Hirudinea is a small and ecologically important group of aquatic organisms. However, up to date, the leech fauna of Kazakhstan is poorly studied. The presence of large under-collected areas, such as the Upper Irtysh basin, makes biodiversity studies concerning these invertebrates from Kazakhstan relevant. In this paper, the latest information on species diversity of the freshwater hirudofauna of the Upper Irtysh cascade of water reservoirs, the Kazakhstan part of Irtysh River, is presented. It includes 10 free-living and parasitic species, of which 7 and 9 inhabit the Shulbinsk and the Bukhtarma reservoirs, respectively. These species belong to 2 orders, 3 families and 6 genera. The faunal list highlights four potentially new morphological species (Alboglossiphonia sp., Erpobdella sp., Piscicola sp. 1 and Piscicola sp. 2). Besides them, another three species Erpobdella vilnensis, Helobdella stagnalis and Theromyzon tessulatum recorded for the first time in the area. The exact systematic position is stated for all leech taxa. Each species from the list accompanied with information on taxonomic synonymy, data on its geographic distribution, and brief summary of morphological and ecological characteristics.

Hirudinea , species diversity, Upper Irtysh water reservoirs

The Irtysh River with a catchment area of more than 300 000 km² is the main water artery of the Eastern Kazakhstan, which meets the regional requirements of water resources. The hydrological level of the river is controlled by the Upper Irtysh water cascade consisting of Bukhtarma, Shulbinsk and Ust-Kamenogorsk storage reservoirs. Using these reservoirs, a multi-year, seasonal and weekly regulation of the river flow is consistently implemented (Beysembaeva and Dubrovskaya 2014, Vinokurov et al. 2010). The Bukhtarma reservoir is the largest of them; it serves as the main regulator of the cascade as a whole. The close proximity of the mining resource industry and nonferrous metallurgy resulted in ecologically strenuous conditions on the Bukhtarma reservoir (Kulikov et al. 2011). A specificity of biota inhabiting the Bukhtarma reservoir was formed by both the natural dispersal of species from the flooded water bodies and by the use of artificial colonization (Zadoenko et al. 1985, Evseeva 2011). The Ust-Kamenogorsk reservoir is located in the mountain valley of canyon type; it regulates weekly and daily river flow. This reservoir is characterized by significant water exchange, cold water and absence of the littoral zone. A high flowage of the reservoir, with an extremely unstable water exchange and low water temperature are limiting factors for many species of aquatic organisms. The aquatic fauna of this reservoir was formed as a result of biological invasions from upstream reservoirs (Evseeva 2012). The Shulbinsk reservoir in turn completes the cascade of artificial reservoirs, constructed in the Upper Irtysh. The reservoir conducts the seasonal adjustment of lateral afflux (Ulba River and Uba River) in the area between Bukhtarma and Shulbinsk hydropower stations. Operating mode of the Shulbinsk reservoir has a negative impact on its ichthyofauna and causes a significant reduction in biodiversity of benthic organisms (Kulikov et al. 2011). Thus, the exploitation of hydroelectric power stations, increased water consumption and the development of floodplain areas have led to changes in the hydrological regime of the Irtysh River and decrease in the natural potential of the river ecosystem (Beysembaeva and Dubrovskaya 2014). Instability of the hydrological level in the Irtysh cascade reservoirs, industrial impacts, and acclimatization activities conducted earlier necessitate the studying of natural biodiversity and its preserving.

Freshwater Hirudinea is one of the most important ecological groups of hydrobionts. Leeches are of scientific interest as an important link in the food chain of aquatic ecosystems, as well as bio-indicators of water pollution (Bezmaternykh 2007, Romanova and Klimina 2010, Kaygorodova et al. 2014). Moreover, parasitic leeches are involved in the abundance regulation of host species. As it was established, Hirudinea sp. may be directly related to transmission of bacterial and viral infections (Ahne 1985, Mulcahy et al. 1990, Cruz-Lacierda et al. 2000, Faisal et al. 2009, Faisal et al. 2011), as well as hematozoa including trematodes, cestodes, and nematodes (Demshin 1975) and parasitic flagellates (Khan 1976, Khamnueva and Pronin 2004, Burreson 2007), which are considered to be pathogenic organisms for aquatic animals. Moreover, ulceration, hemorrhage, and inflammation associated with leech attachment sites weaken the host and may pose an opportunity hosts to bacterial infections.

Previously, special-purpose research of leech fauna has never been conducted within the Upper Irtysh cascade. There are only scant data on the occurrence of a few leech species in the Bukhtarma water reservoir. As part of the fish parasite fauna, two species of leeches were identified – Piscicola geometra (Linnaeus, 1758) and Caspiobdella fadejewi (Epstein, 1961) (Izumova 1977). Later on, the presence of P. geometra has been confirmed, and the species list has been supplemented by Hemiclepsis marginata (Müller, 1774) and Erpobdella octoculata (Linnaeus, 1758) (Deviatkov 2012). The presence of C. fadejewi is doubtful, since this species belongs to the European faunistic complex and has a limited distribution within the basins of the rivers that flow into the Azov and Black Seas (Epstein 1987) and the Volga River (Lapkina and Komov 1983). Data on its occurrence outside this region are absent. Most likely, the leech species affiliation could be incorrectly identified. Thus, the species composition of the Irtysh leech fauna needs to be clarified, especially since the previously mentioned papers exclude the possibility of a verification due to the absence of morphological descriptions.

The aim of the study was to determine the current state of the species diversity and its spatial distribution and to fulfil a comparative analysis of the parasitic annelid fauna of the Upper Irtysh water cascade.

Expedition works were conducted in August-September 2014. The biological material was collected in the dam areas of Bukhtarma and Shulbinsk water storage reservoirs (Fig. 1). Catching leeches was performed manually or by using hydrobiological nets in the coastal zone of each reservoir in a depth range of 0.5–1.5 m. The specimens were fixated in 80% ethanol with preliminary animal anaesthesia by low percent alcohol solution.

Figure 1. 

Geographical location of the study region with indication of sampling areas: 1 Shulbinsk water reservoir 2 Bukhtarma water reservoir.

Morphological analysis of ethanol-fixed samples was performed using a stereomicroscope MSP-2 var. 2 (LOMO). The leech species affiliation was ascertained under existing systematic keys (Lukin 1976, Nesemann and Neubert 1999) in accordance with the present-day classification of the group. Reference specimens are stored in the annelid collection of the Limnological Institute.

This is the updated checklist of the Irtysh leech species inhabiting the Upper Irtysh cascade of water reservoirs. At present, 10 species were documented. The species diversity includes leeches from two orders (Rhynchobdellida and Arhynchobdellida), three families (Glossiphoniidae, Piscicolidae, Erpobdellidae) and six genera (Alboglossiphonia, Helobdella, Hemiclepsis, Theromyzon, Piscicola, and Erpobdella). Species composition includes both free-living and parasitic freshwater leeches. Parasitic forms are represented by seven species, and include representatives of 5 genera – Theromyzon tessulatum, Hemiclepsis marginata, Alboglossiphonia sp., Helobdella stagnalis, Piscicola geometra, Piscicola sp. 1, Piscicola sp. 2. Among free-living macrophagous leeches, there are only three erpobdellid species, namely Erpobdella vilnensis, Erpobdella octoculata, and Erpobdella sp.

The taxonomic list includes both Palaearctic species (H. marginata, P. geometra, T. tessulatum, E. octoculata, E. vilnensis), and widespread Holarctic species (H. stagnalis). Four species in the checklist, including Alboglossiphonia sp., Erpodella sp. and two representatives of Piscicola (Table 1), were referred in this paper, with caution, to unidentified species since their morphology differed from all currently described species. With high probability, these four unidentified species are potentially new to science. All four of these, for the first time were recorded within the Irtysh River basin.

Hirudofauna of the Bukhtarma and Shulbinsk water reservoirs is represented by 9 and 7 leech species, respectively (Table 1). Higher species diversity found in the Bukhtarma storage reservoir, is probably related to more favourable environmental conditions for freshwater leeches. This reservoir has a greater area and more tributaries (Fig. 1). Moreover, 50 years ago exactly in the Bukhtarma reservoir, experiments on acclimation of fish, molluscs, mysids and amphipods have been conducted. Sixteen alien species (6 species of fish and 10 species of invertebrates) have successfully taken root (Zadoenko et al. 1985, Evseeva 2011), which significantly expanded the number of potential hosts for parasitic leeches.

We thank to Elizaveta Fedorova and Alexander Suleymanov (Semey, Kazakhstan) for their technical help during leech sampling. This work was supported by the Russian Foundation for Basic Research (RFBR), grant no. 14-04-00345_a.