Adherence of Suspended Particles to the Body Surface of Rainbow Trout

Abstract

To determine whether suspended particles adhere to fish, fluorescent latex microspheres, 1μm in diameter, were experimentally administered to rainbow trout fingerlings by bath immersion for 5 minutes. After vital staining in a 0.05% trypan blue solution for 10 minutes, microspheres in the skin and fins were observed in the stained area in a patchy distribution.Histologically, these microspheres were located on the surface of microscopic injuries. It was confirmed by artificial wound experiments that microspheres adhered to the surface of such wounds. By electron microscopy, microspheres were found to adhere to swollen superficial epithelial cells or collagenous matrixes which lack cuticular secretion. In the gills, however, no area stained with trypan blue, but a cluster of microspheres associated with mucus and debris was lodged between the lamellae. We consider that cuticular secretion could prevent particles from adhering to the epidermis of fish.