Agriculture Reference
In-Depth Information
However, if decay has progressed beyond a certain point, the wood may become
unpalatable to particular species (Lenz, 1994). The grass-harvesting termites that store
the sectioned stems of dead grasses in their mounds may well be subjecting them to
a similar period of fungal decomposition prior to their consumption (Holt, 1998).
Termites of the subfamily Macrotermitinae feed on slightly decomposed dead plant
materials including leaf litter, dead grasses, woody litter and standing dead wood
(Darlington, 1994). With the exception of
Sphaerotermes sphaerothorax
considered
below, they cultivate symbiotic fungi of the Basidiomycete genus
Termitomyces
in their
nests which partly assist in the digestion of cellulose and other resistant materials
(Thomas, 1987). The association between the termites and the fungus is obligate: the
fungi of this genus grow nowhere else than in the termite nest and incipient colonies
that fail to develop a comb do not survive (Darlington, 1994).
In colonies of one fungus-cultivator,
Macrotermes michaelseni,
the older workers
return food materials to their mounds in the form of specialised faeces which have been
only slightly degraded by residence in the gut. In the mound, these faecal pellets are
deposited on special structures known as fungus combs where they are ingested by
the younger workers. These latter workers deposit their own faeces onto the comb where
they are then further decomposed by the cultivated fungus. Members of the reproductive
line castes and the younger workers appear to feed on the glucose-rich spores of the
fungus and on comb faecal materials. The older workers feed on senescent comb and
other organic materials in which cellulose, hemicellulose, pectin and lignin are partly
degraded and which have a higher N concentration than the original forage (Bignell
et
al.,
1994). In the g u t of these termites, resistant materials are broken down by a combi-
