Resposta rápida de Leptinaria unilamellata (d’Orbigny, 1835) (Gastropoda: Subulinidae) a condições ambientais, em gerações sucessivas de laboratório: efeito materno e antagonismo entre resistência à dessecação e sucesso reprodutivo

Abstract

There is evidence of the relation between shell morphology and environmental pressures. However, it is not known whether the mechanisms responsible for the shell shape variability results from phenotypic plasticity, genetic determination or even to maternal effect. Some studies address just shell aspects and disregard the relation among shell morphology, protection against desiccation and reproduction. Thus, the present study has two main aims. The first aim is to investigate whether the existence of two morphological patterns (rotund shells and elongate shells) found in Leptinaria unilamellata the antagonism between protection against desiccation and reproductive success. The second one is to find the answer to the following question: what is the role played by phenotypic plasticity in these two patterns? A morphometric study comparing two populations derived from successive laboratory generations was performed to find such answer. In addition, the number of progenies produced by each individual born in the first reproductive event in each generation was quantified. The mollusks were subjected to two treatment conditions to investigate the effect of desiccation on shell morphology over successive generations. The results of the present study confirmed the hypothesis that the morphometric variables influencing the body whorls’ shape and the shell opening size have also influenced the species’ reproductive success. The morphometric variables between the two populations became less evident throughout the successive laboratory generations, thus showing the fast-adaptive response of Leptinaria unilamellata resulting from the maternal effect. The highest progeny production was found in the population of Chácara in all generations, wherein the rotund shape determined the presence of body whorls and larger openings, which enabled oviduct expansion. The results have also shown that mollusks presenting more elongated shells and smaller openings do not invest in large progenies.