Redescription of Aspidogaster limacoides Diesing, 1834 (Aspidogastrea: Aspidogastridae) from freshwater fishes of northern Germany

Aspidogaster limacoides Diesing, 1834 (Aspidogastridae) is redescribed based on light and scanning electron microscopy of specimens from the stomach and intestine of Abramis brama, Rutilus rutilus and Scardinius erythrophthalmus (Actinopterygii: Cyprinidae). The fishes were sampled during 2018 and 2019 at Lake Tollense in Mecklenburg-Western Pomerania, Germany. The prevalence of A. limacoides was highest in R. rutilus (61.7%) followed by Scardinius erythrophthalmus (7.7%) and A. brama (2.9%), while it was absent in Perca fluviatilis from the same lake. The following structures of A. limacoides are described for the first time: a depression on the ventral side of the neck, variations in the number and the arrangement of alveoli, numerous pits scattered all over the body surface, the presence of a few papillae-like structures posterior lateral to the mouth, the number of marginal organs represented by openings of exocrine multicellular glands as shown in histology and the subterminal position of the excretory pore. These characters can be used to distinguish three species of Aspidogaster, namely, A. ijimai, A. conchicola and A. limacoides, suggesting that SEM is a useful and promising tool in differentiating Aspidogaster species. Comparison of molecular data of the ITS1-5.8S-ITS2 regions showed a 94% similarity to A. limacoides from the European part of Russia. Phylogenetic analysis showed that the present specimens clustered in the same clade with A. limacoides sensu stricto, forming a distinct group to the exclusion of congeners.

On the Biological Regulators of Bloodsucking Blackflies(Diptera:Simuliidae) of Mixed Forests of Belorussian and Ukrainian Woodlands

This article considers the natural regulators of blood-sucking Simuliidae subzone of mixed forests on the territory of Belarus and Ukraine. In the mixed forests, the major regulators of preimaginal phases of bloodsucking blackflies are microsporidia (Polidyspirenia simulii, Polidyspirenia sp., Thelohania fibrata, Amblyospora bracteata, A. varians), fungi and mermithides (Gastromermis boophthorae). Caddisfly larvae (Hydropsyche angustipennis, Neureclipsis bimaculata, Polycentropus flavomaculatus, Cyrnus flavidus, Oligostomis reticulata, Brachycentrus subnubilus and Rhyacophila nubila) and fishes (Scardinius erythrophthalmus, Rutilus rutilus, Carassius carassius, Gobio gobio) significantly reduce the number of blackflies larvae and pupae. Adult blackflies are eaten by spiders (Araneus diadematus) dragonflies, robberflies, wasps, frogs (Rana temporaria and Rana terrestris), and insectivorous birds (Delichon urbicum, Hirundo rustica, Apus apus). Bactolarvicid and BLP-2477 are among the most effective biological products.

Molecular data on Phyllodistomum macrocotyle (Digenea: Gorgoderidae) from an intermediate host Dreissena polymorpha (Bivalvia: Dreissenidae) in the Northern Dvina River Basin, Northwest Russia

We report the first molecular identification of Phyllodistomum macrocotyle (Digenea: Gorgoderidae) from the Northern Dvina River Basin, Northwest Russia. Comparative analysis of our sequence was 100% identical to the 28S and ITS2 rDNA sequences of the species P. macrocotyle in zebra mussels discovered in Poland (Wigry Lake), Lithuania (Elektrenai Reservoir and Sirvinta River), Russia, Belarus (Lepelskoe Lake and Lukomskoe Lake), and in fish Leuciscus idus, Scardinius erythrophthalmus in Russia (Rybinsk Reservoir on the Volga River). At the same time, some sequences of the 28S rDNA of P. macrocotyle in zebra mussel detected in Lithuania, and Belarus were different from our sequence on 0.2-0.6%. The ITS2 sequences which have 100% similarity with our specimens of P. macrocotyle were discovered in sporocyst of phyllodistomes from its intermediate host D. polymorpha in Poland, Lithuania, Russia, and Belarus. Our observation in the Yuras and Isakogorka rivers represents the northernmost record of this host-specific parasite, to the best of our knowledge.

Regular Intergeneric Hybridization of Leuciscine Cyprinids (Cyprinidae, Leuciscinae) in the Dnipro Affluant

The large-scale hybridization of fishes of the subfamily Leuciscinae in the subordinate systems of the Dnipro River basin is presented by the data on two pairs of species, roach Rutilus rutilus × bream Abramis brama, and bleak Alburnus alburnus × rudd Scardinius erythrophthalmus. The hybridization and occurrence of F1 hybrids are confirmed with allozyme spectra and morphological characters on series of samples. A complete morphometric analysis of the characteristics of bleak and rudd hybrids was performed. The paper discusses the intergeneric hybridization in nature, which is a unique phenomenon characteristic only of some groups of cyprinids. The most likely reason is the overestimation of the taxonomic status of European cyprinids, which is confirmed by the insignificant level of intergeneric genetic divergence.

The Annual Reproductive Cycle of Rudd, Scardinius erythrophthalmus (Cyprinidae) from the Lower Oder River and Lake Dąbie, (NW Poland)

The rudd is a common freshwater species of the European ichthyofauna, however, this species' sexual cycle has not yet been described based on the histological analysis of its gonads. The aim of this study was to analyze the annual gonad development cycle of rudd from the watercourses of north-western Poland. Adult individuals aged 2+ to 13+, of both sexes were caught in the Oder River and Lake Dąbie. A standard paraffin technique and six-stage scales were used to assess the development of gonad maturity in both sexes. Rudd gonads developed similarly in the Oder River and Lake Dąbie. Eggs were deposited in batches from the beginning of May to the half of June. Females deposited at least two batches of eggs. In the majority of females collected from these sites, the gonads developed asynchronously throughout the year. Rudd males attained reproductive readiness in the same period as the females, but retained gametes in their gonads for a month longer than the females. Rudd avoid locations with warmer water discharged from power plants.