Abstract
This paper reports on a new species of the Baikal endemic sponge (fam. Lubomirskiidae) Swartschewskia khanaevisp. nov. The description of this species is based on morphological and molecular data (ITS and mitochondrial IGRs). Morphologically, S. khanaevisp. nov. differs from S. papyracea by loose tracts arranged in an irregular network as well as the presence on strongyles of compound spines looking like tubercles densely ornamented with simple spines. Moreover, specimens of S. khanaevisp. nov. show a peculiar structure of the aquiferous system at the body surface that may be an adaptive trait for environmental conditions. Phylogenetic analysis has revealed that S. khanaevisp. nov. forms a well-supported (0.99) monophyletic clade with S. papyracea and is allocated as its sister taxa.
Highlights
Baikal is the most ancient and deepest lake on the Earth with the huge water volume
This study showed that the nucleotide substitution rate of intergenic regions (IGRs) of the Baikal sponge mitochondrial DNA (mtDNA) is significantly higher than coding sequences, which makes them very promising for phylogenetic reconstructions of closely related species (Lavrov 2010, Maikova et al 2012)
The ITS and mitochondrial IGRs sequences were obtained from six specimens of S. khanaevi sp. nov. and two specimens of S. papyracea, which were deposited into GenBank (Table 1)
Summary
The lake is considered to be 25–30 million years old (Mazepova 1995); its maximum depth is 1641 m, and the volume of water body exceeds 23 000 km (Mats et al 2001). Due to these facts, the lake is characterised by minor environmental oscillations.
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