Growth, Differentiation and Sexuality

y septation, the nucleus within the oidial hypha
divides, and a septum is laid between the daughter
nuclei, separating the oidial hypha into two equally
sized cells. These cells split into separate uninuclear
haploid arthroconidia by schizolysis at the septum
within the oidial hypha, and at the septum between
the oidial hypha and the oidiophore stalk. The rodshaped,
hyaline oidia (2 by 4–6 μm) are collected
(up to 200) in a liquid droplet secreted from the
tip of the oidiophore (Bensaude 1918; Brodie 1931;
Polak et al. 1997a; Kües et al. 2002a; Fig. 14.9). Consistent
with their wettable character (cf. classification
“wet oidia”; Kemp 1975), oidia do not have an
outer hydrophobic layer formed by hydrophobins
(Ásgeirsdóttir et al. 1997). Most of the surface of
the oidia is coated by double-layered primary cell
walls covered with hair-like structures (Heintz and
Niederpruem 1971; Polak et al. 1997a; Kües et al.
2002a) of possibly collagenous structure (Castle
and Boulianne 1991; Celerin et al. 1996). This may
help to keep a mucilaginous layer surrounding the
oidia (Watling 1979; Polak et al. 1997a). Due to
this gelatinous layer, the spores stick to surfaces
(Polak et al. 1997b), including to carapaces of in-
Fungal Asexual Sporulation 281
sects acting as vectors for their distribution (Brodie
1931).
Apart from the generalized scheme of oidiation
described above (type 1 oidiophores), there is considerable
morphological variation within a given C.
cinereus strain, and also between strains. The stalk
of the oidiophore may be branched (type 2A), divided
into two or more cells (type 2B) or the stem
cell may not elongate (type 3). In type 4, stems
are not formed; rather, oidial hyphae arise directly
from a cell in the vegetative mycelium, either singly
(type 4A) or in bundles (type 4B). Furthermore,
oidial hyphae may also branch, they may develop
ononesidealongthelengthofanoidiophoreor
they may split into more than two spores. Usually,
asinglestrainshowsthewholespectrumofvariation
but, preferentially, only one or two types of
oidiophores are formed (Polak et al. 2001; Kües
et al. 2002a).
2. Genetics
Absolute oidia production in C. cinereus is influenced
by the relative incidences of carbon and
Fig. 14.9. Development of oidiophores
of Coprinus cinereus with time. In the
images to the left, a young bulge is seen
on an aerial hypha which, during the
following 3 h, elongates into a structure
starting to successively produce oidial
hyphae. Two hours later, the first two
spores are released, followed by more
within the next 5 h. Intheimagesto
the right, developmentofalargeroidiophore
with more oidial hyphae and
spores can be seen. The scale bar represents
10 μm.PhotostakenbyE.Polak