Structure and density population of the invasive mollusc Limnoperna fortunei associated with Eichhornia crassipes in lakes of the Middle Paraná floodplain

Abstract

<p>The roots of <em>Eichhornia crassipes</em> provide different microhabitats for invertebrates, including substrate for the Asian invasive bivalve <em>Limnoperna fortunei</em>. This work evaluated the density and size structure of <em>L.</em> <em>fortunei</em> on the roots of <em>E. crassipes</em> in lentic waterbodies associated with the Middle Paraná floodplain. The field work was carried out between November 2009–2010, covering different phases of the hydrological regime. Floating meadows of <em>E. crassipes</em> were sampled monthly in two lakes with different degrees of connection to the main channel of the Paraná River. Bivalve densities were not associated with variations of the biomass of <em>E. crassipes </em>roots and the highest mussel densities were recorded during months of high temperature. The maximum size recorded in both lakes corresponded to individuals approximately 2.5 years old; however, up to 75% of the molluscs were represented by pre-reproductive individuals (up to 6 months old). In these lakes with soft bottom and limited hard substrates, <em>E. crassipes</em> is an important site for the mussel attachment during its early stages of development and could not be the final site of settlement during its lifecycle.</p>