Introduction to Fungi, Third Edition

214 ZYGOMYCOTA
develop. These are termed primary cornute (type 1)
conidia and are illustrated in Fig. 7.42a. They are
discharged from the conidiophores by septal
eversion. If a type 1 conidium floats on the
water surface, it will germinate to produce a
balloon-shaped secondary globose (type 2) conidium
on its upper side, projecting into the air.
The type 2 conidium contains a single large lipid
body and a two-ply septum capable of discharge
by eversion (see Fig. 7.42b).
When primary cornute conidia become
submerged in water, they germinate to produce
a secondary conidium of a different type. Its body
has four branches (i.e. it is tetraradiate) and the
position of attachment of this conidium to the
short conidiophore is the central point from
where the four arms radiate (see Fig. 7.42c).
This type of spore is termed a secondary stellate
(type 3) conidium. If a dead infected insect is
continuously bathed in water or is submerged,
the conidiophores emerging from it will develop
primary conidia which are also tetraradiate,
but these are attached at the tip of the main
arm from which three upper arms radiate
(see Fig. 7.42d). This type of conidium is a primary
coronate (type 4) conidium. So types 1 and 2 are
aerial conidia, formed and discharged into air,
whilst types 3 and 4 are aquatic conidia, formed
and released under water. Tetraradiate conidia
are a typical adaptation of fungi to dispersal in
aquatic environments and are produced also by
aquatic hyphomycetes (see p. 685).
Most of the four types of conidium can
germinate by repetition, by germinating to
form conidia of one of the other types, or by
the formation of germ tubes. For example, a type
1 conidium can germinate by repetition to
form a secondary conidium morphologically
identical to itself, i.e. another type 1 conidium.
This is described in shorthand as 1 1
Fig 7.42 Erynia conica.The four types of conidia. (a) Primary cornute conidium (type1). Note the bitunicate wall. (b) Primary
cornute conidium germinating to produce a secondary globose conidium (type 2). (c) Secondary stellate conidium (type 3) which has
developed from a submerged primary cornute conidium.The point of attachment of the conidium is between the three backwardly
directed arms (arrow). (d) Primary coronate conidium (type 4) with the point of attachment at the end of the main, vertical, arm
(arrow).The single large nucleus is visible below the point of branching.Bar ¼ 20 mm, all images to same scale.From Webster (1992),
with kind permission of Springer Science and Business media.