Monoicomyces homalotae Thaxt.

MB#181116

Figs 83B, 86

Proceedings of the American Academy of Arts and Sciences 35: 412 (Thaxter 1900). –

Type: “ On Homalota putrescens Woll., British Museum, No. 412, Azores ”; FH.

Monoicomyces ternatus Speg. (Spegazzini 1915b: 67) [MB#191957]

Monoicomyces unilateralis Speg. (Spegazzini 1915b: 68) [MB#192287]

Diagnostic features

Cell I ± globose, often heart-shaped (Fig. 86A–B). Primary appendage variably branched. Cell III barrel-shaped, longer than broad, usually broadened distally, with a darkened outer margin. Usually four secondary appendages for each antheridium. Each antheridium with eight phialides. [Detailed descriptions: Thaxter 1908; Majewski 1988, 1994b; Santamaria 1989]

Distribution and hosts

Reported on many genera and species of Aleocharinae (Col. Staphylinidae), mostly Atheta, but also on others like Evanystes, Geostiba, Ischnopoda, etc. (Majewski 2008). Its geographical distribution is difficult to delimit because of confusion with similar species, in particular M. britannicus . It has been recorded from Europe: Finland, France, Germany, the Netherlands, Italy, Spain; Africa: Algeria; America: Argentina, USA; Asia: Japan; and Azores (Santamaria et al. 1991). Reported subsequently from Zaire (Rossi & Santamaria 1992), Poland (Majewski 1994a), United Kingdom (Weir 1996; record on Drusilla may be M. drusillae), Greece (Castaldo et al. 2004), Norway (Majewski 2008), Slovakia, Czech Republic (Rossi et al. 2010), Sweden (Huggert 2010), Belgium (De Kesel 2010), Turkey (Rossi 2016), China, Armenia, and Bulgaria (Rossi et al. 2019a).

Collections examined from Denmark

On Aloconota gregaria (Erichson, 1839) (Col. Staphylinidae Aleocharinae) DENMARK – Nordøstsjaelland (NEZ) • Asserbo Plantage; 56°1.984′ N, 12°0.817′ E; UC11; 28 Apr. 2019; JP 1455; JP det.; ZMUC C-F-124006 . – Sydsjaelland (SZ) • Tryggevaelde Å ved Varpelev; 55°21.055′ N, 12°15.877′ E; UB23; 6 Jan. 2018; JP 1593; JP det.; ZMUC C-F-124354 .

On Atheta castanoptera (Mannerheim, 1830) (Col. Staphylinidae Aleocharinae) DENMARK – Nordøstsjaelland (NEZ) • Naerum; 55°49.077′ N, 12°32.686′ E; UB48; 1 Dec. 2019; JP 1565; JP det.; ZMUC C-F-124325 .

On Atheta graminicola (Gravenhorst, 1806) (Col. Staphylinidae Aleocharinae) DENMARK – Østjylland (EJ) • Klostermølle; 56°2.432′ N, 9°41.629′ E; NH41; 14 Feb. 2019; JP 1348; JP det.; ZMUC C-F-123887 • Tange å vest for Kjellerup; 56°17.959′ N, 9°23.462′ E; NH23; 17 Feb. 2018; JP 985; JP det.; ZMUC C-F-123492 • Vest for Ørnsø ved Silkeborg; 56°9.126′ N, 9°30.588′ E; NH32; 10 Nov. 2018; JP 1230; JP det.; ZMUC C-F-123757 • Viemose ved Ringkloster; 56°0.632′ N, 9°57.400′ E; NH50; 12 Mar. 2017; JP 536; JP det.; ZMUC C-F-123020 . – Lolland, Falster, Møn (LFM) • Vest for Bandholm; 54°50.303′ N, 11°28.050′ E; PF57; 3 Jan. 2019; JP 1339; JP det.; ZMUC C-F-123878 . – Nordøstsjaelland (NEZ) • Indelukket ved Frederiksborg Slot; 55°56.191′ N, 12°17.861′ E; UC30; 19 Mar. 2017; JP 677; JP det.; ZMUC C-F-123166 • Kongelunden; 55°34.369′ N, 12°34.189′ E; UB46; 26 Sep. 2013; H. Liljehult 208; JP det.; ZMUC C-F-122687 . – Nordvestjylland (NWJ) • Nord for Landting ved Vinderup; 56°30.049′ N, 8°45.384′ E; MH86; 19 Jan. 2015; JP 560; JP det.; ZMUC C-F-123046 • Vest for Vinderup; 56°28.727′ N, 8°44.810′ E; MH85; 19 Jan. 2015; JP 767; JP det.; ZMUC C-F-123261 . – Nordvestsjaelland (NWZ) • Bognaes Skov på Tuse Naes; 55°44.966′ N, 11°45.817′ E; PG78; 10 Dec. 2013; JP 892; JP det.; ZMUC C-F-123390 • Nordøstbredden af Tissø; 55°35.612′ N, 11°18.461′ E; PG46; 1 May 2013; JP 761; JP det.; ZMUC C-F-123255 • Vesterlyng; 55°44.195′ N, 11°17.276′ E; PG47; 9 Feb. 2014; JP 635; JP det.; ZMUC C-F-123124 . – Sydsjaelland (SZ) • Even Bro; 55°8.694′ N, 12°0.601′ E; UB11; 17 Feb. 2019; JP 1362; JP det.; ZMUC C-F-123900 • Holtug Kalkbrud; 55°20.470′ N, 12°26.678′ E; UB33; 21 Sep. 2013; JP 351; JP det.; ZMUC C-F-122833 • Tryggevaelde Å ved Varpelev; 55°21.055′ N, 12°15.877′ E; UB23; 5 Jan. 2013; H. Liljehult 209; JP det.; ZMUC C-F-122688 . – Vestjylland (WJ) • Velling; 56°3.078′ N, 8°18.596′ E; MH51; 16 Dec. 2018; JP 1264; JP det.; ZMUC C-F-123792 .

On Atheta melanocera (Thomson, 1856) (Col. Staphylinidae Aleocharinae) DENMARK – Nordøstsjaelland (NEZ) • Amager Faelled; 55°39.168′ N, 12°34.750′ E; UB47; 14 Apr. 2001; H. Liljehult 388; JP det.; ZMUC C-F-122871 .

On Atheta triangulum (Kraatz, 1856) (Col. Staphylinidae Aleocharinae) DENMARK – Lolland, Falster, Møn (LFM) • Vest for Bandholm; 54°50.303′ N, 11°28.050′ E; PF57; 3 Jan. 2019; JP 1340; JP det.; ZMUC C-F-123879 .

On Atheta pallidicornis (Thomson, 1856) (Col. Staphylinidae Aleocharinae) DENMARK – Nordøstsjaelland (NEZ) • Åsen ved Lellinge; 55°27.948′ N, 12°8.785′ E; UB15; 26 Jun. 2019; JP 1485; JP det.; ZMUC C-F-124070 .

On Geostiba circellaris (Gravenhorst, 1806) (Col. Staphylinidae Aleocharinae) DENMARK – Vestjylland (WJ) • Velling; 56°3.078′ N, 8°18.596′ E; MH51; 16 Dec. 2018; JP 1265; JP det.; ZMUC C-F-123793 .

On Schistoglossa aubei (Brisout de Barneville, 1860) (Col. Staphylinidae Aleocharinae) DENMARK – Sydsjaelland (SZ) • Denderup Sø i Denderup Vaenge; 55°15.075′ N, 11°57.366′ E; PG82; 5 May 2016; JP 497; JP det.; ZMUC C-F-122981 .

Remarks

First record from Denmark. Efforts to distinguish M. homalotae and M. britannicus begun soon after their original descriptions. Thaxter (1908) thought that the receptacle of both species was two-celled. He described M. homalotae with “the basal cell of the primary appendage” ± deeply suffused including blackish brown.After examination of many thalli we believe what Thaxter called the basal cell of primary appendage corresponds to cell III.

The compound antheridium of M. homalotae seems to have been misunderstood by Thaxter (1908) and therefore his drawings are imprecise. Thaxter failed also regarding the number of phialides formed by the two middle tiers (2 nd and 3 rd) of the antheridium. Although not described, his drawings show four phialides. Nowadays, the correct observation of this part of the thallus requires a high-quality microscope with high magnification, preferable with DIC optics, because the planes of focus are very close and difficult to discern. Upper (Fig. 86C) and lower focus (Fig. 86E) of the antheridium consists of several cells which seem to serve as wall cells for sealing the central cavity where phialides eject their spermatia. The middle focus shows the area with phialides and the cavity with spermatia (Fig. 86D). We think the number of phialides is very important for distinguishing M. homalotae from other very similar species, with eight (two for each cell in 2 nd and 3 rd tiers) in M. homalotae (Fig. 86D), whereas the phialides are four (one for each cell) in other species, as the related but distinct M. britannicus .

Thaxter (1908) increased the confusion by including under M. homalotae thalli with constricted and darkened perithecial stalk cells; this seems inappropriate, and probably some of these forms belong to species described here, such as M. brachiatus sp. nov. and M. validus sp. nov. In 1989, 17 slides of M. homalotae were borrowed from FH (labelled with references FH2402 to 2418) by SS (see M. britannicus). In Fig. 83B the only thallus included in the type slide (FH2402) is reproduced with an old photograph taken at that time. The material was in very poor condition but it is easy to deduce that this is the thallus which appears in Thaxter (1908: fig. 8).

The perithecial basal cells (m, n, n’) and the secondary stalk cell (VII) are provided with darker and prominent spots (“stigmata”) of unknown function and origin (Fig. 86I–J), which are also present on other species, such as M. drusillae (Santamaria et al. 2020a) .