Termitomyces arjunii sp.nov.

A species new to science — and, within that, new to Goa, new to India, new to Asia, and new to the global record

A single, unusual mushroom was found growing in a private organic garden at Chamunda Gardens, Karaswada, Mapusa, standing apart from a nearby cluster of Termitomyces heimii.

It is being presented as a species new to science — and, within that, new to Goa, new to India, new to Asia, and new to the global record of Termitomyces-hosting sites anywhere in the world.

It was named Termitomyces arjunii, honouring both the legendary archer Arjun from the Mahabharata and young Arjun Gupte, from the family whose garden yielded the specimen.

The cap measured just 2.7 to 3 centimetres across — small, even by the standards of this already modest-sized genus.

A distinct layer of cells just beneath the spore-bearing gill surface — a cellular subhymenium — was found, packed with fatty, lipid-like globules.

This cellular subhymenium matches a pattern seen across several smaller-bodied Termitomyces species in Goa, reinforcing the idea that this structure tracks body size across the genus.

Within that same subhymenium, a cell type was found that has not, to current knowledge, been described in this genus before anywhere: a fragile, colourless cell filled with fatty inclusions, named a “spherocyst.”

These spherocysts behave chemically unlike every other cell type nearby, marking them as a genuinely distinct cell type rather than damaged or collapsed tissue.

Spherocysts were not confined to one spot — they turned up scattered through the deeper tissue and again at the gill’s edge, indicating a real, widespread cell type.

This unique cellular subhymenium, and the spherocysts within it, stands as some of the strongest evidence for treating this mushroom as a new species, independent of its outward shape.

The spores were found to be polymorphic — oval, round, and egg-shaped forms all occurring side by side on the very same gill.

Many of these polymorphic spores carried small oil droplets inside them, echoing the same fatty inclusions found in the subhymenium and spherocysts.

This spore variability reflects real genetic diversity, since spores arise from sexual reproduction — unlike the clonal spores this fungus also produces asexually.

Digital chromotyping — a technique being applied to this genus for the first time anywhere in the world by this research programme — resolved 215 individually named colours across the cap and gills, giving the most detailed colour dataset yet generated for any Termitomyces species.

Both cap and gills were found dominated by warm orange-brown tones, with the gills leaning more strongly into that palette (84% orange-brown) than the cap (66%).

The cap and gills were found to differ in colour by just enough to count as visually distinguishable — a genuinely close, marginal difference.

This modest cap-gill colour difference is explained on a developmental and chemical basis: the cap surface is directly exposed to sunlight, air, and weathering from the moment it emerges, while the gills develop shielded beneath a protective universal veil and are only unveiled later — meaning the two surfaces have had very different exposure histories by the time both were photographed.

Colour readings also varied within the cap surface itself, consistent with its unprotected, weather-exposed nature — darkening where it met direct sunlight and staying paler in patches that remained shaded.

The mushroom’s overall colouring is consistent with a sulphur-rich melanin pigment previously identified chemically in a related species from the same research programme, giving a real chemical basis — rather than a purely descriptive one — for the colours measured here.

The gill tissue was found unusually packed with calcium oxalate crystals in at least five distinct shapes — compact clusters, star-shaped rosettes, and fine needle-like forms — distributed right through a single gill.

This density and variety of crystal forms in fully mature reproductive tissue is striking, since such crystals are more typically reported in young, actively growing fungal tissue.

Dense, dark, granular masses consistent with melanin-like pigment were separately found within the same lamellar tissue, distinct from the calcium oxalate crystals.

A latex-conducting hyphal element (laticifer) was found running alongside a cluster of rounded cells in the same tissue, a further unusual inclusion type in this one small piece of gill.

The species-new-to-science claim is being treated as tentative, since only one basidiocarp was found — pending additional specimens from the same locality and formal herbarium deposition of the holotype.

All underlying data — photographs, colour measurements, and micrographs — is being made openly available via Zenodo under a fully open-access licence.