Figs. 1a, b. Fig. 1a. A sporophore apex showing the origin of the single, spine covered sporangiola arising from a pedicellate subsporangial vesicle. Several pedicels arise from vesicle on the sporophore. Fig. 1b. A single sporangiolum showing the acicular spines with the hexagonal base and the typical naviculate sporangiospores. The spores germinate to produce a new colony. Photo credit: Gerald Benny, Department of Plant Pathology, University of Florida, Gainesville, Florida

Hesseltinella vesiculosa (Mucorales), the type and only species in the genus Hesseltinella, was isolated from paddy field soil collected in Brazil (Upadhyay 1970). This genus and species is known from only a single culture. Hesseltinella was originally thought to be related to Radiomyces (Radiomycetaceae) because of the morphological similarities between the two genera (Benny and Benjamin 1991). However, current molecular studies (Hoffmann et al. 2013) place H. vesiculosa in the Cunninghamellaceae (Mucorales, Mucoromycotina). Sporangiospores of H. vesiculosa are produced in multispored sporangiola covered with acicular spines that have hexagonal bases.  The spines are composed of calcium oxalate. Sexual reproduction has not been reported in this species.

Mucoromycotina, one of four subphyla, as well as the phylum Entomopthoromycota, were previously classified in the now defunct phylum Zygomycota. Taxa in Mucoromycotina are saprobes or facultative parasite in nature.  Some species are important as plant and post-harvest pathogens, in industry for production of enzymes and organic acids, and as the causative agents of mucormycosis in humans and some other animals.  Mucoromycotina is the largest subphylum of zygomycete fungi.

References

Benny, G.L., and R.K. Benjamin. 1991. The Radiomycetaceae (Mycorales; Zygomycetes). III. A new species of Radiomyces, and cladistic analysis and taxonomy of the family; with a discussion of the evolutionary ordinal relationships in Zygomycotina. Mycologia 83: 713-735.

Hoffmann, K., J. Pawlowska, G. Walther, M. Wrzosek, G.S. de Hoog, G.L. Benny, P.M. Kirk, and K. Voigt. 2013. The family structure of the Mucorales: a synoptic revision based on comprehensive multigene-genealogies. Persoonia 30: 57-76.

Upadhyay, H.P. 1970. Soil fungi from north-east and north Brazil—VIII. Persoonia 6: 111-117.