Introduction to Fungi, Third Edition

AQUATIC HYPHOMYCETES (INGOLDIAN FUNGI)
687
the teleomorph, but in practice, because the
teleomorphs are less frequently encountered
than the anamorphs, it is the name of the
latter which is generally used.
25.2.1 Tetraradiate and other branched
conidia
A few examples of the development of branched
conidia illustrate great variation which can be
followed by making observations of spore development
over a period of a few hours on leaf
fragments bearing conidiophores or from pieces
of agar culture incubated in water. In some cases
development is aided by placing culture pieces
in special flow cells which permit microscopic
observations to be made under continuous water
flow over time.
Phialidic tetraradiate conidia
A good example is Lemonniera aquatica
(Fig. 25.10a), probably the most common of the
six species in this genus. Conidiophores develop
from mycelium embedded in the leaf tissues or
from chlamydospores or sclerotia, and terminate
in 1 3 phialides. From the tip of the phialide
a tetrahedral conidium primordium develops,
and the four corners of the tetrahedron extend
simultaneously to form cylindrical arms which
may become septate. The mature conidium is
thus attached centrally to the phialide at the
point of divergence of the arms. When the firstformed
conidium is detached to be carried away
by water currents, a second conidium develops,
and others follow.
Phialides of Alatospora (Fig. 25.10b) develop
singly at the tips of short, inconspicuous conidiophores.
Midway along the length of an
elongated spore initial, two divergent lateral
arms arise and extend simultaneously.
Heliscus lugdunensis (Fig. 25.10c) is a common
early colonizer of the bark of twigs which have
fallen into streams. Its conidiophores develop on
sporodochium-like pustules and branch repeatedly,
terminating in phialides. Conidia which
develop underwater are clove-shaped with short,
conical projections at the upper end, whereas
more cylindrical conidia are produced under
aerial conditions, e.g. on a twig incubated in
a moist chamber or on agar culture. The
Fig 25.10 Three phialidic aquatic hyphomycetes.
(a) Lemonniera aquatica.(b)Alatospora acuminata.(c)Heliscus
lugdunensis.
teleomorph is Nectria lugdunensis which forms
bright red perithecia on half-submerged twigs.
Blastic tetraradiate conidia
There are numerous examples of blastic conidial
development in aquatic hyphomycetes.
Articulospora tetracladia (Fig. 25.11a) forms short
conidiophores extending from mycelium within
a leaf. At the tip of the conidiophore the first
arm develops as a cylindrical bud. At the apex
of this first arm, three further cylindrical buds
develop in turn. A narrow constriction or
joint marks the point of attachment of these
later-formed arms to the first (hence the name
Articulospora, a jointed spore). The mycelium and