Laboulbeniomycetes (Fungi, Ascomycota) of Denmark Author Santamaria, Sergi Unitat de Botànica, Departament de Biologia Animal, de Biologia Vegetal i d’Ecologia, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès (Barcelona), Spain. sergi.santamaria@uab.cat Author Pedersen, Jan Natural History Museum of Denmark (Zoological Museum), University of Copenhagen, Universitetsparken 15, 2100 København Ø, Denmark. japedersen@snm.ku.dk text European Journal of Taxonomy 2021 2021-11-26 781 1 425 http://dx.doi.org/10.5852/ejt.2021.781.1583 journal article 305924 10.5852/ejt.2021.781.1583 592281fb-ec34-447a-869b-e2722722534e 2118-9773 5828924 Eusynaptomyces hydrobii (T.Majewski) I.I.Tav. MB#105312 Fig. 3B–D Mycologia Memoirs 9: 220 ( Tavares 1985 ) . – Basionym : Rhynchophoromyces hydrobii T.Majewski, Acta Mycologica 7(2): 274 ( Majewski 1972a ) [MB#322804]. – Type : “ On metasternum of Hydrobius fuscipes L. (Col., Hydrophilidae ): Lomianki Dolne , Nowy Dwor Maz. county, small water body south of village, 24.4.1970 , leg. T. Majewski ”; KRAM . (fig. 7a – holotype ,…) ( TM 245 , Majewski, 2008: 69 ). [ Poland ] Fig. 3. A . Eusynaptomyces enochri Scheloske ; reduced form showing the lateral outgrowth (arrow). – B–D . Eusynaptomyces hydrobii (T.Majewski) I.I.Tav. ; mature thalli. – E . Rhynchophoromyces anacaenae Scheloske ; mature thallus with broken appendage. – F . Thripomyces italicus Speg. ; mature thallus showing the characteristic broadened cells at the base of the receptacle (*). Scale bars: 50 µm. Photographs from slides ZMUC C-F-122569 (A), ZMUC C-F-123552 (B–D), ZMUC C-F-123749 (E), and ZMUC C-F-122983 (F). Diagnostic features Receptacle very variable in length and number of cells, consisting of 11–80 superposed cells. Perithecium nearly straight to ± arcuate, with an almost undistinguished venter, tapering distally to an undifferentiated, rounded apex. [Detailed descriptions: Sarna & Milewska 1978 ; Majewski 1994b ] Distribution and hosts Only known from Poland on Hydrobius and Hydrophilus Geoffroy, 1762 (Col. Hydrophilidae ). Collections examined from Denmark On Hydrobius rottenbergii Gerhardt, 1874 (Col. Hydrophilidae ) DENMARK – Nordøstsjaelland (NEZ) • Amager Faelled ; 55°38.631′ N , 12°34.729′ E ; UB47; 15 Apr. 2018 ; JP 1036 ; JP det.; ZMUC C-F-123552 . Remarks First record from Denmark . Second world record, the first outside the type country. The separation of this species from reduced forms of Eusynaptomyces benjaminii Scheloske is difficult because such thalli lack the horn on the perithecial apex, which is not the case for the Danish thalli. The host was previously considered as a subspecies of Hydrobius fuscipes . A photo of this species is given here for the first time.