Thamnidiaceae (Synonym of Mucoraceae)


The Thamnidiaceae was first proposed by Brefeld (1881, as Thamnidieen) using an invalid non-Latin ending (Greuter et al., 2000, Art. 18.5 of the ICBN). Brefeld also proposed Chaetocladiaceae (as Chaetocladieen, also invalid [see above]) for Chaetocladium, a genus usually included in the Thamnidiaceae. Members of the Thamnidiaceae have also been placed in the Mucoraceae (Schröter, 1889) or subfamilies of the latter family, Mucoreae (Schröter, 1897) or Thamnidieae (Fischer, 1892). The majority of the students of the Mucorales have recognized the Thamnidiaceae (Fitzpatrick, 1930; Hesseltine, 1955; Benjamin, 1959, 1979; Hesseltine and Ellis, 1973; Benny, 1982; Hawksworth et al., 1983).

The family was validly published by Fitzpatrick (1930), and classically, five genera ( Chaetocladium, Chaetostylum [Hesseltine and Anderson, 1957], Thamnidium [Benny, 1992], Helicostylum [Benny, 1995b], Dicranophora [Dobbs, 1938]) were usually included in the Thamnidiaceae (Zycha, 1935) although at that time Chaetocladium (Benny and Benjamin, 1976) might have been placed in the Chaetocladiaceae (q.v.). Later, Dicranophora was usually included in the Mucoraceae and Lendner (1908) also included Actinomucor Schöst. (C. R. Benjamin and Hesseltine, 1957) in Thamnidiaceae.

After World War II several genera were added to the Thamnidiaceae: Cokeromyces (Benny and Benjamin, 1975), Radiomyces (Benny and Benjamin, 1991), Choanephora (including Gilbertella, (Kirk, 1984; Benny, 1991) Backusella (Benny and Benjamin, 1975), and Hesseltinella (Benny and Benjamin, 1991) were added to the Thamnidiaceae by Pidoplichko and Mil’ko (1971) and Mil’ko (1974) and Mycotypha was transferred the family by Young (1969). Thamnostylum was added by von Arx (1970). These realignments were all examined by Benny (1973) and Benny and Benjamin (1975, 1976). They determined that several of the aforemented genera were not thamnidiaceous, including: Actinomucor, Blakeslea, Choanephora, Dicranophora, Gilbertella, Hesseltinella, and Radiomyces.

The taxa considered valid members of the Thamnidiaceae (Benny, 1973; Benny and Benjamin, 1975, 1976) included the previously described taxa, Backusella, Chaetocladium, Cokeromyces, Helicostylum, Mycotypha, Thamnidium, Thamnostylum. Several genera were then added by Benny (1973) and Benny and Benjamin (1975) including those classified in Cunninghamellaceae, Phascolomyces (Benny and Benjamin, 1975) and Mucoraceae, Pirella (Benny and Schipper, 1992) and taxa described as new, Dichotomocladium, Ellisomyces, Fennellomyces, Zychaea Benny and Benjamin, 1975). This treatment of Thamnidiaceae (Benny, 1973; Benny and Benjamin, 1975, 1976) included 13 genera, Backusella, Chaetocladium, Cokeromyces, Dichotomocladium, Ellisomyces, Fennellomyces, Helicostylum, Mycotypha, Phascolomyces, Pirella, Thamnidium, Thamnostylum, Zychaea, and it was followed by Benjamin (1979), O’Donnell (1979), Benny (1982), and Hawksworth et al. (1983). The Thamnidiaceae contained genera that can be placed in two categories: (1) those genera producing both deliquescent-walled sporangia and persistent-walled sporangiola, Backusella, Fennellomyces, Helicostylum, Pirella, Thamnidium, Thamnostylum, and, (2) taxa that only produce multispored, persistent-walled sporangiola, Cokeromyces, Ellisomyces, Zychaea. Backusella spp. are unusual in their production of both uni- and multispored sporangiola (all of the other spp. of Thamnidiaceae produce only multispored sporangiola).

At least some isolates of three species, Thamnidium elegans, Thamnostylum piriforme, and T. repens, can reproduce asexually without forming the terminal sporangium, especially when growing on a natural substrate. These fungi normally produce sporangia in the laboratory when grown on ordinary culture media, but T. repens normally does this only when grown under special conditions (Benny and Benjamin, 1975). Benjamin (1979) considered the Thamnidiaceae to be a polyphyletic family when it contained the original 13 genera (Benny, 1973; Benny and Benjamin, 1975, l976).

Members of the Thamnidiaceae can be isolated from soil, but most spp. are coprophilous.

Thamnidiaceae Fitzpatrick, 1930 ( The Lower Fungi Phycomycetes, p. 253)(Benny, 1973—monograph with keys and descriptions; Benny and Benjamin, 1975, 1976).

Sporophores erect or ascending, simple or branched, arising from the substrate mycelium or from stolons. Terminal columellate, multispored, deliquescent-walled, sporangia present or absent; lateral columellate, uni- or multispored, persistent-walled, sporangiola always produced. Sporangiola subtended by short to long, straight, twisted or recurved pedicels. Sporangia and sporangiola apophysate or nonapophysate. Sporangiospores variously shaped, thin- and smooth walled. Zygospores with a rough zygosporangial wall; suspensors opposed, equal to stongly unequal, appendaged or usually nonappendaged.

Type genus: Thamnidium Link.

Updated Feb 10, 2005