Stigmatomyces thoracochaetae Santam., 2021

Santamaria, Sergi & Pedersen, Jan, 2021, Laboulbeniomycetes (Fungi, Ascomycota) of Denmark, European Journal of Taxonomy 781, pp. 1-425 : 269-271

Stigmatomyces thoracochaetae Santam. sp. nov.

MB#840610

Fig. 62

Diagnosis

Similar to S. crassicollis , but differing by overall paler colour, brown wall thickenings below cell II and under perithecium, appendage axis with fewer rounded cells which are longer than broad, as well as by the distal area of appendage axis being curved backwards.

Etymology

The species epithet is derived from the name of the host insect ( Thoracochaeta ).

Type material

Holotype DENMARK – Nordvestsjaelland (NWZ) • On Thoracochaeta brachystoma (Stenhammer, 1855) ( Diptera Sphaeroceridae ); Bjerge Sydstrand ; 55°34.046′ N, 11°9.459′ E; PG35; 24 Oct. 2018; JP 1207; V. Michelsen det.; ZMUC C-F-123733 .

Description

Habitus slender. Thallus hyaline to pale yellowish, with slightly darker perithecial venter, and much darker basal cell of appendage. Basal cell of receptacle (I) obconical, about two times as long as broad, enlarged distally. Suprabasal cell of receptacle (II) almost cylindrical, longer than broad; bearing a brown wall thickening on the lower ventral side ( Fig. 62A–B, D, H–J , arrows). Cell III outwards convex, about twice as long as broad, with its base at the same level as the II–VI septum.

Axis of appendage consisting of a dark, flattened basal cell above a constricted yet darker primary septum and five rounded, externally bulging, superimposed cells which are longer than broad, some of them slightly suffused with brown at their dorsal side. The lower four of these cells (including the basal) bearing one flask-shaped antheridium inwards, each with short, straight necks, and with squarish supporting cells. The two uppermost axial cells bear 1(–2) squarish cells supporting what seem to be sterile antheridia-like cells which are strongly backwards oriented ( Fig. 62F , arrow).

Perithecial stalk cell (VI), secondary stalk cell (VII) and basal cells (m, n, n’) showing brown thickenings on the walls ( Fig. 62J , *). Perithecial venter rounded, almost spherical. Neck long and narrow, gradually tapering until septum w 2 -w 3 which is marked by slight elevations, to the perithecial apex showing four lips, two of them ± protuberant ( Fig. 62C ). Preapical area slightly constricted.

Length from foot to tip of perithecium 220–303 µm. Perithecium (including basal cells) 151–170(–219) × 38–47 µm. Appendage length from primary septum to the apex 55–63(–80) µm. Ascospores length (including expanded sheath at basal area) 16–18 µm.

Thalli were found on the wings and sternites of the hosts. The hosts were sifted from moist, rotten seaweed on a sandy beach.

Remarks

This is the first species of a laboulbeniaceous fungus described on the genus Thoracochaeta . The species is particularly similar to S. crassicollis but may be separated from it by several characteristics like those mentioned in the diagnosis above, specially remarkable those related to the appendage arrangement.

Figures

Fig. 62. Stigmatomyces thoracochaetae Santam. sp. nov. A–B, D. Mature thalli showing brown wall thickening on the lower ventral side of cell II (arrows). C. Perithecial apex in detail. E. Ascospore. F–G. Primary appendage in detail; in F the arrow points to uppermost axial antheridium-like cell which is oriented strongly backwards. H–J. Receptacle and lower area of perithecium in detail at three focusing levels, far (H), middle (I), near (J), showing cells II, III, VI, VII, m, n, n’, thickening on the lower ventral side of cell II (arrows), and brown thickenings on the walls (*). Scale bars: A–B, D = 50 µm; C, E = 10 µm; F–J = 20 µm. Photographs from slide ZMUC C-F-123733 (holotype).