Laboulbenia tschirnhausii W. Rossi & M. Leonardi, sp. nov.
Index Fungorum number: IF 559788; Mycobank number: MB 559788; Facesoffungi number: FoF 12927; Fig. 1
Etymology: Named after the German dipterologist Michael von Tschirnhaus, who supplied us with the flies bearing the new parasites.
Holotype: CAMB WR3382.
Basal cell (cell I) large brownish yellow, short, trapezoidal, slightly broader than long. Suprabasal cell (cell II) concolorous with the former but much longer, slightly and evenly enlarging from below upwards. Stalk cell of the appendage (cell III+IV + V) darker, slightly longer than broad, with the outer margin distinctly convex and the inner united to the stalk- and basal cells of the perithecium. Insertion cell small, dark brown, nearly isodiametric, adherent to the base of the perithecium on the inner side, bearing apically four cells, of which the two outer ones are larger and more elongate. These cells give rise to short and irregularly ramified branches ending in elongate antheridia or slender, hyaline and curled branchlets. Stalk cell of the perithecium (cell VI) almost flattened. Perithecium, with its basal cells, chestnut brown, becoming paler above and below, flaskshaped, the inflated venter evenly tapering to the long neck, ending with two large, short, cylindrical, truncate and symmetrically diverging outgrowths, which are subtended by a rounded prominence on the ventral side. Length from insect surface to perithecial apex 360–430 µm; length from insect surface to tip of longest appendage 290 µm; perithecium 215–270×85–105 µm.
Material examined: Australia, Queensland, Carnarvon National Park, Mt. Moffatt Camp Site along small creek, 10 October 2002, M. von Tschirnhaus, on the head of an undescribed species of Apotropina (Diptera, Chloropidae), CAMB WR3382 (holotype), FI WR3383.
Notes: Laboulbenia tschirnhausii clearly belongs to a small group of species occurring on flies characterized by rhizoids penetrating the body of the host insects and by an undivided stalk-cell of the appendage. This group includes L. dahlii, L. curtonoti, L. penetrans and L. perforans (Thaxter 1901; Rossi and Kirk-Spriggs 2011; Rossi and Leonardi 2018; Rossi et al. 2019). Laboulbenia tschirnhausii differs from all the latter parasites for its stockier habitus, the nearly isodiametric stalkcell of the appendage, the more inflated perithecial venter, and especially the peculiar perithecial outgrowths. The thalli of Laboulbenia tschirnhausii were all found projecting forward from the head of the host insects, which means that the transfer of the sticky spores from a parasitized insect to other members of the same species did not happen during sexual contacts. Actually, although sexual contacts represent the more frequent method by which Laboulbeniales pass from one host to another, these fungi take advantage also of other contacts resulting from social behaviors not directly related with mating. The contacts by means of the antennae, which are frequent among insects, seems to be the way utilized by Laboulbenia tschirnhausii. Several other Laboulbeniales benefit from this behavior. For example, among the species occurring on flies can be cited Stigmatomyces hydrelliae and the above mentioned Laboulbenia dahlii (Thaxter 1901; Weir and Rossi 1995).
Figure 1 – Laboulbenia tschirnhausii (FI WR3382, holotype). a group of 5 mature thalli. b tip of perithecium, enlarged. c tuft of thalli emerging from the face of the host insect (paratype MLUH Dipt-Chlor 0021 m—photo by A. Stark).Scale bars: a=100 µm, b=25 µm