Helicascus gallicus Y. Zhang

Zhang, Ying, Liu, Yanjiao, Zhou, Yupei, Zhang, Xiaodong, Cui, Baokai, He, Shuanghui & Fournier, Jacques, 2014, Helicascus gallicus sp. nov., a new freshwater pleosporalean ascomycete from France, Phytotaxa 183 (3), pp. 183-192 : 185-189

Helicascus gallicus Y. Zhang ter & J. Fourn. sp. nov. ( Fig. 1–3 ).

MycoBank no.: MB 809033

Type :— FRANCE. Ariège , Vernajoul , Vernajoul Brook, Pont Fagé, ca. 350 m, on submerged wood of Alnus glutinosa , 18 July 2013, JF 13153 ( BJFC200224 !, holotype) .

Diagnosis:— Helicascus gallicus differs from other known species in the genus by the freshwater habitat in temperate Europe combined with 25–31 × 9–12 µm brown ascospores with a smooth wall and lacking a mucilaginous sheath, and different ITS and LSU sequences.

released from the ascus. Scale bars: M, N, R, S: 10 µm; O – Q: 5 µm.

Pseudostromata depressed-spherical to lenticular with a flattened ( E) or irregularly obconical ( H, I) base, 340–420 µm high × 580–920 µm diam, scattered, rarely in contact ( A, B), immersed, comprising 2–3 locules beneath a common clypeus ( E, F, H, I), flush with the surface ( E) or raising it into a dome-shaped structure ( B, H, I), with a discoid ( C) to short-cylindrical (D) 80–100 µm diam ostiole, up to 170–200 µm high, porate, at times with pallid orange interior ( C, G) or surrounded by pallid orange tissue ( E, F), common to several locules ( E – I). Peridium 35–55 (–70) µm thick, pseudoparenchymatous, pale-brown, composed of a single region of thin-walled cells textura angularis ( J, K), 4.5– 13.5 µm in their greatest dimension, turning thick-walled and dark brown beneath the clypeus ( L). Clypeus 80–100 (–140) µm thick, black, dark brown in section, opaque, composed of host tissue and thick-walled highly melanised hyphae ( J, L), forming a pseudostroma, isolated or merging with those of adjacent ascomata and blackening the wood surface ( A, B). Hamathecium of cellular pseudoparaphyses 0.8–2.5 µm wide, slightly ramified above asci, embedded in gel matrix ( Q). Asci bitunicate, fissitunicate, clavate, short to long-pedicellate ( M, N), with eight ascospores that are biseriate in upper part and obliquely uniseriate below, the spore-bearing parts 112–128 × 18–22 µm broad, the stipes 24–38 (–45) µm long, with endoascus coiled in the pedicel ( N, O) but rarely involved in a moderate stretching upon dehiscence, with an ill-defined apical ocular chamber visible on immature asci ( P). Ascospores (24.2–) 25.1–31.3 (–33) × (8.8–) 9.3–12.1 (–12.6) µm, Q = (2.1–) 2.2–2.8 (–3); N = 120 (Me = 28.2 × 10.7 µm; Qe = 2.6), obliquely uniseriate and partially overlapping, ellipsoid-fusiform, upper end broadly rounded, lower end more narrowly rounded, slightly curved in side view, with 2–4 large refractive guttules, 1-euseptate, septum submedian (Qc = 0.53–0.58, N = 20), constricted at the septum, the upper cell longer and broader than the lower one, rarely with two delicate additional septa ( S), wall olivaceous brown to medium brown, smooth, surrounded by some fugacious mucilaginous remnants visible in India ink just after release from the ascus ( T) but lacking a defined sheath or appendages.

Culture characteristics:—Colonies on MEA (malt extract agar) reaching up to 2 cm diameter in 14 days at 26– 28 ° C in the dark. Dense, circular, grey in the middle and white at the edge, raised, fluffy with aerial mycelium, edge fimbriate, reverse darkened ( Fig. 3 ). Numerous ascostroma were produced on the sterilized young stems of Koelreuteria sp. after 3 months on MEA, while no sexual or asexual spores were produced on the sterilized pine needles ( Fig. 3 ).

Etymology:—The epithet gallicus refers to Gallia (from Latin Gallia = France), the country from which it is described.

Known distribution:— France.

Asexual state: Unknown.

Additional specimens examined:— FRANCE. Ariège , Vernajoul , Vernajoul Brook, Pont Fagé, ca. 350 m, on submerged wood of Fraxinus excelsior , 2 July 2007, J. Fournier, JF 07137 ( BJFC200033 !, paratype) ; same location ,

on submerged wood of Corylus avellana , 30 June 2008 (JF 08158!, paratype); same location and date, on submerged wood of Robinia pseudoacacia, JF 13155 (BJFC200228!, paratype). Haute Garonne, Mancioux, brook along road D 635 to Aurignac, on submerged wood of Fraxinus excelsior , 28 February 2009 (JF 09012!, paratype). Morbihan, Ste Brigitte, Forêt de Quénécan, Etang du Fourneau, wood of Salix sp. in a dry ditch next to a brook, 23 October 2002, J. Fournier (JF 02202-2!). Vendée, Martinet, Le Jaunet Brook, on submerged wood of Fraxinus excelsior , 20 May 2010, R. Pacaud (JF 10077!).

Note:—Based on several collections in different parts of France, this species appears widespread on submerged wood of various angiospermous trees. The relatively high number of collections studied allowed a good overview of the morphological variations, especially in terms of degree of immersion of pseudostromata, development of the clypeus and ostiolar shape. For example it is assumed that the slightly different configuration in JF 02202-2 is linked to its occurrence in a ditch that had temporarily dried out while all other collections were on typically submerged wood.

Figures

FIGURE 1. Helicascus gallicus. A–D, G–L: Paratype BJFC 200033; E, F: Paratype JF 02202-2. A: Blackened host surface; B: Host surface in close up showing the pseudostromata; C, D: Ostioles in close-up; E: Vertical section of a fully immersed pseudostroma; F: Vertical section of a pseudostroma mounted in chloral-lactophenol showing the multilocular arrangement of ascomata and the common ostiole surrounded by orange material; G: Vertical section of a papillate ostiole in close-up showing the ostiolar canals merging beneath surface; H, I: Vertical sections of pseudostromata showing the multilocular arrangement and the thick clypeus; J–L: Sections of periderm and clypeus mounted in chloral-lactophenol. Scale bars: A: 5 mm; B: 1 mm; E: 0.5 mm; C, D, F, G: 100 µm; H, I: 200 µm; J: 50 µm; K, L: 20 µm.

FIGURE 2. Helicascus gallicus. M–T: Paratype BJFC 200033. M, N: Mature and immature asci in Pelikan black ink showing the pedicels; O: Ascus base with coiled endoascus, in Pelikan black ink; P: Apex of an immature ascus showing the faint ocular chamber,in Pelikan black ink; Q: Hamathecium in India ink, showing cellular pseudoparaphyses embedded in mucilage; R: Two typical ascospores in water; S: Deviating ascospores with two additional septa, in water; T: Ascospore in India ink, with remnants of mucilage after being

FIGURE 3. Helicascus gallicus (BJFUCC200224). Upper (A) and reverse (B) views of colony on MEA 40 days after inoculation. Bars: 1 cm.