New observations on Helicella stiparum (Rossmässler, 1854) (Gastropoda, Pulmonata, Helicidae)

A population of Helicella stiparum (Rossmässler, 1854) from the surroundings of the city of Almeria (Spain) is studied anatomically and conchologically. In comparison with other ten Spanish species of the subgenus Helicella, H. stiparum differs in the presence of a free vaginal neck, the smaller dimensions of the dart sacs relative to the size of the shell and genitalia, and in the shape and the inner structure of the dart sacs complex. The eastern species, Helicella obvia, Hellicelia spiruloides and Helicella pappi, show female anatomical similarities. H. stiparum shares with them some of these characters but differs from these species in the thinness of the vaginal neck, the position of the dart sacs relative to the vagina and the shape of the dart sacs complex. The haploid chromosome number (n=25) differentiates H. stiparum from the rest of the genus Helicella. However, the available knowledge concerning most of the Helicella species does not allow determination of phylogenetic relationships in this group. New anatomical studies and probably the analysis of new characters are needed to clarify the taxonomy of this genus.