Agaricus cervinoculus Palestina-Villa, Medel, R. Garibay-Orijel, Linda J. Chen & L.A. Parra

Palestina-Villa, Elvia Naara, Garibay-Orijel, Roberto, Chen, Jie, Parra, Luis Alberto, Águila, Bernardo & Medel-Ortiz, Rosario, 2024, Agaricus cervinoculus sp. nov. (Agaricaceae), a new wild edible mushroom from Mexico, Phytotaxa 642 (4), pp. 229-241 : 233-237

Agaricus cervinoculus Palestina-Villa, Medel, R. Garibay-Orijel, Linda J. Chen & L.A. Parra , sp. nov. ( Figs. 2–3 ) MycoBank: MB 852840

Type:— MEXICO. Veracruz: Perote municipality, Tembladeras , 2998 m elev., 19°33’11.4’’ N, 97°06’35.9’’ W, in zacatonal ( Muhlenbergia spp .) near Pinus-Quercus forest , 23 September 2022, coll. E. N. Palestina-Villa (Holotype: MEXU-HO 30375; Isotype: PV129)

Etymology:—From the Latin cervinus (belonging to a deer) and oculus (eye), a Latin translation of the Mexican traditional name of this species “ ojo de venado ”.

Diagnosis:— A. cervinoculus can be distinguished from any other species of A. sect. Subrutilescentes in having ochre to blackish discoloration on the stipe surface when rubbed or over time, the yellowish context at the junction of the stipe with the pileus when cut, the complex, variable and peculiar smell of wood, chocolate or fruit, the more positive bluish KOH reaction on the pileus surface.

Description:— Pileus (7.5)9.5–13.5(16.5) cm in diam., at first convex, then plano-convex, slightly umbonate at the center, covered by small reddish brown to dark brown appressed triangular scales, less dense towards the margin on a whitish background, smooth and dry. Margin initially decurved, smooth, sometimes undulating or crenulate, not exceeding the lamellae. Lamellae free, up to 0.6 cm broad, crowded, straight, intercalated with numerous lamellulae, at first white, then grayish pink, finally dark brown, with concolorous even edge. Stipe (13.4)13.6–15.6 × 1.5–2.6 cm, cylindrical, bulbous at the base (up to 3.5 cm), fistulose, with an annulus on the upper third, above annulus smooth to slightly striate, orange to grayish brown, below annulus covered with abundant semi-erect white fibrils arranged in horizontal zig-zag bands; surface whitish, becoming ochre on handling or over time, then blackish. Base covered with felted mycelium. Annulus superous, up to 1.7 cm broad, white, membranous, double, upper surface smooth, lower surface floccose-fibrillose with thin, narrow, dark brown bands of universal veil around the margin. Context white on cutting, becoming pinkish on the cortex of the stipe and yellowish in the central area at the junction with the pileus. Odor strong and variable among collections, of molasses, chocolate, wood, or slightly citric.

Basidiospores (5)5.1–5.7–6.2(6.5) × (3)3.2–3.6–3.9(4.2) µm, Q = (1.3)1.4–1.6–1.7(1.8), ellipsoid to ellipsoidelongate, smooth, brown, thick-walled, without apical pore, unigutulate, bigutulate or with granular content. Basidia (15.3)16–20.8(23.2) × (5.9)6.4–7.9(8) µm, tetrasporic, clavate, hyaline, sterigmata up to 2.8 µm long. Cheilocystidia (16.9)17.7–24.4(38.7) × (11.3)11.7–16.7(18.3) µm, hyaline, usually pyriform or sphaero-pedunculate, some globose or broadly clavate, abundant. Pleurocystidia absent. Lower surface of the annulus composed of hyaline hyphae, 6.2– 8.7 µm wide, cylindrical, not or slightly constricted at the septa. Pileipellis composed of cylindrical hyphae, 8.5–12 µm, constricted at the septa with some terminal elements progressively attenuated with rounded apex. Intracellular diffuse brown pigment. Clamp connections not observed.

Macrochemical reactions:—KOH on pileus surface of fresh specimens olive green to slightly bluish.

Habitat:—Solitary to gregarious, on ground with decomposed leaves, in Pinus-Quercus forests. Occurring from September to October.

Edibility:—Edible, a combination of mature and immature sporocarps is generally sold in local markets.

Additional specimens examined:— MEXICO. Veracruz: Xalapa municipality, San José Market, specimens bought from markets, 3 October 2019, coll. E. N. Palestina-Villa PV62. 8 October 2020, coll. E. N. Palestina-Villa PV70A, 3 September 2021, MEXU-HO 30386 (duplicate PV83). 16 September 2021, coll. E. N. Palestina-Villa PV92. 30 September 2021, coll. E. N. Palestina-Villa PV98, PV100. 03 October 2021, coll. E. N. Palestina-Villa, PV103. 10 October 2021, coll. E. N. Palestina-Villa MEXU-HO 30388 (duplicate PV106). Veracruz: Perote municipality, Tembladeras, 2952 m elev., 19°32’01’’ N, 97°06’04’’ W, in Pinus-Quercus forest, under Pinus , 04 September 2021, coll. E. N. Palestina-Villa MEXU-HO 30387 (duplicate PV86).

Comments:—Morphologically, A. cervinoculus can be distinguished from other species of A. sect. Subrutilescentes in having ochre to blackish discoloration on the stipe surface when rubbed or over time, the yellowish context at the junction of the stipe with the pileus when cut, the complex, variable and peculiar smell of wood, chocolate or fruit, the more bluish positive KOH reaction on the pileus surface. The complex odor of this species is due to the combination of volatile compounds (an alcohol, an aldehyde, and an acid) that will be described in a later publication.

In Mexico, two species from this section have been cited: A. impudicus and A. subrutilescens , which are morphologically similar to A. cervinoculus . However, they differ in having a context not becoming yellow when cut ( Kerrigan 1986, 2016). Furthermore, A. impudicus has no bluish olive-green positive KOH reaction, and A. subrutilescens has smaller spores (5.2 × 3.3 µm on average). The remaining species in the section do not present a yellow context when cut at the junction of the stipe with the pileus or a bluish KOH reaction on the pileus surface. Molecularly, A. cervinoculus lacks any species-specific ITS marker within A. sect. Subrutilescentes. However, A. cervinoculus and A. omphalodiscus L.A. Parra, Fiard, Callac & B. Ortiz (2021:406) share an exclusive single nucleotide agcag[A]–tgc@159 as a relevant distinguishing character from all other species of the section. Agaricus omphalodiscus , recently described from the Caribbean, can be easily distinguished from other species because it possesses many species–specific ITS markers ( Ortiz-Santana et al. 2021).

Figures

FIGURE 2. Macroscopic characteristics of Agaricus cervinoculus. A–C. Basidiomata (A: MEXU-HO30375 holotype, B–C: MEXU- HO30387). D–F. Annulus detail (D: MEXU-HO30375 holotype, E: PV105, F: PV70A). G. Color change in context (PV70A). H. KOH reaction (PV62). Photos by E.N. Palestina-Villa.

FIGURE 3. Microscopic characteristics of Agaricus cervinoculus. A. Spores (PV83). B. Basidia (PV83). C–E. Cheilocystidia (C-D: MEXUHO30387, E: PV98). F. Hyphae of the lower surface of the annulus (PV72). G–H. Pileipellis hyphae and a terminal element with an asterisk (G: MEXU-HO30387, H: PV105). Scale bars = 5 µm. Photos by E. N. Palestina-Villa.