On a recent survey on Kangaroo Island, South Australia, in early August 2024, we collected a small bird’s nest fungus (PSC4956) growing on kangaroo dung; morphologically the fungus conforms to Mycocalia denudata. The site is low woodland with Eucalyptus baxteri, Acacia myrtifolia, and Xanthorrhoea semiplana ssp. tateana that had been burnt in the 2019-2020 fires. The dung pellet was wet and had a greenish hue due to filaments of algae growing on it. In spite of careful searching, no further specimens were found on dung or vegetation.

The fungus was small and in the field its structure difficult to elucidate, even under ×10 magnification of a hand lens. The lumpy, pale cinnamon fruit-bodies were scattered over the surface of the dung. Also on the pellet were minute orange-tan discs which we suspected might be disc fungi. Examination of field photographs that evening provided one of those eureka moments: the lumps were peridia of Mycocalia, a bird’s nest fungus and the discs were peridioles, neat packets containing spores (Fig. 1). Specimens of Mycocalia are rarely collected and we had not come across any before in our 25 years of collecting.

Bird’s nest fungi (family Nidulariaceae, class Agaricomycetes) (Brodie 1975) are characterised by their peridia (singular peridium), usually vase-shaped structures resembling tiny bird’s nests, containing spore-bearing ‘eggs’, the peridioles. They are saprotrophic, growing on dead or decaying wood and organic matter including dung. The Fluted Bird’s Nest Fungus, Cyathus striatus (Fig. 2), may be found on wood chip mulch and leaf litter.

The peridia in species of Cyathus, Crucibulum, Nidula and Nidularia are firm and well-shaped, but thin and fragile in Mycocalia. Peridia of Cyathus, Crucibulum and Nidula have a lid, an epiphragm which ruptures when the peridioles are mature, opening the peridium and exposing their egg-like contents. Peridia of Nidularia and Mycocalia do not have an epiphragm, their peridioles being released as the peridium disintegrates. In Cyathus (Fig. 3) and Crucibulum species, each peridiole has a funiculus, a cord, attaching it to the lining of the peridium. The peridioles of Nidula and Nidularia lack a funiculus but are instead embedded in a gel. The peridia of Cyathus, Crucibulum and Nidula act as splash-cups, their peridioles splashed out when hit by falling raindrops, while the peridioles of Nidularia and Mycocalia are scattered as their peridia fragment.

Mycocalia species occur in temperate and tropical regions but are rarely collected. The type species Mycocalia denudata was first described from England as Nidularia denudata Fr. (Fries and Nordholm, 1817). Based on differences in the structure of peridia, Palmer (1961) separated Mycocalia denudata from Nidularia, designating M. denudata (Fr.) J.T.Palmer as the type. Mycocalia species are phylogenetically distant from other genera of bird’s nest fungi and Kraisitudomsook et al. (2021, 2024) suggest that they retain some of the ancestral characteristics of the family.

Mycocalia denudata is common in England and has been found in Denmark and Canada. In the southern hemisphere it is known from both New Zealand and Australia. There are 14 Australian records in the Atlas of Living Australia (ALA), 12 from Victoria and two from Tasmania (Mycocalia denudata | Atlas of Living Australia (ala.org.au)). A South Australian collection identified as Mycocalia sp. was made in 1979 by J.H. Warcup from soil, possibly from the Waite Institute, that had been heated to 60°C for 30 mins. This collection is held in the National Herbarium of Victoria (MEL) (Record: MEL:MEL 2024748A | Occurrence record | Atlas of Living Australia (ala.org.au). The ALA also includes a record of a specimen collected by J.B. Cleland in South Australia from Mt Compass in “Cleland’s Gully”, April 1930. This collection, listed as Nidularia deformis (Willd.) Fr., was identified by G.H. Cunningham as Nidularia pisiformis (Roth) Tul. (Cunningham 1944) and is held by the New Zealand Fungarium at Landcare Research NZ Ltd. (Record: PDD:PDD 8505 | Occurrence record | Atlas of Living Australia (ala.org.au).

The dozen or so peridia of the collection from kangaroo dung on Kangaroo Island were mostly on the upper surface of the dung pellet (Fig. 1). Some were intact, the walls of others were fragmenting, exposing their densely packed peridioles, yet others had collapsed completely, leaving small heaps of peridioles (Fig. 4). The walls of the peridia formed a fragile, pale cream-orange envelope enclosing the numerous tiny peridioles. These were orange- to red-brown biconcave discs, 350–550 µm in diameter. Spores were ellipsoid, smooth, colourless, 5–7(–8) x 3.5–5 µm. The walls of the peridioles were composed of compacted, jigsaw-like cells (Fig. 5).

The current SA collection of Mycocalia PSC4956 is probably an introduction from the northern hemisphere of M. denudata. However, it is not infrequently the case that morphologically similar specimens from southern hemisphere collections turn out to be genetically distinct species.

The genome of M. denudata has been sequenced (https://mycocosm.jgi.doe.gov/Mycden1/Mycden1.home.html) so checking the ribosomal ITS DNA sequences of Mycocalia PSC4956 will enable confirmation or otherwise of the identification based on morphology and, if that is indicative of a new species, a culture David established will permit sequencing its genome.

We are grateful to the Flinders Chase Conservation Management Committee for supporting our survey.

References
Brodie, H.J. (1975). The Bird’s Nest Fungi. pp. 1-199. (University of Toronto Press: Canada).
Cunningham, G.H. (1944). The Gasteromycetes of Australia and New Zealand. 236 p. (McIndoe: Dunedin).
Fries, E.M. & Nordholm, J. (1817). Symbole Gasteromycorum Ad Illustrandam Floram Suecicam, pp. 1-25
Kraisitudomsook, N., Healy, R.A., Smith, M.E. (2021). Molecular systematics and taxonomic overview of the bird’s nest fungi (Nidulariaceae). Fungal Biology. 125(9):693-703.
Kraisitudomsook, N., Ahrendt, S., Riley, R., LaButti, K., Lipzen, A., Daum, C., Barry, K., Grigoriev, I.V., Rämä, T., Martin, F., Smith, M.E. (2024). On the origin of bird’s nest fungi: Phylogenomic analyses of fungi in the Nidulariaceae (Agaricales, Basidiomycota). Molecular  Phylogenetics and Evolution. 193(4):108010
Palmer, J.T. (1961). Observations on Gasteromycetes IX. The Conservation of Nidularia Fr. and the Separation of Mycocalia J.T. Palmer, gen. nov. Taxon. 10:54–60.

Fig. 1 Mycocalia sp. (Cover photo)
Fig. 2 Cyathus striatus
Fig. 3 Cyathus striatus showing a funiculus attaching a peridiole to the peridium
Fig. 4 Mycocalia sp.
Fig. 5 Part of peridiole wall and spores of Mycocalia sp.

All images by P. Catcheside