Arcyria aeruginosa Yang Gao, G.W. Wang et Shuang L. Chen, 2018

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 : 52-55

Arcyria aeruginosa Yang Gao, G.W. Wang et Shuang L. Chen , sp. nov. FIGURE 1 .

MycoBank: MB 823954

GenBank: —MG696633 (18S rRNA gene).

Holotype: — CHINA. Hunan Province: Dong’an County, Shunhuangshan National Forest Park, 26°23’59” N, 111°2’18” E, elevation 647 m, on rotten stem of unidentified bamboo, 13 Jul 2015, collected by Gang He (holotype, MCCNNU 1898!).

Etymology: —aeruginosa refers to the alice blue sporangia.

Sporangia densely aggregated on a common hypothallus, stipitate, alice blue, fading to drab with age, cylindrical, 5–6 mm tall, 0.5–0.8 mm in diameter when expanded; hypothallus continuous, membranous, hyaline; cup 0.3–0.4 in diameter, dark brown, membranous, funnel-shaped, plicate externally, the inner surface densely ornamented with spines which rarely coalesce to form a reticulum; columella absent; stalk slender, black, 0.6–1.0 mm long, filled with spore-like cells; capillitium slightly elastic, firmly attached to the margin and center of the cup, the threads branched and anastomosed, 4.8–6.0 μm in diameter including ornamentations, marked by continuous half-rings arranged in a loose spiral, the remaining surface roughly spined, the half-rings and spines also connected by low ridges forming an irregular reticulum; spores free, concolorous in mass, colorless by transmitted light, subglobose, (7.6) 8.0–8.8 (9.2) μm in diameter, marked with dense warts and grouped prominent warts; Plasmodium unknown.

Additional specimen examined: — China. Hunan Province: Dong’an County, Shunhuangshan National Forest Park, 26°23’59” N, 111°2’18” E, elevation 644 m, on rotten stem of unidentified bamboo, 13 Jul 2015, collected by Gang He (Paratype, MCCNNU 1899!).

Habitat: —On rotten stem of unidentified bamboo.

Distribution: —Currently known only from the type locality.

Remarks: —The genus Arcyria , established by Wiggers in 1780 ( Martin & Alexopoulos 1969), is one of the most common genera in the family Trichiaceae of the order Trichiales . It is typically characterized by having a netted capillitium. The other characters include the usually stalked sporangia, fugacious peridium remaining at the base as cup and pale spores ( Martin & Alexopoulos 1969). It is represented by 53 species worldwide of which 30 have been reported in China ( Lado 2005 –2018, Li et al. 2008, Zhang et al. 2012).

The most unusual characteristic of A. aeruginosa is the cup which has dense spines on inner surface. The combination of the above character and the alice blue sporangia is unknown in any other species of the genus. The new species is most similar to Arcyria glauca Lister in having bluish sporotheca and comparable ornamentation on the capillitium. Arcyria glauca is characterized by short stalks (0.2–0.3 mm), faintly reticulated cup, usually presence of smooth part or spirals on capillitial threads (2.5–3.0 μm in diameter), and nearly smooth spores ( Lister 1925; Martin & Alexopoulos 1969). Arcyria aeruginosa , by comparison, has longer stalks (0.6–1.0 mm), densely spined cup, evenly ornamented capillitium (4.8–6.0 μm in diameter), and larger spores which also ornamented by two types of warts.

Other Arcyria species have blue or green sporangia are Arcyria brooksii T.N. Lakh. & K.G. Mukerji , A. fasciculata Dhillon & Nann. -Bremek., A. nigella Emoto and A. virescens G. Lister. Arcyria brooksii is distinguished from A. aeruginosa for its smaller sporangia (0.8–1.5 mm long), persistent peridium, reticulated inner surface of cup, and capillitial threads marked by prominent blunt spines ( Lakhanpal & Mukerji 1979). Arcyria fasciculata is characterized by subglobose to short cylindrical, yellowish green or reddish grey sporangia, deep cup, weak attachment between sporotheca and cup ( Dhillon & Nannenga-Bremekamp 1978), unlike the counterpart of A. aeruginosa . Arcyria nigella differs in its small and globose sporangia (1.0– 1.5 mm in diameter), strongly netted cups, spinose and reticulated capillitium ( Emoto 1928). Arcyria virescens has narrow funnel-shaped cups with inner surface reticulated, weak attachment between sporotheca and cup, and prominent transverse ridges on capillitium ( Lister 1921).

The ornamentation of cup or capillitium of A. aeruginosa resembles that of A. colloderma Nann. -Bremek. & S.L. Stephenson, and A. verrucosituba Nann. -Bremek. & Schinner. However, A. colloderma is distinguished by its red-brown to grey-brown sporangia with very short stalks (Stephenson & Nannengabremekamp 1990). For A. verrucosituba , the capillitial net was mainly connected to the stalk apex and easily broke away. Furthermore, it differs in its smaller (1.3–2.5 mm long) and ochraceous sporangia, deep and netted cups, and smaller spores (6–7 μm in diameter) ( Nannenga-Bremekamp & Schinner 1986).

Figures

FIGURE 1. Morphological characters of Arcyria aeruginosa. a Groups of mature sporangia on rotten bamboo stem in the field.b Scanning electron micrograph (SEM) of a completely expanded sporangum. c A complete stalk under light microscope with differential interference contrast (LM, DIC). d Outer surface of the cup and connection between cup and sporotheca (SEM). e Spines on inner surface of cup (arrow). f Capillitium ornamented with half-rings and spines (SEM). g Spores under under LM with DIC. h A spore showing two types of warts. Scale bars: a=10 mm; b=1 mm; c=200 μm; d=100 μm; e,f,g=10 μm; h=2 μm