Anatomical differences among specimens of Pinctada imbricata Rí­¶ding, 1798 from different South American localities

Abstract

In the present study, we compared the internal and external anatomy of pearl oyster (Pinctada imbricata Rí­¶ding, 1798) from some South American localities, including Venezuela and several regions of Brazil. The anatomical data shows non-geographical variations characterized by variable outline in adults, different degrees of posterior auricle shell development and mantle papillae ranging from normal to digitiform. The geographical variations can be divided into two major groups: the Venezuelan group presents a more folded mantle; pallial muscle grouped in anterior and median-posterior sets; poorly-developed perpendicular mantle groove; and inner lamella not extended into the anterior mantle. Brazilian group specimens present a smoother mantle, with less clear separation between anterior and posterior mantle muscle groups; externally-developed perpendicular groove; and inner lamella extension developed in anterior mantle. These differences may represent ecophenotypes or differences among isolated South American populations, which may be elucidated by subsequent phylogeographic studies.