Mycocladus

MYCOCLADUS Beauverie, 1900 (Ann. Univ. Lyon, Sér. 2, Sciences, Médicine 3:162); 1 sp. (Beauverie, 1900; Mirza et al., 1979; Hoffmann et al., 2007).

Absidia van Tiegh. subgen. Mycocladus (Beauv.) Hesseltine & Ellis, 1964 (Mycologia 56:569).

Colonies growth optimum C, temperature maximum 40 C; mesophilic. Mycocladus (as are Absidia and Lentamyces) is characterized by the formation of relatively small, apophysate sporangia with deliquescent walls, a single septum is formed in the subtending sporangiophore, and the production of stolons and rhizoids; the sporangiophore is never formed opposite the rhizoids (as in Rhizopus). The zygospore has an ornamented zygosporangial wall; the suspensors are opposed and non-appendaged.

Type species: M. verticellatus

Species of Mycocladus:
M. blakesleeanus; = transferred to Lichtheimia (q.v.).
M. hyalospora; = transferred to Lichtheimia (q.v.).
M. ramosus; = transferred to Lichtheimia (q.v.).
M. verticellatus Beauverie, 1900 (Ann. Univ. Lyon 3:162).

Mycocladus was described by Beauverie (1900) for a fungus (M. verticellatus) that forms an anamorph that is identical to that of some species of Absidia but which produces zygospores that lack suspensor appendages. Mycocladus has usually been treated as a subgenus of Absidia (Hesseltine and Ellis, 1964).

Mirza et al. (1979) recognized Mycocladus at generic rank based on the additional characters of producing good growth (vs. poor or lacking for Absidia) at 37 C, determinate (vs. in determinant for Absidia) aerial mycelium, sporangiophores borne randomly (vs. in umbels or verticels for Absidia) on the stolons, and the optimal temperature for zygospore formation is 31 C (vs. 26 C for Absidia). Five species (A. blakesleeana, A. corymbifera, A. hyalospora, A. parricada, A. ramosa) were transferred from Absidia to Mycocladus by J.H. Mirza (Mirza et al., 1979). The following three species (Absidia corymbifera, A. hyalospora, A. ramosa) were transferred to Mycocladus in Mirza et al. (1979) but they are considered invalid according to Art. 36.1 of the ICBN (McNeill et al., 2006). Mirza et al. (1979) provided a key to the six species of Mycocladus that they recognized. Schipper (1990) accepted species in Absidia subgenus Mycocladus based on the formation zygospores with unadorned suspensors or those species that grew at 37 C if zygospores were not formed. Mycocladus parricida does not grow above 31 C (Hesseltine and Ellis, 1966) and, therefore, Schipper (1990) did not consider it a member of Absidia subgenus Mycocladus but M. parricida does produce zygospores with unadorned suspensors, the key character for Mycocladus. Schipper (1990) accepted the following species in Mycocladus: A. blakesleeana (= A. griseola), A. corymbifera (= A. hesseltinei, = A. ramosa), and A. hyalospora. Absidia atrospora was considered a variety of A. blakesleeana (Schipper, 1990). Absidia atrospora and A. griseola (Naganishi and Hirahara, 1970) were examined and treated as indicated above. Schipper (1990) accepted three species and two varieties in Absidia subgenus Mycocladus.

All of the species that Mirza etal. (1979) and Schipper (1990) included in Mycocladus, except M. verticellatus, are included here in Lichtheimia either as one of the accepted species, or as a synonym of those species, in the latter genus.

Mycocladus verticellatus Beauverie (1900), is a monotypic genus, that may be based on a culture composed of Lentamyces parricida and an unidentified Absidia (Hoffmann et al., 2009). If Mycocladus verticellatus is not a pure culture then it has to be considered an invalid taxon according to the ICBN (Art. 52.1; McNeill et al., 2006). The family name Mycocladaceae also is invalid if it is based on an invalid genus name (Art. 18.3 of the ICBN; McNeill et al., 2006). I am treating Mycocladus as valid until a final determination is made on the suggestion of Hoffmann et al. (2009).

Absidia parricida is the type species of Lentamyces (Hoffmann and Voigt, 2009).

Bibliography

Beauverie, J. 1900. Mycocladus verticillatus (gen. nov. sp. nov.). Ann. univ. Lyon, Sér. 2, Sci., Méd. 3:162-180.

Hesseltine, C.W., and J. J. Ellis. 1964. The genus Absidia: Gongronella and cylindrical-spored species of Absidia. Mycologia 56:568-60l.

Hesseltine, C.W., and J. J. Ellis. 1966. Species of Absidia with ovoid sporangiospores. I. Mycologia 58:761-785.

Hoffmann K, Discher S, Voigt K. 2007. Revision of the genus Absidia (Mucorales, Zygomycetes) based on physiological, phylogenetic, and morphological characters; thermotolerant Absidia spp. form a coherent group, the Mycocladiaceae fam. nov., Mycological Research 111: 1169-1183.

Hoffman, K. and K. Voigt. 2009. Absidia parricida plays a dominant role in biotrophic fusion parasitism among mucoralean fungi (Zygomycetes): Lentamyces, a new genus for A. parricida and A. zychae. Plant Biology 10: 537-554.

Hoffmann, K., G. Walther, and K. Voigt. 2009. Mycocladus vs. Lichtheimia: a correction (Lichtheimiaceae fam. nov., Mucorales, Mucoromycotina). Mycol. Res. 113: 277-278.

McNeill, J., F.R. Barrie, H.M. Burdet, V. Demoulin, D.L. Hawksworth, K. Marhold, D.H. Nicolson, J. Prado, P.C. Silva, J.E. Skog, J.H. Wiersema and N.J. Turland. [eds.]. 2006. International code of botanical nomenclature (Vienna code). [Regnum Vegetabile Vol. 126]. A.R.G. Gantner Verlag KG, Ruggell, Liechtenstein. 568 p.

Mirza, J. H., S. M. Khan, S. Begum, and S. Shagufta. 1979. Mucorales of Pakistan. University of Agriculture, Faisalabad, Pakistan. 183 p.

Naganishi, H., and S. Hirahara. 1970. Two new species of the Absidia genus isolated from ‘Kurone’ developed during the manufacture of soy sauce Kojé. Bull. Hiroshima Jogakuin agric. Coll. 20:13-17.

Schipper, M.A.A. 1990. Notes on Mucorales—I. Observations on Absidia. Persoonia 14:133-149.

Voigt, K., E. Cigelnik, and K. O’Donnell. 1999. Phylogeny and PCR identification of clinically important Zygomycetes based on nuclear ribosomal-DNA sequence data. J. Clin. Microbiol. 37:3957-3964.

Updated May 31, 2010