Introduction to Fungi, Third Edition

152 CHYTRIDIOMYCOTA
Fig 6.18 Neocallimastix hurleyensis. (a) Rhizoidal
thallus with zoosporangium. (b) Release of
zoospores. (c) Tracing of T.E.M. of zoospore
with 14 flagella in longitudinal section.
Diagrams based on Webb and
Theodorou (1991).
from mitochondria (Embley et al., 2002). Whereas
mitochondria of most fungi contain a limited
amount of DNA, hydrogenosomes of rumen
chytrids seem to have lost their genome altogether
(Bullerwell & Lang, 2005).
Granular inclusion bodies which contain
aggregates of ribosome-like particles and also
free ribosome-like arrays are found anterior to
the nucleus. Rosettes of glycogen represent the
energy reserve of the zoospore. The shafts of
the flagella contain the familiar eukaryotic 9 þ 2
arrangement of microtubules, but in N. frontalis
the microtubules do not extend into the tips
of the flagella which are narrower than the
proximal part.
Ecologically, these anaerobic fungi play an
important role in the early colonization of
ingested herbage and have a wide range of
enzymes which enable them to utilize monosaccharides,
disaccharides and polysaccharides
such as xylan, cellulose, starch and glycogen
(Theodorou et al., 1992). They may play an active
role in fibre breakdown. It is likely that colonization
of straw particles by these fungi aids further
attack by bacteria. The survival of anaerobic
fungi outside the unusual and protective environment
of the herbivore gut occurs in dried
faeces in the form of cysts or as melanized
thick-walled thalli whilst transmission to young
animals takes place in saliva during licking