In this paper, the very first checklist of the freshwater leeches of Maloe More Strait, a special part of Lake Baikal, is presented. It includes 14 free-living and parasitic species, of which four species belong to endemic Baikal genera – two species from Baicalobdella and one species each from Baicaloclepsis and Codonobdella. The checklist highlights six potentially new morphological species recorded for the first time in the area. The exact systematic position is stated for all leech species. Each species from the list is provided with information on taxonomic synonymy, data on its geographic distribution, and ecological characteristics. New species records are additionally provided with brief morphological characteristics and photos of their external morphology.

Hirudinea , checklist, endemic, Maloe More Strait, Lake Baikal

The Baikal leeches (Hirudinea) are one of the least studied groups of invertebrates due to underestimation of their role in aquatic ecosystems and intractability of their taxonomy. In fresh and brackish waters, some leeches serve as invertebrate predators while others are infamous for their ability to feed on the blood of either invertebrates or vertebrates. The first group includes macrophagous leeches. These leeches have a large size relative to other freshwater invertebrates and a high density in the littoral zone of reservoirs and lowland streams making them critical to fish nutrition. This role is obviously underestimated at present. This may be attributed to peculiarities of their habitation and consequently of their sample collection. Macrophagous leeches are rarely found in hydrobiological collections; therefore, their abundance has not been taken into account and their role in ecosystems has often been undervalued. The second group consists of parasitic forms, which constitute the main part of the leech diversity, and their role in ecosystems is absolutely different. Being epizoic parasites, they have relevance to transmission of bacterial and viral infections (e.g. Faisal and Schulz 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.

An exploration of the Baikal parasitic leech diversity was begun by pioneering 19^th century German zoologist Adolf Eduard Grube. Clepsine echinulata Grube, 1871 (now Baicaloclepsis echinulata (Grube, 1871)), Piscicola torquata Grube, 1871 (now Baicalodbella torquata (Grube, 1871)) and Codonobdella truncata Grube, 1873 may have been the first freshwater leeches recorded from Lake Baikal, but their host relationships had not been identified. Non-parasitic leeches of Lake Baikal were excluded from any scientific interest for a long time due to their belonging to the common Siberian faunal assemblage, and the scientific pursuit of unique endemic elements. Later, the famous Russian scientist Nikolai Livanow, studying Baikal samples, described the species Protoclepsis tesselatoides Livanow, 1902, which has some morphological differences from the Palaearctic Protoclepsis tessulata (Müller, 1774) (now Theromyzom tessulatum) parasitizing waterfowl. Next, the endemic “flat” leech Torix baicalensis Shchegolew, 1922 (now Paratorix baicalensis) was discovered by Shchegolew (1922) in collections from 1916, but the host remains unknown. No publications on Baikal leeches appeared for the subsequent 35 years until the description of a new endemic genus and species Baicalobdella cottidarum (Dogiel and Bogolepova 1957), found on cottoid fish. Subsequently, Lukin and Epstein (1960a) described a new genus (Baicaloclepsis) and a new species (B. grubei), the first leech record from the Maloe More Strait. The same authors then created a new subfamily (Toricinae), which included the genus Baicaloclepsis Lukin et Epstein, 1960 and newly established Paratorix (Lukin and Epstein 1960b). Since, in addition to the above, the following papers on the Baikal leeches have been published: Dogiel et al. 1949; Epstein 1961, 1973, 1987; Lukin 1967, 1976; Finigenova and Snimschikova 1991; Kozhova and Izmest’eva 1998; Rusinek 2007. In order to revise the Lake Baikal leech fauna, the most recent target investigations have worked towards clarifying the taxonomic status of various species as well as adding to the species list with new records (Kaygorodova 2012, 2013; Kaygorodova and Natyaganova 2012; Kaygorodova and Utevsky 2012; Kaygorodova and Pronin 2013, Kaygorodova et al. 2013, Kaygorodova and Mandzyak 2014, Kaygorodova and Sorokoivikova 2014, Kaygorodova and Petryaeva 2014). Despite a recent surge of interest, the study of Baikal hirudinids is still in its infancy and, at the very least, there is a need for a provisional checklist as a starting point for further study. The present paper aims to provide such a list for the Maloe More Strait, a special part of Lake Baikal.

The data included here are based on previously published records and additional field investigations from 2002–2014. Collected material has been deposited in the laboratory of Molecular Systematics, Limnological Institute SB RAS, Irkutsk, Russia. The list provides morphologic and taxonomic notes where needed, as well as distribution ranges of genera and species. The accepted modern names of the type species of genera are provided. The systematic arrangement at family and more inclusive levels is based on the currently accepted classification system. Within this paper, family, subfamily, genus and species names are arranged alphabetically. The checklist includes 14 species and subspecies along with several new distribution records, including four endemic species, and six potential new species.

Previously published information and an extensive collection of specimens, collected by the author in the period from 2002 to 2014 were used in this paper. Most of the specimens came from the task-oriented expedition on the Maloe More Strait which was undertaken in 2013. All sampling locations are shown in Fig. 1. Since the usual hydrobiological equipment (sweep net, dredge, scraper, bottom grab, etc.) is often less effective in procuring leeches than searching for many other aquatic invertebrates in order to catch parasitic and predatory leeches we inspected various aquatic plants and animals as well as different underwater objects (rotten wood, driftwood, snags, stones, etc.), to which hirudinids can be attached. Some leeches were picked out from zoobenthic samples. In most cases piscine and endemic flat leeches (glossiphoniids) were gathered directly in captured living hosts. Fish, molluscs and amphipods were collected by scuba divers at a depth of 2–42 m and by dredge or fishing gear at 30–200 m.

Figure 1. 

Map of the Maloe More Strait of Lake Baikal. Red dots indicate leech sampling localities: 1 Tutay Bay 2 Sakhurte Bay 3 Olkhon Gates Strait 4 Kurkut Bay 5 Ulirba Bay 6 Mukhor Bay 7 Shide Bay 8 Khuzhir-Nugho Bay 9 Khuzhir-Nugho Bay against of Sarma village) 10 Sarma River 11 Mukhor-Khale Bay 12 Khagden-Khale Bay 14 Kurma Bay 15 Otto-Khushun Bay 16 Lake Surkhaytor-Hur 17 Lake Zunduk 18 Zunduk Bay 19 Codoviy Bay 20 Lake Zama 21–24 Northern transit of the Maloe More 25 Cape Khoboy 26 Nyurgon Bay 27 Kharansa Bay 28 Odonim Bay 29 Khuzhir Bay 30 Elgay Bay 31 Lake Khankhoy 32 Shibetey Bay 33 Semisosennaya Bay 34 Khargoy Bay 35 Kharin Irgi Bay 36 Khul Bay 37 Zagli 38 Lake Nur 39 Ushun Bay.

Newly collected specimens were photographed alive, placed in separate vials, fixed and kept in 80% ethanol solution. Current systematic keys (Lukin 1976, Epstein 1987, Nesemann and Neubert 1999) and several original taxonomical descriptions (Lukin and Epstein 1960a,b; Dogiel and Bogolepova 1957) were used for species identification. Morphological analysis was conducted using a stereomicroscope MSP-2 var. 2 (LOMO). All images were taken with a camera NIKON D700. All voucher specimens were deposited at the Laboratory of Molecular Systematics, Limnological Institute, Russia.

This is the first comprehensive checklist of the Baikal leech species inhabiting the Maloe More Strait. At present, 14 species are documented. This species diversity includes both widespread Holarctic and Palaearctic leeches and also endemic leech species from two different orders (Rhynchobdellida and Arhynchobdellida), three families (Glossiphoniidae, Piscicolidae, and Erpobdellidae) and nine genera. The most diverse is the group of glossiphoniid leeches, which consists of nine species belonging to six genera (Alboglossiphonia – 2 spp., Glossiphonia – 2 spp., Helobdella – 1 sp., Hemiclepsis – 1 sp., Theromyzon – 2 spp., Baicaloclepisis – 1 sp.). The Maloe More piscine leeches include representatives of two endemic genera (Baicalobdella – 2 spp. and Codonobdella – 1 sp.). Among the Arhynchobdellida, two species of the genus Erpobdella were found in the Maloe More. Six species in the checklist, including both representatives of Erpobdella, two of Glossiphonia, as well as one each from Theromyzon and Codonobdella were referred in this paper, with caution, to unidentified species since their morphology differed from all currently described species. With high probability, these six non-identified species are potentially new to science. All six of these, for the first time were recorded within the Maloe More. Some of these new morphotypes had previously been found in other parts of Lake Baikal. Thus, leeches similar to Erpobdella sp. 1 had already been reported from Chivyrkuy Bay (Kaygorodova 2012, 2013; Kaygorodova and Pronin 2013), whereas unidentified piscicolids Codonobdella sp. had been found throughout the lake (Kaygorodova 2012, 2013).

This study was financially supported by the Russian Foundation for Basic Research (RFBR) grant nos. 11-04-01394, 12-04-10007, and 14-04-00345. The author is grateful to Natalya Sorokovikova and Lyudmila Fedorova for support of the field work. Professional divers Igor Khanaev and Alexey Bormotov assisted us in obtaining samples from inaccessible places (for hydrobiological tools).