Periplasma W.W. Martin & A. Warren, Mycologia 112(5): 998 (2020)
Index Fungorum number: IF831248; Facesoffungi number: FoF12586
Type: Periplasma isogametum W.W. Martin & A. Warren, sp. nov.
Diagnosis: Distinguished from related genera by the formation of elongate branching thalli converted directly into zoosporangia or gametangia, zoosporogen- esis in which the peripheral protoplasm collapses to the center of the cell and undergoes plasmotomy to form zoospore initials, sexual reproduction involving mor- phological isogamy and physiological anisogamy of rounded and walled gametes produced in adjacent thalli, and formation by male gametes of elongate fertilization tubes that extend between adjacent thalli to fertilize female gametes and induce oospore formation.
Etymology: Periplasma (Greek), referring to the peripheral position of the protoplasm around a large central vacuole in the hyphae.
Description: Typically holocarpic and facultative saprophyte of moribund aquatic insect adults but eucar- pic in common mycological media including mPmTG and YPSS. Elongated and branching hyphae containing protoplasm peripheral to a prominent central vacuole. Thalli converting into zoosporangia and narrowing to form short papillae with slightly thickened walls. Zoosporogenesis intrasporangial, involving collapse of the peripheral protoplasm to the cell center and subse- quent plasmotomy of zoospore initials to form primary zoospores. Zoospores dimorphic, slipper-shaped pri- mary zoospores undergo a period of motility before transforming into ellipsoidal to ovate secondary zoos- pores. Thalli functioning as gametangia, giving rise to rows of rounded, thin-walled male and female isoga- metes. Sexual reproduction by a thin fertilization tube arising from the male gamete that passes through the cell walls of adjacent hyphae to fuse with a female gamete, which is converted into a thick-walled oospore with an eccentric oil globule.
Distribution: Southeast United States (Virginia).