AN ODOROUS BASIDIOBOLUS OFTEN PRODUCING CONIDIA PLURALLY AND FORMING SOME DICLINOUS SEXUAL APPARATUS

A coarse fungus isolated from decaying plant detritus originating in northern Wisconsin and western Maryland is newly described as Basidiobolus magnus. Like B. ranarum, it gives off an odor recalling benzene hexachloride. Its mycelium, especially while young, includes many long segments markedly wider in the middle than at the ends. Its distally phototropic conidiophores sometimes are branched in their procumbent or submerged portions, and each propulsive distention may bear 1-3 globose conidia, which may be shot off forcibly or may fall through collapse of the supporting hypha. The primary globose conidia of B. magnus are generally larger than those of B. ranarum, from which they differ further in sometimes giving rise to plural secondary conidia of either the globose or the elongated adhesive type. The zygospores, like those of B. ranarum, show abundantly undulated sculpture but differ in their generally larger size, their occasional origin through conjugation between cells of separate hyphae, their rather frequent binary development, and their germination by production, often, of 2 globose uninucleated conidia. The elongated conidia, which seem generally no bigger than those of B. ranarum and are often only meagerly tipped with adhesive material, sometimes undergo conversion into sporangia through internal segmentation. IN EARLIER studies Basidiobolus ranarum Eidam (1886) was found readily distinguishable by the undulate sculpture of its zygospores not only from B. meristosporus Drechsler (1955) and B. haptosporus Drechsler (1956) but also from a congeneric fungus (Drechsler, 1958) isolated from a human patient in Indonesia (Emnmons et al., 1957). From the 3 congeners mentioned and from B. microsporus Benjamin (1962), it is promptly distinguishable also by the production of a Streptomyces-like odor resembling the odor associated with benzene hexachloride. Nearly all strongly odorous Basidiobolus cultures I have isolated, whether from decaying plant materials or froma frog excrement, soon produce zygospores of undulate profile which in their dimension show agreem-ent with Eidam's account of B. ranaruman agreement sustained by close correspondence with respect to morphology of mycelial hyphae, of phototropic conidiophores, and of globose conidia. However, a few odorous cultures with zygospores of undulate profile have been isolated that in several respects disagree so markedly with Eidam's description and diverge so widely from the many cultures held properly referable to Eidam's species as to preclude their assignment to B. ranarum. MATERIALS AND METHODS-Divergence from the famiiliar developmental habit of Basidiobolus ranarum was observed in an odorous culture obtained by canopying a Petri plate of maizemeal agar with a small quantity of decaying plant detritus taken from marshy ground in northern I Received for publication February 25, 1964. Wisconsin on November 18, 1954. The nmyceliuni invited attention because of its slow growth and unusually coarse hyphae. It gave rise to no conidiophores or conidia, but formed in moderate number large zygospores of undulate sculpture. Asexual reproduction again failed to ensue when the fungus was transferred to several slanted tubes of maizemeal agar containing some finely divided maizemeal in suspension, and again sexual reproduction took place, so that after 20 days the substratum was amply seeded with zygospores of correct internal structure. The several tubes were then stored at room temperature for use eventually in longevity tests. No measures were taken to reduce evaporation from the agar substratum, which accordingly dried to a horny consistency in a few months. In March 1963, when the cultures were more than 8 years old, 5 ml of sterile distilled water were added to each of them, with proper precautions being taken to avoid contamination by alien microorganisms. Within 10 days, renewed development was observable in each culture. Emission of many gernm hyphae gave proof that a large proportion of the zygospores had survived. Active production of phototropic conidiophores, of globose conidia, and later of elongated adhesive conidia, indicated that the softened watery substratum furnished conditions more favorable for growth and asexual reproduction of the fungus than had been provided earlier by the unwet, firmii culture medium newly prepared with 15 g of agar to the liter. Three additional isolates of the fungus were obtained from Petri plates of soft maize-meal agar that had been canopied with plant detritus