Determination of pH and oxygen status in the guts of lower and higher termites

Abstract

The pH of the gut was determined in vitro in six species of termite by means of indicator dyes and a pH electrode. In the lower termite Zootermopsis nevadensis the pH was close to neutrality throughout, ranging 6.0–7.5, but in Reticulitermes lucifugus, acid conditions (pH 5.5–6.0) occurred in the crop and paunch. In the higher termites Nasutitermes costalis, Microcerotermes arboreus, Cubitermes severus and Procubitermes aburiensis, there was a common trend of incresing pH from the crop, which was slightly or moderately acidic, to the first proctodaeal segment (P1) where moderately ( N. costalis) and strongly ( M. arboreus, C. severus and P. aburiensis) alkaline conditions prevailed. A pH of 10.4 was measured in C. severus, equalling the highest recorded in any insect. In the posterior regions of the hindgut there was a return towards neutral or acidic conditions. When termite guts were homogenized with air-saturated Ringer's solution, the dissolved O 2 content of the Ringer's was reduced. This was shown to be largely attributable to an oxygen deficit generated within the gut in situ. The combined effects of strongly alkaline conditions and reduced oxygen tension on digestive processes and intestinal micro-organisms are discussed.