Introduction to Fungi, Third Edition

216 ZYGOMYCOTA
apparent (Fig. 7.43e). Recently discharged conidia
have a dried out drop around them which
represents the cytoplasm squirted from the
conidiophore (Figs. 7.43d f). This cytoplasmic
coating may act as a protective agent against
desiccation and may possibly help in attaching
the primary conidium to the cuticle of an insect.
If the conidium impinges on the body of a fly, it
develops an adhesive pad which attaches it firmly
to the cuticle (Fig. 7.43h). Penetration of the
cuticle is probably brought about by a combination
of mechanical and enzymatic means (Brobyn
& Wilding, 1983). A few hours after infection, triradiate
fissures can be seen in the cuticle beneath
attached conidia. When the cuticle in such a
region is examined from the inside, a thin-walled
bladder-like expansion can be seen. From this cell
mycelial branches develop. The hyphae grow
towards the fatty tissues, and as these are
consumed the hyphae break up to form wall-less
protoplasts which are carried by the circulatory
system to all parts of the body. Eventually the
protoplasts secrete walls and become converted
into hyphal bodies (Fig. 7.43c). Infected flies show
behavioural changes, often crawling to the top of
a grass stem and clasping it or adhering to walls
or window panes by the proboscis (Maitland,
1994). The sexual behaviour of the host may also
be affected (Moller, 1993). Males attempting to
mate with diseased females may themselves
Fig 7.43 Entomophthora muscae.
(a) House fly adhering to a window pane,
surrounded by a halo of discharged
conidia. (b) L.S. house fly showing palisade
of unbranched conidiophores projecting
between segments of the exoskeleton.
The conidiophores and conidia are
multinucleate. (c) Hyphal bodies from
recently dead fly extending to form
conidiophores. (d) Primary conidium
immediately after discharge surrounded
by cytoplasm from the conidiophore.
(e,f) Germination of primary conidia to
form secondary conidia which are
discharged by bouncing off (septal
eversion). (g) Germination of secondary
conidium by germ tubes. (h) Attachment
of primary conidium to integument
of a fly. (i) Two primary conidia
attached to integument and penetrating
it by a tri-radiate fissure. (j) View of
penetration from within the integument.
Note the bladder-like expansion within
the tri-radiate fissure. (b g) to same
scale, (h j) to same scale.