Surface topography by SEM of Henneguya sp. infecting skin of Synbranchus marmoratus. a: mature myxospore in valvular view showing smooth valve cell with presence of mucous (white star) in a small area and caudal appendage. Scale bar. 1 µm. b: amplified area of the caudal appendage evidencing density of caudal appendage likely to be identical to that of its valve. Scale bar. 200 nm c: myxospore evidence a conspicuous sutural line in sutural view. Scale bar: 100 nm.