Didymium serpula Fr.

Baba, Hayri, Gündoğdu, Fatma & Sevindik, Mustafa, 2021, Myxomycetes biodiversity in Gaziantep Province (Turkey) with four new records, Phytotaxa 478 (1), pp. 105-118 : 110-112

Didymium serpula Fr. ( Fig. 5 )

Fruiting body is a depressed plasmodiocarp, scattered or solitary, effused, thin, dark grey or greyish white, flat, 0.1–0.15 mm thick, 2–8 mm long but sometimes to 40 mm, sometimes perforated; hypothallus inconspicuous; peridium membranous, translucent, covered to white, stellate, or sometimes less regular, lime crystals; columella absent; capillitium of slender, yellow-brown threads attached to subglobose vesicles, 30–50 µm diam., filled with yellow granular material; spore-mass brown, spores pale violet-brown, 8–11 µm diam., minutely warted, verruculose; plasmodium yellow.

Comments:— The fructifications were produced in the laboratory by the use of the moist chamber technique. This specimen is distinctive by the very thin flat plasmodiocarp which is olive grey or white depending on the thickness of the surface white lime crystals. Peridium grey, iridescent, covered with calcium crystals. White when lime is abundant, dull grey or iridescent where it is scanty or has fallen away, Capillitium abundant, dense, very flexuous and interconnected, of yellow-brown colour, and united with abundant globose vesicles, of 25–55 µm diam. The presence of the abnormally large vesicular bodies in the sporangium is also a characteristic of this rare species ( Martin & Alexopoulos 1969).

Didymium serpula was considered a rare species in the area, but was certainly overlooked by the inconspicuous, crusty growth. In upper Austria, only in the past few years has it become apparent that this is a common species ( Neubert et al. 1995). The species appears in summer and early autumn. The crust-like fructifications with the honey coloured bubbles on the capillitum prove to be species-specific, so that despite macroscopic similarity with D. dubium , a confusion must be disregarded. Comparable to the bubbles elements can be found in D. flexuosum , which differs by the distinct columella and the spiny to reticular spores ( Neubert et al. 1995).

Specimens examined:— Çamlık, on dead bark of Pinus sp. , Gündoğdu 91,92,93,94.

World distribution:— Africa, Australia, Austria, China, Japan, New Zealand, Pakistan, USA.

Family: Physaraceae

Craterium obovatum Peck ( Fig. 6 )

Sporocarps gregarious or scattered, often forming extensive fruitings, stipitate or sessile on a restricted base, total height 1–2 mm, sporothecae obovoid, 0.5–0.7 mm diam., dark greyish or purplish brown; peridium thin membranous, brittle, light purplish brown, paler and somewhat calcareous above, more persistent and darker below where it is often clearly delimited as a calyculus/cup, merging into the stalk; stalk erect, cylindrical or flared basally, smooth or rugulose, reddish brown, more or less stuffed with whitish lime, usually half the total height, sometimes extending as a columella into the sporotheca for up to two-thirds of its height, or replaced by a pseudocolumella; columella clavate, fusiform or cylindrical, up to two-thirds the height of the sporotheca; capillitium dense, white or pale brown, radiating from the columella when one is present, sometimes with a few hyaline connecting threads; hypothallus dark, thin, confluent or membranous, discoid or continuous for a group of sporangia, colourless to brown; spore-mass dark brown, spores dark violet or purple-brown, moderately to strongly warted-reticulate, mostly 11–17 µm diam.; plasmodium yellow.

Comments:— Craterium obovatum can be recognised macroscopically by its stalked, subglobose to obovoid sporocarps in large groups and by circumscissile dehiscence leaving a deep cup. With SEM the spore ornamentation is densely pilate, with wide base and verrucose apex. Sporocysts in groups, stippled or sessile, 1–2 mm high, obovoid, greyish to purplish brown. Peridium obovate, rugose-wrinkled, thin and fragile, pale above, more persistent and darker below, lilac-brown where it is often clearly delimited in section. Stipe coloured like the peridium, brown-red, half height, extending in columella until 2/3. Capillitium dense white or pale brown. Spores globose, purplish brown, black, moderately to strongly warty. On leaves, plant debris, decaying wood and fallen leaves ( Lizárraga et al. 1999).

This type is a genuine columella, a badhamioid-trained capillitium and spiky spores that distinguish it from the other species of the genus with true columella ( Neubert et al. 1995). C. obovatum is very similar externally to C. dictyosporum , but the latter is slightly smaller up to 1 mm, and the spores are slightly larger with broad spines fused into small crests that join in an incomplete network ( Poulain et al. 2011) and the spores have large ridges forming a reticulum, the apex of each ridge. C.muscorum is also closely related to C. obovatum but the former has completely reticulate spore ornamentation ( Lizárraga et al. 1999).

Specimens examined:— Şahinbey, on dead bark of Acacia sp. , Baba 22. Nizip, on dead bark of hawthorn, Natural, Baba 29, Oğuzeli, on dead bark of apricot, Baba 7.

World distribution:— Asia, Europe, Mexico, New Zealand, USA.

Figures

FIGURE 5. Didymium serpula. a. Sporocarp. b–d. Spores, capillitium and lime crystals.

FIGURE 6. Craterium obovatum. a. Sporangium. b, c. Spores and lime crystals. d. Spore.