HISTOLOGICAL EFFECTS OF 3-TRIFLUORMETHYL-4-NITROPHENOL (TFM) ON LARVAL LAMPREY AND TROUT

Abstract

Larvae of the lamprey, Entosphenus lamottei (Le Sueur), and rainbow trout, Salmo gairdneri Richardson, were exposed to the sodium salt of 3-trifluormethyl-4-nitrophenol (TFM) in concentrations of 0.75 p.p.m., 3.00 p.p.m., and 6.00 p.p.m. Microscopic examination of changes induced in the gills, liver, cloacal region, and musculature were made on 7-micron sections stained with Harris' haematoxylin and Bowie's eosin, and in the gill region with periodic acid Schiff reagent. A comparison of the degree of the effects in the two species was made by planimetry of the vascular, cellular, and edematous areas from enlarged drawings of sections.Upon exposure to lethal concentrations of TFM, the body of the larval lamprey becomes distended at the pharyngeal level and heavy cords of mucus emerge from the external gill clefts. A deep red coloration is evident in the pharyngeal region consequent upon vasodilatation of the arterioles and capillaries of the gill filaments. Trout exhibit a similar vasodilatation of the gills together with increased mucous secretion. Edema in the connective tissue between the respiratory epithelium and the vascular endothelium is induced in both species. After prolonged exposure to TFM, the mucous cells in the lining of the branchial chamber and covering the tips of the gill filaments are actively discharging their secretions or completely spent.Certain effects induced by TFM in the larval lamprey are not evident in the trout. The cloacal region takes on a deep red coloration due to dilatation of the venous sinuses and the liver becomes reddish because of sinusoidal dilatation. Extensive edema of the fibrous connective tissue of the skeletal musculature is characteristically present. A slightly increased secretory activity of mucous-secreting cells may occur in the epidermis.With the techniques employed in this study, there was no evidence in either species of cytological or histological changes in the nervous tissue, cardiac musculature, notochord, alimentary canal (including the haemopoietic typhlosole of the lamprey), or mesonephros.