Halteromycesis anAbsidia-like fungus that forms dumbbell-shaped, columellate, multispored sporangia. Several simple sporangiophores arise verticellately from the subtending stolon; each sporangiophore is uniseptate. Zygospores are unknown (Shipton and Schipper, 1975).This fungus is known only from the initial isolate.(Zygomycetes.org2015)
A.Taxonomy and Phylogeny
Halteromyces radiatus is a species in the order Mucorales, family Cunninghamellaceae, broader classification not defined . It was first found in Australia and was first described by W.A Shipton and M.A Schipper in 1975. The authors studied the growth of the fungus on beerwort agar, PDA, and SMA. They found that growth and sporulation were profuse on beerwort agar. Growth on SMA had colonies that were a “very light lavender in color, becoming a pale olivaceous grey, odor absent”. Growth on PDA were similar to that of SMA. Sporulation was more abundant on PDA (Shipton and Schipper, 1975).
Halteromyces has some similarities with the genus Absidia. These similarities include sporangiophores arising along stolons and minute, one-celled, hyaline, and non-striate sporangiospores. The distinguishing character of Halteromyces are the dumbbell shaped sporangia, which are pyriform in the genus Absidia (Shipton et.al, 1975). Absidia, according to Hoffmann et.al, in a revision of the genus, has a trichotomy consisting of a mesophilic group, a fast-growing thermotolerant, and a slow- growing mycoparastic group. The mycoparasitic group is characterized by Mucor-like rough-walled zygospores (Hoffmann K, 2007).
In a study on isolating Zygomycetes published in the Journal of Systematic and Evolutionary Botany, Gerald L. Benny mentions the methods used by Dr. R. K Benjamin, among other mycologists, which included studying Halteromyces radiatus. In this study, Dr. Benjamin used different kinds of media to try and isolate many Zygomycetes to determine on what kind of agar the fungi grew best. Halteromyces was described on MEA, OMA, and SMA (Benny, 2008). MEA is malt extract agar, which is a general purpose media designed to contain a good balance of carbon, protein, and other essential nutrients (Thom.C, 1926). OMA, oatmeal agar, is most suitable for production of pycnidia and conidia (Y.K. Kim et al). These methods helped to isolate species of the Mucorales to be isolated and studied from soil in order to describe their morphology and other characteristics such as life cycles.
B.Morphology
Typically, fungi in the order Mucorales are saprobic and fast growing (Kendrick). The morphology is similar to Absidia. Halteromyces form dumbbell shaped, columellate, multispored asexual sporangia. The columella, which protrudes into the sporangium, is a “trade-mark” characteristic of the family Mucoraceae. The spores are contained in the peridium. Uniseptate sporangiophores arise vertically from the stolon, and so far, zygospores are unknown (Benny, 2005). See Figure 1, from Shipton and Schipper (1975), below for illustrations of features of H. radiatus.
Figure 1: Halteromyces radiatus. A, habit; b, stolon, nodular swelling, mature sporangia; c, sporangia; d, collumellae and apophyses; e, columellae collapsed; f, deliquescing sporangium; g, mature sporangiospores (Shipton and Schipper, 1975, pg. 339).
C.Ecology
Have been found in mud from mangrove forest contaminated with effluent in Queensland, Australia (ATCC).
Halteromyces radiatus is described as a new genus and species in the order Mucorales. The genus is referred to the family Mucoracease and has close affinities to the genus Absidia. The fungus grows readily in pure culture. The asexual structures are described; no sexual structures have been found despite extensive contrasts with members of the genus Absidia and Gongronella.
