Mortierella calciphila Wrzosek, sp. nov.
MycoBank number: MB 814918, Facesoffungi number: FoF 02063, Figs. 1, and 2
Etymology – refers to the type of soil where the species was found (limestone soil)
Holotype – WA18944

Radiate colonies fast-growing (6 – 9 mm per day on PDA), without characteristic zonate growth nor garlic odour. Sporangiophores arising from the substratum with 2 – 4 (7) basal sympodial ramification or formed on aerial hyphae (then 0–1 ramification), slender, 2 – 3 μm under sporangium, 600 – 1400 μm long, without any cross wall. Sporangia (27–) 70 (–80) μm in diam., many-spored, with early deliquescent wall. Columella strongly reduced, without apophysis sometimes with tiny projection (up to 1 μm) on the top. Spores broadly ellipsoidal, smooth-walled, regular in shape (8–) 9 (–11) μm (SD = 0.8) × (6–) 7 (–9) μm (SD=0.8). Gemmae abundantly produced in substratum or aerial hyphae, in chains or irregular clusters often connected by anastomosis, globose, hyaline to pale ochraceous (11–) 18 (–25) μm (SD = 3.44) in diam.

Habitat and distribution – humid soil in beech forest on limestone, Northern Poland

Material examined – POLAND, West Pomeranian Voivodeship, Polanów Forest District, Wapienny Las area (‘forest on limestone soil’), 53°59′59.16 N, 16°42′47.75 E, elev. 110 m, 26 August 2015, collector Marta Wrzosek; holotype WA18944 (dried culture), ex-holotype CBS 140728 (lyophylised culture); ex type (living culture) is deposited in Jena Microbial Resource Collection (University of Jena and Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany) (JMRC:SF:012173).

Notes – The phylogenetic analyses (Figs. 157 and 158) show that this species belongs to group lignicola as defined by Wagner et al. (2013). However, the similarity of ITS sequence to any previously described taxa in this group is low: BS = 85 % to M. beljakovae, BS=84 % to M. paraensis, BS= 83 % to M. formicicola, BS = 81 % to M. gemmifera and M. kuhlmanii.

The species is morphologically most similar to Mortierella zychae Linn., which is placed by Wagner et al. (2013) in Clade 7 grouping some species from former section “elongata” and to M. parazychae from Clade 5, containing M. wolfii and relatives. The most characteristic feature of this fungus is formation of gemmae in clusters, both in substrate and on aerial mycelium. Gams (1976) use the term “chlamydospores” for gemmae, what seems to be not always proper because the cell wall of these structures is very thin and it could be easily mechanically damaged. In young cultures of M. calciphila the clusters of gemmae are quite loose, regularly placed, and globose with enlargements. Sometimes they are arranged in chains with thin liaisons (Fig. 2c, d). The cross walls were observed sporadically. Large clusters, up to 0.8 mm diam. built by dense layers of gemmae, with very short liaison, and with numerous anastomosae could be observed in older cultures (Fig. 2e). The arrangement of the gemmae/chlamydospores in chains and clusters has been observed also in M. zychae, M. parazychae, M. beljakowae, M. kuchlmanii and others (Gams 1976). The gemmae of M. calciphila (as well as these of M. parazychae) are usually completely rounded, in contrast with M. zychae Linnem., where the gemmae outline merges gradually into the connecting hyphal parts (Gams 1976). We suggest that gemmae are organs of symbiotic associations with bacteria, which seem to be quite widespread among Mortierellales, rather than resting structures (Fujimura et al. 2014; Ogawa et al. 2012).

The sporangiophores of M. calciphila are more slender than in M. beljakovae and do not have an apophysis, nor collerate. The sporangiophores of M. calciphila are often larger than sporangiophores of M. zychae and others species of section “elongata”. The spores of M.calciphila resemble those of M. zychae, but they are colourless and some granules in cytoplasm could be seen. They are much more regular than spores of M. parazychae, M. beljakowae and M. kuhlmanii.

The most closely related species to M. calciphila was M. formicicola D.S. Clark & W. Gams. The ITS and LSU sequences of that species were generated by Wagner et al. (2013) for phylogenetic studies, but the description of this fungus is not available and probably this species is not validly published.

Fig. 1 Mortierella calciphila (holotype) a Branching sporophore emerging from substrate b Typical sporophore with sporangium on aerial mycelium c Loose cluster of young gemmae d Top of sporophore e Spores from sporangium, and germinating spore. Scale bars: a = 100 μm, b = 50 μm, c = 20 μm, d, e = 10 μm.

Fig. 2 Mortierella calciphila (holotype) a Type of growth (24 h colony) b Branching sporophore c, d, e Gemmae forming loose (c, d) or dense (e) clusters f Small sporangium formed on short sporophore emerging from aerial hyphae g, h Spores. Scale bars: b = 500 μm, c – e = 20 μm, f = 50 μm, g, h = 20 μm.