Total DNA samples, isolated from several dozen individuals identified on the basis of morphological and anatomical features as Lymnaea stagnalis (L.), Stagnicola corvus (Gmelin), S. palustris (O. F. Müller), S. turricula (Held), and S. occulta (Jackiewicz) were used for amplification of DNA fragments by RAPD. In this way, molecular characters of each individual were identified. Pairwise distances were the smallest (0.0008–0.0188) among conspecific individuals from the same population. Conspecifics from different populations were generally less similar (pairwise distances 0.0177–0.0589). Greater differences were observed among individuals of different species (distances 0.1257–0.6505, i.e. at least 10-fold larger than distances within and between populations). RAPD markers are useful for analyses of taxonomic relationships within the Lymnaeidae. The results confirm the specific status of L. stagnalis, S. corvus and S. occulta. A separate group is formed by S. palustris/turricula, although these two taxa are very similar, and RAPD analysis does not explain if they are distinct species or subspecies.
The results of research on abundance, distribution and structure of the Roman snail (Helix pomatia L.) populations, conducted in 2011 in Podlaskie voivodeship, are presented. All the communes were thoroughly checked in the spring and summer. In 374 sample sites 4,109 individuals of H. pomatia were recorded. The average density for the voivodeship was approximately 0.6 individual per 1 are (= 6 thousand individuals/1 km2). The biomass of adult individuals was estimated at 900 tons. Most of the surveyed local populations were stable or dynamic, characterised by a high proportion of juveniles.