In Eastern Siberia, specifically in the Olekma region in the south of the Republic of Sakha (Yakutia), a population of Fruticicola transbaicalia transbaicalia was discovered (Schileyko, 1978). The mollusks were collected by P. D. Gabyshev and P. R. Nogovitsyn at the foot of the steep slope along the bank of the Chara River at the confluence of the Tokko River. The Chara River flows into the Olekma River, which is a right tributary of the Lena River. The found population is the most northeastern point of the range of F. t. transbaicalia. The species inhabits a clayey rocky slope composed of carbonate rocks. On the slope there is a sparse pine forest with an undergrowth of Juniperus sibirica and Phlojodicarpus sibiricus. The moss-lichen layer is poorly developed, the grass-shrub cover is sparse, represented by Dasiphora fruticosa and Sanguisorba officinalis. The overall dimensions of the shells correspond to those of B. t. transbaicalia, previously indicated for this subspecies. All shells have four lines, indicating growth pauses in the autumn-winter periods, suggesting that the snails experienced five winters before reaching sexual maturity and complete shell formation. The only live juvenile snail found displays dark brown coloration at the anterior end of its body and tentacles. The body of the mollusk visible through the shell is mottled. It determines the snail’s coloration. Research in recent years has cast doubt on the species independence of F. transbaicalia. Analysis of the distribution of these species in Yakutia can contribute to resolving this controversial issue.
Fruticicola transbaicalia transbaicalia (Schileyko), terrestrial mollusks of the Republic of Sakha (Yakutia), fauna of Siberia
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