Paweł Buczyński

Parasitism of Odonata by Arrenurus (Acari: Hydrachnidia) larvae in the Lake Świdwie, nature reserve (NW Poland)

Larvae of a vast majority of water mite species are parasites of aquatic insects. Owing to this, they migrate to new localities, and are able to survive unfavourable environmental conditions. This also concerns species from subgenus Arrenurus s. str., parasites of dragonflies. The detailed analysis of this phenomenon, however, has only been possible in the last several years, since the key to the identification of larvae from genus Arrenurus Dug. was published. In 2010, the parasitism of Arrenurus s. str. larvae on dragonflies in the Lake Świdwie reserve (NW Poland) was analysed. Larvae of 9 species of water mites were recorded on 107 imagines of dragonflies from 8 species. The following were identified as hosts of water mites for the first time: Anax imperator, Libellula quadrimaculata, and Leucorrhinia caudalis. The highest prevalence occurred in the case of: Erythromma najas and Lestes dryas (100%), Coenagrion pulchellum (96.5%), and C. puella (80.0%). Coenagrion pulchellum was infested by 9 species of parasites, C. puella by 6, and Erythromma najas and Lestes dryas by three species. The highest number of host species occurred in the case of Arrenurus maculator (5); followed by A. cuspidator, A. batillifer cf., A. bicuspidator, and A. tetracyphus (3 each); A. papillator, A. tricuspidator, and A. bruzelii (2 each), and A. claviger (1). Differentiation of preferences of particular parasites towards various parts of the host body was observed, probably related to the coevolution of parasites and hosts, and competition between the host species. The body sizes of the parasites suggest that approximately 50% of body size growth of water mites from subgenus Arrenurus s. str. occurs at the stage of parasitic larva.

Water mites (Acari, Hydrachnidia) of water bodies of the Krąpiel River valley: interactions in the spatial arrangement of a river valley

The present study is a discussion of the interactions between different types of water bodies in the spatial arrangement of a river valley, taking into account landscape data. The Hydrachnidia assemblages in particular types of valley water bodies (oxbows, riparian pools, permanent ponds, flooded alder carrs, sedge marshes, and springs) are strongly influenced by the spatial arrangement of the water bodies in the landscape. Moreover, the formation of a fauna in a particular type of valley water body is also influenced by its origin. For example, the faunas of the oxbow lakes and riparian pools would have many characteristics in common, as these two types of water body can be characterized as originating in the river. As many as 61 species common to the valley water bodies and the Krąpiel River were noted. In the interactions between the valley water bodies and the river, the direction of migration from the former to the latter was clearly predominant. Migration in the reverse direction, from the river to the valley water bodies, took place to a far lesser degree. CCA analysis of landscape variables showed the influences of certain landscape parameters on water mites. These should be regarded as indirect influences, but as a consequence of their effects, they influence the formation of specific types of Hydrachnidia assemblages.

Early post-dredging recolonization of caddisflies (Insecta: Trichoptera) in a small lowland river (NW Poland)

An analysis was made of the effect of dredging on the caddisfly fauna (Trichoptera) of the river Krąpiel (north-western Poland) a short time after the intervention. Pronounced changes were observed in the qualitative and quantitative structure and the biodiversity of Trichoptera. These changes should not, however, be characterized as unfavourable from an ecological perspective if we consider only the one group of insects analysed. Some species — Brachycentrus subnubilus and Lepidostoma hirtum — disappeared from the dredged parts of the river, but significantly more appeared, and these were typical river species. This replacement of species can be linked to habitat changes and the uncovering of larger patches of sandy bottom. The recolonizing species included accidental (eurytopic) species, which is typical in ecological succession for periods immediately following disturbances. On balance, despite the replacement of species, there was no decrease in species diversity, and typical river species appeared in larger numbers. In Trichoptera, recolonization following dredging first takes place as a result of drift of larvae, and then via dispersion of adults.

Occurence and threats of the medicinal leech (Hirudo medicinalis L.) in Poland (Annelida: Hirudinea)

Paweł B u c z y ń s k i*, Piotr D ą b r o w s k i **, Andrzej Z a w a l **, Radomir J a s k u l a ***, Grzegorz T o ń c z y k ***, Michał G r a b o w s k i***, Edyta B u c z y ń s k a ****, Krzysztof L e w a n d o w s k i******, Dariusz J a n i c k i**, Stanisław Cios*****, Lech P i e t r z a k *******, Przemysław M r o w i ń s k i ********, Joanna P a k u l n i c k a ******, Aleksandra JABŁOŃSKA*** and Marek G u z i k *********

Impact of pH and conductivity on species richness and community structure of dragonfl ies (Odonata) in small mining lakes

Although acidifi cation in freshwaters reduces the richness of aquatic species in general, dragonfl ies are less affected. However, detailed knowledge regarding the effects of very acidic (pH 700 µS cm -1 ) water on dragonfl y species richness and composition is still scarce. To assess this, 19 anthropogeni- cally infl uenced waters with a wide range of pH (2.64 - 6.81) and conductivity (113 - 2620 µS cm -1 ) were investi- gated in the Muskau Arch area (western Poland, eastern Germany). Of the 41 dragonfl y species found, 31 were autochthonous. Both total (St) and autochthonous (Sa) species richness correlated positively with pH and negatively with conductivity. However, the correlations for autochthonous species were strongly infl uenced by the samples from the extremely acidic (pH 2.64 - 2.86) and most ion-rich (conductivity > 1200 µS cm -1 ) waters, where no spe- cies developed. The Sa values from acidic waters with slightly higher pH values (between 3.0 and 4.0) did not differ signifi cantly from those found in neutral waters. Nevertheless, species preferring acidic or neutral conditions, re- spectively, were clearly separated, showing a direct or indirect effect of pH on the community structure in the area. We thus conclude that only pH values below 3.0 and conductivity above 1200 µS cm -1 have a detrimental effect on dragonfl ies. Other acidic waters are suitable habitats for specialists, which do not develop in neutral waters. Thus, moderate acidifi cation enhances the dragonfl y species richness of a region like the Muskau Arch area.

Groynes: a factor modifying the occurrence of dragonfly larvae (Odonata) on a large lowland river

The regulation of rivers and their valleys has had a strong, negative influence on the maintenance of their original biota. Nevertheless, some hydro-engineering works conducted along already regulated rivers may be beneficial, creating habitats for endangered species and assemblages. Such works include the construction of groynes. We analysed this effect on the occurrence of dragonfly larvae along middle and lower stretches of the Oder, where groynes were built over a distance of 306km, creating an area of uniform habitat. We demonstrated that the presence of groynes increased not only the abundance of dragonfly larvae, but also the species richness and diversity of these insects. Habitats were recreated for assemblages typical of a river with highly diverse habitat conditions, from typically riverine assemblages to those occurring in oxbow lakes, also endangered by regulations. The fauna along the stretches with groynes was richer and more valuable than that along the stretches without groynes, achieving values approaching those obtained from modelled unregulated rivers. This can be put down to greater habitat heterogeneity and groyne-reduced levels of waves produced by ships. The presence of groynes provides the key to the restoration or stabilisation of the populations of certain species and to renaturalisation processes.

New host-parasite associations of Hydrachnidia (Acari) on Chironomidae (Diptera) from Poland

Abstract We present the first data from Poland concerning parasitism of Hydrachnidia on Chironomidae. Larvae of Hygrobates sp., H. setosus, Unionicola aculeata and Piona stjoerdalensis were found attached to adult Chironomidae (Cricotopus triannulatus, Tanytarsus sp., Paratanytarsus sp., Critocopus sp. and Orthocladius sp.). Intensity of infestation ranged between 1 to 2 larvae. All of the parasites were attached to abdomens of the hosts. The determination of parasitism of U. aculeata on Paratanytarsus and Tanytarsus genera extends the list of the hosts of this water mite species to the mentioned genera of Chironomidae. In case of H. setosus, the parasitism of this water mite on currently known hosts from the family Chironomidae has been confirmed.

The influence of environmental factors on water mite assemblages (Acari, Hydrachnidia) in a small lowland river: an analysis at different levels of organization of the environment

Research on the ecology of water mites in flowing water has focused mainly on analysis of factors directly affecting these organisms in the aquatic environment. The hypothesis of this study was that apart from factors acting within the aquatic environment, the formation of Hydrachnidia communities in lotic ecosystems may also be affected by factors acting in the terrestrial environment. The analysis was made at three different levels of organization of the environment: (1) landscape level (sub-catchments, terrestrial environment), (2) macrohabitat level (sampling sites, aquatic environment) and (3) mesohabitat level (sampling sub-sites, aquatic environment). Some correlation was noted between certain species and some sub-catchment parameters. This may indicate a link between some landscape features (terrestrial environment) and the formation of water mite assemblages in the river. The low percentage for physicochemical parameters together in explaining the variance in occurrence of species, very low correlations between species and physicochemical parameters and the discrepancy in the grouping of sites in the case of faunal data and data on the physicochemical indicates that physicochemical factors had little influence on water mites. Taking into account all three levels of organization of the environment analyzed, we can say that at the landscape level we can find only indirect relationships between environmental factors and the fauna inhabiting the aquatic environment; at the macrohabitat level the description of Hydrachnidia is more precise but still of a general nature. Only analysis at the mesohabitat level fully explains the specific character of Hydrachnidia assemblages.

Are beetles good indicators of insect diversity in freshwater lakes

Abstract The study verifies the usefulness of aquatic beetles as an indicator of biodiversity of a simple ecological system. Detailed analyses were carried out at the elementary level for the purpose of determining the significance of correlations between the biodiversity of Coleoptera and other groups of aquatic insects in single samples. The relation of selected taxa to selected habitats of the lake Wukśniki (north-eastern Poland) was also investigated. Moreover, the possibility of application of biodiversity surrogates, i.e. higher taxonomic units (genera and orders), in the determination of biodiversity was examined. A significant high correlation was determined between Coleoptera and the total remaining taxa (RR - Remaining Richness) in samples collected in the entire lake. The correlation has the highest value at the species level. The complementarity analysis reveals that the percentage contribution of Coleoptera in the overall biodiversity of the lake is similarly high at the species and genus level, and substantially lower at the family level. In accordance with the hypothesis, aquatic beetles can be used as indicators of the overall biodiversity of insects in the ecosystem of a mesotrophic lake. Biodiversity surrogates, i.e. higher taxonomic units (genera and families), can be applied instead of the species level.

First record of parasitism of water mite larva (Acari: Hydrachnidia) on the pupa of Trichoptera

During the studies on ecology of Trichoptera of anthropogenic water bodies we have unexpectedly discovered the parasitic larvae of water mites of the species Tiphys torris on the pupa of Triaenodes bicolor. This is the first documented case of the parasitism of water mites on the caddisfly pupa as well as the first ever record of the species which is regarded as a dipteran parasite on caddisflies. The situation is very untypical for preimaginal stages of caddisflies are used by phoretic and not parasitic water mite larvae. Parasitism has been confirmed in this case by the formation of stylostomes and enlarged sizes of the bodies of the larvae. This is probably the case of facultative parasitism in which the pupa has served as a substitute of the adult form of a caddisfly.