Taxonomy
Microvesuvius Fryar & D.E.A. Catches. gen. nov. MB848293
Conidiomata pycnidial, immersed in substrate, semi-immersed, or superficial, globose to ellipsoid, black, ostiolate. Wall made of indistinct dark brown cells, irregular thickness and an inner layer of hyaline, ellipsoid, thick-walled cells. Conidiogenous cells hyaline, cylindrical, percurrent proliferation. Conidia hyaline, appendages absent, sheath present.
Etymology: This genus is named after Mount Vesuvius due to the resemblance of the some of the pycnidia to small volcanoes.
Microvesuvius unicellularis Fryar & D.E.A. Catches. sp. nov. MB848294, Figs. 3 & 4
Typus: Australia, South Australia, Scott Creek Conservation Park (S35° 5' 45.90", E138° 40' 59.16) on submerged decaying wood in an ephemeral stream, S. Fryar (holotype AD291633). GenBank numbers: ITS - OQ799382; 28S - OQ799391; TEF1 - OQ866585.
Etymology: The epithet refers to the aseptate conidia.
Saprobic on decaying wood in an ephemeral freshwater stream. Sexual morph undetermined. Asexual morph: On natural substrate. Conidiomata pycnidial, immersed in substrate, semi-immersed or rarely superficial, globose to ellipsoid, lying horizontal to substrate, scattered, black, ostiolate, (134)335–840 ⋅ (135)194–480 µm. Conidiomatal wall made of indistinct dark brown cells, irregular thickness up to 80 µm and an inner layer of hyaline, ellipsoid, thick-walled cells, irregular thickness up to 50 µm. Conidiogenous cells hyaline, cylindrical, percurrent proliferation, (12)22–29(35) ⋅ 3.5–4 µm. Conidia hyaline, aseptate, 1 large oil globule and multiple smaller oil globules, appendages absent, thin irregular sheath surround most conidia, 11–18 ⋅ 10–15 µm.
Culture characteristics: On PDA after 13 days 18 x 14 mm, irregular shape, 1 main colony, several satellite colonies, grey tinged with brown, margin white, 1 mm, slimy appearance, centre fluffy. Agar not discoloured. Reverse grey interior, white margin. Hyphae hyaline, twisted and intertwined, branched, septate, 2.5–3 µm wide. Aerial hyphae hyaline to dark grey, breaking easily, verrucose, 2–4 µm wide.
Additional material examined: Australia, South Australia, Scott Creek Conservation Park (S35° 5' 45.90", E138° 40' 59.16) on submerged decaying wood in an ephemeral stream, S. Fryar, AD291626, AD291608, AD291689. GenBank numbers (AD291626): ITS - OQ799384; 28S - OQ799383; TEF1 - OQ866586.
Notes:
Phylogenetic analyses of ITS and 28S sequences place our specimens in a clade representing Morosphaericaeae (Pleosporales) alongside Aquilomyces and Clypeoloculus as a separate lineage (Fig. 1). There were very few comparison TEF1 Morosphaeriaceae sequences in GenBank, so those data were not used in our analyses.
Most of the species described in the Morosphaericaeae only have descriptions of the sexual morph, so morphological comparisons are mostly not possible. However, the asexual morph of Neohelicascus aquaticus, also within the Morosphaeriaceae, is described and is coelomycetous (Zhang et al., 2013). Microvesuvius unicellularis is different to N. aquaticus in many ways. The conidia of M. unicellularis are globose to subglobose compared with the ellipsoid to obovoid conidia of N. aquaticus, the conidiogenous cells of M. unicellularis are larger, and percurrent, and the pycnidia are immersed and black, rather than superficial and brown.
Morphologically, M. unicellularis shares characters with Hongkongmyces aquaticus. They both have globose to subglobose, hyaline, aseptate conidia with large oil globules. However, the conidia of H. aquaticus do not have a sheath and the conidiogenous cells of H. aquaticus are shorter and not described as percurrent. Hongkongmyces is a member of the family Lindgomycetacae, also within the Pleosporales (Tsang et al., 2014).
Achrochaeta rivulata Fryar & D.E.A. Catches. sp. nov. MB848295, Figs. 5 & 6
Etymology: The epithet refers to the habitat where this species was found, a small stream.
Typus: AUSTRALIA, Scott Creek Conservation Park (S35° 5' 46", E138° 40' 59"), on decaying wood submerged in a stream, 26 August 2020, AD291612. GenBank numbers: ITS - OQ799381; OQ799389; TEF1 - OQ866587
Saprobic on decaying wood in an ephemeral freshwater stream. Sexual morph undetermined. Asexual morph: On natural substrate. Conidiophores, mononematous, macronematous, 77–170 ⋅ 2.5–3.6 µm, simple, dark brown, hyaline or subhyaline at the apex, septate, single or branched at the base into 3, straight or slightly flexuous, cylindrical. Conidiogenous cells 20–37 ⋅ 3 µm, monophialidic, tapering towards the apex, hyaline to subhyaline. Collarettes funnel shaped, 1.5–2 ⋅ 1.5–2 µm. Setae 70–99 ⋅ 3–3.5 µm, rounded, slightly bulbous apex, dark brown at base graduating through to subhyaline at the apex, septate. Conidia 6–10 ⋅ 2.5 µm, hyaline, aseptate, without appendages, straight or curved, ornamentation or sheath, smooth, ellipsoid, one end rounded, one end pointed.
On PDA
Colonies on PDA after 4 weeks 15 ⋅ 12 mm, margin undulate, finely furrowed, velvety, dark grey in patches, white in patches, white outer zone, slightly convex (indented), reverse dark grey, with white margin. Hyphae hyaline, septate, branching, 2.5–4 µm wide. Sheath 8–18 ⋅ 7–10 µm, on some of the darker hyphae, often near the base of the conidiophores. Conidiophores monophialidic, tapering towards the apex, 12–54 ⋅ 2.5–4 µm, mononematous, subhyaline to brown, collarette funnel-shaped 1–2 x 1–2 µm. Conidia 5–13 ⋅ 2–3 µm, hyaline, mostly straight, some curved, aseptate, without sheaths or appendages, ellipsoid, one end pointed, other end rounded.
Additional material examined: AUSTRALIA, Scott Creek Conservation Park (S35° 5' 46", E138° 40' 59"), on decaying wood submerged in a stream, 26 August 2020, (AD291619, AD291630, AD291604, AD291618, AD219605. GenBank numbers (AD291619): ITS - OQ799348, 28S - OQ799390, TEF1 - OQ866588
Notes:
The conidiophores of Achrochaeta rivulata on PDA appear different to those on the natural substrate, wood. They are shorter and lighter in colour. There is also a sheath present on some hyphae which is not visible on the natural substrate. Also, no setae were observed in culture.
The phylogram of ITS, 28S and TEF1 sequences (Fig. 2) shows our new species to be in a clade with Achrochaeta talbotti, Chaetosphaeria hebetiseta and C. dilabens, sister to A. talbotti. In a megaBLAST search of ITS sequences, Achrochaeta rivulata was most similar to A. talbotii (MT454480) with 92% similarity. The two specimens share many characters such as unbranched, brown, septate conidiophores with hyaline phialidic conidiogenous cells, and funnel-shaped collarettes. However, A. talbotti (ICMP 15161) does not have setae, and the conidia are cylindrical-clavate rather than the ellipsoid. In addition, A. rivulata only has an apical opening, whereas A. talbotti (ICMP 15161) has either a single apical opening on the conidiogenous cells or also has lateral openings.
Achrocheata talbotti was originally described as Chaetosphaeria talbotii S. Hughes, W.B. Kendr. & Shoemaker (Hughes & Kendrick, 1968). The original collection of C. talbottti by Hughes and Kendrick was in Kuitpo Forest, South Australia, which is 20 km from the collection site of A. rivulata. There are close similarities between the original description of C. talbotti and A rivulata, but as with the comparison with A. tablotti (ICMP 15161), A. rivulata is monophialidic, not polyphialidic, has setae, and has ellipsoid conidia rather than cylindrical-clavate conidia.