Radiomyces, a New Genus in the Mucorales

Abstract

Embree, Robert W. (U. California, Berkeley.) Radiomyces, a new genus in the Mucorales. Amer. Jour. Bot. 46(1): 25‐30. Illus. 1959.—Radiomyces spectabilis is described as a new genus and species in the order Mucorales of the Phycomycetes. This fungus readily grows in pure culture, and developmental stages of the asexual and sexual reproductive structures are described. The genus is referred to the family Thamnidiaceae, and in doing so, the family concept is necessarily broadened to include almost colorless, smooth‐walled zygospores with appendiculate suspensors.

Observations on Thamnidiaceae (Mucorales). II. Chaetocladium, Cokeromyces, Mycotypha, and Phascolomyces.

“…Bessey ( 1950) assigned Mycotypha to the Choanephoraceae along with Blakeslea Thaxter ( 1914) , Choanephora Currey ( 1873) , Cunninghamella Matruchot ( 1903) , Sigmoideomyces Thaxter ( 1891) , and Thamnocephalis Blakeslee ( 1905). Hesseltine ( 1952Hesseltine ( , 1955 placed Mycotypha in th e Cunninghamellaceae with Cunninghamella and Thamnocephalis; his opinion subsequently was followed by several other mycologists (Benjamin, 1959;Milka, 1967Milka, , 1974Pidoplichko and Milka, 1971) , but Zycha et al ( 1969) included Mycotypha in their relatively broad concept of the Choanephoraceae which comprised, in addition, Blakeslea, Choanephora, Rhopalomyces Corda ( 1839) , Cunninghamella, Racliomyces Embree ( 1959) , Thamnocephalis, and Sigmoicleomyces. Young ( 1969) was the first to suggest a thamnidiaceous relationship for Mycotypha wh en he dernonsb·ated that the sporangiolar wall of M. africana Novak & Backus ( 1963) is clearly separable from the sporangiospore.…”

“…The latter genus also was established by Pidoplichko and Milko at this time to accommodate Racliomyces embreei Benjamin ( 1960) which differs from R . spectabilis Embree ( 1959 ) primarily in having unisporous sporangiola formed on elongate, stalked, secondary vesicles ( Benjamin, 1960: Pls. 3c-j;4c-d) rather than multispored sporangiola borne on globose, stalked, secondary vesicles (Embree, 1959: Figs.…”

The Merosporangiferous Mucorales

“…whereas terminal multispored sporangia are absent in Cokeromyces, Chaetocladium, and Radiomyces (Embree, 1959). However, members of this family always give rise to sporangiola produced on simple or ramiform branchlets borne singly or in clusters, laterally or terminally, on the main axes of the sporangiophores.…”

“…In the absence of convincing evidence to the contrary, the writer is inclined to interpret the spore-bearing structures of Syncephalastrttm as sporangiola which, except for the usually uniseriate spores, are not fundamentally different from those of other genera of Mucorales like Cokeromyces and Radiomyces (Embree, 1959). Although numerous modifications of vegetative and reproductive structures have been effected during the evolution of the more highly derived merosporangiferous genera such as Piptocephalis, Syncephalis, Dispira, and Coemansia, the alliance of these and related genera with Syncephalastrum in a single phylogenetic complex seems to me to be most natural.…”

Addenda to "The Merosporangiferous Mucorales" II

“…5 h) in which the zygosporangial membrane does not become noticeably modified. When stripped of its outer, often very distinctive, membrane, or when this membrane is thin and inconspicuous as in Radiomyces (Embree, 1959;Benjamin, 1960), the typical mucoralean zygospore may be very chlamydospore-like in appearance. However, its consistent origin from the copulation of distinctive hyphae arising from the same or different thalli marks the mucoraceous zygospore as sexual in nature.…”