Comparative Cytogenetic Analysis of Three Stylommatophoran Slugs (Mollusca, Pulmonata)

system is still controversial because phylogeny and systematic relationships at the family level are poorly understood. Besides morphological studies, ribosomal RNA genes and the H3/H4 histone gene cluster (Ambruster et al., 2005; Wade et al., 2006) have also been used to resolve the relationships within this order. Recently, by comparison of primary sequence of mitochondrial and nuclear genes, Grande et al. (2004) resolved the Stylommatophora as the early split monophyletic sister group of all the other gastropod taxa. Available data on the cytogenetics of Stylommatophora are extremely poor (reviewed by Patterson, 1969, and Thiriot-Quievreux, 2003) and mostly concern the haploid (n) and/ or diploid (2n) chromosome numbers and karyotype morphology. Vinogradov (2000) determined genome size (GS) and genome base composition in 15 pulmonate species, with