Podaxis

Fungalpedia – Note 214, Podaxis

Citation if using this entry: Bera et al. 2024 (in prep) – Fungalpedia, Basidiomycota 1.

Index Fungorum, MycoBank, Facesoffungi, GenBank, Fig. 1

Classification: Agaricaceae, Agaricales, Agaricomycetes, Basidiomycota, Fungi

Podaxis has captivated many scientists and explorers for centuries due to less-known facts about the biology behind its evident association with termites (Conlon et al. 2016). Podaxis has a well-documented history of being observed in connection with the grass-harvesting termite Trinervitermes from Africa and Nasutitermes in Australia (Massee 1890, Lenz & Priest 1999). The initial representation of Podaxis was identified as Fungus melitensis (Boccone 1697), with a detailed description and an additional suggestion that it is “well suited to the treatment of dysentery” (Boccone 1697, Conlon et al. 2019). In the initial documentation, three species of Podaxis were described under Lycoperdon Pers. as Lycoperdon pistillare L., L. carcinomale L. f., and L. axatum Bosc (Linnaeus 1771, 1781, Bosc 1792, Conlon et al. 2019). Desvaux (1809), for the first time, described Podaxis. Lycoperdon axatum from Senegal underwent a renaming process, becoming P. senegalensis Desv. (Desvaux 1809) and was subsequently assigned as the type species. Following that, numerous additional species were later documented, but most were acknowledged as synonyms by Massee (1890). Subsequently, mainly documenting the North American specimens, Morse (1933) reduced the previously reported thirty-two species into one polymorphic species, namely P. pistillaris (Morse 1933, Bottomley 1948, Conlon et al. 2016). Despite criticism from some (Heim 1938, 1977), this classification found widespread acceptance throughout the latter part of the 20^th century and extended into the 21^st century (Bottomley 1948, Doidge 1950, Conlon et al. 2016).

The basidiomata of Podaxis is mostly grayish to whitish when young but turns brown on maturity and consists of long bulbous stipe (Medina-Ortiz et al. 2017). The pileus has a bi-layered peridium and a capillitium (Medina-Ortiz et al. 2017). The exoperidium is scaly with deciduous scales at maturity, whereas the endoperidium is membranous, persistent, and degraded by longitudinal fissures (Medina-Ortiz et al. 2017). The capillitium threads are hyaline or pigmented, septate, and branched (Medina-Ortiz et al. 2017). The basidiospores are generally smooth and pigmented with two-layered walls (Medina-Ortiz et al. 2017). The intraspecific distinction is primarily based on the basidiospore morphology (Heim 1977, McKnight & Stransky 1980, De Villiers et al. 1989, Lenz & Priest 1999), and less comprehensive phylogenetic inferences have been undertaken (Conlon et al. 2016). In the revisionary works, nrITS and nrLSU sequence data have been used for phylogeny (Conlon et al. 2016, Medina-Ortiz et al. 2017). Also, the feeding habits of termites on Podaxis remain uncertain, but it is plausible that this fungus utilizes the concentrated nutrients within the termite nest without impacting the termites (Conlon et al. 2016).

Alternatively, there is a probability that Podaxis is a parasite growing inside the nest of the termite colony (Conlon et al. 2016). Even if it benefitted from the termites, the species of Podaxis has not been documented exclusively with the association of termites (Conlon et al. 2016). The association has only occurred in the overlapping host-termite ranges in mostly sandy and dry savannah habitats (Massee 1890, Herbert 1953, Dring 1964, Zoberi 1972, Hilton & Kenneally 1981, Lenz & Priest 1999, Conlon et al. 2016). This unique lifestyle makes Podaxis a potential model organism study for various adaptations in extreme environments (Conlon et al. 2019). Currently, there have been 28 species documented in Species Fungorum (2024) under Podaxis.Top of Form

Synonyms: Catachyon (Ehrenb. ex Fr.) Fr., Cauloglossum Grev. ex Fr., Chainoderma Massee, Herculea Fr., Schweinitzia Grev.

Type species: Podaxis senegalensis Desv.

Other accepted species: (Species Fungorum – search Podaxis)

Figure 1 – Podaxis pistillaris a,b Basidiomata. c Basidiospores. Scale bars: c = 10 μm. Drawn and taken from Lenz & Priest (1999) and https://www.mushroomexpert.com/podaxis_pistillaris.html.

References

Boccone P. 1697 – Museo di fisica e di esperienze variato, e decorato di osservazioni naturali, note medicinali, e ragionamenti secondo i principij de’moderni. Baptistam Zuccato, Venice.

Bosc LAG. 1792 – Lycoperdon axatum. Actes de la Société d’Histoire Naturelle de Paris, 1, 47.

Bottomley AM. 1948 – Gasteromycetes of South Africa. Bothalia 4(3), 474–810.

Conlon BH, Aanen DK, Beemelmanns C, De Beer ZW et al. 2019 – Reviewing the taxonomy of Podaxis: Opportunities for understanding extreme fungal lifestyles. Fungal biology 123(3), 183–187.

Conlon BH, De Beer ZW, Henrik H, Aanen DK, Poulsen M. 2016 – Phylogenetic analyses of Podaxis specimens from Southern Africa reveal hidden diversity and new insights into associations with termites. Fungal biology 120(9), 1065–1076.

De Villiers JJR, Eicker A, Van der Westhuizen GCA. 1989 – A new section and two new species of Podaxis (Gasteromycetes) from South Africa. South African Journal of Botany 55(2), 159–164.

Desvaux NA. 1809 – Observations sur quelques genres a etablir dans la famille des champignons. Journal de Botanique, Paris 2(38), 97–99.

Doidge EM. 1950 – The South African fungi and lichens to the end of 1945. Bothalia 5.

Dring DM. 1964 – Gasteromycetes of west tropical Africa. Mycological Papers 98, 1–60.

Heim R. 1938 – Observations sur la flore mycologique malgache. VI. Les champignons des termitieres. Premiere note: Basidiomycetes. Boletim da Sociedade Broteriana 13, 45–63.

Heim R. 1977 – Termites et Champignons. Boubee, Paris.