Two New Dentigerate Species of Phlyctochytrium (Chytridiomycetes)

SUMMARY

Two new dentigerate chytrids, Phlyctochytrium circulidentatum Koch and P. multidentatum Umphlett are described. Both species have a whorl of about 14 usually simple tooth-like enations about the broad apical discharge region of the epibiotic zoosporangium, and both have an endobiotic apophysis. At zoospore discharge in P. circulidentatum the apical wall may deliquesce before planonts are released, or thin curls of wall material may peel off or peel back before deliquescence giving the impression of a fragmenting operculum. The empty zoosporangium retains its original shape, and frequently a rim of wall material is visible inside the whorl of teeth outlining the large discharge pore. In P. multidentatum planont discharge may occur following complete dissolution of the apical wall, or may begin while the wall is intact in which case the zoospores begin escaping at one side of the broad apex, and the apical wall swings back in a seemingly operculate fashion as deliquescence of this portion of the wall proceeds very rapidly. During discharge by either method the remaining lower portion of the zoosporangium reflexes and assumes a broad, saucer-shaped configuration. The zoospore in both species has a spherical body, and a single posteriorly attached and directed flagellum. These chytrids are presently classified in an inoperculate group of fungi, but the existence of degrees of operculation between euoperculation and inoperculation is discussed.