Ancylidae (Mollusca, Heterobranchia, Pulmonata, Basommatophora) do Estado do Rio de Janeiro, Brasil: morfologia, sistemática e distribuição geográfica

Abstract

The pateliform freshwater molluscs of the Neotropical region are commonly attributed to Ancylidae sensu latum, comprising seven genera with at least 13 valid species and seven with dubious identification. Ancylids are small, reaching up to 15 mm length. The shell is fragile, composed of two regions: protoconch and teleoconch, which microsculpture, which is relevant to systematic. In the soft part mantle scars, pigmentation of mantle, radula and reproductive system are important for the study of the family. There are several records of occurrence of ancylids in the State of Rio de Janeiro (SRJ) but few morphological data. The main objective of this study was to provide and expand morphological and geographical information about Ancylidae species found in the SRJ. The materials were come from own collections, material deposited in scientific collections and data for review. A comparative study of shell morphology was carried out by light and scanning microscope images. To compare the soft parts, specimens were stained and dissected under a research stereomicroscope. Interpopulation and intrapopulation variation were studied by shell morphometric analysis. The richness of Ancylidae in SRJ were increased from five to seven species: Burnupia sp., Ferrissia sp., Gundlachia radiata (Guilding, 1828), Gundlachia ticaga (Marcus & Marcus, 1962), Gundlachia sp., Hebetancylus moricandi (d`Orbigny, 1837) e Uncancylus concentricus (d`Orbigny, 1837). Gundlachia radiata and U. concentricus are new records for SRJ, and G. radiata to Southeast Brazil. The most frequent three species in SRJ were: G. ticaga (66%), Ferrissia sp. (37%) and Gundlachia sp. (18%). The wide distribution of G. ticaga may be due to the ability to survive in impacted environments. With respect to morphology, the single Burnupia species described from Brazil, Burnupia ingae Lanzer, 1991, differs from Burnupia sp. in shell microsculpture and also in the shape of muscle scars. Ferrissia sp. differs from F. gentilis Lanzer, 1991, due to differences in apical microsculpture and number of cusps on radula central tooth. Gundlachia sp. is different from G. ticaga and G. radiata, by presenting the shell opening rounder, more curved apex surpassing the edge of the shell, irregular punctuations across whole protoconch and the more elliptic right anterior and posterior adductor muscle scars. The morphology also shows differences between Gundlachia sp. and G. ticaga, as the terminal appendix of the uterus and the number of follicles of ovotestis. Shell morphometric analysis found that the indices provided better discrimination of species than the linear measurements to Burnupia, Ferrrissia and Gundlachia, probably because these indices decrease the effect of the shells size range that are strongly influenced by ecophenotipics variations. However, the diagnostic characters of the shells (microesculpture apical) and soft tissue (muscle scars and mantle pigmentation) are essential to identify genera and species of Ancylidae. Keywords: Mollusca. Freshwater snails. Morphology. Geographic distribution. Rio de Janeiro State. LISTAe pateliform.