Lophiostoma
Lophiostoma Ces. & De Not., Comm. Soc. crittog. Ital. 1(fasc. 4): 219 (1863).
Index Fungorum number: IF 2933; Facesoffungi number: FoF 00403, 110 morphological species (Species Fungorum 2022), 25 species with molecular data.
Saprobic on herbaceous and woody substrates in terrestrial and aquatic environments. Sexual morph: Ascomata scattered to gregarious, semi-immersed to densely erumpent, carbonaceous, dark brown to black, globose to subglobose. Ostiole slit-like with a small to large flat crest-like apex, which is variable in shape, and apex composed of pseudoparenchymatous cells. Peridium thick at the sides, broad at the apex and thinner at the base, one layered, composed of small lightly pigmented thin-walled cells of textura prismatica. Hamathecium of septate, long, hyaline, anastomosing and branched, cellular pseudoparaphyses, embedded in gelatinous matrix between and above the asci. Asci 8 spored, bitunicate, fissitunicate, cylindrical to clavate, with furcate pedicel, rounded at the apex with a minute ocular chamber. Ascospores uniseriate or partially biseriate, narrowly fusiform with acute ends, 3–5-septate and slightly constricted at each septum, with a distinct oil drop in each cell, smooth-walled, with terminal appendages, senescent ascospores becoming hyaline to pale brown. Asexual morph: Mycelium septate, walls smooth to rough or verrucose, comprising yellowish-brown to reddish brown hyphae. Pycnidia scattered or semi-immersed, uniloculate or rarely biloculate, subglobose, reddish-brown, comprising dark reddish-brown cells. Ostiole circular, surrounded by a thick-walled, well-developed neck, surrounded by flexuous hyphae and an ostiolar canal filled with a tissue of hyaline cells. Conidiophores reduced to conidiogenous cells arising within the acervuli, cylindrical, septate and branched at the base, hyaline. Conidiogenous cells cylindrical, smooth, phialidic, formed at the apex and on the sides, hyaline. Conidia cylindrical, aseptate, hyaline (adapted from Hyde et al. 2013).
Type species: Lophiostoma macrostomum (Tode) Ces. & De Not.
Notes: Lophiostoma is characterised by semi-immersed to densely erumpent ascomata, one layered peridium comprising textura prismatica, and narrowly fusiform, 3–5-septate ascospores. The asexual morph is characterised by uniloculate or rarely biloculate, subglobose pycnidia, conidiophores reduced to conidiogenous cells arising within the acervuli, cylindrical, smooth, phialidic conidiogenous cells and cylindrical, aseptate, hyaline conidia. Chesters and Bell (1970) and Holm and Holm (1988) mentioned that the crest-like apex in Lophiostoma is not a stable character and varies greatly even in the same specimen. Chesters and Bell (1970) treated Lophiotrema as a synonym of Lophiostoma. Chesters and Bell (1970) and Holm and Holm (1988) mentioned Lophiostoma caulium and allied taxa as a species complex. Holm and Holm (1988) added five varieties to this complex and named them as L. caulium var. a to e, based on ascospores size and septation but none of these taxa were formally published. Tanaka and Harada (2003) re-studied three of these varieties (a, d, f) and suggested that their morphology is different in several aspects. Tanaka and Harada (2003) revised Lophiostoma and provided a key to species. Holm and Holm (1988) treated Platystomum as a synonym of Lophiostoma, and this treatment was followed other authors (Yuan & Zhao 1994, Checa 1997, Kirk et al. 2001). Holm and Holm (1988) also considered Lophiotrema as a distinct genus from Lophiostoma based on the differences in the peridium features and asci, while Hirayama and Tanaka (2011) confirmed this observation based on both morphology and phylogenetic analysis of SSU and LSU sequences. Barr (1990) considered Platystomum and Lophiostoma as two distinct genera and placed Platystomum in the Melanommatales based on the trabeculate hamathecium. This concept was followed by Abdel Wahab and Jones (2000) and Tanaka and Harada (2003). In the combined phylogenetic analysis of Zhang et al. (2009) and Suetrong et al. (2009) based on LSU and SSU sequence data, Lophiostoma was reported to be polyphyletic grouping into two well-supported monophyletic clades. Zhang et al. (2009) re-studied the phylogeny and circumscription of Lophiostoma, Lophiotrema and Massarina. Taxa of Lophiostoma are delineated based on the compressed crests, some with raised crests, the uneven width of the peridium, clavate asci and 1 to several septate, hyaline to dark brown ascospores with terminal appendages or mucilaginous sheaths (Holm & Holm 1988, Tanaka & Harada 2003, Zhang et al. 2009). Members of Lophiotrema differs from Lophiostoma in having a peridium of nearly equal thickness, comprising textura angularis and inner layer of small, hyaline cells with thickened walls, and cylindrical or oblong asci (Holm & Holm 1988, Zhang et al. 2009). Lophiostoma has been reported to have phylogenetic affinity with some Massarina taxa (Liew et al. 2002) but species of Massarina have a rounded papilla and hyaline ascospores (Holm & Holm 1988, Hyde & Aptroot 1997). In the phylogenetic analysis of Hirayama and Tanaka (2011) and Thambugala et al. (2014), the three varieties mentioned by Chesters and Bell (1970) and Holm and Holm (1988) formed separate sub-clades. Thambugala et al. (2015) introduced a new genus to accommodate these varieties and established Lophiostoma sensu stricto with Lophiostoma macrostomum as type species. Thambugala et al. (2015) also transferred L. caulium, L. arundinis and L. caudatum to Sigarispora and L. winteri and L. fuckelii to Lophiopoacea and Vaginatispora based on morphology and phylogenetic analyses of LSU, SSU, ITS and TEF1. Thambugala et al. (2015) considered L. macrostomum, L. semiliberum, L. crenatum, L. multiseptatum as Lophiostoma sensu stricto and L. macrostomoides and L. heterosporum as Lophiostoma sensu lato based on phylogenetic analyses. Lophiostoma is a distinct genus in Lophiostomataceae but is still not well-resolved. This genus needs revision as several taxa may belong to other genera. Fresh collections are needed for epitypification. Molecular markers available for Lophiostoma are ITS, LSU, SSU, RPB2 and TEF-1.
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