Russula antsikana Buyck & Randrianjohany, 2020

Rossi, Walter, Das, Kanad, Hembrom, Manoj Emanuel, Santamaria, Sergi, Parihar, Arvind, Ghosh, Aniket, Henkel, Terry W., Hofstetter, Valerie & Randrianjohany, Émile, 2020, Fungal Biodiversity Profiles 91 - 100, Cryptogamie, Mycologie 20 (4), pp. 69-107 : 92-98

98. Russula antsikana Buyck & Randrianjohany , sp. nov.

( Figs 16-19)

Well-characterized by the combination of its medium-sized, firm stature, frequently forked gills, a dry, almost felty, brownish to cream or whitish pileus, white stipe, pale spore print, whitish context with an unpleasant, somewhat fishy smell, and pinkish brown discoloration upon handling, subglobose to shortly ellipsoid spores with low and dense, subreticulate spore ornamentation of interconnected warts and fine crests, and a non- to faintly amyloid, verruculose suprahilar spot, a pileipellis composed of densely intricate, often very irregularly formed, long and repeatedly branched hyphal extremities with often tapering terminal cells, intermixed with inconspicuous, capitulate pileocystidia, as well as by its occurrence in seasonally dry woodlands.

HOLOTYPE. — Madagascar. Central Plateau, along RN7 between Antsirabe and Ambositra, at km 40, in secondary Uapaca bojeri woodland with Pinus ingression, 26. I.2008, Buyck 08.178 (holo-, PC [ PC 0124727!])

MYCOBANK. — MB 834837.

GENBANK. — DQ422028 (ITS BB99.250), KU237557 (LSU), KU237405 (mitSSU), KU237702 (RPB1), KU237843 (RPB2), KU237988 (tef1alpha), all from holotype.

ETYMOLOGY. — Named after “ Antsikana”, a vernacular name for Xerochlamys bojeriana ( Sarcolaenaceae ), a possibly ectomycorrhizal, small shrub that is a typical inhabitant of Uapaca bojeri woodland and frequently observed to grow close to this Russula species.

ADDITIONAL EXAMINED MATERIAL. — Madagascar. East Coast. Toliara Prov. Just north of Fort Dauphin (Taolagnaro), littoral forest of Madena, 25.I.1999, Buyck 99.241 (PC[PC0125076]), 32 km south of Fort Dauphin, littoral dry forest of Petriky, 26.I.1999, Buyck 99.242 (PC[PC0125077]), Buyck 99.250 (PC[PC0125074]), Buyck 99.251 (PC[PC0125075]), Sainte Lucie, in dense, humid littoral forest North of Fort Dauphin, 27.I.1999, Buyck 99.255 (PC[PC0125078]), Buyck 99.259 (PC[PC0125079]), Central Plateau, Antananarivo Prov., along RN7 between Antsirabe and Ambositra, at km 40, in secondary Uapaca bojeri woodland with Pinus ingression, 26.I.2008, Buyck 08.180 (PC[PC0125073]).

DESCRIPTION

Basidiomata

Medium-sized, fleshy, isolated or more often in small groups of up to ten individuals.

Pileus

37-62 mm diam., quite regular in shape to slightly wavy near the margin, weakly depressed in center, not becoming deeply infundibuliform, smooth near margin; surface feltyvelutinous, separable up to mid-radius, dull, never viscid, even not when wet, continuous and smooth in the pileus center, the very surface minutely cracked under a hand lens, then becoming coarsely cracked closer to the pileus margin, eventually even deeply fissured or completely split radially from the pileus margin to almost mid radius when fully expanded in sunexposed places, usually pale-colored, from whitish to cream or pale yellowish over pale grayish brown to even occasionally darker reddish brown, not concentrically zoned, mostly remaining darker in the center.

Fungal Biodiversity Profiles 91-100

Gills

Hardly adnate and subfree, equal or with rare lamellulae, frequent forkings present at different distances from stipe, c. 3-5 mm high, brittle, normally spaced (c. 1 L+l/mm) or slightly denser, off-white to ivory, then becoming cream to almost yellowish or dirty isabelline with age and often tinged with pinkish brown toward the gill edge; gill edge even, concolorous when young.

Stipe

Central, (35)41-52 × 8-16 mm, not annulate, subcylindrical or somewhat inflated in the middle, sometimes slightly narrowing downward, smooth to longitudinally wrinkled, glabrous, off-white, developing brownish-yellowish stains toward the base; the latter sometimes fragmenting transversely as in R. cellulata ; stipe interior compact and firm, in age becoming more spongy in the center.

Context

Firm, fleshy, c. 6-7 mm thick above gill attachment, whitish, developing pale brown to pinkish brown stains in stipe context when cut, reacting greenish gray to FeSO 4 inside and on stipe.

Taste

Mild.

Odor

Disagreeable, somewhat fishy.

Spore print

Pale cream (IIa Romagnesi).

Spores

(sub)globose to shortly ellipsoid, (6.9)7.07-7.43-7.8(9.0)×(5.8) 6.3-6.69-7.0(7.7) µm, Q = (1.03)1.07-1.11-1.16(1.21); ornamentation quite variable, composed of strongly amyloid,

obtuse warts of variable dimensions but overall quite low, generally <0.5 µm high, sometimes laterally prolonged or fused in irregular short crests or interconnected by subtle lines in a subrecticulate network, mixed with some smaller interstitial isolated warts; suprahilar spot not or partly amyloid, often verruculose; apiculus long and distinct.

Basidia

Slender, largest in their upper part, (34)43-55(60) × 8-10 µm, four-spored, although two-spored ones are not rare close to the gill edge; basidiola strongly clavate; sterigmata slender and long, up to 7 × 2 µm for normally developed four-spored basidia.

Hymenial gloeocystidia

Moderately numerous (1000-1500/mm2), slender, mostly 60-80 × 7-9 µm, nearly always minutely capitate, at the gill edge more abundant but frequently smaller, e.g. 42 × 5 µm, also narrowing or obtuse rounded at the tip shorter than on gill sides, thin-walled or with slightly thickened, refringent wall; contents usually restricted to the upper part, amorphousguttulate to coarsely crystalline, SV-negative.

Subhymenium

Pseudoparenchymatic, composed of small cells, neither deep nor particularly well-developed.

Lamellar trama

With many sphaerocytes, neither very compact nor dense, also with frequent oleiferous hyphae or hyphal fragments.

Marginal cells

Not differentiated.

Pileipellis

Orthochromatic in cresyl blue, not distinctly delimited from the underlying trama. composed of a single layer that is a dense tissue of first more or less horizontal and then, closer to the pileus surface, more ascending hyphal extremities, embedded in a glutinous matrix that is not extending much further above the hyphal surface; hyphal extremities strongly branching and densely septate, composed of chains of 3-6 or more, often irregularly inflated cells that are frequently branching or just diverticulate, normally 3-7 µm wide, but some – particularly near branching points – more inflated and 10-15 µm diam., often more or less filled with refringent, dense contents, not or hardly pigmented, thin-walled but often sheathed with some hyaline substance, not exactly distinctly zebroid encrusted; terminal cell mostly 20-40 (70) µm long, usually tapering or variably restricted near the tip. Pileocystidia not abundant, but often not very apparent because of their sometimes poor, amorphous-granular, refringent contents, easiest to locate in the pileus center and best recognized when constituting the terminal cell of a typical extremity because of their globose – capitate tip, usually conical to flask-shaped, in the lower part of the pileipellis much longer and subcylindrical, measuring e.g. 100 × 5 µm, not observed in pileus trama.

Clamp connections

Absent in all tissues.

NOTES

This species is a frequent inhabitant of the tapia ( Uapaca bojeri ) woodlands on the Central Plateau, but we found it equally in dry littoral forest at Petriky – and one collection even in somewhat more humid littoral forest at St Luce – at the very southeastern coast of Madagascar near Fort Dauphin, where its natural habitat is strongly endangered by mining activities. We have never found this species on the east coast in the more humid dense littoral forests north of Tamatave, nor in humid forests at higher altitudes such as at Ambohitantely or Andasibe.

A single ITS sequence, obtained from a specimen (Buyck 99.250) of R. antsikana Buyck & Randrianjohany , sp. nov. from the southeast coast had previously been deposited in GenBank (GenBank: DQ422028) in the context of an earlier study ( Buyck et al. 2008) and is identical to the one obtained from the holotype, except for some erroneous readings at the very sequence start for the former.

Our recent multigene phylogeny ( Buyck et al. 2018) placed Russula antsikana Buyck & Randrianjohany , sp. nov. (as “ R. hatsikiana sp. ined.”) firmly in Russula subg. Malodora Buyck & V. Hofst. There are no representatives of this subgenus known from Europe, but other northern hemisphere, i.e. Asian and North American, species, as well as Oceanian species of this subgenus are all part of section Pseudocompactae Buyck & V. Hofst. (see Das et al. 2017), while all African–Malagasy species with frequently forking gills were placed in section Edules Buyck & V. Hofst. , typified by R. edulis Buyck (see Das et al. 2017). African- Malagasy species of subg. Malodora without forking gills are not part of sect. Edules , e.g. the recently described R. capillaris Buyck (in Wang et al. 2019), and these species likely merit to be placed in a new section of their own. The here newly described R. antsikana Buyck & Randrianjohany , sp. nov. is evidently part of sect. Edules and shares the frequently forking gills, presence of bad smell and very similar pileipellis composition with the other species of this section, such as the recently described R. blennia Buyck (in Wang et al. 2018) or R. fissurata Sanon & Buyck ( Sanon et al. 2014) . From all these species, R. antsikana Buyck & Randrianjohany , sp. nov. can easily be distinguished based on spore ornamentation and general habit. Spore size for Buyck 99.250, collected along the southern east coast, is slightly larger, but still very similar, compared to spore size for collections from the Central Plateau: (7.3) 7.7- 8.21-8.7 (9.0) × (6.2) 6.7-7.14-7.6 (7.9) µm, Q = (1.05) 1.10-1.15-1.20 (1.25).

Russula antsikana Buyck & Randrianjohany , sp. nov. can be quite variable in general appearance with its overall color varying from reddish brown over pale grayish brown to cream or even white, but the abundantly forking gills and dry tomentose, minutely areolate pileus surface are reliable features. Depending on weather conditions, the pileus surface can become more strongly areolate or even deeply fissured around the center and toward the margin; a feature it shares with most other species in subgenus Malodora sect. Edules .

A C B D

Several somewhat similar Russula species have been described from Madagascar nearly a century ago but remain insufficiently known. These comprise R. murinacea Heim , R. cinerea Heim ( Heim 1938) as well as R. cinerella Pat. and R. schizoderma Pat. ( Patouillard 1927) . For none of these, the presence of frequently forking gills has been noted, and all three might have distinctly more ellipsoid spores judging from the drawings made by Heim (1938); moreover, all were collected in humid forest types. The lack of good field illustrations or sufficient microscopic detail for these older species makes further comparisons impossible as their type specimens are either lost or in too bad a condition for microscopic study. Performing nBLAST of the ITS sequence of R. antsikana Buyck & Randrianjohany , sp. nov. on GenBank, while allowing for environmental sequences, produces no hits on highly similar sequences. This is somewhat surprising as R. antsikana Buyck & Randrianjohany , sp. nov. is in our opinion not rare at all in Madagascar.

There is no doubt that our new species is also very close and very similar to R. liberiensis Sing. Singer (1948) described this new species based on a collection made by G. W. Harley in Nimba, Liberia (West Africa). We have studied the type specimen and provide its detailed description in the next entry of this compilation. It differs essentially by the absence of pileocystidia and absence of reticulation in the spore ornamentation (see below).