Bull. Natl. Mus. Nat. Sci., Ser. B, 33(3 · 4), pp. 123–125, December 21, 2007

Notes on Japanese Myxomycetes (V)*—A New Species of Diachea
Found on Moss Covering an Old Concrete WallYukinori Yamamoto
1010–53, Ohtsu-ko, Kochi-shi, 781–5102, Japan

Abstract Diachea muscicola, a new myxomycete species, was found on moss covering an old
concrete wall along the road in Toyama Prefecture, central Japan. This new species is characterized
by an orange stalk and spores that are the largest among all known species of Diachea.
Key words : Diachea muscicola, Japan, myxomycetes, taxonomy.

In Japan, concrete walls are often built along
the road to prevent landslides. With time, thewalls get covered by moss, on which a large
quantity of myxomycetes belonging to the order
Physarales grow during and after the rains insummer (June–July) and fall (September–October) (Yamamoto, 2004, 2006). An interesting
myxomycete was found on moss covering an old
concrete wall during the 2007 annual meeting of
the Japanese Society of Myxomycetology held inToyama Prefecture. Examination revealed thatthe myxomycete was an undescribed species. Its
description and illustration are provided in thispaper.
Diachea muscicola Y. Yamam., sp. nov. [Fig. 1]
Sporocarpia gregaria vel aggregata, stipitata,raro subsessilia, usque ad 1.2 mm alta. Sporotheca plerumque globosa, circa 0.5 mm diam.,
metallica, iridescens, interdum caerulea. Stipes
robustus, calcareus, usque ad 2/3 altiduninis
sporocarpii metiens, apice usque ad 200 m mdiam., prope basin vulgo valde expansus, supra
aurantiacus, in parte inferiore candidus vel pallide aurantiacus, cum crystallis calcis intus etextus. Hypothallus calcareus, aurantiacus velcandidus. Peridium gracile, membranaceum,paene hyalinum. Dehiscentia irregularis superne.
* Notes on Japanese Myxomycetes (IV), in Bulletin of theNational Science Museum, Tokyo, Series B, 26: 107–122,2000.

Columella elongationem stipitis formans, usquead 1/2 altitudinis sporothecae attingens, paeneconica, aurantiaca versus aurantiaculosa. Capillitium e columella radians, divisum dichotome etanastomosans, reticulum incompletum formans,
fuscum, cum extremis multis acutis. Sporae globosae, interdum ellipsoideae, 17.9–20.8 m mdiam. ubi globosae, paene atrae luce reflexa,
cinereobrunneae luce transmissa, cum area aliquantum pallida, valde et irregulariter verrucosae, verrucae magnae, parvae vel connatae.
Plasmodium ignotum. Holotypus: YY-31002(TNS)
Fructifications sporocarpous, rarely subplasmodiocarpous. Sporocarps gregarious or crowded, stipitate, rarely subsessile, up to 1.2 mm tall.
Sporotheca nearly globose, ca. 0.5 mm in diameter, metallic, iridescent, sometimes bluish. Stalkrobust, calcareous, up to 2/3 the length of sporocarp, up to 200 m m in diameter at the apex, usually distinctly expanded near the base, orange inthe upper part, white or pale orange in the lowerpart, with lime crystals within and also on thesurface. Hypothallus calcareous, orange or white.
Peridium thin, membranous, nearly transparent.
Dehiscence irregular from above. Columella acontinuation of the stalk, up to 1/2 the height ofsporotheca, nearly conical, orange to pale orange.
Capillitium radiating from the columella, usuallydivided dichotomously and anastomosed to form
an incomplete net, dark brown, with many pointed free ends. Spores globose, sometimes ellip-124

Yukinori YamamotoFig. 1. Diachea muscicola (YY-31002). A: Three stalked sporocarps. B: Apical part of capillitium. C: Limecrystals in a stalk. D: Apical part of capillitium and a spore.

soid, 17.9–20.8 m m in diameter (mean  19.1,
sd  0.77, n  20) when globose, nearly black inmass, grayish brown by transmitted light, somewhat paler on one side, distinctly and irregularlyverrucose. Plasmodium not observed.
Specimens examined: YY-30944 (on mosscovering a concrete wall, Shogawa-cho, Tonamishi, Toyama Pref., Japan, collected by Y. Yamamoto, 28 VII 2007, mixed with Diderma
chondrioderma and Diderma rugosum), and YY31002 and YY-31003 (on moss covering a concrete wall, Shogawa-cho, Tonami-shi, Toyama
Pref., Japan, collected by T. Kimura, 31 VII2007).
Holotype: YY-31002 in TNS. Isotype: YY31003.
Etymology: Latin muscus-cola (mossdweller).
Japanese name: Koke-jikuhokori.
This new species is characterized by its orange
stalk and spores that are the largest among allknown species of the genus Diachea. With regard
to the orange stalk, it is somewhat similar to D.
arboricola H. W. Keller et M. Skrabal, D. megalospora K. S. Thind and Manocha, D. silvaepluvialis M. L. Farr, D. thomasii Rex, and D. verrucospora Nann-Bremek and Y. Yamam. However,D. muscicola differs from the above-mentioned
species as follows. In D. arboricola, the apex andbase of the capillitium threads are pale and thespores are 11–14.5 m m in diameter (Keller et al.,2004). In D. megalospora, the distinctly verrucose spores have a few clusters of small warts
and are (12.8–)13–14(–16) m m in diameter(Thind and Manocha, 1964; Martin and Alexopoulos, 1969). In D. silvaepluvialis, the columella reaches to the tip of the sporotheca and its
irregularly spinulose spores have denser smallwarts and are 10–14 m m in diameter (Farr, 1976).
In D. thomasii, the pale verruculose spores havelarger darker clusters of small warts and are
11–13 m m in diameter (Rex, 1892; Martin andAlexopoulos, 1969). Further, in D. verrucospora,the spores have scattered spines with discoid tips
and are 12–17 m m in diameter (Nannenga-Bremekamp and Yamamoto, 1987).
Acknowledgements
My sincere thanks go to Dr. Hiromitsu Hagiwara for reading the manuscript. I am also thankful to Mr. Takahiro Kimura for providing valuable specimens.
References
Farr, M. L. 1976. Flora Neotropica. Monograph No. 16.
Myxomycetes. 304 pp. The New York Botanical Garden, New York.

Notes on Japanese Myxomycetes (V)Keller, H. W., Skrabal, M., Eliasson, U. H. and Gaither, T.
W. 2004. Tree canopy biodiversity in the Great Smoky
Mountains National Park: ecological and developmental observations of a new myxomycete species of Diachea. Mycologia 96: 537–547.
Martin, G. W. and Alexopoulos, C. J. 1969. The Myxomycetes. 560 pp. 41 pls. The University of Iowa
Press, Iowa City.
Nannenga-Bremekamp, N. E. and Yamamoto, Y. 1987.
Additions to the Myxomycetes of Japan III. Proceedings of the Koninklijke Nederlandse Akademie van
Wetenschappen, Series C 90: 311–349.

125Rex, G. A. 1892. New American Myxomycetes. Proceedings of the Academy of Natural Sciences of Philadelphia 44: 329–330.
Thind, K. S. and Manocha, M. S. 1964. The Myxomycetes of India-XVII. Mycologia 56: 712–717.
Yamamoto, Y. 2004. Studies on the microhabitats of Myxomycetes (3). Moss growing on concrete. Botany in
Kochi Prefecture, (18): 42–51. (In Japanese).
Yamamoto, Y. 2006. Studies on the microhabitats of Myxomycetes (8). Species on moss growing on concrete infall. Myxomycetes (24): 27–30. (In Japanese).