The fauna of annelid worms (Oligochaeta, Hirudinea) of the Naroch lakes system (Belarus)

Study Extent

The first review of the fauna of the oligochaetus of the lakes of Belarus was carried out in 1947-48. N.L. Sokolskoy (Sokolskaya, 1953). For eight lakes, 38 species of oligochaetes were indicated, of which directly in Lake Twenty-four species were noted. Later, 1972 N.P. Finogenova and in 1978 S.I. Gavrilov (Ecologicheskaya systema..., 1985) expanded the species lists of oligochaetes for the lakes Naroch, Miastro and Batorino. The total composition of the Oligochaeta fauna of the lakes of the Narochanskaya system, including the literary and authors own data, is represented by 48 species and forms above the species rank, 35 of which are noted in modern collections (1997-2018). Since 1997, only 5 species have been recorded in all three lakes: Limnodrilus hoffmeisteri Claparède, 1862, L. udekemianus Claparède, 1862, Potamothrix hammoniensis (Michaelsen, 1901), Psammoryctides barbatus (Grube, 1861), Lumbiculus varielatus (1761). Previously, the share of common species, including meiobenthos, between lakes was 47%. As a result of the leech specimens analysis, the species composition of the Naroch hirudofauna was significantly expanded in comparison with previous data (Shalapenok 2003). At present, 21 species belonging to two orders have been identified. The jawless leeches (Rhynchobdellida Blanchard, 1894) are represented by 14 species belonging to the two families - Glossiphoniidae Vaillant, 1890 and Piscicolidae Johnston, 1865. Among the gnathic or jaw leeches (Arhynchobdellida Blanchard, 1894), there are representatives of 7 species belonging to three families - Erpobdellidae Blanchard, 1894, Haemopidae Richardson, 1969, and Hirudinidae Whitman, 1886. Together, species list represent 10 genera. A representative of Hirudo Linnaeus, 1758 was first identified for Lake Naroch and Belarussia as a whole.

Sampling

Oligochaete samples were taken with a grab (sampling area 0.25 m2) on soft bottoms and with a handle blade trawl (Zinchenko et al. 2014) on gravel bottoms. Since the common hydrobiological equipment (sweep net, dredge, scraper, bottom grab, etc.) is often ineffective in collecting parasitic and predatory leeches, we inspected various aquatic plants and animals, as well as submerged objects (rotten wood, driftwood, snags, stones, etc.) for attached hirudinids. Some leeches were picked out from zoobenthic samples. Newly collected specimens were fixed and kept in 80% ethanol solution. Faunistic collections and observations were carried out along the coastline of Lake Naroch in June 2018. Leeches were sampled at depths from the water edge to depth of 0.8 m, where there is different aquatic vegetation like as reed, elodea, teloresis, coontails, pondweed and brittleworts. A handle blade trawl was used on soft and gravel substrates, with the trawling distance about 1 m. Macrophytes and submerged objects (stones, driftwood, rotten tree trunks, etc.) were visually examined, then found leeches were collected manually.

Method steps

1. Morphological analysis specimens was performed using a LOMO MSP-2 var. 2 stereomicroscope and compound microscope Leica DM 4000. Leech and oligochaetes species identification was based on available taxonomic keys (Chekanovskaya 1962; Lukin 1976; Nesemann & Neubert 1999; Timm 2009) with accordance of modern classification system. The material is deposited in the collection of the Limnological Institute, Irkutsk, (Hirudinea) and Institute of Biology, Syktyvkar, Russia (Oligochaeta).

This dataset provides current data on annelid fauna of three lakes: Naroch, Myastro and Batorino (Belarus) and consists of 56 species, including 35 oligochaete species and 21 leech species

1. Animalia
   rank: kingdom
2. Annelida
   rank: phylum
3. Clitellata
   rank: class
4. Hirudinea
   rank: subclass
5. Oligochaeta
   rank: subclass
6. Arhynchobdellida
   rank: order
7. Enchytraeida
   rank: order
8. Lumbriculida
   rank: order
9. Rhynchobdellida
   rank: order
10. Tubificida
    rank: order
11. Enchytraeidae
    rank: family
12. Erpobdellidae
    rank: family
13. Glossiphoniidae
    rank: family
14. Haemopidae
    rank: family
15. Lumbriculidae
    rank: family
16. Naididae
    rank: family
17. Piscicolidae
    rank: family

Naroch (54°51'18.24"N; 26°46'1.03"E); Myastro (54°52'0.91"N; 26°52'49.86"E) Batorino (54°50'47.94"N; 26°58'3.36"E) The system of Naroch Lakes is situated in the Northwestern Belarus in the Neman River basin and includes the following water bodies: Lake Batorino, Lake Myastro and Lake Naroch. Lakes are interconnected by channels. The lakes are polymictic. Lakes have different surface area but similar morphometric features, including the relatively small average depth, resulting in intense mixing of waters. The surface of the Naroch Lakes is completely frozen during the period from the late November to April. The greatest depths were noted in the profundal zones of the lakes (5.5 - 20.0 m), in contrast to the littoral, more shallow (0.1 - 2.0 m) zones. The maximum depths (about 25.0 m) were recorded in the lake Naroch. In the lake Batorino to a depth of 1.5 m spreads higher aquatic vegetation and covers 19.6% of the total bottom area. In the lake Naroch the lower boundary of macrophyte distribution is 7 m (about 42.0% of the total bottom area). In the lake Myastro, due to the lower transparency of the water, vegetation is spread up to 4-5 meters, covering more than 30.0% of the bottom. For these lakes from 1997 to 2018 the trophic status did not change and was determined: Naroch - oligo-mesotrophic, Myastro - mesotrophic, Batorino - eutrophic.