Didymium saturnus H.W. Keller, Mycologia

Gao, Yang, Yan, Shu-Zhen, Wang, Gao-Wei & Chen, Shuang-Lin, 2018, Two new species and two new records of myxomycetes from subtropical forests in China, Phytotaxa 350 (1), pp. 51-63 : 57-58

Didymium saturnus H.W. Keller, Mycologia 62(5):1061, 1970. FIGURE 3 .

GenBank: —MG677145 (18S rRNA gene).

Sporangia dispersed or grouped, occasionally effused, sessile, subglobose or slightly elongated, 0.2–0.3 mm in diameter, silvery gray when lime crystals is present or drab when it is lacking; hypothallus inconspicuous; peridium membranous, colorless, covered with cuboidal calcareous crystals, dehiscence irregular; columella spherical to columnar, white, calcareous, occasionally absent; capillitium abundant, hyaline, arising from the columella or sporangia base, broader at base and containing expansion, threads 2.2–3.2 μm in diameter, branch and anastomose to form a loose reticulum with the extremities attached to the peridium; spores free, black in mass, dark brown by transmitted light, subglobose, encircled by a prominent equatorial ring, (10.0) 10.5–11.3 (11.9) μm in diameter, densely warted, with some warts fused in line patterns; plasmodium white.

Specimens examined: — China. Henan Province: Neixiang County, Baotianman National Nature Reserve , 33°30’48.02” N, 111°56’0.62” E, elevation 1412 m, on bark of Acer sp. in moist chamber culture, collected on 27 Oct 2015, Yang Gao, cultured on 8 Nov 2015, harvested on 22 Nov 2015 (MCCNNU 2256!) ; Neixiang County, Baotianman National Nature Reserve , 33°30’43.28” N, 111°56’14.52” E, elevation 1626 m, on bark of Quercus sp. in moist chamber culture, collected on 26 Jun 2016, Yang Gao, cultured on 5 Jul 2016, harvested on 24 Jul 2016 (MCCNNU 2510!) ; Neixiang County, Baotianman National Nature Reserve , 33°30’43.22” N, 111°56’4.56” E, elevation 1508 m, on bark of Toxicodendron sp. in moist chamber culture, collected on 22 Jul 2016, Yang Gao, cultured on 4 Aug 2016, harvested on 26 Aug 2016 (MCCNNU 2547!) .

Habitat: —On straw stacks ( Keller 1970), leaves, dung of herbivore ( Ranade et al. 2012) and bark of living tree (this study).

Distribution: — USA ( Keller 1970, Eliasson 1991), India ( Ranade et al. 2012), Ethiopia ( Dagamac et al. 2017), Pakistan ( Neubert et al. 1995), Japan ( Neubert et al. 1995) and China (this study).

Remarks: — Didymium saturnus described by Keller (1970) in details has ringed spores. Compared with the descriptions of Keller (1970), the Chinese materials have a slightly smaller spores (11–12 μm in diameter according to Keller) and different shape of lime crystals on the peridium (cuboidal according to Keller). But the same spore ornamentation including the truncate processes of warts confirmed that our collection is D. saturnus ( Keller & Schoknecht 1989) . The above differences are treated as intraspecific variations.

Fuligo luteonitens L.G. Krieglst. & Nowotny , in Neubert, Nowotny & Baumann, Myxomyceten 2:213, 1995.

Figures

FIGURE 3. Morphological characters of Didymium saturnus. a, b Sporangia on bark and filter paper under the dissection microscope. c Cuboidal calcareous crystals on the peridium (SEM). d Spores showing the equatorial ring (arrow, LM, DIC). e Capillitium (arrow) and spores (SEM). f A spore showing the fused warts (SEM). Scale bars: a, b=0.5 mm; c=20 μm, d,e=10 μm; f=5 μm