Ultrastructure of the gill ciliary epithelium of Limnoperna fortunei (Dunker 1857), the invasive golden mussel.

Abstract

Background: Limnoperna fortunei is a freshwater bivalve mollusc originally from southern Asia that invaded South

America in the 1990’s. Due to its highly efcient water pumping and fltering, and its capacity to form strong adhe- sions to a variety of substrates by byssus thread, this invasive species has been able to adapt to several environments

across South America, causing signifcant ecological and economic damages. By gaining a deeper understanding of the biological and ecological aspects of L. fortunei we will be able to establish more efective strategies to manage its invasion. The gills of the mollusc are key structures responsible for several biological functions, including respiration and feeding. In this work, we characterized the ultrastructure of L. fortunei gills and its ciliary epithelium using light

microscopy, transmission and scanning electron microscopies. This is the frst report of the morphology of the epithe- lial cells and cilia of the gill of L. fortunei visualized in high resolution.

Results: The analysis showed highly organized and abundant ciliary structures (lateral cilia, laterofrontal cirri and fron- tal cilia) on the entire length of the branchial epithelium. Mitochondria, smooth endoplasmic reticulum and glycogen

granules were abundantly found in the epithelial cells of the gills, demonstrating the energy-demanding function of these structures. Neutral mucopolysaccharides (low viscosity mucus) were observed on the frontal surface of the gill flaments and acid mucopolysaccharides (high viscosity mucus) were observed to be spread out, mainly on the lateral tract. Spherical vesicles, possibly containing mucus, could also be observed in these cells. These fndings demonstrate the importance of the mucociliary processes in particle capture and selection. Conclusions: Our data suggest that the mechanism used by this mollusc for particle capture and selection could contribute to a better understanding of key aspects of invasion and also in the establishment of more efcient and economically viable strategies of population control.