Tremella occultixanthoriae Diederich, Geyselings & Millanes

• Region

  Europe

• Country

  Belgium

• Locality

  (Brab.), Leuven, city cemetery, Nieuwe Kerkofdreef, 3001 Heverlee

• Elevation

  Alt. 40 m. (131 ft.)

• Coordinates

  50.8701, 4.71491

• Distribution

  Map all specimens of this taxon

Tremellomycetes - Tremellales
Class Tremellomycetes
Order Tremellales
by P. Diederich, A. M. Millanes & M. Wedin
Diederich, P., A. M. Millanes A M. Wedin. 2022. Class æDemellomycetes, order TremeHalts, In: Diederich et al. (eds.), Flora of Lichenicolous Fungi,
Vjl. 1, Basidiomycoia. National Museum of Natural Histoiy, Luxembourg: 105-282.
Tremella occultixanthoriae Diederich, Geyselings &
Millanes, sp. nov.
Diagnosis: Characterized by the pulvinate, pale orange-brown,
waxy-gelatinous basidiomata growing on the lower thallus
surface of Xanlhoria pane Una, the subsphcrical to ellipsoid,
4-celled, longitudinally septate basidia, 8.5-11.5 x 8-10.5
pm, and the reduced epibasidia acting as conidiogenous cells,
producing hyaline, aseptate conidia, 4.5-5.5 n 4-4.5 pm,
most with a hyaline basal appendage.
Etymology: From occultus, hidden, referring to the basidiomata
hiding under the host thallus, and Xanlhoria, the host lichen.
Type: Belgium, Leuven, city cemetery, Nieuwe Kerkhofdreef,
3001 Heverlee, 50.8701¦N, 4.7149¦E, 40 m, on horizontal
and vertical surface of hard limestone of a grave, on Xantho-
riaparietina, 3 July 2021, P. Diederich 19596 & D. Ertz (BR
- holotype; NY, S - isotypes).
LICHENICOLOUS FUNGI OF BELGIUM
Herbarium Paul Diederich
Belgium (Brab.): Leuven, city cemetery, Nieuwe Kerkhofdreef, 3001 Heverlee.
3.7.2021, alt. 40 m, IFBL E5.24.ll, Lat/Long (WGS84) 50.87006¦N 4.71491¦
E (¦ 10 m).
Hard limestone of a gravestone, horizontal and vertical surface, on Xanthoria
parietina (L.) Th. Fr.
Tremella occultixanthoriae Diederich, Geyselings & Millanes
1 -rs -rx- 1 ò 1	1 mm	a	r ? '	NEW	YORK	BOTANICAL	GARDEN
leg. P. Diedench 19596 & D. Ertz, det. P. Diederich :
Isotype.	04285311
Tremella occultixanthoriae, Belgium, holotype. A, Basidia, conidia and haustoria (left photo). B, Conidia, each with a hvaline basal annen,W
In phloxine Scale bar: 10 pm	-w*	oage.
________________________________Tremellomycetes - Tremellales
MycoBank: MB844668
Basidiomata developing on the lower surface of the host
thallus, pulvinate, waxy-gelatinous, pale orange-brown,
roundish to slightly elongate, well delimited, dispersed but
occasionally fusing, 0.25-0.6 mm diam. Context hyphae
not observed; subbasidial hyphae thick-walled, 3.5-4.5
pm thick; haustoria present, tremelloid, subspherical to el-
lipsoid, 3-4.5 pm diam. Hymenium containing numerous
subspherical to ellipsoid probasidia with a basal clamp.
Basidia, when mature, subspherical to ellipsoid, 4-celled,
with longitudinal septa, 8.5-11.5 * 8-10.5 pm, wall 0.8-1
pm; epibasidia reduced, functioning as conidiogenous
cells, with conidia appearing as produced directly from the
basidia. Basidiospores unknown. Conidiogenesis probably
holoblastic. Conidia hyaline, aseptate, ellipsoid, 4.5-5.5 *
(3.5-)4-4.5 pm, wall c. 0.5 pm thick, basally truncate, fre-
quently with a hyaline basal appendage, 3.5-6 * 1.5-4 pm.
Notes. This species is unusual in two ways. First, basidi-
omata develop exclusively on the lower surface of the host
thallus, making them thus invisible in the field, unless thal-
li are removed from the substrate, and second, epibasidia
are reduced or missing and basidiospores not produced,
while basidia produce instead sessile conidia. A similar co-
nidiogenesis is known from Tremella cetraculeata and T.
cetrariae, which differ by the black, gelatinous, pustulate
basidiomata and conidia lacking a basal appendage.
Ecology and host. On the lower thallus surface of Xanlho-
ria parietina, mainly saxicolous on a grave, also on an old
Fagus.
Distribution. Europe (Belgium), known only from the type
locality.
Additional specimens examined. Belgium: Same locality as the
type, Geyselings (BR); id., on Fagus, Diederich 19597 (BR).
Tremella occultixanthoriae, Belgium, type locality. All examined saxi-
colous and some coiticolous thalli of Xanthoria parietina were infected.
Tremella occultixanthoriae, Belgium, Geyseling (BR). Basidiomata
on the lower thallus surface ofXanthoria parietina. Scale bar: 500 pm.
04285311