Arenariomyces Hohnk

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Arenariomyces Höhnk, Veröff. Inst. Meeresf. Bremerhaven 3: 28 (1954) Description. Saprobic on wood, sand or calcareous substrates. Sexual morph. Ascomata solitary, sometimes gregarious, globose to subglobose, papillate, periphyses absent, carbonaceous, dark brown to black, superficial or immersed, sometimes fully or slightly covered with scattered brownish black spines, subiculum present on materials such as sand grains and shells. Peridium variable in arrangement of cells, usually comprised of dark, thick-walled cells, cell spherical to subsphaerical with inconspicuous pit connections. Pseudoparenchyma thin-walled, and deliquescing at maturity. Catenophyses absent or deliquescing if present. Asci 8 - spored, fusiform to subclavate or pyriform, short-stalked, unitunicate, thin-walled and deliquescing early. Ascospores 1–3 septate, fusiform, cylindrical, ellipsoidal or oblong, constricted / slightly constricted at the septa, hyaline and appendaged. Appendages 3 - subterminal appendages at each end of the spore, straight or curved, with a bulbose base and long attenuated arms initially wrapped along the length of the ascospore and unfolding at maturity. Asexual morph. Undetermined. Type species. Arenariomyces trifurcatus Höhnk, Veröff. Inst. Meeresf. Bremerhaven 3: 30 (1954). Notes. Arenariomyces species are saprobes on wood and in wood associated with sand grains, the mycelium growing out from the wood into the surrounding sand, and forming fruiting bodies on sand particles (Jones et al. 1983 a; Kohlmeyer and Volkmann-Kohlmeyer 1989; Jones et al. 2009; Koch 2013). Also reported on dead mangrove wood, mangrove leaves, seaweeds, seagrasses, sand and sea foam. They are mostly reported from temperate parts of the world (Jones et al. 2009; Koch 2013). Morphologically, this genus is distinguished from Corollospora by the ascospores lacking equatorial appendages, primary polar and secondary exosporial appendages, and presence of subterminal appendages, appendages being outgrowths of the spore wall and composed of a bulbous base and rigid spine terminating in a bifurcated or disc-like structure and lacking an exosporium (Jones et al. 1983 a). Arenariomyces truncatellus and A. majusculus ascomata are formed in the outermost part of the wood substrate and bearing spines in contrast to A. parvulus, A. trifurcatus, and A. triseptatus (Jones et al. 2009). However, the stability of ascomatal characters in the genus is variable (on wood / on hard surfaces, spines / no spines). Arenariomyces majusculus is lignicolous with ascomata embedded in wood, in contrast to other species which form subicula on grains of sand or calcareous substrates (Kohlmeyer and Volkmann-Kohlmeyer 1989). Arenariomyces species are different from each other mainly by ascospore septation and dimensions; A. majusculus (33 × 11.5 µm), A. truncatellus (21.4 × 10.2 µm), A. parvulus (16–25 × 3–6 µm), A. trifurcatus 28–32 × 9–11 µm are 1 - septate while A. triseptatus is 3 - septate (Kohlmeyer 1984; Koch 2013). Considering the ascospore appendage ontogeny, ascospore appendages are initially wrapped along the length of the ascospore, the appendages unfolding at maturity. Appendages are outgrowths of the spore wall, with a bulbous base, slender, rigid, round shaft, terminating in an apical thickening, pad or bifurcated structure (Jones et al. 1983 a). Fully developed spores lacking an exosporium; the episporium laciniated and absent at the point of appendage attachment. The outer surface of the basal third of the appendage composed of 2–4 laminae, the shaft containing a granular core bounded by an electron-opaque homogeneous layer (Jones et al. 1983 a). Molecular sequence data is available for all the Arenariomyces species in the GenBank. Pang et al. (2008 a), based only on 28 S rDNA sequence data, showed that the taxonomic placement of this genus within Halosphaeriaceae is polyphyletic, while with combined 18 S and 28 S rDNA analyses Jones at al. (2017) showed that Arenariomyces species formed a monophyletic group and suggested that the phylogenetic placement of this genus within Halosphaeriaceae is well-resolved. In this study, the five Arenariomyces species formed a monophyletic group with Haiyanga salina in the Halosphaeriaceae (Fig. 4) all possessing 3 - subterminal appendages at each end of the ascospore and this is supported by molecular data, all with low support (Jones et al. 2017). Arenariomyces triseptatus, with 3 - septate ascospores and constricted at the septa, differs from other species in the genus. Molecular evaluation. The genus grouped well within the Halosphaeriaceae (Sakayaroj et al. 2011; Jones et al. 2015) and this is accepted by Maharachchikumbura et al. (2015) and Jones et al. (2019). Our divergence-time analysis indicates that Arenariomyces originated from the mid-Cretaceous (~ 111 MYA, 95 % CI: 34.8–352.2 MYA), supporting its recognition as a distinct and independently evolving lineage within the family (Fig. 5).

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.