Genus Stigmatomyces H.Karst.

MB#5253

Chemismus der Pflanzenzelle. Eine morphologisch-chemische Untersuchung der Hefe: 78 (Karsten 1869). –

Type species: S. baeri (Knoch) Peyrit.

Appendicularia Peck, Annual Report on the New York State Museum of Natural History 38: 95 (Peck 1885) [MB#288]

Appendiculina Berl., Malpighia 3: 59 (Berlese 1889) [MB#290]

Peckifungus Kuntze, Revisio Generum Plantarum 2: 864 (Kuntze 1891) [MB#3783]

Fanniomyces T.Majewski, Acta Mycologica 8 (2): 229 (Majewski 1972b) [MB#1973]

Brief description

Monoecious. Receptacle three-celled (Fig. 56A). Cell III (within this genus sometimes known as “appendage stalk cell”) laterally adnate to cell VI (Fig. 56B). Primary appendage free, consisting of a basal cell (Fig. 56A, bc a) supporting a series of superposed cells bearing sidewise paired or solitary antheridia with corresponding supporting cells, alternatively bearing short ramified branchlets including terminal solitary flask-shaped antheridia (formerly species included in the genus Fanniomyces, Fig. 56A–D); sometimes basal and apical cells show variations of this arrangement. Perithecium with four cells in each vertical row of outer wall cells.

Remarks

This is a large genus consisting of 156 species, of which 49 in Europe, 14 in Denmark. The most recently described species are S. ferrugineus (Rossi & Leonardi 2020) and S. scaptodrosophilae (Rossi & Christian 2020) . Nowadays, the genus Stigmatomyces only comprises species living on Diptera . The primary appendage design displays a great uniformity (except for the species included in the disputed genus Fanniomyces) and is a main characteristic to separating species.

According to Haelewaters et al. (2020), based on SSU-LSU ribosomal DNA two-locus studies, the genus Stigmatomyces is paraphyletic, including four clades: (I) two species formerly in Fanniomyces ( F. burdigalensis and F. ceratophorus); (II) three species, viz. S. gregarius, S. scaptomyzae and S. entomophilus, the latter being the type of the previously described genus Appendiculina; (III) species included at present in the genus Gloeandromyces, and a clade (IV) including the remaining five analyzed species of Stigmatomyces . Based on this study, Fanniomyces and Appendiculina are reinstated for the species included in clades I and II, respectively. In that work, 14 species of Stigmatomyces have been sequenced, a number which is recognized by the authors themselves to be too low to pretend a phylogenetic reconstruction of the genus. Although the taxa formerly included in Fanniomyces show distinctive morphological characteristics in the appendage structure, Weir & Rossi (1995) considered these of minor importance and synonymized the genus. The three species placed in the genus Appendiculina reinstated by Haelewaters et al. (2020) do not show any distinctive morphological characteristic that separate them from the species of Stigmatomyces included in clade IV. Also, because the number of the analysed species is very limited, because the distances in the phylogenetic tree are small, and because the split is not supported by morphological differences we prefer to treat the genus Stigmatomyces in a broad sense.

Key to the Danish species

1. Appendage branched (the cells forming the appendage axis give rise to short branchlets bearing antheridia). Former genus Fanniomyces .................... S. burdigalensis (Balazuc) A.Weir & W.Rossi

– Appendage unbranched (compact series of superposed cells bearing lateral antheridia with respective supporting cells). Stigmatomyces s. str. ............................................................................................ 2

2. Perithecial apex showing a lip which extends into a pointed projection; w 3 and w 4 inflated by constrictions of septa w 3 -w 4 and w 2 -w 3. On Hydrellia Robineau-Desvoidy, 1830 ( Diptera Ephydridae). ....................................................................................................... S. hydrelliae Thaxt.

– Perithecial tip different. On other hosts ............................................................................................ 3

3. Antheridia directed outwards. On Diptera Drosophilidae ................................................................ 4

– Antheridia directed inwards. On other Diptera ................................................................................. 6

4. Venter of perithecium distally enlarged; perithecium with an arcuate neck. On Scaptomyza Hardy, 1850 and Parascaptomyza Duda, 1924 ( Diptera Drosophilidae)................... S. scaptomyzae Thaxt.

– Venter of perithecium broadest in the middle; perithecium with an almost straight neck. On Drosophila Fallén, 1823 ( Diptera Drosophilidae)............................................................................................... 5

5. Appendage consisting of a basal cell supporting five superposed cells. On Drosophila subgenus Drosophila Sturtevant, 1939 .............................................................. S. entomophilus (Peck) Thaxt.

– Appendage consisting of a basal cell supporting four superposed cells. On Drosophila subgenus Sophophora Sturtevant, 1939 ...................................... S. majewskii H.L.Dainat, Manier & Balazuc

6. Appendage consisting of a ± darkened and usually flattened basal cell supporting a series of several obliquely located, outwards bulging cells, bearing elongated antheridia on the inner side. Cell VI as long or longer than cell III. Mostly on Diptera Sphaeroceridae ....................................................... 7

– Appendage consisting of cells which are longer than broad, with straight outer margins, separated by horizontal septa. Cell VI shorter than cell III. On other Diptera ..................................................... 11

7. Venter of perithecium with ± distinct protuberances below the neck............................................... 8

– Venter of perithecium without such protuberances .......................................................................... 9

8. Appendage consisting of a slightly darkened basal cell and a series of 3–9 superposed cells. Cell VII not protruding. On Diptera Sphaeroceridae belonging to the genera Leptocera Olivier, 1813, Spelobia Spuler, 1924, Apteromyia Vimmer, 1929, and Limosina Macquart, 1835 .......... S. divergatus Thaxt.

– Appendage consisting of a darkened basal cell and a series of 5–6 superposed cells. Cell VII protruding below the perithecium. On Pullimosina Roháček, 1983 ( Diptera Sphaeroceridae)............................ ................................................................................................................................. S. platensis Speg.

9. Perithecial stalk cell (VI), secondary stalk cell (VII) and basal cells (m, n, n’) forming a well distinguished peduncle, longer than the appendage ............................................ S. limosinae Thaxt.

– Perithecial stalk cell (VI), secondary stalk cell (VII) and basal cells (m, n, n’) not forming a peduncle; taken together much shorter than the appendage............................................................................ 10

10. Appendage hyaline, contrasting with the dark, flattened basal cell; consisting of 5–6 cells which are much longer than wide, giving rise to broad antheridia with their large supporting cells. Distal part of appendage directed backwards. On Thoracochaeta Duda, 1918 ( Diptera Sphaeroceridae) .......................................................................... S. thoracochaetae Santam. sp. nov.

– Appendage ± brownish pigmented, consisting of up to 12–13 almost strongly flattened cells, giving rise to antheridia bearing very elongated necks. Distal part of appendage oriented normally. On other genera of Diptera Sphaeroceridae ...................................................................... S. crassicollis Thaxt.

11. Perithecial outer wall cells arranged spirally and forming conspicuous ridges on the venter........ 12

– Perithecial outer wall cells arranged vertically, not forming ridges ............................................... 13

12. Appendage consisting of a darkened basal cell giving rise to a series of five cells. On Geomyza Fallén, 1810 ( Diptera Opomyzidae) .............................................................. S. geomyzae W.Rossi & Cesari

– Appendage consisting of a hyaline basal cell giving rise to a series of three cells. On Scatella Robineau-Desvoidy, 1830 ( Diptera Ephydridae) ................................................................ S. purpureus Thaxt.

13. Appendage consisting of a small basal cell giving rise to a series of three cells, the lower cell much longer than the others. Perithecium with eight round prominences, four at w 1 -w 2 and four at w 2 - w 3 septa. On Diptera Chloropidae ...................................................................... S. constrictus Thaxt.

– Appendage consisting of a basal cell giving rise to a series of four similar cells. Perithecium with four distal prominences on the venter. On Diptera Ephydridae .... S. ephydrae L.Mercier & R.Poiss.