Unusual occurrence of rare Geastrum species with an abnormal stoma development found in Madurai, Tamil Nadu, India

Introduction

The species of the genus Geastrum, classified under order Geastrales, is rare and the species are red listed (Piętka & Kujawa in 2012; Wojewoda et al., 2006). Although in the distant past they were recorded in several locations worldwide, sightings of this attractive earthstar in plains are now highly limited due to anthropogenic activity. Kirk et al. (2008) and Perez (2009) described 50 species of Geastrum in a dictionary of fungi. Zamora et al. (2014) described 100 to 120 species of Geastrum based on field and herbarium studies.

There have been many reports about the pluralistic distribution of Geastrum species in Western Ghats by Karun & Sridhar, 2014, in Central India by Verma et al. (2018) and in Tamil Nadu by Meenakshi & Selvam (2020). Geastrum species share morphology with Myriostoma species, as reported by Alexov et al. (2012); Esqueda (2009); Outcoumit et al. (2009) and Pawłowski & Adamska (2008).

Many mycologists classify Myriostoma in between Geastraceae and Astraeaceae. However, currently it is classified under Geastraceae (Dring, 1973; Sunhede, 1989). Using rDNA and other genetic markers, its molecular taxonomic position within Geastraceae was confirmed, and it is closely associated with the genus of Geastrum (Hosaka et al., 2006; Krüger et al., 2001).

These inedible fungi are widely distributed in Africa, Asia, North and South America, and Europe, where they grow in humus-rich forests. Geastrum are rather rare fungi; they have been characterized as critically endangered, red listed and threatened in many European countries like Poland, Montenegro, Bulgaria, Slovakia, Sweden, Switzerland and Czech Republic (Wojewoda et al., 2006 and Piętka & Kujawa, 2012). Consistent and periodical surveys of macrofungi result in identification of new fungi. The present objective of this work is to report the Geastrum species found in the riverbank canal of Madurai, Tamil Nadu, India with an abnormal stoma development.

Methods

Results and discussion

The specimen (TMC 1001) has been deposited in the collection of Gasteroid fungi at the Department of Botany, Thiagarajar college, Teppakulam, Madurai, Tamil Nadu, India.

The fruiting body size measures 40 mm in width by 20 mm in height, is solitary, and consists of an upper stalked spore case and radiating rays below (Figure 1 and Figure 2). The exoperidium has 10–12 rays, which are revolute, thin, united in the base and free at the tips, and triple layered, with a blackish brown mycelial layer (Figure 3). The tips curve towards the basal position. The peridium is bilayered. The endoperidium body spore case is greyish brown, up to 19 mm in diameter, with many stalks attached. The spore case opens by many pores through which spores escape.

The fungus has brown basidispores with a globose and verrucose structure. Brown eucapillitium threads are thin walled, straight, aseptate and up to 3μm in diameter. The exoperdium is composed of hyaline, aseptate to rarely septate, unbranched, thick walled, tightly packed hyphae, up to 4μm in diameter, wall thickness up to 1.7 μm. The endoperidium is unbranched, aseptate, brown in colour, with tightly packed hyphae measuring up to 3μm in diameter.

Although these fungi are cosmopolitan in distribution, due to the periodical environmental disruption nowadays, occurrence of these fungi is highly limited. According to Signalarter (2000) and Benkert (2003), the Geastrum species serve as indicators of specific habitats in need of conservation.

Figure 1. Geastrum dorsal view.

Figure 2. Geastrum ventral view.

Figure 3.

A) Geastrum in field. B and C) Geastrum size measurement.

Data availability

All data underlying the results are available as part of the article and no additional source data are required.