A scanning electron microscopic study of secondary lamellae and chloride cells of rainbow trout (Salmo gairdneri)

Summary Scanning electron micrographs of gill tissue from rainbow trout fixed with 50% glutaraldehyde revealed the presence of microridges on surfaces of epithelial cells of the secondary lamellae. These microridges vary in length from 1 to 7 , with a mean height of 0.75 . Calculations show that they increase the total lamellar epithelial surface area approximately 2.5 fold. Mucus secreting cells are present on the body of the filament and on secondary lamellae. Chloride cells are located primarily in the interlamellae filamental epithelium and on the basal area of lamellae. Extensions of the chloride cell epithelium are microvillous in nature and their height is only slightly greater than that of the microridges of typical lamellar epithelial cells. A reduction in number or complete absence of microvilli on chloride cells appeared to be related to degenerative changes in these cells observed in transmission electron micrographs. Non secretory interlamellae filamental epithelial cells have microridges of very attenuated lengths.This research was supported by EPA Grant R-801034, USPHS Training Grant HL-05873, the Mich. Agr. Exp. Sta., Proj. 122 (Journal Article No. 5801), and OWRR Grant A-064.Acknowledgements: The authors wish to express their gratitude to Mrs. J. Mack and Mr. Wm. McAffe for their technical assistance with the electron microscopes.