スミレニガイグチ

Tylopilus obscureviolaceus Har. Takah., Mycoscience 45(6): 374 (2004)

今のところ西表島のみで確認されている希なイグチ類です。子実体の類型はニガイグチモドキに近い大形種で、傘が暗青紫色を呈します。

肉眼的特徴: 傘は径70–100 mm, 最初半球形, のち饅頭形～ほぼ平開し, 平坦, 縁部は管孔側に僅かに突出する; 表面は乾性, やや密綿毛状, 幼菌から成菌に至るまで傘全体が一様に暗青紫色を呈する. 肉は厚さ10 mm, 固くしまり, 白色, 空気に触れても変色しない; 特別な臭いはなく, 強い苦みがある. 柄は80–100 × 20–30 mm, 基部が多少球根状に脹らみ, 中心生, 中実, 上部または頂部に淡青紫色の繊細な網目模様を表す; 表面は乾性, やや密綿毛状, 時に縦皺を表し, 頂部類白色, 下方に向かって帯褐色～帯褐青紫色を帯びる; 根本は類白色の密綿毛状菌糸体に被われる. 管孔は長さ8 mm以下, 直生～僅かに垂生, 幼時白色, のち帯紅色, 空気に触れても変色しない; 孔口は小型 (2–3 per mm), 類円形, 縁取りはなく, 傷を受けても変色しない.

顕微鏡的特徴: 担子胞子は6–7.2 × 3.3–4 µm (n = 20 spores per two specimens, Q = 1.8), 楕円形～やや紡錘形, 下部側面に不明瞭でなだらかな凹みがあり(イグチ型), 平坦, 帯紅色, 厚壁. 担子器は15–20 × 5–8 µm, こん棒形, ４胞子性. 偽担子器はこん棒形. 縁シスチジアは群生し, 30–40 × 5–10 µm, 亜円柱形～亜紡錘形, 平滑, 無色, 薄壁. 側シスチジアは散生し, 縁シスチジアに似る. 子実層托実質はイグチ亜型; 菌糸は幅3–6 µm, 円柱形, 無色, 薄壁. 傘表皮組織は緩く錯綜した毛状被を形成する; 末端細胞は30–60 × 4–7 µm, 円柱形, 赤褐色の色素が細胞内に存在し, 薄壁, 傘シスチジアは分化しない. 傘実質の菌糸は緩く錯綜し, 幅4–11 µm, 円柱形, 平滑, 無色, 薄壁. 柄表皮組織は柄シスチジアが子実層状被を成す; 柄シスチジアは13–19 × 5–7 µm, 広こん棒形, 平滑, 帯褐色の色素が細胞内に存在し, 薄壁. 柄実質の菌糸は縦に沿って配列し, 幅4–10 µm, 円柱形, 時に分岐し, 平滑, 無色, 壁は厚さ0.5 µm以下. 全ての組織において菌糸はクランプを欠く.

生態および発生時期: スダジイ，オキナワウラジロガシを主体とする常緑広葉樹林内地上に孤生または散生, 5月～6月.

分布: 沖縄 (西表島).

主な形態的特徴

ア）子実体は中～大型のヤマドリタケ型.

イ）傘は暗青紫色.

ウ）柄は基部が多少球根状に脹らみ, 帯褐青紫色, 上部または頂部に繊細な網目模様を表す.

エ）肉は白色, 強い苦みがある.

オ）担子胞子は相対的に小形 (長さ8 µm以下); 傘表皮組織は緩く錯綜した毛状被からなる.

カ）細胞内に帯褐色の色素を持つ広こん棒形の柄シスチジアが柄表皮組織において子実層状被を形成する.

コメント: 白色で強い苦みがある肉そして白色のち帯紅色の管孔はSinger (Singer 1986) の分類概念によるニガイグチ属Tylopilus, ニガイグチ節section Tylopilusに所属することを示唆している. 節内において北米産Tylopilus plumbeoviolaceus (Snell & E.A.Dick) Singer (Bessette et al. 2000; Singer 1947; Snell 1936; Snell and Dick 1941, 1970; Wolfe 1986) および日本産ニガイグチモドキ Tylopilus neofelleus Hongo (Hongo 1967) は本種に最も近縁と思われるが，北米産種は傘の表面が成熟時褐色または灰色を帯びること，紡錘形の傘シスチジアが子実層状被を形成すること (Wolfe 1986)，そして担子胞子がより長形である: 7–11 µm (Snell and Dick 1941) 点で有意差が認められる．ニガイグチモドキは傘の表面がオリーブ褐色～帯紅褐色で，孔口は最初から青紫色に縁取られる．

Tylopilus obscureviolaceus Har. Takah., Mycoscience 45 (6): 374 (2004).

Etymology: The specific epithet means “dark purple”, referring to the dark purple basidiomata.

Macromorphological characteristics: Pileus 70–100 mm in diameter, at first hemispherical, becoming convex to broadly convex, smooth, with slightly appendiculate margin; surface dry, subtomentose, persistently and evenly colored greyish Magenta (13–14D7 to 13–14E7) or deep Magenta (13–14D8 to 13–14E8). Flesh up to 10 mm thick, firm, white, unchanging when cut; odor indistinct, taste very bitter. Stipe 80–100 × 20–30 mm, more or less bulbous at the base, central, terete, solid, finely reticulated above or only at the extreme apex by a thin-veined, purplish reticulum; surface dry, subtomentose, sometimes longitudinally rugulose, whitish to greyish ruby (12D4–5) at the apex, greyish red (10D5 to 11D4–5) to brownish red (10D6) toward the base, violet brown (10E6–7) when fresh; base covered with whitish mycelial tomentum. Tubes up to 8 mm deep, adnate to slightly decurrent, white when young, dull pinkish in age, unchanging when cut; pores small (2–3 per mm), subcircular, concolorous, unchanging where handled.

Micromorphological characteristics: Basidiospores 6–7.2 × 3.3–4 µm (n = 20 spores per two specimens, Q = 1.8), ellipsoid-subfusiform, inequilateral with a shallow suprahilar depression in profile, smooth, pinkish, thick-walled. Basidia 15–20 × 5–8 µm, clavate, four-spored. Basidioles clavate. Cheilocystidia gregarious, 30–40 × 5–10 µm, subcylindrical to subfusiform, smooth, hyaline, thin-walled. Pleurocystidia scattered, similar to the cheilocystidia. Hymenophoral trama bilateral-divergent of the Boletus-subtype; element hyphae 3–6 µm wide, cylindrical, smooth, colorless, thin-walled. Pileipellis a trichoderm of vertically arranged, loosely interwoven elements; terminal cells 30–60 × 4–7 µm, cylindrical, with reddish brown (9D7) to brownish red (10D7) intracellular pigment, thin-walled, without pilocystidia. Pileitrama consisting of loosely interwoven, cylindrical hyphae 4–11 µm wide, smooth, colorless, thin-walled. Stipitipellis hymeniform, consisting of caulocystidia; caulocystidia 13–19 × 5–7 µm, broadly clavate, smooth, with intracellular brownish pigment, thin-walled. Stipe trama composed of longitudinally running, cylindrical cells 4–10 µm wide, sometimes branched, smooth, colorless, with walls up to 0.5 µm. Clamps absent.

　Habitat and phenology: Solitary to scattered on ground in evergreen broad-leaved forests dominated by Quercus miyagii Koidz. and Castanopsis sieboldii (Makino) Hatus. ex T. Yamaz. et Mashiba, May to June.

Known distribution: Okinawa (Iriomote Island).

Specimen examined: KPM-NC0010099 (holotype), on ground in an evergreen broad-leaved forest dominated by Q. miyagii and C. sieboldii, Iriomote Island, Taketomi-cho, Yaeyama-gun, Okinawa Pref., 31May 2002, coll. Takahashi, H.

Japanese name: Sumire-nigaiguchi.

Comments: This species is characterized by its medium to large, boletoid basidiomata with a dark purple pileus and a brownish purple, finely reticulate, bulbous stipe; the white, bitter, unchanging flesh; the relatively small basidiospores (up to 8 µm long); the pileipellis made up of an loosely interwoven trichoderm; the hymeniform stipitipellis consisting of broadly clavate caulocystidia with intracellular brownish pigment; and the habitat of Quercus-Castanopsis forests.

　　The white, unchanging flesh and the white then pinkish pores suggest that this species belongs in the section Tylopilus of the genus Tylopilus as defined by Singer (Singer 1986). Within this section, North American Tylopilus plumbeoviolaceus (Snell & E. A. Dick) Singer (Bessette et al. 2000; Singer 1947; Snell 1936; Snell and Dick 1941, 1970; Wolfe 1986) and Tylopilus neofelleus Hongo, originally described from Japan (Hongo 1967), are similar to T. obscureviolaceus. The North American taxon differs in having a pileus colored more brownish or greyish when mature, much longer basidiospores: 7–11 µm (Snell and Dick 1941), and a hymeniform pileipellis composed of fusoid-ventricose to narrowly fusoid-ventricose pilocystidia (Wolfe 1986). Tylopilus neofelleus is distinct in forming an olive-brown to avellaneous pileus and purplish pores from the first.

References 引用文献

Bessette AE, Roody WC, Bessette AR. 2000. North American Boletes. A color guide to the fleshy pored mushrooms. Syracuse University Press, New York.

Hongo T. 1967. Notes on Japanese larger fungi (19). J Jpn Bot 42: 151–159.

Singer R. 1947. The Boletineae of Florida with notes on extralimital species III. Am Midl Nat 37: 1–135.

Singer R. 1986. Agaricales in modern taxonomy, 4th edn. Koeltz, Koenigstein.

Snell WH. 1936. Notes on Boletes. V. Mycologia 28: 463–475.

Snell WH, Dick EA. 1941. Notes on Boletes. VI. Mycologia 33: 23–37.

Snell WH, Dick EA. 1970. The boleti of northeastern North America. Cramer, Vaduz.

Takahashi H. 2004. Two new species of Agaricales from southwestern islands of Japan. Mycoscience 45 (6): 372–376.

Wolfe CB. 1986. Type studies in Tylopilus. III. Taxa described by Walter H. Snell, Esther A. Dick, and co-workers. Mycologia 78: 22–31.