Physarum bivalve Pers.

Baba, Hayri, Gündoğdu, Fatma & Sevindik, Mustafa, 2021, Myxomycetes biodiversity in Gaziantep Province (Turkey) with four new records, Phytotaxa 478 (1), pp. 105-118 : 113-114

Physarum bivalve Pers. ( Fig. 7 )

Fructification plasmodiocarpous, or pulvinate sessile sporangia, sitting on the substratum by a narrow line or a constricted base, crowded, laterally compressed, white, grey, or yellowish, 0.5–0.6 mm wide, up to 4 mm long; peridium double, the outer layer usually thickly calcareous, white and limy on the inside surface of the outer peridium, opaque, ruptured from preformed fissure which is more or less longitudinal or lobate, the inner layer delicate, translucent and hyaline; dehiscence regular, preformed longitudinal fissure; capillitium abundant, with large white lime-nodes and angular, connecting the short, colourless and branched threads; spore-mass black-brown, spores dull violet brownish by transmitted light, very minutely warted or spinulose, 8–11 µm diam.; plasmodium grey, pallid or yellowish.

Comments:— A very distinctive species and a new record from Turkey. The colour and form of plasmodiocarps are characteristics readily recognized. The plasmodiocarp creeping in long vein-like reticulations or curves, laterally compressed, or sometimes sporangiate, distinct and crowded, sessile, white-grey, short to long, sinuous. Plasmodiocarpous and sporangiate fructifications often occur side by side, or merge into one another from the same plasmodium. Where the substratum affords room the plasmodiocarpous style prevails; in narrower limits single sporangia stand. A double peridium and regular dehiscence by a longitudinal fissure all along the edge, when the fructification appear just like a bivalve. The calcareous deposit on the peridium is usually very rich and under a lens appears made up of countless snowy or creamy flakes. Forms occur, however, in which these outer deposits are almost entirely wanting; the peridium becomes transparent, the capillitium visible from without. The amount of lime on the outer peridium is also very variable, fruitings with nearly or quite limeless peridia occur. Capillitium with large white calcareous nodes. It is close to P. laevisporum which, however, possesses smaller spores and in which the peridial lobes become reflexed after dehiscence. Widely distributed in USA and often common, Taıwan, frequent in Europe and reported from all continents except Australia. Habitat various, but not infrequently the upper surface of the leaves of living plants, a few cm from the ground ( Macbride & Martin 1934, Liu 1982).

P. bivalve occurs in the area scattered to occasionally very often in the months of July to October, substrates are fallen leaves, thin branches and very often living plants. There is a possibility of confusion with P. bitectum which, however, does not open like a slit but rather through irregular erosion of peridia and has coarser, sharply sculptured, darker spores that are brighter on one side ( Neubert et al. 1995).

Specimens examined:— Nizip, on dead wood of pomegranate, Gündoğdu 14.

World distribution:— Argentina, Australia, Brazil, Colombia, Costa Rica, Cuba, France, India, New Zealand, Peru, South Africa, Taiwan, USA, Venezuela.

Figures

FIGURE 7. Physarum bivalve. a. Sporocarp. b–d. Spores, capillitium and lime crystals.