アミガサホウライタケ

Marasmius brunneospermus Har.Takah., Mycoscience 40: 477-481, 1999　 

熱帯～亜熱帯に広く分布する Marasmius silvicola 近縁種群の仲間で、一般に傘の表面に不規則な網状のシワを表し、基質上に発達した菌糸マットを形成し, 大型の紡錘形側シスチジアを持つ特徴があります。青木実氏が記載したシロシバフタケ並びにチャシバフタケは恐らくアミガサホウライタケの変異型と思われます。また川崎市青少年科学館発行の｢生田緑地のきのこ｣において日本新産種として掲載されているモリノホウライタケ(Marasmius silvicola Singer)はアミガサホウライタケの変異型もしくは近縁種群の一つである可能性があります。

基準産地において白色が混合した褐色の胞子紋を有する性質が確認されていますが、細胞内壊死色素(intracellular necropigments)の可能性が考えられます。

necropigments (Locquin 1953)は、細胞壊死の状態で細胞内に形成される色素で、菌糸細胞、担子器、担子胞子、シスチジアに見られます。ヒメキシメジ属の担子胞子と担子器に典型的と言われていますが、Hygrocybe属の子実層托実質の菌糸細胞にも見られます。

壊死色素が発見された当初、ヒメキシメジ属(Callistosporium)に特異的であると騒がれたのは、それまで無色と考えられてきたキシメジ科の仲間の胞子に有色の色素が発見されたためで、もし壊死色素が胞子以外の菌糸細胞やシスチジアで見つかっていた場合は、ありふれた色素として脚光を浴びることはなかったかもしれません。壊死色素は、キシメジ科やアセタケ類、アカヤマタケ類、変色性があるニガイグチ属など、ハラタケ型軟質菌の菌糸細胞やシスチジアに恐らく普通に存在しているものと推測されます。

韓国 (Antonin et al. 2010)から本種の類似菌が報告されています。

  肉眼的特徴: 傘は径15-50 mm, 最初半球形で縁部は内側に巻き, 後饅頭形になり, 中丘を欠き, 中央部に不規則な網状のしわ～凹みを表し, 半透明の条線を表す周縁部は平坦になり, 吸水性, 平滑, 湿時全体に褐色, 乾くと淡褐色になる. 肉は厚さ3 mm, 類白色, 特別な味や匂いはない; 肉質はホウライタケ属としてはややもろい.　柄は40-70×2-5 mm, ほぼ上下同大であるが基部は僅かに拡大し, 中心生, やせ型, 中空, 表面は全体に粉状, 淡褐色; 根本は発達した剛毛状～綿毛状の白色菌糸体に被われ, 落ち葉の堆積に厚い菌糸マットを形成する.　ヒダは上生,やや疎(柄に到達するヒダは20-24), 幅4-6 mm, 白色～淡褐色,僅かに連絡脈が見られる. 胞子紋は白色部分が混在した褐色.

  顕微鏡的特徴: 担子胞子は 6.4-8×2.4-3.6μm, 楕円形～長楕円形, 無色, 平坦, 非アミロイド, 薄壁, 発芽孔を欠く. 担子器は23-27×3.3-4.6μm, こん棒形, ４胞子性; 偽担子器はこん棒形. 縁シスチジアは30-57×4-13μm, 群生し, 紡錘状片脹れ形または類円柱形～類こん棒形, 無色, 非アミロイド, 薄壁. 側シスチジアは50-95×5-13.5μm, 紡錘形～片脹れ状, 長く屈曲した脚部を持ち, 無色, 非アミロイド, 薄壁. 傘の表皮は子実層状被をなし, 広こん棒形～洋梨形の細胞(16-35×8-13.3μm)からなり (Globularis-type), 淡褐色, 非アミロイド, 時に隔壁にクランプを有し, 薄壁. 柄シスチジアは多生し, 25-55×7-12 μm, 片脹れ状または不規則な円柱形, 平坦, 無色, 偽アミロイド, 薄壁. 全ての組織の菌糸はクランプを持つ.

  分布: 日本 (神奈川, 千葉), 韓国 (Antonin et al. 2010).

  供試標本: KPM-NC0005011 (基準標本), on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 27 May 1998; KPM-NC0005008, on leaf litter in broad-leaved forest,Yamato-shi, Kanagawa-ken, 12 Jun. 1997; CBM-FB-24134, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 16 Jun. 1997; KPM-NC0005013, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 11 Jul. 1997; KPM-NC0005009, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 16 Sept. 1997; KPM-NC0005012, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 15 Jul. 1998; CBM-FB-24135, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 3Jun. 1998; KPM-NC0005010, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 23 Jun. 1998; CBM-FB-24136, on leaf litterin broad-leaved forest, Yamato-shi, Kanagawa-ken, 24 Jul. 1998; CBM-FB-16859, on leaf litter in broad-leaved forest, Chiba-shi, Chiba-ken, 3 Oct. 1998; KPM-NC0005007, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 28 Apr. 1999.

　コメント: ホウライタケ属シバフタケ節 (Marasmius section Globulares Kuhner)に所属し, 傘の表皮に不規則な網状のシワを表し, 基物の間に発達した菌糸マットを形成し, 大型の側シスチジアを持つ. また本種は白色が混合した褐色の胞子紋を持つ点でホウライタケ属の所属種としては異質である. 本州中部の広葉樹林内落ち葉の堆積上で採集された．標本は神奈川県立生命の星・地球博物館 (KPM) 及び千葉県立中央博物館 (CBM) の標本庫に登録, 収蔵されている.

  アミガサホウライタケに外観が似て, 同様に顕著な側シスチジアを有するが, 胞子紋は白色で, 子実体の色はより淡色(ほぼ白色～淡黄褐色) になり, 子実体の類型がオオホウライタケ型～シバフタケ型になる種類 (アミガサホウライタケは通常傘が褐色で, 肉質がもろく, 子実体はナヨタケ型) を, 最近神奈川と千葉において高橋が確認している. これはアルゼンチン, インドネシア (ジャワ）, ニューギニア (？) などの主に熱帯～亜熱帯に分布する Marasmius silvicola Singer (モリノホウライタケ) に近い種類と考えられる. なお, 青木実氏によって記載されたシロシバフタケ並びにチャシバフタケも本菌に近い種類と思われる.

  最近韓国 (Antonin et al. 2010: Persoonia 24, 2010: 49-59)からも本種の分布が確認された.

参考文献

1) Antonin V., Ryoo R., Shin H.-D. 2010. Marasmioid and gymnopoid fungi of the Republic of  Korea. 2. Marasmius sect. Globulares. Persoonia 24: 49-59

https://www.semanticscholar.org/paper/Marasmioid-and-gymnopoid-fungi-of-the-Republic-of-Anton%C3%ADn-Ryoo/29474cda64abbdb1b003e28564f391c9075015e6

2) Desjardin DE and Horak E. 1997. Marasmius and Gloiocephala in South Pacific Region:  Papua New Guinea, New Caledonia, and New Zealand Taxa. Bibl. Mycol. 168: 1-152

3 Desjardin DE, Retnowati A, Horak E. 2000. Agaricales of Indonesia. 2.  A preliminary monograph of Marasmius from Java and Bali. Sydowia 52(2): 92-194

4) Singer R. 1976. Marasmieae (Basidiomycetes - Tricholomataceae). Flora  Neotrop. Monogr. 17: 1-347

Marasmius brunneospermus Har.Takah., Mycoscience 40: 477-481, 1999

  Etymology: brunneospermus = referring to brown spore print.

  Pileus 15-50 mm in diam, at first hemispherical with incurved margin, then broadly convex, not umbonate, center irregularly rugulose- reticulate to pitted, less so toward the translucent-striate margin, hygrophanous, glabrous, evenly colored brown (7D7-7D8, 6D7-

6D8) when wet, drying out to light brown (6D4-6D5) to brownish orange (6C4-6C5) or sometimes whitish overall. Flesh up to 3 mm thick, whitish, odor and taste none; consistency somewhat brittle. Stipe 40-70×2-5 mm, almost equal or slightly enlarged at the base,

central, slender, terete, hollow, light brown (6D4-6D5) or sometimes white overall, entirely pruinose; base covered with white, strigose mycelial hairs or tomentum attached to an extensive mycelial mat in the substratum. Lamellae adnexed, subdistant (20-24 reach the

stipe), 4-6 mm broad, paler concolorous with the pileus, rarely pale brownish in age, slightly intervenose; edges even, concolorous.

  Spore print predominantly brown (6E4-6E6), mottled with white parts (?intracellular necropigments). Basidiospores 6.4-8×2.4-3.6μm, ellipsoid to oblong-ellipsoid, colorless or pale brownish in water, smooth, inamyloid, thin-walled, without germ pore. Basidia 23-27×3.3-4.6μm, clavate, four-spored;

basidiole clavate. Cheilocystidia 30-57×4-13μm, forming a compact sterile edge, fusoid-ventricose or subcylindric to subclavate, colorless when fresh, pale melleous in dried material, inamyloid, thin-walled. Pleurocystidia 50-95×5-13.5μm, fusoid-ventricose, with a long and curved pedicel, colorless when fresh, pale melleous in dried material, inamyloid, thin-walled. Hymenophoral trama of subparallel, subcylindric hyphae with element cells 30-60×4-7μm, smooth, colorless, dextrinoid, with clamped septa, thin-walled. Pileipellis hymeniform, consisting of broadly clavate to pyriform (Globularis-type) cells 16-35×8-13.3μm, pale brown, inamyloid, sometimes with a clamped septum, thin-walled. Pileitrama of subparallel, subcylindric hyphae with element cells 25-60×4-8μm, smooth, colorless, dextrinoid, with clamped septa, thin-walled. Stipitipellis a cutis of parallel, repent hyphae 2-5 μm wide, cylindric, smooth, colorless or pale brown, dextrinoid, with clamped septa, thin-walled; caulocystidia numerous, 25-55×7-12 μm, ventricose or irregularly cylindric to strangulated, smooth, colorless, dextrinoid, thin-walled. Stipe trama composed of longitudinally running, cylindric hyphae 4-15 μm wide, smooth, colorless, dextrinoid, with clamped septa, thin-walled.

  Known distribution: Japan (Chiba, Kanagawa), Republic of Korea (Antonin et al. 2010: Persoonia 24, 2010: 49-59).

  Habitat: Solitary to caespitose on leaf litter in broad-leaved forest dominated by Quercus serrata Thunb. and Pasania edulis Makino, from April to October, common.

  Holotype: KPM-NC0005011, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 27 May 1998. Other specimens examined: KPM-NC 0005008, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 12 Jun. 1997; CBM-FB- 24134, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 16 Jun. 1997; KPM-NC0005013, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 11 Jul. 1997; KPM-NC0005009, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 16 Sept. 1997; KPM-NC0005012, on leaf litter in broad- leaved forest, Yamato-shi, Kanagawa- ken, 15 Jul. 1998; CBM-FB-24135, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 3 Jun.1998; KPM-NC0005010, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 23 Jun. 1998; CBM-FB-24136, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 24 Jul. 1998; CBM-FB- 16859, on leaf litter in broad-leaved forest, Chiba-shi, Chiba-ken, 3 Oct. 1998; KPM-NC0005007, on leaf litter in broad-leaved forest, Yamato-shi, Kanagawa-ken, 28 Apr. 1999.

  Japanese name: Amigasa-houraitake.

  Notes: The diagnostic features of this species are the collybioid basidiomata with a hygrophanous, irregularly wrinkled to rugulose reticulate pileus, the white, extensive mycelial mat attached to base of the stipe, the brown spore print mottled with white parts, and the

fusoid-ventricose pleurocystidia with a long and curved pedicel. The collybioid habit, the dextrinoid tramal hyphae, and the hymeniform pileipellis dominated by Globularis-type cells suggest placement of this taxon in the genus Marasmius section Globulares Kuhner in Singer'

s classification (Singer, 1986). However, its brown spore print mottled with white parts is apparently unusual as an infrataxic character in the genus Marasmius. It is possible that a new section needs to be proposed, but more material, especially fresh specimens, and chemotaxonomical analysis concerning its spore pigment are considered to be necessary before final disposition of this taxon can be made. Within the section Globulares, Marasmius brunneospermus seems to be most closely allied with three tropical and subtropical taxa which have conspicuous fusoid-ventricose pleurocystidia, viz, Marasmius phlebodiscus Desjardin & Horak (Desjardin & Horak, 1997) from New Guinea, Marasmius silvicola Singer (Singer, 1976) from Argentina, and Marasmius trogioides Corner (Corner, 1996) from Borneo. According to the literature, M. phlebodiscus has an obtusely umbonate pileus, crowded lamellae (28-34), an insititious, appressed fibrillose stipe without caulocystidia, and occasionally catenulate, fusoid and mucronate cheilocystidia. M. silvicola has a smooth, deep colored pileus, greyish cinnamon to yellowish lamellae, and vesiculose cheilocystidia. M.trogioides forms a bright cinnamon fawn to fulvous ochraceous pileus, insititious stipe, much larger basidiospores (9-11.5×4.7-5.5 μm in var.trogioides, 10.5-13.5×6-7 μm in var. megaspora), clavate cheilocystidia, occasionally clustered, clavate caulocystidia, and clampless hyphae.