Geastrum crystallinum Dourado-Barbosa, R. L. Oliveira, A. A. Lima, P. Marinho, Baseia & R. Cruz, 2025

Geastrum crystallinum Dourado-Barbosa, R. L. Oliveira, A. A. Lima, P. Marinho, Baseia & R. Cruz , sp. nov.

( Fig. 4 View FIG )

DIAGNOSIS. — Basidiomata small and completely whitish in the field, from exoperidium, mesoperidium, endoperidium, peristome and gleba. Hyaline basidiospores under light microscope, showing bypiramidal crystals of calcium oxalate in the gleba.

ETYMOLOGY. — Based on the presence of crystals in the hyaline gleba under optical light microscopy.

MATERIAL EXAMINED. — Brazil • Bahia, Barreiras, Família Barbosa Farm, Cerrado stricto sensu; found on sandy soils in a gregarious growth; 12°7’11.25”S, 45°4’26.43”W; 27.II.2021; K.D. Barbosa , KD 0055; Holotype: BRBA-Fungos 0137 ; GoogleMaps Isotype: UFRN-Fungos 3682 . GoogleMaps

HABIT. — Gregarious, growing on sandy soils.

MYCOBANK. — MB#849826.

GENBANK ACCESSION NUMBER. — OR479887 (ITS), OR479889 (LSU).

DESCRIPTION

Unexpanded basidiomata absent.Expanded basidiomata saccate, 5-6 mm high (including peristome), 11-17 mm wide. Exoperidium with 7-9 triangular rays, revolute, non-hygroscopic. Mycelial layer cotonous to furfuraceous, encrusted with debris, completely whitish (1A1) when fresh and ivory when dry (4B3). Fibrous layer coriaceous, persistent, completely whitish (1A1) when fresh and grayish orange (5B3) when dried. Pseudoparenchymatous layer showing a pattern that varies from slightly rimose in newly expanded basidiomata to extremely rimose in older expanded basidiomata, white (1A1) when fresh and light brown (5D5) when dehydrated, collar absent. Endoperidium globose, 3.5-6 mm high (including peristome)× 3-5.5 mm wide, surface non-pruinose, with small vermiform hyphae, entirely white (1A1) when fresh and whitish orange (5A2) when dry. Apophysis and stalk absent. Peristome fibrilose, flat to mammiform, concolour to slightly darker than the endoperidium, 0.1-0.2 mm high, whitish yellow (1A2) to pale yellow (2A2). Gleba whitish (1A1), with bipyramidal crystals (4.2-7.3 µm diam). Mycelial layer composed of hyaline hyphae, 1.8-3.7 µm in diameter, thick walled (0.3-0.6 µm), not encrusted, slightly sinuous, unbranched, with lumen evident. Fibrous layer composed by hyaline hyphae, 1.8-3.7 (5) µm in diameter, thick-walled, 0.3-1.2 (1.88 µm), not encrusted, slightly sinuous, unbranched, lumen evident. Pseudoparenchymatous layer composed of subglobose, globose to ellipsoid cells, hyaline, 24.7-66.1× 19.2-36.6 µm in diameter, thin-walled (<1µm). Eucapillitium hyaline, 1.3-4.3 µm in diameter, thin-walled (<1 µm), encrusted, slightly sinuous, unbranched, lumen evident. Basidiospores globose to slightly elliptical, hyaline (Q=1.00-1.25), 3.8-5.1×3.7-4.9 µm [x=4.4 ±0.4×4.2 ±0.3. Qm = 1.06, n=30], conspicuous ornamentation (0.2-0.9 µm in height) under LM and verrucose under SEM.

COMMENTS

Geastrum crystallinum sp. nov. ( Table 3 View TABLE ), is characterized by having a small basidioma, being completely whitish in the field, both in the rays, endoperidium, peristome and gleba, in addition to presenting hyaline basidiospores and the presence of bipyramidal crystals in the gleba.

Geastrum crystallinum sp. nov. groups phylogenetically with the Sect . Corollina, Subsect. Marginata , forming a group with G. saccatum Fr. (<50 bs MP/ <50 bs ML/ 95 Bayesian pp), at the base of other species in the Subsect. Marginata ( G. flexuosum (L.S. Domínguez & Castellano) Jeppson & E. Larss. , G. corollinum (Batsch) Hollós and G. caatingense J.O. Sousa, M.P. Martín & Baseia ). This Subsection is characterized by the presence of fibrillose, non-folded, thickened and distinctly delimited peristome ( Zamora et al. 2014, 2015; Sousa et al. 2019). However, contrary to these characteristics present in the other species of Subsect. Marginata , G. crystallinum sp. nov. have a non-delimited peristome, which is the unique character that distinguishes the new species in this Subsection.

In addition to this characteristic that separates all these species, representatives of G. saccatum and G. corolinum commonly present elongated, non-faceted and circular calcium oxalate monohydrate (COM) crystals, almost filiform or even in arachnoid structures with radial patterns that are often abundant, forming substantial amounts of powdery masses ( Zamora et al. 2013). The specimens of G. caatingense , on the other hand, have color patterns in the basidiome that are completely different from those of G. crystallinum , with a pale orange (5 A 3) micelial layer, white orange (5 A 2) fibrous layer, a dark brown (6E4) pseudoparenchymatous layer, a grayish orange (6 B 2) endoperidium, and a brownish gray (6C2) to yellowish white (5 A 2) gleba, while specimens of G. crystallinum are completely whitish in colors ( Sousa et al. 2019).

Geastrum crystallinum sp. nov. resembles G. flexuosum in the presence of globose and verrucose basidiospores, with similar sizes between 4.0 to 5.0 µm in diameter ( Kers 1976; Domínguez de Toledo & Castellano 1996). Both species have hyaline eucapillitium, with thin, sinuous walls covered in debris ( Jeppson et al. 2013). However, G. flexuosum has a rounded semi-hypogeous basidiome that open irregularly at maturity and not like a typical star with rays, as observed in G. crystallinum and other species of the genus ( Domínguez de Toledo & Castellano 1996; Jeppson et al. 2013). Although the basidiome of G. flexuosum also has a whitish color like G. crystallinum , its representatives can also have a brownish color and irregular rupture of the peridium ( Jeppson et al. 2013), a characteristic not observed in the specimens of G. crystallinum . Additionally, G. flexuosum has a dark brown gleba without crystals ( Kers 1976), while G. crystallinum has a whitish gleba with bipyramidal crystals.

Another strongly similar species is Geastrum hyalinum Freitas-Neto, N.M. Assis, J.O. Sousa, & Baseia by the mature basidioma saccate, whitish gleba and hyaline spores under light microscopy ( Assis et al. 2019). However, the gleba of G.hyalinum has a more whitish yellow color (1 A 2) ( Assis et al. 2019), instead of the completely white color (1 A 1) when fresh and only whitish yellow (1 A 2) in dehydrated basidiomata of G. crystallinum . Another similar feature in G. crystallinum and G. hyalinum is the morphology of the endoperidium, that varies from globose to subglobose, also showing prominent small vermiform hyphae, absence of crystalline matter and apophysis ( Assis et al. 2019). However, in G. crystallinum the size of this structure is almost four times smaller than in G. hyalinum . The peristome of both species is fibrillose and flattened, but in specimens of G. hyalinum the peristome is delimited, which is completely different from the non-delimited peristome of G. crystallinum ( Assis et al. 2019) . Both species have hyaline, globose basidiospores with conspicuous ornamentation, but in G. crystallinum there is no presence of bipyramidal crystals in the gleba ( Assis et al. 2019). Unfortunately, no molecular data are available for the species G. hyalinum to be used in a genetic comparison, forcing us to compare the samples based solely on the morphological features.

Geastrum crystallinum sp. nov. also morphologically resembles two other species that have saccate basidiomata: Geastrum floriforme Vittad. and G. lageniforme Vittad. ( Fries 1829; Vittadini 1842). However, G. floriforme has a strongly hygroscopic exoperidium and a yellowish-brown gleba (5E4), while G. crystallinum has a non-hygroscopic exoperidium and a whitish gleba ( Vittadini 1842; Sousa 2015). In G. lageniforme , the species has long rays with thin ends, a mycelial layer with distinct longitudinal grooves, and basidiospores with prominent columnar warts up to 1.2µm in height, while G. crystallinum has short rays that do not taper at the base, absence of longitudinal grooves in the mycelial layer, and short verrucous ornamentations, smaller than 1 µm in height ( Vittadini 1842; Sousa 2015). Thus, G. crystallinum sp. nov. is a unique and characteristic species, both in its macroscopic form in the field and microscopically in the laboratory.