B
aral
& M
arson
: Deltopyxis triangulispora gen. et sp. nov.
179
Apothecia
. The small ascomata of Deltopyxis tri
angulispora are clearly recognizable only in the
hydrated state. Their size is usually 0.1-0.2 mm
but varies between 0.07-0.15 and 0.2-0.28 mm,
rarely 0.35 mm, sometimes within a collection.
According to the apothecial diameter, the height
of the apothecia varies considerably. The hyme-
nium is usually greyish-cream but especially in
larger or older apothecia it may get dark blackish-
brown due to more abundant exudate over the
paraphyses.
Young (immature) apothecia of D. triangulispora
are blackish and almost globose when rehydra-
ted, with a diameter of 70-80 µm and a height of
60-70 µm. At their apex they possess a 15-20 µm
wide pore. At this development stage no or only
a few very immature asci are present. When the
first asci attain maturity, the hymenium is distinct-
ly exposed and bordered by the protruding dark
margin.
Hamathecium ontogeny
. In young apothecia
the paraphyses grow upwards from the bottom
of the young hymenium, but also from the sides
of the hymenial cavity. Those that arise from the
bottom form their short, capitate terminal cell
only when they reach their final length.
During apothecial growth, new paraphyses were
seen to be formed exclusively at the margin. At
the junction of hymenium and ectal excipulum,
new paraphyses emerge laterally from inner cells
of the ectal excipulum (Fig. 1.3). When starting
as lateral outgrowths, they resemble periphyses,
but they soon bend upwards and elongate until
they reach the hymenial surface. At this develop-
ment stage they are still much shorter than the
adult paraphyses, but they will elongate when the
lateral excipulum becomes the bottom of the ex-
panding hymenium.
Young paraphyses in Deltopyxis were never ob-
served to develop between the asci, neither
emerging from the subhymenium, nor by branch-
ing of adult paraphyses. This peculiar feature of
marginal development of new paraphyses might
support the isolated position of Deltopyxis in com-
parison to members of the Helotiales and Orbil
iomycetes, in which young paraphyses generally
develop also between the asci during apothecial
growth.
Lipid bodies in excipular cells
. In the holotype
and some other collections, the cells of the ectal
excipulum contained a more or less high amount
of larger and smaller lipid bodies (LBs, Figs 1.1d,
1.2b, 5c). In some other collections the cells were
often devoid of these droplets or contained them
in lower abundance. We conclude that the lipid
content in the excipular cells is subjected to exter-
nal circumstances rather than having a genetical
origin.
Asci
. Based on our observation of living asci at
different stages of development, the ascospores
of Deltopyxis triangulispora are formed by multiple
mitoses after meiosis of the fusion nucleus, i.e.,
the asci are “truly polysporous” in the terminol-
ogy of M
artens
(1937). True polyspory is also ob-
served in the genera Sarea Fr. and Tromeropsis
with similar elongate-saccate, multispored asci
and small ascospores (H
awksworth
& S
herwood
1981).
The asci are unitunicate and open by a large api-
cal pore which is distinctly slit-like (Fig. 5g images
on the upper right). An apical thickening is only
slightly developed. In very young asci the entire
ascus is thick-walled in the dead state (e.g., when
mounted in KOH, Fig. 5g, images on the left), ex-
cept for a small region at the very apex. Later the
thickened part of the wall is restricted to the apical
region (Fig. 1.1i), though this wall thickening is of-
ten rather inconspicuous, and immature asci may
also be uniformly thin-walled (Fig. 1.1g).
The asci are inamyloid in IKI, with or without KOH
pretreatment. In CR
SDS
the ectotunica is distinct-
ly stained, but only in the apical region (Fig. 5g,
in another collection the wall did not stain). This
congophily of the apical ectotunica could not be
observed in any of those taxa of Helotiales and
Orbiliomycetes that we have tested so far.
The spores are arranged in a dense elongate
cluster in the living ascus (Figs 1e, 5f, 6c), which
is actively discharged. When rehydrated and
placed in a Petri dish, apothecia started to eject
spore clusters after ca. 5 min.When shot on agar,
the spores form dense, single-layered heaps
which allow quite exact counting of the spores
(Fig. 5h-i). These heaps suggest that the spores
are ejected as one entity, similar as in the Orbil
iomycetes.
Ascus length was in some specimens consistently
around 25-30 µm but in others always around 30-
40 µm. Likewise, the width of the asci varied be-
tween 7-9 and 10-12 µm. These differences are
only to a certain degree due to real variation, but
mainly depend on the living versus dead state.
However, contrary to many other ascomycetes,
the asci of Deltopyxis shrink only insignificantly
when they loose turgor, as long as the spores re-
main alive. In fact, adding KOH to dead asci that
contain living spores provokes an unexpected as-
cus shrinkage for 10-17 % in length and 5-20 %
