Piromyces irregularis Fliegerová, K. Voigt & P.M. Kirk, sp. nov.
Index Fungorum number: IF550065; Facesoffungi number: FoF01019; Fig. 178
Etymology: Referring to irregularily shaped sporangia.
Holotype: JMRC SF:011205

Colonies tiny (Ø 3 mm) with irregular edges on agar plates and fragile mycelium in liquid M10 medium (Caldwell and Bryant 1966) enriched by 25 % (V/V) rumen fluid with either glucose or cellobiose (both 4 g/l) as carbon source. Thallus with highly branched rhizoidal system without evidence of a subsporangial swelling formed by fine rhizoids with a multitude of tiny lateral stolons. Sporangiophores of varying length and shape, from short to long, narrow to very wide, simple, as well as flexuous or branched. . Sporangia consistently produced, highly variable in both shape and size, globose, ellipsoidal, elongated, pestle-shaped, triangular, pyriform or rounded rectangular, often also bifurcated, horned and with irregular shape, both open to the sporangiophore or with a basal septum, nuclei present both in the sporangium and the sporangiophore. Zoospores when freshly released from sporangium globose, free floating zoospores ovoid to somewhat lamp-bulb shaped, mononucleate, with variable flagellation, ranging from uniflagellate to quadriflagellate or multiflagellate.

Material examined: CZECH REPUBLIC, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, v.v.i., Videnska 1083, 14220 Prague, Czech Republic, from rumen fluid of slaughtered cow, July 2009, by K. Fliegerova, KF 9 (holotype Jena Microbial Resource Collection (University of Jena and Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany) JMRC SF:011205).

Nuclei may remain in the zoospore cyst, which has developed into single sporangium and sporangiophore; rhizoids are anucleate. The accompanying illustrations display also a more complex development when some sporangiophores are not terminated by sporangia, they do, however, contain nuclei. Both types of development occurs together in one culture. Barr et al. (1989) described this as two types of thallus development, type I as endogenous and monocentric, type II as exogenous and monocentric. However, the rhizoid system is always in both cases anucleate and in our opinion, therefore, it represents only the endogenous and monocentric development.

Notes: The species thus exhibits all types of morphological variations described by Barr et al. (1989) for P. communis, however analysis of ITS1-5.8S-ITS2 rDNA revealed sequence divergence sufficient to justify the description of a new species of Piromyces (Fig. 177). The new species introduces a new character: zoospores of all previously described species of Piromyces are uni – or bi – flagellate, and when polyflagellate, there are no more then 4 flagella.