Mucor heterogamus NRRL 1489 v1.0
Mucor heterogamus: A) spherical multispored sporangia, B) a sporangial wall that deliquesces at maturity, revealing a columella, C and D) ornamented zygospores formed between suspensors that differ greatly in size. Photos by Kerry O'Donnell and Connie Robertson
Mucor heterogamus: A) spherical multispored sporangia, B) deliquesced sporangial wall, revealing a columella, C and D) ornamented zygospores formed between suspensors that differ greatly in size. Photos by Kerry O'Donnell and Connie Robertson

Mucor (= Zygorhynchus) heterogamous Vuill. NRRL 1489 is a homothallic or self-fertile zygomycete fungus classified in the family Mucoraceae [Order Mucorales; Hesseltine et al. 1959].  Recent molecular phylogenetic analyses of the nuclear ribosomal internal transcribed spacer region (ITS rDNA) and partial nuclear ribosomal large subunit (LSU rDNA) sequences revealed that Zygorhynchus is polyphyletic and not phylogenetically distinct from Mucor (Walther et al. 2013).  Consequently, the genus Zygorhynchus was abandoned and all of the species were reclassified in Mucor.  The eight homothallic species within this group are most commonly found in diverse soils in both hemispheres (Domsch et al. 1980).  The now abandoned genus Zygorhynchus was distinguished originally from Mucor by the following combination of characters:  formation of spherical multispored sporangia (Fig. 1A), a sporangial wall that deliquesces at maturity, revealing a columella (Fig. 1B), and brown to black, ornamented zygospores formed between suspensors that differ greatly in size (Figs. 1C-D).  Whole genome sequencing of M. heterogamous will advance the 1000 Fungal Genome Project by providing a representative of the Mucoraceae, and additional insight into the evolution of the mating type locus in early diverging fungi.

References:

1) Domsch KH, Gams W, Anderson T-H. 1980. Compendium of Soil Fungi. Academic Press, New York.
2) Hesseltine, C.W., C.R. Benjamin, and B. S. Mehrotra. 1959. The genus Zygorhynchus. Mycologia 51:173‒194.
3) Walther G, Pawlowska J, Alastruey-Izquierdo A, Wrzosek M, Rodriguez-Tudela JL, Dolatabadi S, Chakrabarti A, and de Hoog GS. 2013. DNA barcoding in Mucorales: an inventory of biodiversity. Persoonia 30:11‒47.