Pyrenocollema japonicum, a New Freshwater Species of Pyrenocarpous Lichen from Japan

Abstract

Pyrenocollema japonicum H. Harada is described as new on the basis of a specimen from Iwate-ken, northern Japan. It is characterized by having a purplish-brown, smooth thallus; + sessile (or immersed only at base), + globose, black perithecia without thalline cover; I-septate ascospores (20 x 5 ,im); and ellipsoid pycnoconidia (2-3 x ca 1 ,im). It occurs on periodically submerged rocks in forested gorges. Pyrenocollema had long been considered as a monotypic genus with the only species-P. tremelloides Reinke (Zahlbruckner 1924, 1926). In recent decades, however, many species have been transferred from Arthopyrenia (Arthopyreniaceae) and Verrucaria to Pyrenocollema (Coppins et al. 1992; Tucker & Harris 1980). The genus is now regarded as a pyrenocarpous cyanolichen of uncertain taxonomic position, with about 10 species from a wide variety of habitats including maritime (intertidal zone on seashore), freshwater (on rocks in rivers), and terrestrial (Hawksworth et al. 1995; Purvis et al. 1992). They are known mainly from Europe and North America, and only a single maritime species, Pyrenocollema sublitorale (Leight.) A. Fletcher has been recorded for Japan (Santesson 1940, as Arthopyrenia sublitoralis). During a field trip for my taxonomic study of pyrenocarpous lichens in northern Japan, a freshwater species of this genus was collected on riverside rocks in Iwate-ken on the Pacific side of northern Honshu. It differs from all the previously known species of this genus and is here described as new. MATERIALS AND METHODS The description of external morphology is based on airdried material. For anatomical observations, sections were made with a razor blade under a dissecting stereomicroscope. GAW (glycerol:ethanol:water = 1: 1: 1) preparations of sections were used for color description. By replacing the medium of GAW preparations to water, ethanol and finally lactophenol cotton-blue (LPCB), LPCB preparations were made for anatomical drawings, photographs, and descriptions. The K, I, and KI tests were conducted on sections of perithecia and thallus by using ca 10% aqueous solution of KOH and/or a diluted Lugol's solution. The specimen used in this study is deposited in the herbarium of Natural History Museum and Institute, Chiba (CBM).