TWO NEW SPECIES OF CONIDIOBOLUS THAT PRODUCE MICROCONIDIA

Abstract

THE TWO readily culturable fungi herein described as new species of Conidiobolus include in their asexual reproduction the simultaneous development of several-usually 5-15-microconidia on short sterigmata borne radially on of the large globose type familiar in many insectivorous members of the Entomophthoraceae. Such multiplicative development was first made known by Costantin (1897) in the original account of his readily culturable Boudierella coronata, being there presented as a very distinctive feature requiring the erection of a new genus. When Saccardo and Sydow (1899) took occasion to replace the preempted name Boudierella with a new generic term, Delacroixia, they referred to the microconidia as merely conidia secundaria. Gallaud (1905) regarded the microconidia (or en couronne) as borne on protuberances of the same category as tht hair-like outgrowths present on the villous resting spores (or echinulees) he found to originate in D. coronata through conversion of smooth conidia. Kevorkian (1937) apparently shared this view, and held further that the microconidia of D. curonata were equivalent to the secondary produced in the several insectivorous species which Thaxter (1888) assigned to the subgenus Triplospoirium. In describing another readily culturable entomophthoraceous fungus, which, though given to forming microconidia, produced smooth zygospores instead of villous resting spores, Couch (1939) placed primary emphasis on resemblance in sexual reproduction by bringing it into the genus Conidiobolus under the binomial C. brefeldianus. He recognized the production of villous resting spores rather than the formation of microconidia as the chief distinguishing character of Del,acroixia. Thus the mode of sporulation observed by Costantin has lost esteem as a diagnostic feature. The formation of microconidia now appears of moment less as a developmental oddity than as a multiplicative phase of asexual reproduction homologous with the development of zoospores in the Oomycetes and of sporangiospores in the Mucorales (Drechsler, 1946, 1953b). The homology is sustained by observations on asexual reproduction in the two new species, for here no less than in Delacroixia coronata the microconidia develop simultaneously and tend strongly toward uniformity in size irrespective of variations in the dimensions of the parent conidia. Abundant production of