Mycena caeruleogrisea Q. Na, Y.P. Ge & H. Zeng, 2022

Na, Qin, Liu, Zewei, Zeng, Hui, Ke, Binrong, Song, Zhizhong, Cheng, Xianhao & Ge, Yupeng, 2022, Taxonomic studies of bluish Mycena (Mycenaceae, Agaricales) with two new species from northern China, MycoKeys 90, pp. 119-145 : 119

Mycena caeruleogrisea Q. Na, Y.P. Ge & H. Zeng sp. nov.

Figs 2 , 3 , 4

Diagnosis.

This species is characterised by blue pileus, turning bluish-grey with age, pileus covered by a separable, gelatinous pellicle, stipe pruinose and with a blue base and stipe basal disc and acanathocysts of pileipellis absent. Mycena subcaerulea differs from M. caeruleogrisea by a greenish-blue to greyish-brown pileus that turns yellow and remains blue at the centre and margin with age, a greenish-blue to brownish-blue stipe and smaller, globose to subglobose basidiospores.

Holotype.

China. Ningxia Hui Autonomous Region: Liangdianxia, Liupan Mountains National Forest Park, Jingyuan County, Guyuan City, 35°21'74"N, 106°18'37"E, 19 July 2020, Qin Na, Yupeng Ge, Hui Zeng, Junqing Yan and Zewei Liu, FFAAS 0001 (collection number MY0164).

Etymology.

Refers to the pileus colour: blue when young, becoming bluish-grey with age.

Description.

Pileus 12-25 mm in diameter, hemispherical when young, conical, obtusely conical, campanulate with age, shallowly sulcate, translucently striate, almost smooth when young, becoming slightly brownish scaly at the centre, pruinose, with a glabrescent margin, dull blue (23D5) at the centre, margin pallescent to pastel blue (23A4), turning bluish-grey (23D2-23D3), a bit sticky, covered by a separable, gelatinous pellicle. Context white, thin, fragile. Lamellae 16-28 reaching the stem, adnate to slightly adnexed with a short tooth, narrowly spaced, white, with intervenose veins, edges concolorous with the face. Stipe 48-76 × 1.5-2.0 mm, equal or slightly broadened below, hollow, fragile, entirely pruinose (Fig. 2g-i ), white, base greyish-blue (23B5) (Fig. 2j, k ), covered with white fibrils, a basal disc absent. Odour and taste indistinctive.

Basidiospores [60/3/2] (8.8) 9.3- 10.4 -11.3 (11.8) × (5.5) 5.7- 6.5 -6.9 (7.3) μm [Q = 1.57-1.68, Q = 1.60 ± 0.072] [holotype [40/2/1] (9.1) 9.4- 10.3 -11.3 (11.6) × (5.6) 6.0- 6.5 -6.9 (7.2) μm, Q = 1.55-1.63, Q = 1.59 ± 0.049], ellipsoid, hyaline in 5% KOH, smooth, guttulate, thin-walled, amyloid. Basidia 22-29 × 7-9 μm, 4- or 2-spored, clavate. Cheilocystidia 40-62 × 4-6 μm, clustered, abundant, elongated clavate or cylindrical, apically broadly rounded, thin-walled, hyaline, forming a sterile lamellae edge. Pleurocystidia absent. Pileipellis an ixocutis with 1-4 μm wide hyphae, smooth or sparsely coated with simple cylindrical excrescences or inflated cells, 3-11 × 1-2 μm, embedded in gelatinous matter; acanathocysts absent. Hypodermium undifferentiated. Hyphae of the stipitipellis 3-8 μm in diameter, smooth, hyaline; caulocystidia 38-69 × 6-8 μm, long cylindrical, smooth, transparent. All tissues dextrinoid. Clamps present in all tissues.

Habit and habitat.

Scattered on humus and fallen leaves in mixed forests of Acer , Populus , Pinus and Quercus .

Known distribution.

Ningxia Hui Autonomous Region, China.

Additional material examined.

Ningxia Hui Autonomous Region: Xiaonanchuan, Jingyuan County, Guyuan City, 20 July 2020, Qin Na, Yupeng Ge, Hui Zeng, Junqing Yan and Zewei Liu, FFAAS 0002 (collection number MY0169).

Remarks.

The original description of M. subcaerulea Sacc. was as follows: " Pileo tenuissimo, campanulato v. convexo, striato, glabro, pallide cæruleo-viridi; stipite tenui, æquali, roseo-albo, subtiliter pruinoso; lamellis angustis, confertis, antice attenuatis, candidis; sporis subglobosis. 4 µ. d. Hab. In trunco fagineo in montibus Adirondack Amer. bor. - Cæspitosa, 5 cm. alta; pileus 8-13 mm. latus. Discus margine saturatius coloratus atque pileus cuticula secernibili obtectus. " ( Saccardo 1887). This North American species, which also has bluish basidiomata, is the taxon most closely resembling M. caeruleogrisea in both macro- and microscopic features; however, M. subcaerulea differs by a greenish-blue to greyish-brown pileus that turns yellow and remains blue at the centre and margin with age, a greenish-blue to brownish-blue stipe and smaller, globose to subglobose, basidiospores [6-8 × 6-7(8) µm] ( Saccardo 1887; Smith 1947). In addition, M. subcaerulea was found solitary, scattered or gregarious on debris, decaying wood or bark around the bases of living trees, especially of oak, but also occurring quite frequently on decaying wood of basswood, elm, beech and other hardwoods ( Smith 1947). The following microscopic characteristics of M. subcaerulea were also observed on the 11 CUP-A and TENN-F specimens in our study: basidiospores 5.6-8.3 × 5.3-7.9 µm, globose to subglobose; basidia 19-24 × 6-8 µm, clavate, 4-spored; cheilocystidia 36-55 × 3-6 µm; pileipellis hyphae 2-4 μm wide, coated with cylindrical excrescences or inflated cells, 1.1-14.9 × 0.7-1.4 μm, embedded in gelatinous matter; hyphae of the stipitipellis 4-10 μm in diameter; caulocystidia 42-70 × 4-10 μm, fusiform or cylindrical, smooth; clamps present (Figs 5 , 6 ). In M. cyanorhiza , the base of the stipe can be strikingly sky blue, but it has a pale brown, grey to almost white pileus, a stipe base arising from a patch of fine fibrils, clavate to obpyriform cheilocystidia with finger-like excrescences and basidiospores that are elongated ellipsoid (Q = 1.6-2.2); these features all contrast with those of the new species ( Aronsen and Læssøe 2016; Perry et al. 2020) (Table 2 ). In addition, M. amicta can be easily mistaken for M. caeruleogrisea , as it sometimes also has a bluish pileus when mature and similarly-shaped basidiospores, cheilocystidia and caulocystidia, but M. amicta can be distinguished from the latter species in having a pileus generally more brownish with a bluish tinge more or less present, an indistinct to raphanoid odour, a greyish-brown stipe that has a blue to blue-green base and is covered with a dense, fairly coarse, white pubescence and smaller cheilocystidia (16-45 × 3.5-7 µm); in addition, M. amicta is restricted to growth on wood and woody debris ( Robich 2003; Aronsen and Læssøe 2016) (Table 2 ). Mycena interrupta , which is well characterised by its acid blue to dull blue pileus and translucent stipe, is easily distinguished from M. caeruleogrisea by having smaller basidiomata, free lamellae, a white hirsute basal disc with blue margins on the stipe, broadly ellipsoid to subglobose spores and cheilocystidia covered with coarse excrescences ( Grgurinovic 2003) (Table 2 ). Mycena lazulina , a new taxon reported from south-western Japan, possesses a blue stipe and cheilocystidia with numerous excrescences, which can be used to differentiate it from M. caeruleogrisea ( Terashima et al. 2016). Another recently-described species of Mycena from Taiwan, M. indigotica , has blue basidiomata; however, the cap has tubes similar to Boletus and possesses globose basidiospores ( Wei and Kirschner 2019).

Figures

Figure 2. Fresh basidiomata of Mycena caeruleogrisea a-d M. caeruleogrisea (FFAAS 0001, holotype) e, f M. caeruleogrisea (FFAAS 0002) g-i entirely pruinose stipe j, k bluish base. Scale bars: 10 mm (a-i); 2 mm (j-k). Photographs by Yupeng Ge (a, b) and Qin Na (c-k).

Figure 3. Microscopic features of Mycena caeruleogrisea (FFAAS 0001, holotype) a-d basidiospores e-g cheilocystidia h pileipellis i stipitipellis and caulocystidia. Scale bars: 10 μm (a-i). Structures were stained with Congo Red medium before photographing.

Figure 4. Morphological features of Mycena caeruleogrisea (FFAAS 0001, holotype) a basidiomata b basidia c basidiospores d cheilocystidia e stipitipellis and caulocystidia f pileipellis. Scale bars: 10 mm (a); 10 μm (b-f). Drawings by Qin Na and Yupeng Ge.

Figure 5. Microscopic features of Mycena subcaerulea a, b basidiospores (TENN-F- 057919) c basidiospores (CUP-A- 002382) d basidiospores (CUP-A- 015138) e-g cheilocystidia (TENN-F- 057919) h, i pileipellis (TENN-F- 057919) j stipitipellis and caulocystidia (TENN-F- 057919). Scale bars: 5 μm (a-d); 10 μm (e-j). Structures were stained with Congo Red medium before photographing.

Figure 6. Morphological features of Mycena subcaerulea a basidiospores b basidia c stipitipellis and caulocystidia d cheilocystidia e pileipellis. Scale bars: 10 μm (a-e). Drawings by Qin Na and Yupeng Ge.