Termitomyces tigrinus S.M. Tang & Raspé
Mycobank number: 836040
Basidiomata medium-sized. Pileus 7–9 cm in diam., convex to plano-convex, circular when seen from above, dark grey (1F1–2) at the centre, greyish white (1B1) to grey (1C1–1D1) towards margin, with regular alternating dark grey and greyish white zones, densely tomentose to tomentose-squamulose, hairs grey to drab, in dry conditions, often cracked into large or small scales; margin exceeding lamellae, undate; perforatorium small, as an acute papilla, dark grey (1C1). context 1–2 mm thick half-way to the margin, tough, white (1A1). Lamellae close, ventricose, 3–5 mm wide, adnexed, crowded, white (1A1) at first, then cream to greyish pink when mature; lamellar edge eroded; lamellulae in 1–2 tiers. Stipe 5–7 × 1–3.5 cm, central, subclavate, white (1A1) at the apex, greyish white (1B1) to grey (1C1–1D1) toward the base, smooth; context white (1A1), solid, fibrous. Annulus absent. Pseudorhiza terete, strongly tapering; surface grey (1D1–2) to dark grey (1F1–1F2), smooth; context solid, fibrous. Odour slightly fragrant. Taste not distinctive.
Basidia of two types conspicuously different by the apex of sterigmata being either acute or obtuse, first type rather abundant, clavate, sterigmata apex acute, mostly 4–spored sometimes 1–spored or 2–spored, 25–32 × 7–12 μm, av. 28 ± 2.4 × 11 ± 0.5 μm, sterigmata 1–3 μm long; the second type fewer in number, clavate, sterigmata apex obtuse, mostly 1–spored, 2–spored, sometimes 4–spored, 24–30 × 9–13 μm, av. 26 ± 2.2 × 12 ± 0.7 μm, sterigmata 2–4 μm long. Basidiospores [90/5/2] (6.1–) 7.2–9.6 (–10.1) × (3.3–) 5.2–7.3 (–7.9) μm, Lm × Wm = 8.1 ± 1.1 × 6.3 ± 0.8 μm, Q = (1.01–) 1.20–2.03 (–2.30), Qm = 1.53 ± 0.20, broadly ellipsoid to ellipsoid, colourless, thin-walled, smooth. Hymenophoral trama regular, element parallel, 51–100 μm wide, made up of thin-walled, ellipsoid to clavate inflated hyphae 16–18 μm wide, filamentous hyphae abundant, 5–10 μm wide. Subhymenium 8–21 μm thick, with 1–2 layers of ovoid, subglobose, fusiform, ellipsoid or irregular cells, 8–11 × 3–6 μm. Pleurocystidia absent. Lamellar edge composed mostly of undifferentiated, basidiole-like cells. Cheilocystidia few, broadly clavate, 17–36 × 9–16 μm, av. 28 ± 2.0 × 14 ± 0.6 μm. Pileipellis 2-layered, suprapellis an ixocutis 22–51 × 5–7 μm av. 30 ± 5.7 × 6 ± 0.5 μm, cylindrical hyphae with obtuse apex, thin-walled, hyaline in KOH; subpellis made up of inflated elements, 31–81 × 7–14 μm, av. 58 ± 7.6 × 10 ± 0.8 μm. Clamp connections not seen in any tissues.
Habitat and distribution: Basidiomata scattered on soil with decaying litter under which termites have built their nest. Occurring in summer. So far only known from southwestern China.
Additional species examined: China. Yunnan Province, Chuxiong city, 20 July 2019, Jun He (HKAS 107561).
Notes: Termitomyces tigrinus is distinguished from other Termitomyces by densely tomentose to tomentose-squamulose pileus with regularly alternating greyish white and dark grey zones, and a small, dark grey perforatorium as an acute papilla, two conspicuously different types of basidia, broadly ellipsoid to ellipsoid basidiospores, clavate, thin-walled cheilocystidia that are rare (HKAS 107560), or absent (in HKAS 107561). Morphologically, T. tigrinus is similar to T. robustus (Beeli) R. Heim in having grey to black stipe. However, T. robustus has a blunt perforatorium (Heim 1951), smaller basidia (20–25 × 7–8 μm) and basidiospores (7.0–8.0 × 5.0–5.5 μm) (Otieno 1969). Termitomyces entolomoides R. Heim with T. tigrinus in having a tapering upwards stipe, dark grey pileus and greyish white to grey stipe. However, T. entolomoides has been originally described from Congo by Heim (1951), has a small basidioma (pileus 3–4 cm diam.), a grey pseudorhiza and relatively smaller basidiospores (6.2–6.6 × 4–4.2 μm; Heim 1951). In our multi-locus phylogeny, T. tigrinus is closely related to T. intermedius, T. radicatus Natarajan and T. striatus. However, T. intermedius has a cylindrical stipe, and cheilocystidia clavate to pyriform, narrowly lageniform, lageniform or broadly lageniform (this study). Termitomyces radicatus has a pale orange pileus, dark brown perforatorium, relatively smaller pileus (1.5–3.5 cm), and cylindrical stipe (Pegler and Vanhaecke 1994). Termitomyces striatus has a white to ocher pileus, irregularity fibrous striate on the stipe surface, long pseudorhiza (30–100 cm), with squama of various sizes and shapes on the surface cheilocystidia and pleurocystidia pyriform,broadly clavate, cylindrical or ovoid, 20–45 × 11–22 μm.
Fig. 1 Strict consensus tree illustrating the phylogeny based on the combined nrLSU, mrSSU, 5.8S and ITS1+ITS2 data set. Maximum likelihood bootstrap proportions equal to or higher than 70%, and Bayesian posterior probabilities equal to or higher than 0.90 are indicated at nodes. The two Asterophora species and two Lyophyllum species were used as the outgroup. The two newly described species are in red. Holotype specimens are in bold.