Dictyochaeta aquatica W. Dong & H. Zhang, 2018

Wei, Ming-Jie, Zhang, Huang, Dong, Wei, Boonmee, Saranyaphat & Zhang, Di, 2018, Introducing Dictyochaeta aquatica sp. nov. and two new species of Chloridium (Chaetosphaeriaceae, Sordariomycetes) from aquatic habitats, Phytotaxa 362 (2), pp. 187-199 : 193-195

Dictyochaeta aquatica W. Dong & H. Zhang , sp. nov. ( Fig. 4 )

Type: — THAILAND. Prachuap Khiri Khan: on submerged wood in a small river, 11 September 2015, W. Dong, 34A (holotype: MFLU 15-2691), ex-type culture MFLUCC 15-0983.

Index Fungorum number: — IF 554809; Facesoffungi number: —FoF 04772

Etymology: — In reference to the aquatic habitat, where the holotype was collected.

Saprobic on decaying, submerged wood in freshwater. Sexual morph: Undetermined.Asexual morph: Colonies on natural substrate, effuse, hairy, brown, with white, glistening conidial mass. Mycelium mostly immersed, consisting of branched, septate, smooth, thin-walled, pale brown to brown hyphae. Stroma and hyphopodia absent. Setae 120–180 × 3.3–4.2 μm (= 156.91 × 3.75 μm, n = 10), cylindrical, erect, slightly curved, septate, unbranched, smooth, sterile, dark brown and robust at the base, fading towards the apex, apical cell with a round end or some with flared collarettes, but seems unfunctional, surrounded by 2–4 (5) conidiophores. Conidiophores 47–68 × 3–4.5 μm (= 58.09 × 3.58 μm, n = 10), mononematous, macronematous, brown at the base, fading to pale brown towards the apex, 4–5-septate, unbranched, cylindrical, apical cell slightly swollen 3.8–5 μm (= 4.42 μm, n = 10), erect, straight or slightly curved, smooth, arising singly or in groups from the bases of setae. Conidiogenous cells 3–5 μm (= 4.22 μm, n = 10), monophialidic integrated, terminal, determinate, oblong with conspicuous funnel-shaped collarettes. Conidia 14–18 × 2–3 μm (= 17.3 × 2.5 μm, n = 20), acrogenous, usually aggregated in slimy mass at the apex of setae, hyaline, 0–1-septate, oblong to allantoid, slightly curved, rounded at ends, smooth, with 8–13 μm (= 10.9 μm, n = 20) long hair-like appendages at both ends.

Known distribution: — Thailand.

Culture characteristics: — On PDA, colony circular or irregularly circular, reaching 35 mm in 17 days at 25°C, luminous yellow to light white from above, dark yellow from below, surface hairy, dry, edge entire.

Notes: — In our phylogenetic analysis, the type species D. fuegiana (FMR 13126) was included. This is, however, not an ex-type strain. Another two species, D. simplex (CBS 966.69) and D. siamensis (MFLU 15-1149, ex-type) were also included to represent Dictyochaeta . The new taxon is not related to any Dictyochaeta species, but is related to Thozetella Kuntze, Revis. , Tainosphaeria F.A. Fernández & Huhndorf and Infundibulomyces Plaingam, Somrith. & E.B.G. Jones ( Fig. 1 ), however, they are morphologically distinct. Although all conidia are hyaline with setula at each end, they can be distinguished from each other by conidiophores and conidiogenesis. Dictyochaeta aquatica is characterized by mononematous, unbranched, cylindrical conidiophores arising from the bases of setae, which are longer than conidiophores, and monophialidic conidiogenous cells with funnel-shaped collarettes. Thozetella possesses sporodochial, synnematal conidiophores ( Jeewon et al. 2009), while Infundibulomyces has stromatic conidiomata and holoblastic conidiogenesis ( Plaingam et al. 2003) and Tainosphaeria has no setae ( Fernández et al. 2005). Dictyochaeta aquatica is somewhat similar to Dictyochaetopsis species in phialidic conidiogenesis, but the latter differs in having lateral conidiogenous cells.

The characters of D. aquatica , especially seta surrounded by 2–4 conidiophores and conidia with setulae at both ends, matches Dictyochaeta well. However, it cannot be assigned to any known Dictyochaeta species ( Kuthubutheen & Nawawi 1991; Whitton et al. 2000). This species is considered to differ from Dictyochaeta aciculata S.S. Silva & Gusmão because the latter species have acicular, 3-septate conidia, as compared with allantoid, 0–1-septate conidia in D. aquatica . Dictyochaeta aquatica can be distinguished from D. malaysiana Kuthub. in its smaller conidia (14.5–17.6 × 2.2–2.8 μm vs. 24–32 × 3–4 μm) ( Kuthubutheen 1987). Dictyochaeta tortuosa B. Sutton is distinct in having loosely coiled setae which are tortuous towards the apex ( Sutton 1980, Whitton et al. 2000). In addition, D. aquatica differs from the recently described D. siamensis by its 0–1-septate conidia (aseptate in D. siamensis ), shorter setae (120–180 × 3.3–4.2 μm vs. 165–365 × 3–6 μm) and shorter conidiophores (47–68 × 3.2–4.1 μm vs. 60–100 × 2–5 μm) ( Liu et al. 2016).

Figures

FIGURE 1. RAxML tree generated based on combined ITS and LSU sequence data of the family Chaetosphaeriaceae. Bootstrap support values for maximum likelihood (ML, red) and maximum parsimony (MP, green) equal to or greater than 50% are given above the nodes. Bayesian bootstrap value equal or higher than 90% are indicated on the branch with dot. Newly generated sequences are indicated in blue. The ex-type isolates are in bold. The tree is rooted to Jobellisia luteola (SMH 2753).

FIGURE 4. Dictyochaetaaquatica (holotype,MFLU 15-2691).a. Colonies onsubstrate.b–d.Conidiophores andsetae.e–h.Conidiogenous cells. i–q. Conidia with appendages. r. Germinating Conidium. s–t. Culture on PDA. Bars: b–d = 20 μm, e–h = 5 μm, i–r = 10 μm.