Tulostoma subreticulatum Hern.

Hernández-Navarro, Eduardo & Cappello-García, Silvia, 2024, Tulostoma subreticulatum (Agaricomycetes, Agaricales): a new species of stalked puffball from Mexico, Phytotaxa 653 (2), pp. 101-114 : 106-109

Tulostoma subreticulatum Hern. -Nav. & Cappello-Gar. sp. nov.

( FIGURES 3 & 4 )

TYPE:— MEXICO. Tabasco State: Macuspana Municipality, Agua Blanca State Park, 17º 37’ 14” N, 92º 28’ 23” W, elevation: 116 m asl., 17 October 2019. On a rock pit filled with organic matter and moss, leg. S. Cappello-García (holotype: MEXU 30552, isotype: UJAT: 4322). Tacotalpa Municipality, Ejido Poaná, 17° 31’ 54.6” N, 92° 44’ 22” W, elevation: 59 m asl., 18 August 2013. Humicolous soil, leg. Gómez-García (Paratype: MEXU 30553).

MykoBank: #852431

GeneBank accession numbers: OR539673 ( ITS-LSU), PP375809 (Tef1α)

Etymology: The name refers to the subreticulate appearance of the basidiospores.

Diagnosis: basidiome up to 48 mm high, stipe 24 × 1.5–2.5 mm, reddish-brown, with a mycelial bulb with hyphae encrusted with debris, spore-sac 5–11 mm diam. × 5–8 mm height, circular mouth, verrucose exoperidium, reddish brown endoperidium, subreticulate basidiospores, hyaline capilitium with visible lumen, slightly swollen at the yellowish septa.

Description: Basidiome up to 48 mm high, stipitated. Spore-sac subglobose, 5–11 mm diam. × 5–8 mm height. Mouth circular to elliptical, less than 1 mm diam. Exoperidium membranous, brown (E6E) to grayish brown (6E4), verrucose, composed of angulous to cubic verrucae up to 200 μm high, easily removable. Persistent in the base of the spore-sac, leaving a sub-reticular pattern in the upper part. Endoperidium reddish brown (8D6), mottled with some verrucae and verrucae scars. Gleba light ferruginous (6B6–6A7). Socket conspicuous, fibrillose, separated from the stem. Stipe, mostly less than 24 mm, but up to 40 mm × 1.5–2.5 mm, reddish brown (8D6), very thin and fragile, striated in the base to slightly squamosal in the upper third, with a conspicuous basal bulb with hyphae strongly mixed with grains of sand and debris, as the rhizomorphs.

Verrucae formed by irregular and pigmented pseudo parenchymatous hyphae, up to 26 μm in the longest portion and up to 14 μm in the shortest, with a cracked to granulose appearance, with cell walls up to 1 μm. Endoperidium is formed by short and wavy hyaline hyphae, 3–6 μm diam., septated, and slightly swollen at the yellowish septa in KOH. Stipe composed of hyphae 19–33 μm in length from one septum to another; 6–10 diam. The external cells are shorter, darker, and swollen; the internal hyphae are sub-hyaline to hyaline and slimmer. Basidia not observed. Basidiospores globose to occasionally subglobose, 3.5–4.5 × 4–5 μm, including ornamentation, yellowish, verrucose to subreticulated. Under SEM, the ornamentation is formed by anastomosed elements, forming variable patterns and an incomplete reticulum. Capilitium hyphae hyaline to slightly yellowish, 3–5 μm wide, lumen visible, with yellowish to light brown pigmented septa, slightly swollen up to 6 μm.

Habit and habitat: growing gregariously in a tropical forest as saprobe, in a rock pit and in soil, with abundant organic matter and moss.

Notes: This is a distinct species due to the combination of characteristics of small to medium-sized basidiomes, tubular stoma, verrucose exoperidium, reddish-brown endoperidium, and small, subreticulate basidiospores. The ornamentation of basidiospores is conformed by anastomosed elements forming irregular patterns that tend to form a subreticulum, visible under L.M. with a good oil-immersion lens ( Figure 4a ). According to Wright (1987), subreticulated basidiospores can be formed by anastomosed verrucae or spines. Some examples are T. subsquamosum Long & S. Ahmad (1947: 241) with fused spines, T. cyclophorum Lloyd (1906:25) with low fused verrucae, or T. purpusii (Henn. 1898: 274) , described as “basidiospores spores with numerous appressed verrucae fusing in rib-like structures” under the LM and “anastomosed crest, which exhibits notorious likeness to a subreticulum”. A similar case is T. dumeticola , which is described as having anastomosed finger-like spines that appear almost reticulated. On the other hand, Wright (op. cit.) describes “asperulated”, some species with asperulated basidiospores both under LM and SEM; for example, T. xerophillum Long (1946: 85) or T. albicans White (1901:428) . In these cases, the basidiospores are almost smooth at 100× with low and irregular verrucae that can be seen with a good oil immersion lens or phase contrast microscopy. Under SEM, both species have irregular verrucae and truly asperulated spores. Other species are described as asperulate at L.M. but with different kinds of ornamentation at SEM; for example, T. nanum (Pat.) J.E. Wright (1987: 160) has asperulate basidiospores at L.M. but with minute verrucae on SEM. In T. macrocephalum Long (1944: 337) , the ornamentation is formed by low-crested verrucae on SEM. Based on ITS nrDNA, T. subreticulatum is close to T.deltaconcavum , but the latter has non-verrucose exoperidium, composed of polymorphous hyphae, yellowish, branched, and septate, without pseudoparenchymatous hyphae. In addition, the basidiospores of T. deltaconcavum present concave, triangular spines, not subreticulated. ( Lima et al. 2023). Both species group with high support as a sister group of Clade 11, which is composed of eight species with circular ostioles, reddish stipes, and coarsely ornamented spores: T. calcareum , T. subsquamosum , T. ahmadii , T. squamosum , T. dominguenziae , T. rufum Lloyd (1906: 18) , T. melanocyclum , and Tulostoma sp. 22 (an undescribed species from South America). All of these species mentioned above present stouter basidiomes than T. subreticulatum . In addition, except for T. subsquamosum , all present echinulate basidiospores with independent spines, not subreticulated, and, in T. subsquamosum , ornamentation is conformed by spines fused at the apex, forming crests. On the other hand, T. subsquamosum and T. rufum present hyphal exoperidium and mycosclereids but no verrucae ( Jeppson et al. 2017; Wright, 1987). T. melanocyclum is characterized by the noticeable dark peristome and hyphal exoperidium but lacks mycosclereids. ( Wright et al. 1987). The rest of the species in the clade 11 present verrucose exoperidium; however, they differ in the hyphal structure of the verrucae, a characteristic that is only sometimes properly measured and described. T. ahmadii , from Pakistan, presents light olive brown verrucae, composed of subglobose to elongated pseudo parenchymatous hyphae, 7–10 × 2–4 μm, irregularly arranged. T. calcareum , from Europe, was described as having a deciduous hyphal-verrucose exoperidium, but the hyphal structure of the verrucae was not described ( Jeppson et al. 2017). T. dominguenziae presents reddish-brown warts conformed by pigmented pseudoparenchymatous hyphae up to 250 × 11 μm (Hernández-Caffort et al. 2011). In T. squamosum , the verrucae are composed of dark sphaerocystis ( Jeppson et al. 2017; Esqueda et al. 2004); however, the size is not specified. Wright (1987) considered T. squamosum , T. mussooriense Henn. (1901: 337) , and T. verrucosum Morgan (1890: 164) as independent species. In the latter, Wright (op. cit.) described vesicular hyphae freely arranged in chains (15–30 × 6–11 μm). These three taxa were considered synonymous by Moreno et al. (1992b), who reported spherocysts or chains of short subglobose to subcylindrical hyphae in the warts of the exoperidium of the type materials of the three species. Exact measurements were not specified, but based on the images presented and their scales, the largest are ~10 × 16 μm diam.

Figures

FIGURE 3. Tulostoma subreticulatum Hern.-Nav. & Cappello-Gar. A. Basidiomes. B. Spore-sac. C-B. Verrucae of the exoperidium. E. Stipes and rhizomorph. F. socket.

FIGURE 4. Tulostoma subreticulatum Hern.-Nav. & Cappello-Gar. A. Basidiospores and capilitial threads. B. Endoperidium hyphae. C. Verrucae seudoparenchymatous hyphae. D. Internal stipe hyphae. E. External stipe hyphae. F-G. Basidiospores under SEM.