Rodlet cells from the gills and kidneys of two brazilian freshwater fishes: an ultrastructural study

ABSTRACT

Rodlet cells (RCs) are fish cells considered to be regulatory elements, ion transportation cells, secretory cells, parasitic cells, transport units of genetic material, non-specific immune cells and endogenous in nature cells. In this report, we describe the ultrastructure of RCs collected from the gills and kidneys of two species of freshwater teleosts (family Curimatidae) in Brazil Curimata macrops Eigenmann & Eigenmann, 1889 from the Poty river, near the city of Teresina in the State of Piauí, and Curimata inornata Vari, 1989 from the Amazon river near the city of Belém in the State of Pará. A variable number of RCs was observed in these tissues, with a higher frequency in gills compared to the kidneys. No other organs were investigated. RCs were observed in healthy fish and in fish parasitized by a myxosporean of the genus Henneguya. The RCs consisted of a thick-layered capsule enclosing a variable number of small, dense rodlets surrounded by several vacuoles and a nucleus. The capsule was a cytoplasmic structure composed of thick fibrillar elements surrounded externally by the plasmalemma. The capsule and surrounding plasmalemma had a smooth, undulating surface with several microvilli projecting towards the surrounding cells. Some of the microvilli located in the apical zone of the RCs were in contact with the disorganized microfibrils of the capsules. The nucleus was located laterally or basally and showed condensed chromatin at the periphery. The ultrastructural organization of the apical zone of the RCs suggested that these cells may be involved in secretory functions. This is the first report of RCs in these two species of Brazilian fish.