MORPHOLOGICAL, MICROBIOLOGICAL AND BIOCHEMICAL-STUDIES OF THE GUT FLORA IN THE FUNGUS-GROWING TERMITE MACROTERMES SUBHYALINUS

The four worker castes of the fungus-growing higher termite Macroterme s subhyalinus (Termitidae, Macrotermitinae) were examined to compare t he morphology, physiology and microbiology of the alimentary canal, In young major and old major worker castes the midgut made up 64.8% of t otal gut volume, while in young minor and old minor workers the figure was significantly less at 53.0% (P < 0.05), Despite this morphologica l difference, all four castes supported a heterogeneous bacterial flor a throughout the gut, with the highest densities (up to 1.3 x 10(11) o rganisms ml(-1)) in the paunch acid colon, Enumerations of the paunch, colon and rectum suggested an increase as both major and minor worker s age, Intestinal pH was close to neutrality in tbe crop, midgut, colo n and rectum, but alkaline in the paunch (pH 9.5 in young major and yo ung minor workers), Redox indicator dyes fed to young major and young minor workers suggested that mildly reducing conditions existed in the paunch, colon and rectum (Eh = -123 mV), Acetate concentration in who le gut homogenates of freshly sampled termites ranged from 6.39 mM in young majors to 18.26 mM in old miners (based on whole gut volume), Ot her short chain fatty acids, notably isovalerate, were present in smal l amounts, Hydrogen and methane were emitted by all four castes but mo lar rates were, respectively, no more than 1.55 and 1.51% that of CO2 production in any single caste, averaging 0.79% (H-2) and 0.71% (CH4) over all castes, Weight specific methane emissions ranged from 0.016 n mol/h/mg in young and old minor workers to 0.141 nmol/h/mg in old majo r workers, These descriptive data on the gut flora of Macrotermes are broadly similar to those reported for members of other subfamilies of higher termites.