Steirochaetomium canariensis Sastoque, Stchigel & Cano, 2025

Sastoque, A. P., Cano-Lira, J. F. & Stchigel, A. M., 2025, Soil ascomycetes from Spain. XIV. The Chaetomiaceae of La Palma (Canary Islands), Persoonia 54 (1), pp. 93-117 : 112

Steirochaetomium canariensis Sastoque, Stchigel & Cano sp. nov. MycoBank MB 849840. Fig. 12 .

Etymology: canariensis , from Canary Islands ( Spain), due to the geographic origin of the fungus.

Typus: Spain, Canary Islands, La Palma, Fuencaliente (Los Canarios), isolated from soil of Teneguía volcano, 15 Jul. 2008, coll. M. Calduch & A.M. Stchigel, isol. A.P. Sastoque (holotype CBS H-25347, culture ex-type FMR 19096 = CBS 150903 ) .

On oatmeal agar after 3 mo at 25 °C: Mycelium mostly aerial, abundant, composed of septate, branching, smooth- and thin-walled, hyaline to brown hyphae, 1–2 μm wide. Chlamydospores, hyaline, smooth- and slightly thick-walled, globose, subglobose or barrel-shaped, 11–19 × 7–13 μm, in chains, with several big lipid vacuoles ( Fig. 12E, F ). Sexual morph not observed.

Culture characteristics (after 7 d at 25 ° C): Colony on PCA 28–29 mm diam., flat and circular; margin filamentous and regular; surface uncoloured with white (4A1) floccose aerial hyphae, sparse on the margins; soluble pigment absent; reverse uncoloured to white (4A1). Colonies on OA 25–27 mm diam., flat, circular, and expansive; margin filamentous and regular; surface greyish yellow (4B3) coloured with white (4A1) sparse aerial mycelium around and at the centre; soluble pigment absent; reverse uncoloured to greyish yellow (4B3). Colonies on CMA 31–32 mm diam., flat and circular; margin filamentous and regular; surface uncoloured with floccose white (4A1) aerial hyphae around at the centre; soluble pigment absent; reverse yellowish white (4A2). Colonies on MEA 40–41 mm diam., flat and circular; margin filamentous and regular; surface greyish yellow (4B3), with white (4A1) floccose aerial mycelium, sparse on the margins; soluble pigment absent; reverse greyish yellow (4B3). Culture iconography after 5 wk of incubation on PCA, OA, CMA and MEA ( Fig. 12A–D , respectively). Minimum, optimum and maximum temperature of growth on PDA after 7 d: 15 °C, 30–37 °C and 45 °C, respectively.

Additional specimens examined. Spain, Canary Islands, La Palma, Fuencaliente (Los Canarios), from soil of Teneguía volcano, 15 Jul. 2008, coll. M. Calduch & A.M. Stchigel, isol. A.P. Sastoque (culture FMR 18932 ) .

Notes: Steirochaetomium canariensis was located as a monospecific fully supported linage related but different to the Chaetomium clade ( Fig. 1 ). Steirochaetomium canariensis does not produce fertile structures. However, it forms big chlamydospores with several big lipid vacuoles, which have not been observed in Arxotrichum , Corynascus , Chaetomium and Parachaetomium . Moreover, it is easily molecularly distinguishable from the other genera of the family Chaetomiaceae ( Wang et al. 2016a, 2019a, b, 2022). Based on a BLAST search of the NCBI’s GenBank nucleotide database, the closest match using the rpb 2 sequence was Parachaetomium mareoticum [CBS 781.71, GenBank MZ342993 ; Identities = 598/688 (86.92 %), four gaps (0 %)]. Lastly, using the tub 2 sequence, the closest match was Parachaetomium biporatum [CBS 244.86, GenBank MK919417 ; identities = 427/521 (81.96 %), 23 gaps (4 %)].

Figures

Fig. 12. Steirochaetomium canariensis CBS 150903. A–D. Colonies on PCA, OA, CMA, MEA (5-wk-old; 25 °C; surface, left; reverse, right). E, F. Chlamydospores with several lipid vacuoles, forming chains. Scale bars = 10 μm.

Fig. 1. Maximum likelihood of the tree obtained from the concatenated ITS-LSU-rpb2-tub2 (3215 bp) alignment of the nucleotide sequences from our strains and those retrieved from the GenBank. Bayesian posterior probabilities (PP) ≥ 0.95 and the RAxML bootstrap support values (BS) ≥ 70 % are presented at the nodes (PP/BS). Thickened branches indicate full support (PP = 1 and BS = 100 %). The new species and combinations are indicated in bold. T represents the ex-type strain of the species. NT represents the ex-neotype strain of the species.