CONICET | Buscador de Institutos y Recursos Humanos

In Argentina freshwater crustaceans decapods are grouped into 4 families: Sergestidae, Palaemonidae, Parastacidae, Aeglidae, Trichodactylidae. The diversity and distribution of these families is the results of evolution where intrinsic and/or extrinsic factors have acted. This work is presented as a synthesis of morphology and molecular studies in a biogeographical context of different taxa to elucidate the actual evolutionary situation. All these aspects continued being studied (morphological) and new (molecular) evidences are added with the objective of finding new pieces of the puzzle concerning the evolution of the freshwater decapods. The geometric morphometrics is a relatively new tool to study shape and size. This technique combines the geometry, the statistics and the biology, allowing the traditional methods based on distances and measures to be replaced by geometric approaches. The analysis of the populations genetic structure has become an useful tool since the existent genetic variability is related to the dynamics of ecological and behavioral variables in wild populations. The measurement of variation at DNA level may allow us to predict the behavior of local populations over time since a considerable level of variation increases the ability of the species to adapt to environmental changes. Populations of Aegla platensis, A. scamosa, A. riolimayana, A. uruguayana, A. neuquensis, and A. affinis (Family Aeglidae) and Trichodactylus borellinauns and T. kensleyii (Family Trichodactylidae) were studied. The geometric morphometrics approach was carried out, exclusively, using landmarks and semilandmarks. Then, the analysis of the shape was carried out principally using the TPS software package. The selection of the landmarks was different for each species, so that different configurations of landmarks and semilandmarks were explored and used. For each analysis relative warps were obtained in an exploratory way. Finally the analysis of shapes of the cephalothorax was conducted as a whole and for some species of Aeglidae considering it as a modular structure. The statistical methods used were uni- and multivariate. It is well known that a population can present an unique gene combination and the genetic structure of a set of reproductively isolated populations can mutually diverge. In this way we have analyzed the genetic structure of different populations of Aegla singularis and Aegla uruguayana. The genetic variation between populations was assessed by using RAPD analysis. The results showed that the populations exhibited different shape patterns. A. scamosa, A. riolimayana and A. uruguayana presents clinal patterns while in A. platensis this pattern was not observed in relation to the distribution of populations. A. riolimayana and A. neuquensis populations presented distributional patterns associated to pseudo-crabs inhabiting rivers vs. those living in lakes. Regarding crabs, T. borellinauns presents different shapes considering a metapopulation structure and environmental parameters in the ventral region but not in the dorsal. T. kensleyii specimens from different basins did not exhibit statistical differences in shape. Molecular analyses considering two populations of A. singularis (from the different basin) showed no population differentiation. However, high levels of polymorphism were found in one population (Pesiguero stream) unlike another (Coaty stream). The same analysis was performed considering 3 populations of A. uruguayana from the same metapopulation. In this case, we found significant differentiation among populations. Genetic distance is possibly due to, a clinal pattern related to colonization events. In this context, through interpretation of data which have long been working together with the incorporation of new tools we began to reinterpret the evolutionary aspects of the freshwater decapods from Argentina and South America.