Variability in the sculpture of the shell aperture of Ruthenica filograna (Rossmassler, 1836) (Gastropoda: Clausiliidae) in specimens from natural populations and from laboratory breeding

An analysis of variability in the sculpture of shell apertures was carried out for 1,087 specimens of Ruthenica filograna from 33 localities and for 20 laboratory-bred individuals reared from parents from a single locality. Nine patterns of aperture sculpture were distinguished. There are usually two kinds of sculpture: with one plica in the aperture being an extension of the inferior lamella, and without plicae in the aperture. Sporadically, the subcolumellar lamella may be connected with the lip of the aperture by a plica. Additional plicae occur in the aperture only rarely. All populations examined showed variations in the number and arrangement of plicae. The coefficient of variation in the number of plicae in the shell aperture ranged from 32.6% to 121.8% within localities. No consistent relationship was found between the geographical location and the shell sculpture pattern. Specimens bred in the laboratory developed shell apertures with a variety of sculptural patterns, including one present neither in the parents, nor in the population from which it came. This characteristic is probably phenotypically plastic. It cannot be used for taxonomic purposes, and it is suggested that great caution is needed before using similar characters in other species.