Meriderma carestiae (Ces. et De Not.) Mar. Mey. & Poulain

Ronikier, Anna, 2022, Revision of the Donald T. Kowalski’s collections of Lamproderma (Myxomycetes, Amoebozoa) reveals twice higher species diversity, Phytotaxa 531 (3), pp. 175-210 : 201-203

Meriderma carestiae (Ces. et De Not.) Mar. Mey. & Poulain , in Poulain et al. (2011: 551). Fig. 21

Sporocarps scattered or in loose groups, stipitate, total height 1.44–2.34 mm ( Fig. 21A ). Sporotheca broadly ovoid to globose, with rounded or broadly conical base, 0.70–1.36 mm high, 0.64–1.10 mm diam ( Figs 20A–B ). Hypothallus, thick, red brown, continuous and connecting many sporocarps. Stalk about one-half (3/7 to 1/2) of the total sporocarp height, 0.74–1.10 mm long, black, tapering upwards, sometimes laterally flattened, often with a membranous hypothallus remnants attached at one side ( Figs 21A–B ). Peridium evanescent, dehiscing in small patches, remaining only at the base of the sporotheca, black, iridescent, with silver and golden reflections under reflected light, pale brown, smooth and transparent in transmitted light ( Figs 21A–B ). Columella reaching about one-half of the sporotheca height, cylindrical to clavate ( Fig. 21B ). Capillitium moderately dense, black when spores are blown out, dark brown in transmitted light, with few to many anastomoses in peripheral part and with funnel-shaped ends ( Figs 20B–C ). Spores black in mass, dark brown in transmitted light, slightly paler at one side, globose, (12)12.5–13.5(15.5) μm in total range, 13.13 ±0.7 μm on average ±SD (n = 30), covered with connected spines forming branched ridges with or without closed meshes, and with some free spines ( Figs 21D–G ), ornamentation up to 1 μm high, composed of fused spines that form incomplete or complete, dense reticulum with perforated muri by SEM ( Figs 21H–K ).

Material examined:— USA. Tehama Co.: 3 miles E of Mineral, 5800 ft., on decaying wood, 15 May 1966, DTK 2937 (as L. atrosporum, UC 1408268!); 3 miles E of Mineral, 5000 ft., on dead wood, 20 May 1967, DTK 6110 (as L. atrosporum, UC 1408220!).

Notes:—Kowalski designated lectotype of L. atrosporum ( Kowalski 1975a) circumscribing the species boundaries as a taxon with funnel-shaped capillitium tips and variable spore ornamentation from spinulose to reticulate, but never banded-reticulate. Two of the Kowalski’s (1970a) specimens of L. atrosporum have spores ornamented with fused spines that form incomplete or complete, dense reticulum and thus belong to L. carestiae (see Poulain et al. 2003), currently classified within the genus Meriderma ( Poulain et al. 2011) . The two examined collections differ slightly in spore ornamentation. Spores of DTK 2937 are covered with connected spines forming ridges without closed meshes ( Figs 21D–E, H–I ), so could be referred to the typical morphotype ( Meriderma carestiae var. carestiae , see Poulain et al. 2011), while the spores of DTK 6110 are covered with spines connected by ridges and forming many closed meshes or dense net-like patterns ( Figs 21F–G, J–K ). The latter collection may be classified as the undescribed morphotype ‘ Meriderma carestiae var. retisporum’ ( Poulain et al. 2011). Meriderma carestiae is known from the Northern Hemisphere ( Poulain et al. 2011) and it has recently been reported from South America ( Ronikier & Lado 2015).

Figures

FIGURE 20. Lamproderma scintillans (Berk. & Broome) Morgan A–B. Sporocarps. C. Open sporocarp. D. Details of columella and capillitium in transmitted light (note hyaline capillitium threads near columella). E. Spores in transmitted light (edge view). F. Spores in transmitted light (top view). G. Spore by SEM. H. Details of spore ornamentation by SEM. Bars: A–C = 500 μm, D = 100 μm, E–G = 10 μm, H = 3 μm. A: coll. DTK 5020, B–F: coll. DTK 4223, G–H: coll. DTK 4777.

FIGURE 21. Meriderma carestiae (Ces. et De Not.) Mar. Mey.et Poulain A. Sporocarps. B. Open sporocarp. C. Funnel-shaped capillitium tips in transmitted light. D, F. Spores in transmitted light (edge view). E, G. Spores in transmitted light (top view). H, J. Spore by SEM. I, K. Details of spore ornamentation by SEM. Bars: A–B = 1 mm, D–H, J = 10 μm, I, K = 3 μm. A–E, H–I: coll. DTK 3967, F–G, J–K: coll. DTK 6110.