We examined the settlement preferences of leeches by analysing colonization patterns on artificial substrates. The intention was to check whether the type of material, texture and size of artificial substrates would influence the abundance of leeches. To test substrate type preferences, we used the following nine artificial substrates: polyester, polycarbonate, aluminium, glass, rubber, steel, polyethylene, ceramics and polypropylene. In addition, substrates of different textures (structural vs. smooth) and sizes (900, 400, 100 cm 2 ) were used. We found that rubber, polyethylene and aluminium were most frequently chosen by the leeches. Surface structure and size of the objects were other factors which determined substrate selection by these organisms. Leeches more readily inhabited rough surfaces and the surfaces of smaller-sized objects. The species composition of leech assemblages on analysed artificial substrates was dominated by predatory taxa of the genus Erpobdella and Helobdella.

Leeches are important members of communities developing on submerged hard substrates. We studied patterns of leech colonization and distribution on artificial substrates, which became more and more common in aquatic ecosystems. We deployed substrates on lake bottom and collected them over a 30‐day period to test the effect of exposure time, orientation in space (upward/downward), surface zone (edge/middle position), as well as interactions among leech individuals with other invertebrates. The results show that the rate of leech colonization depended on exposure time. Leech abundance grew intensively until reaching a stabilization state. The first colonizers were Erpobdellidae species and Helobdella sp. (after 2 days of exposure), whereas the rest of taxa from the Glossiphoniidae family appeared later (7–14 days). Leeches more readily inhabited substratum edges and surfaces directed downwards, than the middle zones and the surfaces facing upwards. Their distribution was contiguous and the tendency for group formation increased with the increasing density. Leeches mostly created small (2–3 individuals), mono or multispecies (groups of individuals less than 2 cm apart) agglomerations on artificial substrates. However, we did not find any relationship between the potential food resources occurring on the plates and leech abundance. Our study shows that leeches are fast colonizers of artificial substrates, with the most important factors affecting their recruitment and distribution including movement and feeding modes, occurrence of other leech individuals on the plates, taxonomic composition of leeches in the surrounding area, substratum orientation and the presence of surface irregularities (edges).

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For the first time, Piscicola brylinskae was described from Lake Vechten in the village of Bunnik, near Utrecht -The Netherlands. Until now, P. brylinskae has been found in Poland in Lake Maróz and in the Lyna River near Olsztyn (the northern part of Warmian-Masurian voivodeship). Thanks to proper conservation the coloration of P. brylinskae was described for the first time. Applying 32 indexes resulted that P. brylinskae clustered to Caspiobdella fadejewi. Analysis based on 113 non-metric characteristics has shown that P. brylinskae is most similar to Piscicola margaritae. Though, P. brylinskae do not form with P. margaritae dichotomic branching nor with any other species from this cluster, it could confirm that it is an individual species of the Piscicola genus.

Batracobdelloides moogi, the species representing the afroasiatic genus, is very poorly known for its biology and anatomy. This species was described on the basis of a small group of samples from south-western Europe. This study presents a morphological analysis and description of the structure of the alimentary tract and reproductive system. Biometry and external morphology were analyzed on 96 individuals and the anatomic structure on 40 individuals. The average length of the examinated specimens was 9.81 mm and the average weight was 0.056 g. The length of proboscis ranged from 2.5 to 4 neurosomites. Lengths of each ovary ranged from 1.5 to 3.5 neurosomites. Lengths of left and right sperm ducts ranged from 0.5 to 2.5 neurosomites. Correlation between the length of sperm ducts and their coiling was recorded.