Heliogaster columellifer (Kobayasi) Orihara & K. Iwase, in Orihara et al., Mycologia 102(1): 112 (2010)
Basidiomata hypogeous to subepigeous, soft, up to 8 cm diam, irregular, variable in size and shape, but generally subglobose to tuberiform, surface smooth or with fulvous scales, primarily pale yellow then ochraceous to light brown at maturity, becoming blackish when rubbed or bruised, often with rudimentary stipe at the base. Gleba soft, sometimes exuding water, whitish to grayish-white, soon becoming bluish to purplish when cut and exposed to air, with minute locules forming labyrinthiform hymenium. Columella present, subgelatinous to cartilaginous, often dendroid but varying in shape, dividing the gleba. Odor sweetish but more or less unpleasant. General staining characteristics on the context of basidiomata. With 70% ethanol, guaiac tincture, phenol or formalin it first was reddish, then navy blue or indigo blue; with 5% KOH there was no reaction.
Basidia clavate to cylindro-clavate, 20–44 x 5–13 μm, 4- spored, more rarely 2- or 3-spored; sterigmata 2– 13 μm long. Cystidia absent. Tramal plates of hyaline, partially inflated, filamentous hyphae 3–10 μm broad, subparallel to hymenium. Columella of interwoven filamentous hyphae 3–7 μm broad. Peridium about 200–1500 μm thick, of thin-walled, sometimes branched, interwoven to subparallel filamentous hyphae, 2.5–7.5 μm broad, in outer part more or less parallel to surface, grading to inner. Spores hyaline to pale ochraceous brown, mulberrylike when immature, globose to ovoid at maturity, warty, with dense, low, longitudinally striated, pyramidal-conical spines 0.5–3 μm high and 1–4 μm broad in water, of which the length varies in different solutions, occasionally with sterigmal appendage at the base; spore wall 1–2.5 μm thick, strongly dextrinoid, covered with hyaline, membranous ectosporium and perisporium normally adhering to inner exosporium (= ornamentation) and thus invisible when mounted in water; spore size 8–(8–)10.8(–13.6)– 15 μm diam excluding ornamentation, Q (length/ breadth) = 1–1.3, (9.9–)10.5–13.5(–17.1)–18 μm diam including ornamentation in water. Clamp connections absent in all tissues.
Habitat, distribution and season: Mainly under Abies firma, but occasionally under Cedrus deodara (Roxb.) G. Don ex Loudon, Quercus serrata Murray, Q. myrsinaefolia Blume, Castanopsis sieboldii (Makino) Hatus., A. veitchii Lindley, Pinus densiflora Sieb. et Zucc. or P. thunbergii Parlatore, ectomycorrhizal; known only from Japan (Honsyu, Shikoku and Kyusyu); autumn to early winter.
Notes: A lectotype specimen was newly designated from the four syntype specimens of the original description by Kobayasi (1937). In addition, although we could not examine an authentic specimen of Arcangeliella mitsueae, of which no additional record has been known since the original description and therefore its taxonomic status remains uncertain, its original description and illustrations by Imai (1957) clearly show H. columellifer basidiomes. The morphology of H. columellifer shows wide variation affected by environmental conditions: the degree of development of the columella and stipe, spore dimensions and broadness of the hyphae often vary even among basidiomes occurring simultaneously at the same location. Moreover the hyphal structure is easily collapsed in lactophenol. This is probably due to a change in osmotic pressure affecting the hyphal cell walls. Such a tendency was not observed in Octaviania spp. (data not shown). Similarly the morphology of the spore ornaments of H. columellifer was strongly affected by alkaline or acidic mounting solutions. For example in cotton blue aqueous solution the morphology was the same as in water but in LCB the spores were immediately stained blue and the ornaments synchronously elongated. Presoaking of the glebal tissue in 5% KOH solution before LCB mounting made the reaction more effective, especially when dried specimens were used. The reactions by this method also were positive in Octaviania spp., but in H. columellifer the perisporium, which covers the ornaments and is absent in Octaviania, expanded slightly as the ornaments elongated. These reactions however were inconsistent when several other mounting solutions (e.g. Melzer’s reagent or 3% KOH) were used for dried specimens; the reaction was positive in some specimens but negative in others.
Overall the micromorphological characters of H. columellifer are apt to be affected by mounting solutions as well as environmental conditions. This feature might be useful to distinguish related species but will require careful microscopic observation in several solutions, including water.
Figure. 1. Bayesian 50% majority rule consensus topology based on the nuclear LSU rDNA dataset of 42 sequences in the Boletales including Octaviania columellifera and Japanese O. asterosperma (5 O. asterosperma sensu Yoshimi & Doi) sequences obtained from 30 002 trees. Bayesian posterior probabilities (PP), and bootstrap (BS) values (%) of 500 BS replicates in ML analysis (MLBS) and of 1000 BS replicates in NJ analysis (NJBS) are indicated as PP/MLBS/NJBS above or below branches or at nodes. Only BS values . 50% are shown.
Figure 2. Bayesian 50% majority rule consensus topology based on the ITS rDNA dataset of 33 sequences in the Boletales including Octaviania columellifera and Japanese O. asterosperma sequences obtained from 33 002 trees. Bayesian PP and BS values (%) of 500 BS replicates in ML analysis (MLBS) and of 1000 BS replicates in NJ analysis (NJBS) are indicated as PP/ MLBS/NJBS above or below branches or at nodes. Only BS values . 50% are shown.
Figure. 3–6. TEM photomicrographs of basidiospores of O. columellifera and related species. 3. Section of an O. columellifera basidiospore wall (specimen TNS-F-17666). 4. Horizontal section of an O. columellifera ornament. 5. Section of a basidiospore wall of Octaviania sp. A (KPM-NC0015344) 6. Section of a basidiospore wall of Xerocomus chrysenteron (specimen TMI-18810; Hachiman Shrine, Baba, Tottori-shi, Tottori Prefecture, 1 Jul 1994, E. Nagasawa 94- 17). En = endosporium; Ep = episporium; Ex = exosporium; Ca = cavity; Pe = perisporium; Ec (arrows) = ectosporium. Scale Bars: 3, 5 = 1 μm; 4,6 = 0.5 μm.