Hydrophilomyces Thaxt.

Santamaria, Sergi & Pedersen, Jan, 2021, Laboulbeniomycetes (Fungi, Ascomycota) of Denmark, European Journal of Taxonomy 781, pp. 1-425 : 47

Genus Hydrophilomyces Thaxt.

MB#2406

Memoirs of the American Academy of Arts and Sciences 13: 431 ( Thaxter 1908). –

Type species: H. rhynchophorus Thaxt.

Brief description

Monoecious. Receptacle consisting of a uniseriate multicellular axis extending into the appendage, bearing branches and antheridia born from corner cells. Unicellular buffer cells often present above the foot ( Fig. 7A–C, F–G , bf). Perithecial outer wall including an elongated accessory cell on the outer side ( Fig. 7D, G , acc), parallel to the longer ventral outer wall cell (w 1).

Remarks

The genus consists of 16 species, of which 11 in Europe, five in Denmark. The most recently described species are H. deflexus and H. riberae ( Santamaria et al. 2020a) . The number and origin of the perithecial basal cells in this genus is puzzling because there seems to be four rather of the typical three (i.e., m, n, and n’).

Key to the Danish species (partially following Majewski 1994b and Santamaria 2003)

1. Corner cells of the appendage separated by constricted dark septa from the arising branchlets or antheridia. On Limnebius Leach, 1815 (Col. Hydraenidae ) .................. H. atroseptatus T.Majewski

– Corner cells without dark septa ........................................................................................................ 2

2. Receptacle consisting of up to 16 cells. On Ochthebius Leach, 1815 (Col. Hydraenidae ) and Laccobius (Col. Hydrophilidae )......................................................................................................................... 3

– Receptacle consisting of 18–44 cells. On Cercyon Leach, 1817 (Col. Hydrophilidae ) ................... 4

3. Thalli dimorphic, depending on the host sex and its specific location of growth on host body. On Laccobius (Col. Hydrophilidae ) .................................................................. H. coneglianensis Speg.

– Thalli not dimorphic, invariable despite host sex. On Ochthebius (Col. Hydraenidae )...................... ........................................................................................................................... H. digitatus F.Picard

4. Mature perithecium with a bent neck. Buffer cells present. Receptacle robust................................... ..................................................................................................................... H. hamatus T.Majewski

– Mature perithecium with a straight neck. Buffer cells absent. Receptacle slender ............................. ....................................................................................................................... H. gracilis T.Majewski

Figures

Fig. 7. Hydrophilomyces spp., mature thalli. A–B. H. coneglianensis Speg. Thallus from female (A) and from male hosts (B). – C. H. digitatus F.Picard. – D–E. H. gracilis T.Majewski. – F–G. H. hamatus T.Majewski. Abbreviations: acc = accessory cell; bf = buffer cells. Scale bars: 50 µm. Photographs from slides ZMUC C-F-122709 (A), ZMUC C-F-124088 (B), ZMUC C-F-124274 (C), ZMUC C-F-124043 (D–F), and ZMUC C-F-124042 (G).