Two new nematode species of the genus Tobrilus Andrássy, 1959 (Nematoda, Triplonchida) from Lake Baikal, Russia

Tatyana V Naumova,Vladimir G Gagarin

doi:10.5852/ejt.2019.579

Abstract

Two new nematode species of the genus Tobrilus Andrássy, 1959 from Lake Baikal are described and illustrated. The first species Tobrilus elginus sp. nov. was found in the littoral zone of Maloye More Bays. The second species Tobrilus juliae sp. nov. dwells on bodies of dead sponges Lubomirskia baicalensis (Pallas, 1776). Tobrilus elginus sp. nov. is most similar to T. amabilis Tsalolikhin, 1974 and T. bekmanae Tsalolikhin, 1975. In contrast to the first species it has a shorter body and spicules, longer gubernaculum and a shorter supplements row. Its body is shorter and thinner, tail and supplement row are shorter and the vulva is more posterior as compared to the second species. The body size of Tobrilus juliae sp. nov. is most similar to T. securus Gagarin & Naumova, 2011 and T. saprophagus Naumova & Gagarin, 2017. From the first of these species it differs by the thinner body, shorter tail, comparatively shorter outer labial setae and shorter spicules. It differs from the second species by a thinner body, shorter male tail and shorter labial setae.

Highlights

Lake Baikal is a fascinating freshwater reservoir known all over the Earth
The aim of this paper is to describe two new nematode species inhabiting Lake Baikal: T. elginus sp. nov. and T. juliae sp. nov
Half of the species in the genus Tobrilus (12 of 22–24 valid species) are inhabitants of Lake Baikal where they are encountered in the depth range of 0 to 1520 m, as well as in the splash zone (0.5 m above the water edge)

Summary

Introduction

Lake Baikal is a fascinating freshwater reservoir known all over the Earth. Its shores and pure, crystal clean water attract numerous tourists as well as experts and researchers. In 1996, UNESCO announced Lake Baikal a World’s Heritage Object. Unique environments of the Lake inevitably provided favourable conditions for the formation of an abundant and diverse fauna including over 2600 species with a high level of endemism (more than 56%) (Timoshkin 2001). The fauna of free-living nematodes comprises 114 species in 32 genera, 16 families and 8 orders according to the latest records (Naumova & Gagarin 2019). These worms are encountered in rocky, sandy and silty substrates occupying all depths from the splash zone (above the water edge) to the abyssal zones. Nematodes often dominate among other benthos groups

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