Population differences in the shape of the freshwater prawn Macrobrachium borellii in a river with a floodplain

TORRES V,; GIRI F.; COLLINS P.

San José

Congreso; Summer Meeting THe Crustacean Society; 2013

Universidad de Costa Rica; The Crustacean Society

Hydrological fluctuations in a floodplain system have a modulating effect on the dispersal and presence of decapods in a particular habitat. For freshwater decapods that live in a floodplain, populations move continually within each aquatic environment of the system. These movements can be induced by both biotic and abiotic factors in a dynamic system and occur over different spatial and temporal scales. Morphological variation among populations of the freshwater prawn Macrobrachium borellii in a floodplain system was studied. Geometric morphometrics were used to compare the shape of prawns. Three different configurations of landmarks were digitised: the cephalothorax with rostrum (13 landmarks and 3 semilandmarks), the cephalothorax without rostrum (5 landmarks and 3 semilandmarks) and the rostrum alone (10 landmarks). Also, the environmental variables were measured at each site. The cephalothorax excluding the rostrum was different between sexes in all sites. The Procrustes pairwise permutation tests with CVA showed that the populations that were closest to one another in terms of hydrological distance were not statistically significantly different, but all of these populations were different from the furthest population. The environmental variables were not the best predictors of shape variation. The swimming characteristics of these prawns and their passive movements together with the dynamics of a floodplain system could explain the low morphological variation between populations in this study. The dynamic characteristics of the system allow populations to remain connected influencing the dispersal of the prawns.