Lactocollybia cf. epia

Bera, Ishika, Wisitrassameewong, Komsit & Thongklang, Naritsada, 2025, New insights into Lactocollybia (Agaricales, Basidiomycota): Morpho-phylogenetic analyses revealing two interesting species and one new record from Thailand and evidence of intercontinental conspecificity, MycoKeys 118, pp. 313-344 : 313-344

Lactocollybia cf. epia

Figs 7 , 8

Description.

Basidiomata small-sized, collybioid. Pileus 4–28 mm diam., broadly convex to planoconvex when young, gradually becoming applanate on maturity; surface moist, smooth, translucent-striate up to 2 / 3 rd of the pileus from margin, hygrophanous; white to yellowish white (1 A 1–2) and translucent when wet, changing to greyish yellow (2 B 3) to the dried and bruised areas; margin entire to undulating, decurved. Lamellae adnate to subdecurrent, white (1 A 1) changing to greyish yellow (2 B 4) on drying and bruising, crowded (31 L + l / cm at pileus margin); lamellulae present in 5 series; edge entire to eroded. Stipe 10–15 × 1.5–2.5 mm, slightly eccentric, cylindrical; surface moist, smooth, hygrophanous; white (1 A 1) and translucent when moist but changing to greyish yellow (2 B 4) on drying and bruising; basal mycelium white. Context in pileus up to 1.5 mm thick, white (1 A 1), unchanged on bruising, exposure, and in 3 % KOH; hollow in stipe, yellowish white (1 A 2), unchanging on bruising, exposure, and in 3 % KOH.

Basidiospores 5.3–6.9 – 8.4 × 3.9–4.4 – 4.7 μm [n = 40, Q = 1.25–1.55 – 1.84], broadly ellipsoid to subamygdaliform; thin-walled, smooth, apiculate, uni- to multi-guttulate, hyaline in 5 % KOH, inamyloid, non-dextrinoid. Basidia 19.8–23.9 × 5.6–7.8 μm, subclavate, thin-walled, hyaline in 5 % KOH, non-dextrinoid, 2 - or 4 - spored; sterigmata up to 4.6 μm long. Gloeocystidia abundant in both lamellae edge and lamellae side, 17.8–28.9 × 6–12.9 μm, mostly ovoid to subcylindrical, inflated, or clavate, sometimes subventricose or subfusoid, thin-walled, yellowish in H 2 O and 5 % KOH, non-dextrinoid; originating from hymenium and subhymenium; non-emergent. Pleurocystidia moderate, 45.1–58.5 × 6.9–9.1 μm, cylindrical with generally obtuse apices and rarely sub-mucronate apices, slightly undulating near apex and sometimes with long neck, thin-walled, hyaline in 5 % KOH, non-dextrinoid; content rare, crystalline; emergent up to 32 μm. Lamellae edge fertile, heteromorphous with basidia, basidioles, and cystidia. Cheilocystidia moderate, 23.4–53.5 × 4.1–7.6 μm, similar to pleurocystidia; emergent up to 33.6 μm. Subhymenium thin, up to 11.8 μm thick, subcellular with ramifying hyphae. Hymenophoral trama composed of compactly arranged, subparallel to parallel, thin-walled, septate hyphae and gloeohyphal elements; hyphae up to 4.8 μm wide. Pileipellis a cutis; composed of interwoven, septate hyphae with numerous scattered long, fusoid gloeohyphal elements; hyphae 4.2–6.9 μm wide, thin-walled, septate, hyaline in 5 % KOH, non-dextrinoid; gloeohyphal elements 23.2–67 × 6–11.5 μm, attenuated at both ends, refractive, yellowish in H 2 O and 5 % KOH, non-dextrinoid. Pileus trama composed of compactly arranged, loosely interwoven hyphae and gloeohyphal elements; hyphae hyaline in 5 % KOH, non-dextrinoid. Stipitipellis a cutis; composed of parallelly arranged hyphae with scattered caulocystidia; hyphae 1.7–3.5 μm wide, thin-walled, septate, hyaline in 5 % KOH, non-dextrinoid; caulocystidia 19.8–70.2 × 3–6.4 μm, similar to pleurocystidia and cheilocystidia. Stipe trama similar to pileus trama, composed of compactly arranged, parallel hyphae and gloeohyphal elements; hyphae hyaline in 5 % KOH, non-dextrinoid. Clamp connections common.

Materials examined.

Thailand • Phrae Province: Rong Kwang roadside , 18°22.28712'N, 100°22.4661'E, Alt. 309 m, gregarious on a dead tree log in a semi-deciduous Dipterocarpus - dominated forest, 2 nd August 2024, S. Khyaju, IB 24-38 ( MFLU 24-0392 ) ; 18°10.1661'N, 100°2.43906'E, Alt. 312 m, gregarious on a dead tree log in a semi-deciduous Dipterocarpus - dominated forest, 3 rd August 2024, I. Bera, IB 24-67 ( MFLU 24-0393 )

Notes.

This species of Lactocollybia belongs to the sect. Albae ( Singer 1986) . Lactocollybia cf. epia is characterized by its white to yellowish-white, hygrophanous basidiomata turning greyish-yellow on drying or bruising; translucent striations around the pileus margin; adnate to subdecurrent and crowded lamellae; broadly ellipsoid to subamygdaliform, uni- to multi-guttulate basidiospores; abundant gloeocystidia in both the lamellae edge and lamellae side; the presence of hymenial and pileal cystidia; abundant gloeohyphal elements in the pileus and stipe trama; and clamp connections.

In the phylogenetic inference (ML and BI) depicted in Fig. 1 , the sequences generated from the collections of this Thai Lactocollybia reveal their relatedness to sequences labelled as L. epia from Italy and China, along with some unidentified Lactocollybia sequences from the USA, Laos, and Russia. All these sequences are from undescribed specimens submitted to the database. Lactocollybia epia was originally described from Sri Lanka ( Pegler 1986). Afterwards, L. epia has been reported from various countries, e. g., South Africa ( Reid and Eicker 1998), China ( Yang 2000), Brazil ( Cortez and Sulzbacher 2009), and India ( Senthilarasu and Kumaresan 2016). Unfortunately, the identification of the holotype and other samples in the published articles lacks molecular verification. Based on the morphology in the protologue and recent descriptions of L. epia , the species possesses differently shaped hymenial gloeocystidia (clavate fusiform with mucronate apices) with greenish yellow content, larger gloeohyphal elements, a complete absence of pleurocystidia, and fine granular surface incrustations of pileus hyphae ( Pegler 1977, 1986; Reid and Eicker 1998; Yang 2000; Cortez and Sulzbacher 2009; Senthilarasu and Kumaresan 2016). However, shorter and yellowish content of gloeohyphal elements and prominent presence of pleurocystidia make our studied species different from L. epia (Table 4 ).

The creamy white, smooth basidiomata and convex to applanate pileus with striated margin of this Lactocollybia resemble those of L. variicystis . However, the minute pruinose surface of the pileus, the adnexed to adnate and close to subdistant lamellae, plicate-sulcate striations rather than translucent, much larger hymenial and tramal gloeocystidia, and mostly fusoid gloeocystidia in lamellae demarcate L. variicystis from L. cf. epia ( Reid and Eicker 1998; Desjardin and Perry 2017; Al-Khesraji et al. 2022; Izhar et al. 2022).

Lactocollybia gracillima looks similar to this species with its white basidiomata, translucent striations in margin, and decurrent attachment of lamellae, ellipsoid basidiospores, and presence of gloeohyphal elements in the trama ( Pegler 1977). However, pileus with truncated apex, absence of any hymenial gloeocystidia and pleurocystidia, shorter cheilocystidia (23–35 μm), and differently shaped (clavate and often constricted) and shorter (18–35 μm) caulocystidia are the prominent differences ( Pegler 1977). The absence of any hymenial gloeocystidia and the smooth margin also demarcate the Chinese L. subvariicystis ( Hosen et al. 2016) .

The water-soaked striated margin of L. piliicystis is similar, but the quite longer stipe, smaller basidiospores (5.75–6.2 × 3.2–4.5 μm), and more lanceolate to elongate cylindric with obtuse to mucronate apexed gloeocystidia in lamellae are very different ( Reid and Eicker 1998). Lactocollybia globosa is characterized by its non-hygrophanous, deep umbilicate pileus with an exceptionally inrolled margin and ovoid to subglobose basidiospores ( Reid and Eicker 1998).

Figures

Figure 1. Phylogram inferred from maximum likelihood (ML) analysis by raxmlGUI 2.0 and Bayesian inference by Mr. Bayes v. 3.2. 6 based on nrITS sequence data. Generated sequences in this study are presented in red bold for the novel species and blue bold for the new record. Sequences of L. cf. epia are presented in green bold. The clade representing L. variicystis, L. polyhabitata sp. nov., and L. cf. epia are demarcated by the yellow, blue, and purple boxes, respectively. Maximum likelihood bootstrap support values (MLB) ≥ 70 % are shown on the left of “ /, ” and Bayesian posterior probabilities (BPP) ≥ 0.95 are shown on the right or below “ / ” at nodes.

Figure 7. Morphological features of Lactocollybia cf. epia (MFLU 24-0392) a – c fresh basidiomata in the field d, e transverse section of pileipellis f – h gloeocystidia in hymenium i, j pleurocystidia k cheilocystidia l caulocystidia m basidiospore. Scale bars: 20 μm (d, e); 10 μm (f – m).

Figure 8. Micromorphological features of Lactocollybia cf. epia (MFLU 24-0392) a basidiospores b basidia c, d gloeocystidia in hymenium e pleurocystidia f cheilocystidia g transverse section through pileipellis h caulocystidia. Scale bars: 10 μm (a – h).