Introduction to Fungi, Third Edition

190 ZYGOMYCOTA
makes contact with adjacent herbage it becomes
firmly attached to it. The sporangium slips off its
columella and dries down onto the herbage.
Pilaira anomala forms zygospores resembling
those of Pilobolus. On germination, a germ
sporangium is produced (Fig. 7.23g).
Nutritional studies on P. anomala indicate a
preference for NH 4 þ and urea over NH 3 or
asparagine as nitrogen sources, and a biotin
and thiamine requirement, but no requirement
of haem compounds for either growth or fruiting,
in contrast to the related genus Pilobolus. In
culture, of the simple carbon sources tested only
glucose and fructose supported good growth,
and there was no evidence of enzymatic ability to
degrade starch, cellulose, pectin or proteins
(Wood & Cooke, 1987). These nutritional characteristics
support the idea that P. anomala is a
typical ruderal fungus, its activities constrained
by the availability of simple soluble nutrients
which would be depleted rapidly in decomposing
dung.
7.3.3 Thamnidiaceae
In this family two kinds of asexual reproductive
structure are found, namely columellate sporangia
of the Mucor type and smaller, few-spored,
usually non-columellate sporangia termed sporangiola,
which are often borne in whorls or at
the tips of branches. The branches bearing
the sporangiola may be borne laterally on the
columellate sporangiophores or may arise separately.
In some cases the branch system bearing
the sporangiola is terminated by a spine. Benny
et al. (2001) have recognized 10 genera but we
shall consider only Thamnidium.
Fig 7.23 Pilaira anomala. (a) Sporangiophore
from rabbit dung showing rupture of the
sporangial wall at the base of the sporangium.
(b) Sporangium with extruded mucilage ring
adhering to an adjacent hypha. (c) Columella
after sporangium has been detached.
(d) Detached sporangium showing basal
mucilage ring. (e) Zygospore. (f,g) Stages in
zygospore germination (e g) after Brefeld,
1881).