Dimeromyces oculatus Santam., 2021

Santamaria, Sergi & Pedersen, Jan, 2021, Laboulbeniomycetes (Fungi, Ascomycota) of Denmark, European Journal of Taxonomy 781, pp. 1-425 : 301-302

Dimeromyces oculatus Santam. sp. nov.

MB#840599

Fig. 72

Diagnosis

Similar to Dimeromyces trilobatus W.Rossi, Bernardi & J.A.Torres , but with female thalli differing by the two round prominences symmetrically flanking the straight snout-like perithecial tip, and smaller male thalli with fewer antheridia.

Etymology

The species epithet means “having eyes” and refers to the two protuberances on the perithecial tip which resemble two prominent eyes when seen in front view.

Type material

Holotype DENMARK – Sydsjaelland (SZ) • Østerskov ved Langebaek ; 54°59.572′ N, 12°6.715′ E; UA19; on Longitarsus luridu s (Scopoli, 1763) (Col. Chrysomelidae ); 3 Jan. 2019; JP 1271; JP det.; ZMUC C-F-123799 .

Isotype DENMARK • same data as for holotype; ZMUC C-F-123800 .

Paratype DENMARK – Lolland, Falster, Møn (LFM) • Vest for Bandholm ; 54°50.303′ N, 11°28.050′ E; PF57; on L. luridus ; 3 Jan. 2019; JP 1304; JP det.; ZMUC C-F-123838 .

Description

Male thallus hyaline except for the blackened foot and a faint brown suffusion around the base and the apex of antheridia. Receptacle consisting of four cells obliquely superposed, the lowermost of which is obtriangular and 2–3 times as long as broad, the following two cells rhomboidal, giving rise to lateral antheridia, the uppermost cell trapezoidal, supporting the unicellular, subulate primary appendage ( Fig. 72H , pa). Two flask-shaped antheridia with a variable, short stalk cell and the neck slightly curved outward.

Total length from foot to apex of appendage 58–73 µm. Length of antheridia (without stalk) 17–23 µm.

Female thallus nearly hyaline except for the blackened foot, the pale brown perithecial venter, and areas of the secondary appendage. Receptacle consisting of five cells: a large basal cell (cell I), two cells derived from cell II (II’ and II”), and two distal small cells (probably resulting from division of cell III) which form the base for the unicellular, subulate primary appendage, which is almost identical to the appendage of male thalli ( Fig. 72F ). Cells I, II’ and II” separated by oblique septa. Cell I extending upwards beside the lower II’ till the basal cell of secondary appendage ( Fig. 72 , bc a). The latter whip-like, distally slender and flexuous, never reaching the perithecial apex in height; unicellular or once divided by a septum near the base ( Fig. 72A , sa).

Perithecial stalk cell (VI), formed from cell II”, vanishing upwards. Perithecium largely fusiform, about twice as long as receptacle, regularly enlarged above the stalk until the upper third of its length, then gradually narrower towards the apex. Tip of perithecium three-lobed above a constricted area, with a middle, snout-like lobe flanked symmetrically by the two other round lobes, which are prominences of the uppermost tier of wall cells ( Fig. 72C–D , arrows).

Length from foot to apex of perithecium 142–188 µm. Perithecium (including stalk cell) 101–144 × 23–37 µm. Maximum length (chord) of secondary appendage 82–99 µm.

Thalli were found numerous on various body parts of the hosts. The hosts were sifted from fresh flood debris on coastal meadows.

Remarks

This species resembles D. trilobatus , described on Apalotrius Clark, 1860 and Physimerus Clark, 1860 (Col. Chrysomelidae Galerucinae Alticini Monoplatina ) from Ecuador ( Rossi et al. 2015) with regard to the peculiar three-lobed perithecial tip, although the lateral lobes are different: ear-shaped, more elongated in D. trilobatus and circular in D. oculatus sp. nov. The diagnosis given above highlights this and other characteristics that distinguish the two species. Similar lobes on the perithecial apex are also present in D. pedalis Thaxt. ( Thaxter 1924) described on a fly from Borneo, which however differs from the new species by several characteristics such as the peculiar shape of the appendages in female thalli. Including D. oculatus sp. nov., 13 species of Dimeromyces have been described on Chrysomelidae so far ( Haelewaters & Rossi 2015).

Dimeromyces oculatus sp. nov. is likely allied to Dimeromyces longitarsi Thaxt. , the only species of Dimeromyces reported to date from Europe on flea beetles Chrysomelidae Alticini. The latter species was described on Aphthona Chevrolat, 1837 and Longitarsus from the USA and from Trinidad and Tobago ( Thaxter 1914); it was subsequently recorded on Longitarsus from France, Poland, United Kingdom and Spain ( Majewski 2008). The two species of fungi are very similar, especially as to the male thallus, but the female thallus of D. longitarsi lacks the “showy” perithecial outgrowths. Dimeromyces bordei Maire , described on Thyamis Stephens, 1831 from Algeria ( Maire 1920), is considered a synonym of D. longitarsi .

Figures

Fig. 72. Dimeromyces oculatus Santam. sp. nov. A–B. Mature female thalli with labelling of secondary appendage (sa) and its basal cell (bc a) in A. C–E. Perithecial apex in detail, frontal view in C–D and side view in E; arrows point to septum separating the two distal wall cells. F. Lower area of a mature female thallus in detail focusing on certain cells, viz., primary appendage (pa), III, II’, II”, and I. G. Young male thallus. H–J. Male thalli at different focus levels, with primary appendage labelled in H. Scale bars: A–B = 50 µm; C–E = 10 µm; F–J = 20 µm. Photographs from slides ZMUC C-F-123800 (A–E) (isotype), ZMUC C-F-123799 (F–J) (holotype).