ヒカゲオチエダタケ

Marasmius occultatus Har. Takah., Mycoscience 41: 313-321, 2000

ハリガネオチバタケ節(sect. Sicci)の仲間で、シスチジアの発達が悪く、長形(14-16×3-4 μm)の胞子を持つ性質があります。中国から報告された Marasmius pseudoconfertus (Deng et al. 2011)は本種の近縁種群の一つで、外観はヒカゲオチエダタケに酷似しますが、広葉樹林内の腐植上に発生し、傘がやや濃色で、柄の幅がより太いとされています。

種小名 occultatus (ｵｩｺｩﾃｪｲﾀｽ)は、「隠匿、秘密、隠すこと」を意味するラテン語の形容詞で、日陰の隠れた場所に発生することに由来します。

　肉眼的特徴: 傘は径 12-27 mm, 最初半球形, のち饅頭形～平開し, 平坦, 周縁部に浅い溝線を表し, 乾性, 光沢を欠き, ビロ－ド状, しばしば成熟すると著しい白色粉状帯を表し, 帯褐橙色～褐色または淡褐色, 中央部はやや暗色になる. 肉は薄く (1 mm以下), 傘より淡色, 特別な味や臭いはない. 柄は 30-50×0.8-1.3 mm, 円柱形, 中心生, やせ型, 強靱, 中空, 光沢があり, 平滑, 傘と同色, 頂部は淡色; 基部は発達した白色の長い剛毛状菌糸体に被われる. ヒダはやや離生～上生, やや疎～やや密 (柄に到達するヒダは 17-20), 幅 2.5 mm, 白色, 発達し

た連絡脈は見られない; 縁部は平坦, 同色. 胞子紋は白色.

  顕微鏡的特徴: 担子胞子は 14-16×3-4 μm, 幅の狭いこん棒形～円柱状紡錘形, 平坦, 無色, 非アミロイド, 薄壁. 担子器は 23-32×6-8 μm, こん棒形, ４胞子性; 偽担子器は紡錘形～紡錘状こん棒形. ヒダの縁部は稔性. 縁シスチジアの存在は稀で, 傘の上表皮細胞に似るがより小型で無色. 側シスチジアを欠く. 子実層托実質は平列型～不規則型; 菌糸は傘実質に似る. 傘の上表皮はハリガネオチバタケ型 (Siccus-type) の細胞からなる子実層状被を形成し, ハリガネオチバタケ型の細胞 (付属糸を除く) は 27-34×7-11 μm, こん棒形または不規則な形状を成し, 時に裂け目を生じ, 頂部に黄褐色の指状付属糸 (2-7×0.8-1.5 μm) が密生し, 細胞壁は黄褐色で厚さ 1 μm以下, 偽アミロイド. 傘実質の菌糸は幅 4-13 μm, 平列するかまたは緩く錯綜し, 類円柱形, しばしば肥大し, 無色, 偽アミロイド, 薄壁. 柄の表皮は円柱形の菌糸 (幅 2-4 μm)が平行菌糸被を成し, 褐色の色素を有し, 偽アミロイド, 薄壁; 柄シスチジアを欠く. 柄の実質は縦に沿って配列した円柱形の菌糸 (幅 5-8 μm) からなり, 細胞壁は淡

黄褐色で厚さ 1 μm以下, 偽アミロイド. 全ての組織において菌糸はクランプを持つ.

  供試標本: KPM-NC0006513 (holotype), solitary to scattered, on dead fallen branches in lowland forests dominated by Aphananthe aspera (Thunb. ex Murray) Planch. and Quercus myrsinaefolia Blume, Yamato-shi, Kanagawa-ken, 5 Jul. 1998; ibid. 11 July 1996; ibid. 23 Sept. 1997; ibid. 17 Sept. 1998; KPM-NC-0006039, ibid. 10 Nov. 1999.

  Japanese name: Hikage-ochiedatake.

Marasmius occultatus Har. Takah., Mycoscience 41: 313-321, 2000　

  Pileus 12-27 mm in diam, at first hemispherical, then convex to plane, rarely subumbonate, smooth toward a somewhat striatulate margin, dull, dry, opaque, minutely velutinous, strongly pruinose in age, brownish orange (7C7-7C8) to brown (7D7-7D8) or brownish orange (6C5-6C6) to light brown (6D5-6D6), with a slightly darker disk. Flesh thin (up to 1 mm), paler concolorous with the pileus, odor and taste not distinctive. Stipe 30-50×0.8-1.3 mm, cylindrical, central, slender, terete, tough, hollow, shiny, glabrous, concolorous with the pileus, paler toward the apex; base covered with white, mycelioid bristles. Lamellae subfree to adnexed, subdistant to subclose (17-20 reach the stipe), up to 2.5 mm broad, white, not intervenose; edges even, concolorous.

  Spore print pure white. Basidiospores 14-16×3-4 μm, narrowly clavate to cylindrical-fusoid, smooth, colorless, inamyloid, thin-walled. Basidia 23-32×6-8 μm, clavate, four-spored; basidioles fusiform to subfusiform-clavate. Edges of lamellae fertile. Cheilocystidia infrequent, similar to the pileipellis elements but smaller and colorless. Pleurocystidia not seen. Hymenophoral trama subregular to irregular; element hyphae similar to those of the pileitrama. Pileipellis a hymeniform layer of Siccus-typed cells 27-34×7-11 μm, clavate or irregular in outline, sometimes lobed, with yellowish brown apical setulae 2-7×0.8-1.5 μm, with smooth, yellowish brown walls up to 1 μm thick, dextrinoid. Tramal hyphae of pileus 4-13 μm wide, subparallel or loosely interwoven, subcylindric, often inflated, smooth, colorless, dextrinoid, thin-walled. Stipitipellis a cutis of parallel, repent hyphae 2-4 μm wide, cylindric, smooth, with brown cytoplasmic pigments, dextrinoid, thin-walled; caulocystidia absent. Stipe trama composed of longitudinally running, cylindric hyphae 5-8 μm wide, with smooth, pale yellowish brown walls up to 1 μm thick, dextrinoid. Clamps present in all tissues.

  Known distribution: Japan (Kanagawa).

  Specimens examined: KPM-NC0006513 (holotype), solitary to scattered, on dead fallen branches in lowland forests dominated by Aphananthe aspera (Thunb. ex Murray) Planch. and Quercus myrsinaefolia Blume, Yamato-shi, Kanagawa-ken, 5 Jul. 1998; ibid. 11 July 1996; ibid. 23 Sept. 1997; ibid. 17 Sept. 1998; KPM-NC-0006039, ibid. 10 Nov. 1999.

  Japanese name: Hikage-ochiedatake.

  Notes: Marasmius occultatus is characterized by its brownish orange or light brown pileus and stipe, the white, strigose basal mycelium, and the lignicolous habitat. In addition, this species is distinct because of the relatively long, cylindrical-fusoid basidiospores, the fusiform basidioles, the Siccus-typed pileipellis elements, and the fertile lamella without hymenial cystidia. The combination of these features suggests that M. occultatus is a member of the section Sicci  Singer, subsection Siccini  Singer, series Leonini Singer (Singer, 1976; 1986).

  Marasmius occultatus is macromorphologically similar to Marasmius cohaerens (Pers.: Fr.) Cooke & Quel., a well defined temperate species (Antonin and Noordeloos, 1993; Breitenbach & Kranzlin, 1991; Gilliam, 1976), and North American Marasmius plicatulus Peck (Desjardin, 1987a, 1987b). Marasmius cohaerens differs in producing much shorter basidiospores (8.0-10.5×4.0-5.5 μm: Antonin and Noordeloos, 1993), Siccus-typed cheilocystidia, and setiform cystidia in the cuticle and hymenium. Marasmius plicatulus differs in having dark reddish brown pileus, broader basidiospores (4.8-6.3μm: Desjardin, 1987), Siccus-typed cheilocystidia, and basidiome formation on humus or grassy areas.