CONICET | Buscador de Institutos y Recursos Humanos

The Aeglidae family had its origin in freshwater environments 74 million years ago approximately. From that, the species in the family has suffered continuous environmental changes. In the present work we present a hypothesis about de carapace structure and their role in the evolution of the family. The structure selected was the carapace due to the multiple interpretations of its interaction in decapods. In addition to the fact that its shape is a distinctive feature of the taxa, species presents lines and grooves whose origin and function are still under debate. This pattern of lines and grooves divides the carapace into discrete units (modules), and appear as an autapomorphy of a genus of uncertain origin and functions. Some authors discuss the function for such lines and grooves as representative of evolutionary ancestral limits, whereas others put forward that some carapace grooves in decapods are secondary structures. Specimens of different species of the Aeglidae Family were photographed and 31 landmarks were selected representing the carapace whose was divided into 5 modules according the lines and grooves. The modules were compared among them intraspecifically and interspecifically and different degrees of variation were observed. Intraspecific analysis reveals that the modules, corresponding to anterior region of the pseudocrabs, present greater variation than those of the posterior region of the carapace. While interspecifically, the pattern of shape variation are the same and statistical significance were observed among the same modules. Then, the evidence analyzed could be interpreted as modules like by product of adaptation in changing environments or exaptation to other functional structures, as different pressures of others appendices or internal organs.

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