Pleurophragmium parvisporum (Preuss) Hol. - Jech.

Réblová, Martina, Nekvindová, Jana, Bauchová, Lucie & Hernández-Restrepo, Margarita, 2025, Pleurophragmium parvisporum (Ascomycota): One name, seven stories – a case highlighting the need for verification of strains from public culture collections, IMA Fungus 16, pp. e 173033-e 173033 : e173033-

Pleurophragmium parvisporum (Preuss) Hol. - Jech. , Česká Mykol. 26: 223. 1972.

Figs 6 , 7 , 8

Basionym.

Cordana parvispora Preuss , Linnaea 25: 728. 1852.

Synonyms.

Acrothecium simplex Berk. & Broome , Ann. Mag. Nat. Hist., Ser. 3 7: 382. 1861.

Acrothecium simplex var. elatum Grove , J. Bot., 24: 203. 1886; Sacc., Syll. fung. 4: 486. 1886.

Acrothecium parvisporum (Preuss) Sacc. , Syll. fung. 4: 485. 1886.

Pleurophragmium bicolor Costantin, Mucéd. Simpl. : 100. 1888.

Acrothecium bicolor (Costantin) Sacc. , Syll. fung. 19: 14. 1910.

Pleurophragmium simplex (Berk. & Broome) S. Hughes , Canad. J. Bot. 36: 798. 1958.

Dactylaria parvispora (Preuss) de Hoog & Arx , Kavaka 1: 58. 1974 [1973].

Synonymy adopted from Hughes (1958) and Holubová-Jechová (1972).

Description on the natural substrate.

Sexual morph. Not observed. Asexual morph. Colonies effuse, hairy, dark brown to black, beige to pale brown when sporulating; vegetative hyphae immersed or semi-immersed, brown. Conidiophores (80 –) 118–250 (– 270) × (3.5 –) 4–5 µm, often inflated at the base up to 8–11 µm wide, macronematous, mononematous, solitary, erect, straight or slightly flexuous, cylindrical, unbranched, elongating percurrently, bearing a visible frill, brown, lower part usually dark brown and thick-walled, upper part pale brown, thinner-walled, smooth-walled, septate. Conidiogenous cells 26–47 (– 51) × 4.5–5.5 µm, integrated, terminal, sometimes intercalary resulting from the formation of a septum within the original cell, polyblastic, occasionally monoblastic, proliferating sympodially forming a rachis with numerous minute pimple-like denticles or protrusions scattered over the surface, cylindrical, tapering or slightly inflated in the upper part, pale brown, subhyaline towards the apex, smooth-walled; conidiogenesis holoblastic-denticulate. Conidia 10–18 × 3.5–6 µm (mean ± SD = 13.8 ± 2.0 × 4.8 ± 0.7 μm), solitary, dry, acropleurogenous, ellipsoidal, obovoid to subclavate, straight, rounded at the apex, tapering towards the base, with a minute basal scar, hyaline to subhyaline, very pale brown in mass, (0 –) 3 (– 4) - septate, mucoid sheath is inconspicuous, ephemeral, disintegrates as the conidium matures and remains collapsed on the conidial wall giving the conidia a longitudinally crumpled appearance, ornamentation absent at the apex; conidial secession schizolytic.

Culture characteristics.

On CMD colonies 46–48 mm diam., circular, flat, margin entire, mucoid, glossy, pale pink-orange, pale yellow pigment diffusing into the agar, reverse orange. On MLA colonies 44–48 mm diam., circular, flat, margin entire, mucoid, glossy, zonate, apricot at the centre, paler towards the periphery, pale ochre at the margin, yellow pigment diffusing into the agar, reverse yellow-orange. On OA colonies 52–54 mm diam., circular, flat, margin entire, mucoid, glossy, distinctly zonate, whitish- to golden-yellow with deep salmon to orange centre and margin, with an intermediate zone of sparse growth and almost no pigmentation, golden-yellow pigment diffusing into the agar, reverse pale yellow. On PCA colonies 48–50 mm diam., circular, flat, margin entire, mucoid, golden-yellow at the centre, pale yellow towards the periphery, pale yellow pigment diffusing into the agar, reverse pale yellow. Sporulation sparse on OA, absent on CMD, MLA and PCA.

Description in culture.

Colonies on OA effuse. Sexual morph. Not observed. Asexual morph. Mycelium composed of hyaline, septate hyphae, 1–2.5 µm wide. Conidiophores, conidiogenous cells and conidia similar to those on the natural substrate. Conidiophores 88–148 × 3–4 µm in 4 wk, inflated at the base up to 8–9.5 µm wide, extending up to 221 µm long in 8 wk due to the repeated sympodial proliferation of the conidiogenous cells, brown to dark brown and thick-walled in the lower part, paler and thinner-walled towards the apex. Conidiogenous cells 12–27.5 (– 34) × (2.5 –) 3–3.5 µm, integrated, terminal, forming transverse septa during sympodial proliferation and often becoming intercalary with clusters of closely spaced minute denticles or protrusions, arranged along most of the conidiophore length, at the apex with a short rachis of minute denticles or protrusions, polyblastic, cylindrical, pale brown to pale olivaceous brown, apex tends to be paler, smooth-walled; conidiogenesis holoblastic-denticulate. Conidia (9.5 –) 10–14 × 3–4.5 µm (mean ± SD = 11.6 ± 1.0 × 3.6 ± 0.3 μm), hyaline to subhyaline to pale brown, 3 - septate, with a wing-like mucoid sheath located around the middle, or covering the upper two-thirds of the conidium; sheath collapses upon aging, becoming inconspicuous, giving the conidia a longitudinally crumpled appearance, ornamentation absent at the apex. Occasionally the sheath disintegrates towards the upper part of the conidium, where it ruptures and partially detaches from the wall.

Specimens examined.

CZECH REPUBLIC • Central Bohemian Region, Týřovické skály National Nature Reserve near Týřovice ; on decaying wood of a trunk of Carpinus betulus ; 7 May 1971; V. Holubová-Jechová 8587 ( PRA -24033 ) ; Ibid.; Prague, in the valley of Radotínský potok between Choteč and Radotín ; on decaying stem of Smyrnium perfoliatum ; 19 May 1990; V. Holubová-Jechová 8553 ( PRA -24032 ) ; • Hradec Králové Region, Orlické hory Mts., W of Hadinec near Neratov ; 830–880 m a. s. l.; on the inner side of decaying bark of a trunk Fagus sylvatica ; 20 Jul 1969; V. Holubová-Jechová 8588 ( PRA -24034 ) ; • Olomouc Region, Hrubý Jeseník Mts., U Kříže forest between Bělá pod Pradědem and Vidly ; on decaying wood of Fagus sylvatica ; 8 Aug 1971; V. Holubová-Jechová 8584 ( PRA -24035 ) ; • Ibid.; Bučina virgin forest above Františkova myslivna cabin near Kouty nad Desnou ; on decaying wood of a branch of Fagus sylvatica ; 4 Aug 1971; V. Holubová-Jechová 8586 ( PRA -24036 ) . JAPAN • Kyoto, Daitokuji Tempel D ; on unidentified dead twigs; 28 Aug 1983; W. Gams & M. Tsuda ( CBS H-3522 , dried culture CBS H-3506 , living culture CBS 770.83 ) . SLOVAK REPUBLIC • Lúčanská Malá Fatra Mts., Šrámková National Nature Reserve, Kýčery ; on decaying wood of Fagus sylvatica ; 26 Sep 1983; V. Holubová-Jechová 8556 ( PRA -24037 ) .

Habitat and geographical distribution.

Saprobe on decaying wood and herbaceous stems of various hosts, such as Arctium lappa , Brassica oleracea , Campanula medium , Carpinus betulus , Conium maculatum , Epilobium hirsutum , Fagus sylvatica , Filipendula ulmaria , Heracleum sphondylium , Lithocarpus edulis , Polygonum sieboldii , Quercus sp. , Sambucus ebulus , Urtica dioica in the Belgium, Czech Republic, Denmark, France, Germany, Japan, Mexico, Netherlands, New Zealand, Slovak Republic, UK and New Jersey and Washington, USA ( Preuss 1852; Costantin 1888; Berkeley and Broome 1861; Ellis 1968; Holubová-Jechová 1972; Matsushima 1975; Wang 2010; GBIF Secretariat 2023).

According to GlobalFungi database, P. parvisporum was detected in 40 samples. Most records originate from Asia, primarily from Japan and China, with a smaller contribution from South Korea. Additional records come from Europe, all from Spain. The species is most frequently detected in freshwater aquatic habitats (45 %), followed by anthropogenic / urban sites (50 %), shrubland (17.5 %), forest (15 %), and cropland (2.5 %) biomes. It was detected from water (45 %), soil (35 %), air (17.5 %), and dust (2.5 %). These samples were collected across a wide elevational range, 26–948 m, suggesting no strong restriction to high- or low-altitude habitats. Occurrences are associated with MAT ~ 15.4 ° C and MAP ~ 1 059 mm / year.

Notes.

Pleurophragmium was originally described with a single species, P. bicolor , with the protologue and accompanying illustration ( Costantin 1888: fig. 70) reproduced here in Fig. 6 . The species was treated in detail under the synonymous names P. simplex by Ellis (1968), and P. parvisporum by Holubová-Jechová (1972) and Matsushima (1975). These authors reported a relatively broad conidial length range based on multiple collections from wood and herbaceous stems: 10–21 µm (mostly 15.2 µm) × 3.5–6 µm (mostly 4.5 µm) ( Ellis 1968), and 12.5–22.5 (mostly 15–18.5 µm) × 3.5–6.5 µm (mostly 5 µm) ( Holubová-Jechová 1972); for Matsushima’s measurements, see below. Collections from the Czech Republic and Japan examined in this study are consistent with these accounts, although the maximum conidial length observed was slightly shorter than in the published ranges. Our observations confirm that within a single species, conidial dimensions can be variable and are fully congruent with previous descriptions.

In the Japanese material used in this study, conidial dimensions observed both in culture ( CBS 770.83 : 9.5–14 × 3–4.5 µm) and on the natural substrate ( CBS H-3522 : 10–13.5 × 3.5–4.5 µm) were highly similar and fall within the range of variability reported for this species from Europe ( Ellis 1968; Holubová-Jechová 1972; this study). Although conidia from the Japanese material were somewhat shorter than those of the Czech specimens (10–18 × 3.5–6 µm on the natural substrate, this study), their overall morphology is indistinguishable, including the subtle characters such as the ornamentation of the outer conidial wall due to collapsing sheath, a feature not previously reported in the literature but clearly visible under DIC and PHC microscopy (Figs 7 , 8 ). Notably, Matsushima (1975) reported three Japanese collections of P. parvisporum from decaying wood of Lithocarpus edulis and Quercus sp. , with varying conidial sizes in culture: 14.5–25 × 4.5–6.5 µm and 10–16 × 4–6 µm. We therefore concluded that CBS 770.83 and the Czech material of P. parvisporum listed above are conspecific and represent a reliable reference for this species. Attempts to extract DNA from the six herbarium specimens from the Czech Republic were unsuccessful.

The ITS distribution data derived from the GlobalFungi database suggest that P. parvisporum has a broad ecological amplitude (Fig. 5 ), occurring across diverse biomes and climatic conditions, but with a notable concentration in aquatic environments in East Asia ( China, Japan). Records from Spain confirm the distribution of the species in Europe, although based on published data (see above) the species has been repeatedly reported from several European countries. Records from North America, from where the species was also reported ( Wang 2010), and other parts of the world ( GBIF Secretariat 2023), are absent in the GlobalFungi database. This broad ecological and climatic range may indicate genuine ecological versatility, or alternatively, the existence of a species complex, as suggested by the variability in conidial length and occurrence on both herbaceous and woody hosts. To clarify its taxonomy, molecular data from additional strains collected across diverse geographical regions are essential for stabilising the species concept.

Among Pleurophragmium species, P. parvisporum is most comparable to P. fluviale , P. luguense , and P. septatum in its conidial morphology. These taxa share obovoid to fusoid-ellipsoid conidia that are broadly rounded at the apex, tapering to a narrow base with a hilum, predominantly 3 - septate, and hyaline to subhyaline, becoming pale brown at maturity. In the absence of molecular data, distinguishing among these species would be highly challenging. For detailed comparison, see Table 3 .

Interestingly, several biologically active compounds, collectively known as dactylfungins, were isolated from P. parvisporum (strain D 500 obtained from a dead leaf in Japan) and were reported to exhibit antifungal activity against Candida pseudotropicalis and other fungi ( Xaio et al. 1993). However, these findings should be interpreted with caution due to the simple morphology of the species and the recently recognised taxonomic ambiguity among preserved strains identified as P. parvisporum .

Figures

Figure 5. Geographical distribution of the studied species based on environmental DNA records from the GlobalFungi database. Each dot indicates a georeferenced sample in which the species was detected, with the number of samples (n) given in parentheses.

Figure 6. Illustration of conidiophores, conidiogenous cells and conidia of Pleurophragmium parvisporum (as P. bicolor, Costantin 1888).

Figure 7. Pleurophragmium parvisporum. A Sporulating conidiophores B – E upper part of conidiophores with terminal and intercalary conidiogenous cells (nodulose swellings) and conidia (arrows indicate mucoid sheath covering the upper two-thirds of the conidium) F – K conidiophores with conidiogenous cells and conidia L – P conidia (in N, O arrows indicate mucoid wing-like sheath; in P arrow indicates mucoid sheath that disintegrates in the upper part and detaches from the wall Q conidium with longitudinally crumpled wall (arrow indicates the original collapsed sheath which causes the ornamentation) R basal cells of conidiophores S diversity of colony morphology on CMD, MLA, OA, and PCA, respectively (from left to right) after 4 wk. Images: CBS 770.83 on OA (A – E, G – K, M – Q); CBS H- 3522 on natural substrate (F, L). Scale bars: 300 µm (A); 20 µm (G, R); 10 µm (B – F, H – Q); 1 cm (S).

Figure 8. Pleurophragmium parvisporum (PRA - 24032). A Sporulating conidiophores B – F conidiophores with conidiogenous cells and conidia G Basal cell H – L conidia. Images: on natural substrate. Scale bars: 300 µm (A); 20 µm (B, C); 10 µm (D – L).