História de vida e variabilidade morfológica e molecular de Leptinaria unilamellata (d’Orbigny, 1835) (Mollusca, Pulmonata, Subulinidae)

Abstract

In this study, were elucidated aspects of life history traits and morphology of the terrestrial gastropod Leptinaria unilamellata (d'Orbigny, 1835). In addition, was verified the occurrence of variability in patterns of shell morphology and shell morphometrics, as well as morphology of the reproductive system of snails from different populations. The life history strategy of L. unilamellata was characterized. We determined growth, reproduction, and longevity patterns of this species and the strategy related to development of embryos were determined. We might conclude from the results that L. unilamellata is a K-strategist species, ovoviviparous, whose life history patterns are determined by the differential allocation of energy for different biological functions, in different stages of life cycle. The reproductive system was characterized in terms of anatomical and histological aspects. The results provided new information about histological morphology of reproductive system of this species, corroborating behavioral aspects, such as simultaneous hermaphroditism and ovoviviparity. We were observed the general pattern of shell morphology of L. unilamellata and its variation among populations from Juiz de Fora, MG; Cruzília, MG, Barra Mansa, RJ, and Floriano, district of Barra Mansa, RJ. To describe the shell growth pattern, was accomplished the study of growth allometry with molluscs of different ages. The relationships between morphometric patterns of the morphotypes demonstrated the presence of two similar groups, one comprising the morphotypes of Barra Mansa and Floriano, and another by morphotypes of Juiz de Fora and Cruzília. The results of the present study clarified the shell growth pattern during the snails’ development, and the relationships between different shell linear variables. There was investigated the morphological variability of the reproductive system of specimens of L. unilamellata from Juiz de Fora, MG; Cruzília, MG, Belo Horizonte, MG, Barra Mansa, RJ and Floriano, RJ. As a result, were found differences in morphology of the reproductive system between molluscs from different populations, especially regarding the penial complex. So, snails from each locality could be recognized as distinct morphotypes. However, such morphotypes could not be distinguished through the molecular profile generated by PCRRFLP. The length of bursa copulatrix, width of epifalo, width of flagellum and width of oviduct were the linear measurements that differed more between snails from different localities and these, therefore, are the variables with greater strength for the distinction of morphotypes. The results of the morphological and morphometric studies, as well as the Euclidean analysis and cluster analysis, confirmed the greatest similarity between the 11

morphotypes from Barra Mansa and Floriano, and between morphotypes from Juiz de Fora and Cruzília. The morphology and morphometry of reproductive system of molluscs from Belo Horizonte were more related to those of the last two morphotypes. The patterns of similarity resulting from discriminant analysis confirmed these results. The variations were observed mainly in organs of the proximal region of reproductive system, probably because they are involved in success of mating, and consequently, more exposed to selective pressures. The present study represents a contribution to a better understanding of the reproductive biology of L. unilamellata, focusing on both biological and behavioral aspects, such as morphology of reproductive system and shell. The study of shell morphometrics has been proved to be a useful tool for understanding the pattern of growth of snails over lifetime and also for detection of morphological interpopulation variability. Similarly, knowledge of reproductive system morphology clarified aspects of life history and allowed distinguish morphotypes from different populations. The combination of the different approaches used in this study constitutes a study model that can be used for reach a better understanding about the biology of different invertebrate species.