Xeromphalina setulipes

Xeromphalina setulipes: A Fungal Gem in the Mycenaceae Family

Imagine stumbling upon a hidden treasure, something so unique and rare that it has only been known to science for just over a decade. That’s exactly what happened with Xeromphalina setulipes, a fascinating species of fungus first collected in 2005 and described in 2010 by Fernando Esteve-Raventós and Gabriel Moreno. This little-known gem is not only a marvel to the mycological community but also a testament to the vast undiscovered biodiversity that still awaits us.

Discovering Xeromphalina setulipes

First discovered in the oak forests of Ciudad Real Province, Spain, this species has become a subject of intense interest among mycologists. The dark reddish-brown caps and distinctive arched brown gills make it stand out from its relatives, much like finding a rare gemstone amidst a sea of ordinary pebbles.

Distinctive Features

The mushrooms produced by Xeromphalina setulipes are not just visually striking; they also possess unique characteristics that set them apart. With flattened-convex caps measuring 8-15 mm in diameter, these fungi have a dark brown hue with reddish undertones that fade as the mushroom dries. The stem is cylindrical and stiff but flexible, ranging from 30 to 45 mm in length by 1-2 mm in width, and its color can sometimes approach black, with purplish hints.

The gills are subdistant and arched, measuring up to 2 mm thick, with edges that can be paler and crenulate. The flesh is firm but flexible, similar in color to the surface, and has an indistinct smell and a taste not bitter. These features make it a unique addition to the Mycenaceae family.

Phylogenetic Relationships

The phylogenetic analysis of Xeromphalina setulipes has revealed intriguing connections with other species within the genus. While further research is needed, initial data from the 60S nuclear ribosomal RNA gene suggest that it is closely related to X. fraxinophila, X. cornui, X. campanelloides, and X. cauticinalis. The ITS data place it in a clade containing X. cauticinalis and X. parvibulbosa.

These relationships hint at the complex evolutionary history of this species and its relatives, much like piecing together a puzzle with missing pieces. Understanding these connections can provide valuable insights into the broader family dynamics within Mycenaceae.

Mycological Characteristics

The spores of Xeromphalina setulipes are smooth, ellipsoid to cylindrical, measuring from 5.0 to 7.3 μm by 2.9 to 3.7 μm. The basidia are narrow clubs, and the cheilocystidia are irregularly shaped. Caulocystidia project prominently on the stem, while circumcystidia form a mass reminiscent of coral. These microscopic traits contribute to its unique identity within the fungal kingdom.

The pileipellis, uppermost layer of hyphae in the cap, forms a cutis made up of cylindrical hyphae with yellowish-brown pigment, and the stipitipellis on the stem also forms a cutis with dark red-brown pigment and clamp connections. These characteristics are crucial for identifying this species accurately.

Comparison with Other Species

While Xeromphalina setulipes shares some similarities with other species like X. cauticinalis in terms of hair color and growth habits, it differs significantly in shape, coloration, and spore width. Its relationship to X. brunneola is also complex, as they share some microscopic traits but are not closely related due to differences in cheilocystidia and pileocystidia shapes, spore size, and habitat specificity.

Campanelloides can be differentiated by the shape of thin-walled caulocystidia and yellow flesh in the stem. These distinctions highlight the intricate nature of fungal classification and the importance of detailed morphological studies.

Habitat and Distribution

Xeromphalina setulipes is only known from Spain’s province of Ciudad Real, making it a rare find indeed. Members of Mycenaceae are saprotrophic and found in woodland made up of cork oak, Portuguese oak, gum rockrose, prickly juniper, and various heathers. These fungi thrive in the acid soil on the forest floor, surrounded by dead plant matter.

Mushrooms grow in clusters, often in softwood forests with Sphagnum moss, where both cap and top sport yellow grains. This habitat specificity adds to its allure as a unique species within the Mycenaceae family.

Conclusion

Xeromphalina setulipes is more than just another fungus; it’s a fascinating glimpse into the vast and mysterious world of fungi. Its unique characteristics, habitat specificity, and phylogenetic relationships make it a valuable addition to our understanding of fungal diversity. As we continue to explore and classify these organisms, who knows what other hidden treasures await us in the mycological realm?