Metatrichia floripara (Rammeloo) Rammeloo, Icon. Mycol.

Lima, Vitor Xavier De & Cavalcanti, Laise De Holanda, 2016, Second world record of Metatrichia floripara (Trichiaceae, Myxomycetes), found in Brazil, Phytotaxa 247 (4), pp. 292-294 : 292-294

Metatrichia floripara (Rammeloo) Rammeloo, Icon. Mycol. 1, pl. 47 (1984) ( Fig. 1 )

Basyonym: Trichia floripara Rammeloo, Bull. Jard. Bot. Belg. 51(1/2):230 (1981)

Stalked sporangia, isolated or united by the stalk. Sporothaeca black, globose to pyriform when closed, dehiscence petaloid, the upper half breaking into 4–6 involute lobes, exposing the capillitium. Spore mass and capillitium reddish orange. Stalk black, roughly cylindrical, furrowed, 0.8–1.2 mm high. Hypothallus black, irregular. Capillitium formed by long, interwoven, unbranched cylindrical threads of 5–5.5 μm in diameter, orange to reddish yellow, with 2–3 smooth, prominent, left-handed spiral bands, free ends often slightly swollen, terminating in a short pointed end, occasionally blunt; 10–14 μm measuring from the beginning of the expansion to the pointed tip, expansion up to 8 μm in diameter. Threads free from the peridium. Peridium double, adherent, inner layer membranous, light yellow, strongly wrinkled forming a reticulate or alveolate pattern; the outer layer thick, cartilaginous and homogenous, dark red. Spores large, subglobose, yellow, with rather large warts disposed regularly, 13–14 μm in diameter (14–15 μm including the warts).

Material examined:— BRAZIL. Rio Grande do Sul: Canela, Floresta Nacional de Canela, 831 m, 29°19’37.50” S, 50°48’18.20” W, 4 November 2013, Xavier de Lima 289 ( URM!).

Habitat:— On standing decaying wood.

Known distribution:— Brazil (this paper), Rwanda ( Rammeloo 1981).

Other specimen:— RWANDA. Uwinka: mountain rain forest, 2400 m, 28 August 1974, Van der Veken 11037 (holotype BR).

The present species is very similar to M. floriformis , which it was first thought to be until a detailed examination of its microscopic structures was carried out. It differs macroscopically from M. horrida , M. rosea and M. vesparia by the stipitate sporangia, often isolated, and globose to pyriform black sporotheca, being similar to M. arundinariae and M. floriformis . It differs microscopically from M. arundinariae by the smaller spores and smooth spiral bands in the capillitium, and from M. floriformis by the much shorter, often swollen capillitial tips and slightly larger spores.

Many of the characteristics of M. floripara overlap with those of M. floriformis , including the habit, colour and the petaloid dehiscence. The lengths of the capillitial tips of M. floriformis are always much larger, with an average of 32–49 μm, measured from six specimens found in the same area in comparison with 10–14 μm for M. floripara ( Fig. 1I–L ), and the spore size of the latter is slightly larger (mean of 11.8–13.25 μm in M. floripara and 9.4–12 μm in M. floriformis ). The peridium of M. floripara is also a distinctive character. The inner membranous peridium has many prominent folds and grooves forming a reticulate or areolate pattern ( Fig. 1C ). Of the specimens of M. floriformis that have been observed, most of them have a smooth internal peridium, and some display some faint reticulate markings, roughly the size of the spores, as pressure mark, but never so obvious as in the Brazilian M. floripara specimen using light microscopy and in the holotype as observed by scanning electron microscopy (Rameloo 1984).

The Brazilian specimen deviates slightly from the holotype in spore size, stalk length and capillitial bands and tip length, but this variation seems to be not significant and falls within the acceptable range for a species of myxomycete. With the newly found specimen, we can expand the range of the spore diameter to 9.7–14 μm, capillitial thread tips to 5.5–14 μm, and number of spiral bands to 2–3(–4).

Unfortunately, M. floripara is too rare to provide any certainty about its ecology, but the assumption that it is a subtropical species should be true. Rwanda is close to the equator but its high elevation provides a cooler environment than other countries at the same latitude. The holotype was found at 2400 m in a montane rain forest. This coincides with where the Brazilian specimen was found, which was a subtropical climate and elevations up to 800 m of the Araucaria forest explored located at the Serra Gaúcha, a mountainous and moist region of the southernmost Brazilian state, Rio Grande do Sul. This uncommonly restricted preference for a myxomycete may be the cause of such a scarcity of records.

Figures

FIGURE 1. Metatrichia floripara (Rammeloo) Rammeloo.A, B. Dehisced sporangia. Scale bar = 1 mm. C. Peridium. Scale bar = 20 μm. D. Capillitium. Scale bar = 20 μm. E–H. Spores. Scale bar = 10 μm. I–L. Tip of a capillitial thread. Scale bar = 10 μm.