Gauthieromyces colombiensis D.E. Baron & L.G. Valle., 2018

Barón, Daniel E. & Valle, Laia Guàrdia, 2018, First record of trichomycetes associated with aquatic insects from Colombian Moorland and Andean forests, Phytotaxa 361 (1), pp. 1-24 : 4

Gauthieromyces colombiensis D.E. Baron & L.G. Valle. sp. nov. ( Figs 2–11 )

Mycobank MB 825122

Type:— COLOMBIA, SANTANDER: Piedecuesta; Río El Rasgón, 7°2’53.67”N 72°58’27.88”W. 2404 m. 13-May-2016, D. Barón, prepared from Mayobaetis sp. nymphs ( Ephemeroptera , Baetidae ). Microscope slide FH-COL11–Tr35 (holotype here designed, FH!), COL 11–Tr34, Tr37 (isotypes, BCB!).

Diagnosis: Gauthieromyces colombiesis is somewhat similar to G. mcrosporus , although the new species has larger trichospores and fertile branches producing a higher number of generative cells. The basal cell has rhizoidal-like sterile branches.

Description:—Dendroidal thallus 250–400 μm long, with a stout basal cell (cell 1) 40–50 × 15–22 μm, from which one or two lateral branches (fertile at maturity) emerge ( Figs 2–3 ). Discoid or disperse holdfast material (7.5–16.5 μm diam) at the proximal area of the basal cell. Holdfast structure often accompanied by thin rhizoid-like branches arising from the basal zone towards the hindgut lining ( Figs 3–5 , 11 ). Cell 2 (above the basal cell), measuring 25–65 × 13–15 μm, thinner than the basal cell 1. Horseshoe-shaped trichospores measuring 11.5–16.5 (arch length) × 1.8–3.4 μm (diam), with very short collar and a single appendage measuring 13–16 μm long ( Figs 6–8 , 11 ). Fertile branches with up to 20 generative cells, variable in length, 8–25(–40) × 3.5–4.5 μm ( Figs 6–7 , 11 ). Elongate or clavate propagules 40–65 × 11.5–13 μm originated from the basal cell and other cells near it ( Figs 9–11 ). Zygospores not found.

Etymology:— Colombiensis, from Colombia.

Comments: — Other species with similar characteristics have been described, including G. microsporus S.T. Moss & Lichtw. from Baetidae nymphs ( Lichtwardt 1983) and G. indicus J.K. Misra & V.K. Tiwari from the same host family ( Misra & Tiwari 2008). Gauthieromyces colombiensis was found in the gut of Mayobaetis spp. nymphs, this being the first record of Harpellales in this genus of mayflies, which have a South American distribution. The species described here resembles most G. microsporus , but can be differentiated by the larger trichospores in G. colombiensis (10–12 μm length in G. microsporus from France, according to Gauthier 1960; 6–7.5 μm length in specimens from Italy, although probably immature, according to Valle et al. (2013). Also, fertile branches in G. colombiensis are highly prolific, producing more generative cells than described in G. microsporus . Up to 5 generative cells per fertile branch were reported in specimens of G. microsporus from Italy ( Valle et al. 2013); up to 4 in specimens from France ( Gauthier 1960, Lichtwardt 1983). Propagules are formed in a similar way as described in other species of the genus, and also in species of the proximal genus Graminella L. Léger and M. Gauthier ex Manier ( Léger & Gauthier 1937, Manier 1962, Valle 2007). The propagules are produced from a stout basal cell, and detach to generate new thalli within the same host. In G. colombiensis , we have observed short rhizoid-like branches arising from the basal cell ( Figs 3–5 ) and directed towards the hindgut lining, a feature not described in G. microsporus . These rhizoidal prolongations may contribute to anchoring the thallus to the hindgut lining. The Mexican species G. viviparus L.G. Valle, M.M. White & Cafaro , had longer branches arising from the basal cell, similar to fertile branches (Valle et al. 2008), but not rhizoidal (and with apparently limited-growth) as in the Colombian species. The Asian species G. indicus was described from India ( Misra & Tiwari 2008) and reported from Southern China ( Strongman & Xu 2006), with the key character being the numerous trichospores arranged on fertile branches and the presence of many appendages in the trichospores ( Strongman & Xu 2006), while only one appendage is present in G. microsporus , G. viviparus and G. colombiensis .

Figures

FIGURE 11. Gauthieromyces colombiensis from Baetidae. Line drawing. Thallus overview. Bc= basal cell. gc= generative cell. Fb= fertile branch. Tr= trichospore. Pr= propagules. Scale bar= 50 μm.

FIGURES 2–10. Gauthieromyces colombiensis from Baetidae. 2. Thallus overview. 3–5. Basal cell with holdfast material and short rhizoid-like branches (arrows).6. Fertilebranches overview.7. Horseshoe-shaped trichospores on generative cells.Trichospore appendages observable inside the corresponding generative cells (arrows). 7b. Detail of an appendage inside a generative cell. 8. Loose trichospore with appendage. 9. Vegetative propagules attached to the basal cell (arrow). 10. Detail of the distal section of various propagules. Scale bar for Fig. 2 = 50 μm; for Figs 3–6, 9 = 25 μm; for Figs 7, 7b, 8, 10 = 10 μm.