ダルマイグチ 

Rubinoboletus monstrosus Har. Takah., Mycoscience 48(2): 95 (2007) 

柄は最初から中空で常に太短いため、子実体は達磨のような形状に見えます。キニガイグチ近縁種群の仲間で、キニガイグチについては Rubinoboletus 属に転属させる考え方もありますが、分子系統ではニガイグチ属に近縁とされています。Rubinoboletus属はコショウイグチ属に分類されてきた Chalciporus rubinus (W.G. Sm.) Singerが基準種とされていることから、属の分類概念に疑問が残ります。

ダルマイグチについて分子解析はまだ行われていませんが、北米産 Tylopilus ballouii 近縁種群との形態的類似性から判断すると, ニガイグチ属に置くのが妥当かもしれません。 

　肉眼的特徴 (Figs. 245–250): 傘は径50–140 mm, 最初半球形のち中高偏平になり, しばしば不規則な形状になり, 時に中央部に亀甲状のひび割れを生じ, 縁部は管孔側に僅かに突出する; 表面は粘性を欠き, やや密綿毛状～ほぼ平滑, 全体に帯赤黄褐色～淡黄褐色, 時に若いときレンガ赤色を帯びる.　肉は厚さ12 mm 以下, 類白色, 変色性を欠き, 不快な臭気と苦みがある. 柄は20–40 × 15–45 mm, 著しく短形, ほぼ上下同大または基部に向かってやや細くなり, 中心生, 最初から中空, 網目を欠く; 表面は乾性, ほぼ平滑またはやや密綿毛状, 傘より淡色～淡黄褐色; 根元は不明瞭な白色綿毛状菌糸体に被われる.　管孔は長さ10 mm以下, 直性または柄の周囲においてやや陥入し, 最初灰橙色のち黄褐色, 空気に触れても変色しない; 孔口は小型 (2–3 per mm), 円形～やや角形, 管孔と同色. 

顕微鏡的特徴 (Fig. 244): 担子胞子は5–6 × 3.5–4 μm (n = 35, Q = 1.4–1.5), 卵形～短楕円形, 平坦, 淡黄色 (水封). 担子器は25–30 × 6–8 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, 34–52 × 8–13 μm, 紡錘形, 平滑, 無色, 薄壁. 側シスチジアは散在し, 30–60 × 5–15 μm, 紡錘形, 黄褐色の内容物を持ち (水封), 薄壁. 子実層托実質の菌糸は幅6–10 μm, 円柱形, 並列し, 平滑, 無色, 薄壁. 傘表皮組織は緩く錯綜した菌糸からなる毛状被; 菌糸は幅 5–8 μm, 円柱形, 黄褐色の細かい粒状色素が沈着し (水封), 薄壁. 傘実質の菌糸は幅4–13 μm, 円柱形, 緩く錯綜し, 平滑, 無色, 薄壁. 柄表皮組織は平行菌糸被; 菌糸は幅2–5 μm, 円柱形, 平滑, 無色, 薄壁; 柄シスチジアは12–35 × 4–10 μm, 広こん棒形, 平滑, 無色, 薄壁. 柄実質の菌糸は幅6–20 μm, 縦に沿って配列し, 円柱形, 無分岐, 平滑, 無色, 薄壁. 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.

分布: 沖縄 (石垣島).

主な特徴

ア）子実体は中～大型で歪な形状になることが多い.

イ）傘は赤褐色～黄褐色.

ウ）柄は最初から中空で常に太短い (長さと太さがほぼ同等).

エ）肉は類白色で変色性を欠き, 不快な臭気と苦みがある.

オ）担子胞子は短楕円形, 淡黄色.

カ）発達した側シスチジアが存在し, 黄褐色の内容物を持つ. 

コメント:  類白色で変色性を欠く肉および淡黄色, 淡楕円形の担子胞子は Rubinoboletus属, クリイロイグチ属Gyroporus, またはニガイグチ属Tylopilusとの類縁を示唆しているが, 柄に網目を欠くこと, 担子胞子が短形且つ淡黄色であること, 有色の内容物を持つ発達した側シスチジアを有すること, そしてクランプを欠く性質は Heinemman & Rammeloo (Heinemman and Rammeloo 1983; Li and Watling, 1999; Watling and Gregory, 1988; Watling and Li, 1999) の定義による Rubinoboletus属に近縁であることを示唆している.

属内において本種は北米産 Rubinoboletus ballouii (Peck)  Heinemman & Rammeloo  (Singer 1947; Snell and Dick 1970; Corner 1972; Heinemann and Rammeloo 1983; Bessette et al. 2000) に近い性質を示すが, 北米産種は傘が明るい橙赤色を帯びること, 柄はより長く, 中実であること, そして孔口が成熟時大型 (幅 2 mmに達する) になる点で区別できる. なお日本産キニガイグチについては傘の色が黄褐色を帯びる点で北米産種とは系統が異なる可能性が高いと思われる.

短形で太い柄を持つ性質はオーストラリア産 Rubinoboletus caespitosus (Clel.) T.-H. Li & R. Watling (Cleland, 1924; Grgurinovic, 1997; Li and Watling, 1999; Watling and Li , 1999) と共通するが, オーストラリア産種は担子胞子がより大型: 8–8.9 × 5–5.5 µm (Cleland 1924) で、子実体は一般に叢生し, 柄が中実とされている.

Rubinoboletus monstrosus Har. Takah. 

Mycoscience 48 (2): 95 (2007) [MB#530008].

Etymology: The specific epithet means “monstrous”, referring to the peculiar habit of the basidiomata which consist of an often irregularly shaped pileus and an extremely short stipe.

Macromorphological characteristics (Figs. 245–250): Pileus 50–140 mm in diameter, at first hemispherical, expanding to broadly convex, often irregularly shaped, sometimes rimose-areolate at the center, with a slightly appendiculate margin; surface dry, subtomentose to nearly glabrous, greyish-orange (5B6) or brownish-orange (5C5-6) to yellowish-brown (5D5) overall, occasionally tinged with reddish-brown (8D7) when young and fresh. Flesh up to 12 mm thick, whitish, unchanging when exposed; odor strongly disagreeable (resembling rotten meat), taste bitter. Stipe 20–40 × 15–45 mm, very short, subequal or tapering toward the base, central, terete, hollow from the outset, non-reticulate; surface dry, almost glabrous to subtomentose, entirely yellowish-brown (5D4-5); base covered with a indistinct, whitish mycelial tomentum. Tubes up to 10 mm deep, adnate or slightly depressed around the stipe, greyish-orange (5B4-5) when young, then yellowish-brown (5D6) at maturity, unchanging when exposed; pores small (2–3 per mm), rounded to subangular, concolorous.

 Micromorphological characteristics (Fig. 244): Basidiospores 5–6 × 3.5–4 μm (n = 35, Q = 1.4–1.5), ovoid-ellipsoid, smooth, pale yellow in water, walls up to 0.5 μm. Basidia 25–30 × 6–8 μm, clavate, four-spored. Basidioles clavate. Cheilocystidia gregarious, 34–52 × 8–13 μm, fusoid-ventricose, smooth, hyaline, thin-walled. Pleurocystidia scattered, 30–60 × 5–15 μm, fusoid-ventricose, smooth, with yellowish-brown to golden-yellow contents (in water), thin-walled. Elements of hymenophoral trama 6–10 μm wide, cylindrical, parallel to each other, smooth, hyaline, thin-walled. Pileipellis composed of a trichoderm formed by loosely interwoven hyphal elements, 5–8 μm wide, cylindrical, encrusted with yellowish-brown fine granules (in water), thin-walled. Pileitrama of cylindrical, loosely interwoven hyphae 4–13 μm wide, smooth, colorless, thin-walled. Stipitipellis composed of parallel, repent hyphae 2–5 μm wide, cylindrical, smooth, colorless, thin-walled; caulocystidia 12–35 × 4–10 μm, broadly clavate, smooth, hyaline, thin-walled. Stipe trama composed of longitudinally arranged, cylindrical cells 6–20 μm wide, unbranched, smooth, colorless, thin-walled. Clamps absent in all tissues.

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.

Specimens examined: KPM-NC0013139 (holotype), on ground in an evergreen broad-leaved forest dominated by Q. miyagii and C. sieboldii, Banna Park, Ishigaki-shi, Okinawa Pref., 19 May 2004, coll. Takahashi, H; KPM-NC0013141, same location, 20 May 2003, coll. Takahashi, H.; KPM-NC0013142, same location, 25 May 2004, coll. Takahashi, H.; KPM-NC0013143, same location, 14 May 2005, coll. Takahashi, H.; KPM-NC0013140, same location, 20 May 2005, coll. Takahashi, H.

Known distribution: Okinawa (Ishigaki Island).

Japanese name: Daruma-iguchi.

Comments: Features delimiting this species include the medium to large basidiomata composed of an often irregularly shaped, brownish-orange to yellowish-brown pileus and an extremely short, non-reticulate, hollow stipe; the whitish, unchanging flesh with bitter taste and unpleasant smell; the short ellipsoid, light yellowish basidiospores; the prominent pleurocystidia containing yellowish-brown to golden-yellow contents; and the habitat of evergreen broad-leaved forests.

The unchanging, whitish flesh and the pale yellow, short ellipsoid basidiospores suggest that this species is closely related to the genera Rubinoboletus, Gyroporus, or Tylopilus. If greater taxonomic emphasis is placed on the non-reticulate stipe, the short ellipsoid, light yellowish basidiospores, the prominent pleurocystidia with yellowish-brown to golden-yellow contents, and the lack of clamp connections, it would be better placed in the genus Rubinoboletus Pilát & Dermek in the sense of Heinemman and Rammeloo (Heinemman and Rammeloo 1983; Watling and Gregory 1988; Li and Watling 1999; Watling and Li 1999).

Within the genus Rubinoboletus, it seems to be allied with Rubinoboletus ballouii (Peck) Heinemm. & Rammeloo, originally described from North America (Singer 1947; Snell and Dick 1970; Corner 1972; Heinemann and Rammeloo 1983; Bessette et al. 2000). The latter species, however, differs from R. monstrosus in producing a bright orange-red pileus, a much longer, solid stipe and larger pores reaching 2 mm at maturity. With respect to the taxonomy of “Tylopilus” [H1] ballouii sense Nagasawa from Japan (Nagasawa 1989), it is likely to be distinct from the North American species in that Japanese specimens have a yellowish-brown pileus.

Rubinoboletus caespitosus T.H. Li & Watling from Australia (Cleland 1924; Grgurinovic 1997; Li and Watling 1999; Watling and Li 1999) is somewhat similar in appearance, but it has a solid stipe, significantly larger basidiospores: 8–8.9 × 5–5.5 µm (Cleland 1924) and a caespitose habit.

References 引用文献

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Cleland JB. 1924. Australian Fungi. Notes and descriptions 5. Trans R Soc South Australia 48: 236–252.

Corner EJH. 1972. Boletus in Malaysia. Government Printing Office, Singapore.

Grgurinovic CA. 1997. Larger Fungi of South Australia. The Botanic Gardens of Adelaide and State Herbarium, Adelaide.

Heinemann P, Rammeloo J. 1983. Gyrodontaceae p.p. Boletineae. Flore Illustrée des Champignons d’Afrique Central 10: 173–198.

Li T-H, Watling R. 1999. New taxa and combinations of Australian boletes. Edinb J Bot 56: 143–148.

Nagasawa E. 1989. Boletaceae. In: Imazeki R, Hongo T (eds), Colored illustrations of mushrooms of Japan II. Hoikusha, Osaka, pp 1–44 (in Japanese).

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

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

Takahashi H. 2007. Five new species of the Boletaceae from Japan. Mycoscience 48 (2): 90–99.

Watling R, Gregory NM. 1988. Observations on the Boletes of the Cooloola Sandmass, Queensland and notes on their distributions in Australia. Part 2B. Smooth-spored taxa of the family Gyrodontaceae and the genus Pulveroboletus. Proc R Soc Queensl 99: 65–76.

Watling R, Li T-H. 1999. Australian Boletes. A preliminary survey. Royal Botanic Garden, Edinburgh.