Terrestribythinella baidashnikovi Sitnikova, Starobogatov & V. Anistratenko, 1992

Anistratenko, V. V., Furyk, Yu. I., Anistratenko, O. Yu. & Degtyarenko, E. V., 2019, A Review Of Species Diversity, Distribution And Ecology Of Freshwater Gastropod Molluscs Inhabiting The Ukrainian Transcarpathian, Vestnik Zoologii 53 (5), pp. 349-374 : 361

Terrestribythinella baidashnikovi Sitnikova, Starobogatov & V. Anistratenko, 1992

D i s t r i b u t i o n. This regionally endemic species for a long time was known from a few localities in the Transcarpathian Region ( Sitnikova et al., 1992). The only one population recently found extra — in the adjacent Ivano-Frankivsk Region ( Anistratenko et al., 2017: shell image is given in fig. 3 , I–K). By now T. baidashnikovi is recorded in 17 localities of Transcarpathia: 4, 5, 19, 28, 31, 35–37, 41, 47, 49, 52, 54, 57–59 and 61 ( fig. 1 , table 1 ).

Remarks. Judging by the number of records the species is one of the most widespread snails in the region occuring in the altitude range between 300 and 1100 m a. s. l. (table 2), although they produce the populations of a very low density. Our observations confirm these small gastropods inhabit here in quite particular biotopes: they live rather under and among the litter leaves on banks of water flows than in the water. Riverine biotopes are not characteristic for the species. Few findings in the rivers were made at the mouths of streams, and these molluscs were not observed upstream and downstream of the rivers. Terrestribythinella hold an intermediate position between terrestrial and freshwater environments and apparently do not require significant amounts of liquid water for their existence. It seems they are neither strictly terrestrial, nor strictly water molluscs. This hidden under the leaves biotope is actually amphibiotic and therefore is usually poorly explored by malacologists who collect either freshwater molluscs or land snails. Occurring of Terrestribythinella snails sympatric with terrestrial gastropods on the wet litter leaves or stones reflect their putative amphibiotic ecological preferences ( Sitnikova et al., 1992; Anistratenko, 1995; Anistratenko et al., 2017). Interestingly, Terrestribythinella , inhabiting mostly springs and streams, sometimes forms a monospecific mollusc community. This can be proved by finding the caddisfly Crunoeсia irrorata (Curtis, 1834) larva with a case built entirely of beech leaves and 22 living snails of Terrestribythinella ( Martynov et al., 2018) .

Figures

Fig. 3. Shells of Transcarpathian gastropod molluscs: 1 — Viviparus viviparus (locality 12); 2 — Contectiana contecta (locality 15); 3 — Viviparus sphaeridius (locality 12); 4 — Bithynia tentaculata (locality 15); 5 — Valvata (Cincinna) ambigua (locality 15); 6 — Bithynia troschelii (locality 13); 7 — Valvata (Cincinna) piscinalis (locality 22); 8 — Lithoglyphus naticoides (locality 9); 9–11 — Planorbis planorbis (locality 15); 12, 13 — Planorbarius corneus (locality 15). Scale bars are given for 1–3, 4–8, and 9–13 correspondingly.

Fig. 1. Map showing the localities of samples studied. Details for each sampling point are given in table 1.