Morfologia e distribuição das espécies de Helicinidae Férussac, 1822, na Ilha Grande, Angra dos Reis, Rio de Janeiro

Abstract

Helicinidae is a family of operculate land gastropods distributed in different regions of the world: South, Central and North America; West Indies; North and West Indian Islands; Indopacífic, Australia and parts of Eastern Asia. The species of this family are able to inhabit different environments and are often found on islands. In Brazil, where probably there is a great diversity that remains unknown, this group lacks detailed studies. For Rio de Janeiro state were mentioned eight species for the family, but there were others species, distributed in different localities, that remain unidentified. Ilha Grande, located in the Municipality of Angra dos Reis, is covered by remnants of Atlantic Forest, a biome considered as threatened, where several species of land snails were recorded including species of this family. Therefore, the main objectives of this study were to identify the species of Helicinidae present on Ilha Grande; compare morphological of shells, internal morphology (reproductive system and radula) and make distribution map of the species of Helicinidae to this study locality. Studied material included samples at the Molluscs Scientific Collection of UERJ and sample collected at different locations on Ilha Grande and at the permanent plots of RAPELD-Ilha Grande, East Module. We study the shell observing the morphology and morphometry, checking linear and angular measurements number of whorls and relationships between the variables. The radula was prepared for observation under scanning electron microscope and specimens were dissected to analyze the female and male reproductive systems. In this study, we found four species, two of the genus Helicina Férussac, 1799 and two of Alcadia Gray, 1840, which have different characters from other species Helicinidae already described for Rio de Janeiro, representing new species still undescribed. They are distinguished externally mainly by the shell shape and protoconch sculpture. Regarding the internal morphology, the principal differences were found in the female reproductive system: bursa copulatrix shape and provaginal sac and, in the radula: rachidian and first laterals teeth shape. The morphometric study also contributed significantly to the discrimination of the species studied. The occurrence of Helicina inaequistriata Pilsbry 1900, Helicina lundi Beck, 1858 and Helicina hispida Hylton Scott,1970 were not confirmed for study area. The species studied are widely distributed on Ilha Grande, from disturbed areas with human presence to inaccessible places preserved in gradients ranging from 0 to 700m altitude