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Approximately 130 individuals of Acanthobdella peledina and 100 individuals of Paracanthobdella livanowi were studied. Morphometric measurements were taken to explore the body form. The digestive and the reproductive systems of leech-like annelids were analyzed for the first time in such a high number of specimens. Observation of A. peledina and P. livanowi revealed crucial differences in the reproductive system of the analyzed taxa, mostly regarding variation in the shape of the testisacs and the length of the ovisacs. The results of a digestive system analysis suggest that blood-sucking parasites of the order Acanthobdellida may also lead a predatory lifestyle. The presented findings support the taxonomic division of the order Acanthobdellida into the families Acanthobdellidae and Paracanthobdellidae. Multiple similarities between Acanthobdellida and Hirudinida were also discussed.

I n t e r n a t i o n a l J o u r n a l o f O c e a n o g r a p h y a n d H y d r o b i o l o g y AbstractHirudinida comprise a constant component of benthofauna in running waters and their taxonomic composition is often analyzed to evaluate the environmental quality. However, the indicatory role of particular species is still arguable. Thus, it is very important to provide more detailed information on the impact of environmental parameters on the species structure within this group of invertebrates. Representatives of nine species were found in the investigated upland stream including mainly Erpobdella vilnensis and E. octoculata. The research has demonstrated that the hydromorphological conditions and feeding behavior are the main factors determining the taxonomic composition of leeches in particular sections of a watercourse.

Erpobdella borisi n. sp. is a predatory leech inhabiting cave waters in Iran. Probably, it is either a troglobiont or troglophile. The leech has no eyes, and the complete mid-body somite is divided unequally into five annuli. Results of phylogenetic analysis based on morphological characters and COI gene sequence indicate the species to be closely related to Erpobdella japonica, E. octoculata and E. testacea.

Summary It is assumed that males and females of spined loach, Cobitis taenia are characterized by different androgen receptor patterns of expression in some of the target tissues and by different concentrations of androgens during their reproductive season. Moreover, still little is examined as to whether tissue sensitivity to androgens follows the changes in androgen concentrations across the fish reproductive cycle. This was verified by determining androgen (testosterone and 11‐ketotestosterone) concentrations in whole fish bodies using ELISA and analyzing AR gene expression in androgen target tissues (gonads, muscles and liver) using RT‐PCR. The partial sequence of the AR gene in C. taenia was also identified. The study was conducted on the spined loach, Cobitis taenia – a multiple spawning species in decline, having hybridized with closely‐related taxa to form allopolyploids. Males (18 individuals) and females (18) were collected from an exclusively diploid population (Legińskie Lake, Baltic Sea basin) in 2013 during pre‐spawning (May), spawning (June) and post‐spawning (August) seasons (six fish per sampling period per sex) using a fry trawl (with a 0.2 cm mesh). The reproductive status of the fish was verified by GSI and gonad histology. The results revealed seasonal variations in the concentration of androgens in C. taenia males and females as well as the dynamic, seasonal nature of AR gene expression in a tissue‐ and sex‐dependent manner. Furthermore, a different seasonal profile of both androgens accompanied by a different pattern of AR expression in various tissues indicated complex physiological mechanisms engaged in AR regulation. These findings appear to be a good physiological basis for further studies using more advanced molecular techniques.