Introduction to Fungi, Third Edition

154 CHYTRIDIOMYCOTA
Fig 6.19 Blastocladiella emersonii zoospore,
fine structure, diagrammatic and not to scale.
(a) L.S. of zoospore along the axis of the
flagellum. (b) T.S. of kinetosome showing nine
triplets of microtubules. (c) T.S. of kinetosome
at a slightly lower level showing the origin of
two of the banded rootlets which extend
into the mitochondrion.The cristae of the
mitochondrion are close to the membrane
which surrounds the banded rootlets.
(d) T.S. of axoneme showing the nine paired
peripheral microtubules and the two central
microtubules.
with it are three striated bodies variously
referred to as flagellar rootlets, striated rootlets
or banded rootlets. They are contained within
separate channels, and each is surrounded by
a unit membrane. Since the energy for propulsion
is generated within the mitochondrion, it is
possible that the banded rootlets are, in some
way, responsible for transmitting energy to the
base of the axoneme. It is also possible that the
banded rootlets serve to anchor the flagellum
within the body of the zoospore.
There are two other obvious kinds of organelle
within the body of the Blastocladiella zoospore.
The lipid sac attached to the mitochondrion
contains a group of lipid droplets which is
surrounded by a unit membrane. It is not
known whether lipid forms the energy reserve
used in swimming, cytoplasmic glycogen deposits
being a more plausible alternative (Cantino
et al., 1968). In the anterior of the zoospore
between the nuclear cap and the plasma
membrane, there is a group of granules about
0.5 mm in diameter, called gamma particles.
They consist of an inner core, shaped like
an elongated cup and bearing two unequal
openings at opposite sides of the cup. This cupshaped
structure is enveloped in a unit membrane
(Myers & Cantino, 1974). Gamma particles
are only present in developing and motile
zoospores but disappear as the zoospore encysts.
Formerly thought to represent the chytrid
equivalent of the chitosome found in higher
fungi (see p. 6), this notion has now been
discarded (Hohn et al., 1984).