatives of the Chironomus genus and Tanypus kraatzi in ponds, and Polypedilum nubeculosum and Cladotanytarsus sp. in channel samples. Cricotopus gr. sylvestris, Paratanytarsus sp. and Endochironomus tendens were dominant epiphytic chironomids (18 taxa). Non-metric multidimensional scaling and analysis of similarity analyses showed there was a clear grouping of sampling locations based on their position in the park and the distance from each other, more evident in the case of benthic chironomid communities. Furthermore, when the water bodies were compared based on the community structure from different locations and substrates, there was also a statistically significant separation. Community composition indicates high productivity and organic matter production of studied water bodies, but moreover, the differences in substrate preferences evident in 16 common out of 31 recorded chironomid taxa, indicate the importance of habitat complexity preservation in a floodplain.

The Influence of Contracaecum larvae (Nematoda, Anisakidae) Parasitism on the Population of Prussian carp (Carassius gibelio) in Lake Sakadas, Croatia.

Contracaecum larvae are geographically widely distributed, utilizing many animal species as hosts; and fish represent an important paratenic host in their life cycle. Their presence in Prussian carp (Carassius gibelio) was studied in Lake Sakadas (Croatia) in 2017 and 2018. Two gill nets of different sizes submerged during a 12-h period were used to collect the fish. Contracaecum larvae were recorded in the stomach, slightly coiled or elongated on the intestine serosa or encapsulated in a gut wall of 20 individuals. The effect of Contracaecum sp. on the health of their host was determined by estimating the effect of the parasites' presence, number, and biomass on fish length, weight, and the Fulton's condition factor (CF). Infected fish showed negative (b < 3; p < 0.05) and uninfected fish positive allometric growth (b > 3; p < 0.05). Fish weight and CF in infected individuals were significantly low in comparison to the uninfected ones (Mann−Whitney U test: U = 1078.00, U = 423.50, respectively; p < 0.004). These results emphasize the importance of evaluating parasitic nematode presence in economically important fish species. Even more, if this endoparasite has a detectable negative impact on a resilient species such as the Prussian carp, it is important to monitor its occurrence in other fish species.

Implications of local niche- and dispersal-based factors that may influence chironomid assemblages in bioassessment.

Local environmental factors and dispersal-based processes can both influence the structure of metacommunities in freshwater ecosystems. Describing these patterns is especially important for biomonitoring approaches that are based on inferences made from benthic macroinvertebrate assemblages. Here, we examine the metacommunity structure of chironomid assemblages collected from 28 sampling stations along the Southern Morava River, Serbia. We examined the extent of dispersal-based processes along a temporal scale. We obtained 8 models for the different sampling seasons that determined the spatial variables that best explained variability in chironomid assemblages. Spatial processes were found to be a significant predictor of variation for chironomids during the late winter/spring (March and May) and autumn (October and November), concordant with the known phenology of common taxa. Species sorting and mass effects were found to be significant processes that structured the chironomid metacommunity. In addition, biological interactions, inferred from fish biomass, and habitat traits, demonstrated by macrophyte and riparian vegetation, were found to influence species sorting. A high variability of chironomid metacommunity structure across sampling seasons suggests that monitoring programs that include macroinvertebrates in bioassessment should avoid months with pronounced spatial processes, and consequently maximize a correlation between community structure and local environmental factors.

Potentially toxic elements in invasive fish species Prussian carp (Carassius gibelio) from different freshwater ecosystems and human exposure assessment.

Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sn, and Zn were detected in the muscle and gills of Prussian carp from three different freshwater ecosystems: isolated ponds and the South Morava River in Serbia, and Kopacko Lake in complex wetland ecosystem of the Kopacki Rit Nature Reserve in Croatia. The main goals of the present research were to assess the concentrations of potentially toxic elements (PTEs) in the muscle and gills of Prussian carp (Carassius gibelio), to examine whether abiotic factors from three different freshwater ecosystems affect the accumulation of PTEs in fish tissues, and to estimate the human health risk resulting from fish consumption. There were only six concentrations of PTEs in the gill tissue (Cr, Hg, Mn, Pb, Sn, and Zn) that were not significantly different among the different freshwater ecosystems. In the muscles, the differences were much less visible. Kopacko Lake distinguished with the highest values of metal pollution index (MPI) for muscles (0.24) and isolated ponds with the highest values of MPI for gills (0.8). The redundancy analysis (RDA) showed that concentrations of Al, Mn, Zn, Cu, and Fe in the gill tissue were significantly correlated with the environmental variables. In contrast, the RDA based on element concentrations in the fish muscles indicated no significant relationship with the environment. Isolated ponds, with no inflow of freshwater, stand out as the most polluted, followed by Kopacko Lake with occasional floods. Flowing freshwater ecosystem South Morava River can be single out as at least polluted with PTEs. The target hazard quotients (THQ) and hazard index (HI) suggested there were no significant noncarcinogenic health risks. The target carcinogenic risk factor (TR) for As and Pb confirmed there were no cancer risks related to human fish consumption. Since the elevated concentrations of toxic Cd and As in Prussian carp were estimated, an early warning should be assumed, especially for fishing activities in these areas.

Chironomidae (Diptera) of Croatia with notes on the diversity and distribution in various habitat types.

The family of non-biting midges (Diptera, Chironomidae) represent one of the most common and abundant group in freshwaters, inhabiting a wide variety of habitats and ecological niches. Although there is a long tradition of limnological research in Croatia, to date no extensive species list has been made for this insect family. Thus, we summarized the results of our research and reviewed published data on chironomid fauna of Croatia in various freshwater habitat types, including extreme ones, such as caves, peatbogs or marine littoral. A total of 239 species were recorded representing five subfamilies: Chironominae (125 species) Orthocladiinae (83 species), Tanypodinae (23 species), Diamesinae (6 species) and Prodiamesinae (2 species). The most frequent species were Cricotopus bicinctus, Dicrotendipes nervosus, Synorthocladius semivirens, each found in more than 20% of the studied localities. Ablabesmyia monilis and Procladius choreus represented the most frequent Tanypodinae species, recorded in more than 12% and 17% of the sites, respectively. The research of chironomid ecology, diversity and distribution continues, which will provide new data and information, but this first comprehensive checklist provides a good starting point for those studying Chironomidae or other freshwater Diptera, in Croatia and Europe.

Phylogeography of Simulium Subgenus Wilhelmia (Diptera: Simuliidae)-Insights From Balkan Populations.

Many morphologically similar species of the simuliid (Diptera: Simuliidae) subgenus Wilhelmia, Enderlein are difficult to distinguish. Thus, the revision of the subgenus using various morphological, cytogenetic, and genetic analyses has been attempted. Neglected until now, the Balkan Peninsula, a crossroad between Europe and Anatolia, provides insight which could resolve problematic interrelationships of the taxa within this subgenus. To uncover the status and relations within the subgenus Wilhelmia, mtDNA was extracted from 47 individuals of six morphospecies: Simulium balcanicum (Enderlein, 1924), Simulium turgaicum Rubtsov, 1940, Simulium lineatum (Meigen, 1804), Simulium pseudequinum Séguy, 1921, Simulium equinum (Linnaeus, 1758), and Simulium paraequinum Puri, 1933 from 21 sites throughout the Balkan Peninsula. Phylogenetic analysis of the Wilhelmia species using mitochondrial DNA barcoding (COI) gene showed two major branches, the lineatum branch, which includes the lineages sergenti, paraequinum, and lineatum, and the equinum branch. In the equinum branch, the mtDNA sequences formed six clades, with high genetic distances, suggesting the existence of different species. Historically, the clades of the equinum branch appeared at numerous islands, perhaps as a result of allopatric speciation. The paraequinum lineage (lineatum branch) is composed of two species. However, six clades of the lineatum lineage overlapped with intra- and interspecific genetic distances. Our results revealed that the species S. balcanicum, S. pseudequinum B, and S. equinum were omnipresent in the Balkans. The results point to not only the fair diversity of Wilhelmia species in the Balkans, but also indicate that most Wilhelmia species live in sympatry.

The potential of chironomid larvae-based metrics in the bioassessment of non-wadeable rivers.

The chironomid community in non-wadeable lotic systems was tested as a source of information in the construction of biological metrics which could be used into the bioassessment protocols of large rivers. In order to achieve this, we simultaneously patterned the chironomid community structure and environmental factors along the catchment of the Danube and Sava River. The Self organizing map (SOM) recognized and visualized three different structural types of chironomid community for different environmental properties, described by means of 7 significant abiotic factors (a multi-stressor gradient). Indicator species analysis revealed that the chironomid taxa most responsible for structural changes significantly varied in their abundance and frequency along the established environmental gradients. Out of 40 biological metrics based on the chironomid community, the multilayer perceptron (MLP), an supervised type of artificial neural network, derived 5 models in which the abundance of Paratrichocladius rufiventis, Orthocladiinae, Cricotopus spp., Cricotopus triannulatus agg. and Cricotopus/Orthocladius ratio achieved a significant relationship (the r Pearson's linear correlation coefficient>0.7) with the multi stressor environment. The sensitivity analysis "partial derivatives" (PaD) method showed that all 5 biological metrics within the multi-stressor gradient were mostly influenced by dissolved organic carbon (DOC). Despite short and monotonous environmental gradients and the absence of reference conditions, the chironomid community structure and biological metrics predictably changed along the multistress range, showing a great potential for the bioassessment of large rivers.