Search

Ants of the genus Oecophyllaare predators of other insects and are able to protect a variety of terrestrial plants against pest insects; however, observations on the ecology of these ants in mangrove forests are lacking. General observations on the ecology of Oecophylla smaragdinawere carried out in a Thai mangrove forest to determine if these ants can protect their host plants in less favorable mangrove habitats. Leaf herbivory and the density of O. smaragdinaants were measured on Rhizophora mucronatatrees at two sites. The results showed a negative correlation between ant density and herbivory. At both sites, the mean percent damaged leaf area was more than four times higher on trees without ants compared to “ant‐trees.” A significant negative correlation was found between tree mean percent leaf damage and the density of ants on the tree. Furthermore, on trees with ants, there was less herbivory on leaves close to ant nests compared to other leaves on the tree. Most damage was caused by chrysomelid beetles (62%) and sesarmid crabs (25%) and both types of herbivory were significantly reduced on ant‐trees.

During the moderate exercise of treadmill walking, steady-state oxygen uptake bears a linear relationship to the work performed (i.e. to the slope of the treadmill), when the speed of walking is kept constant. Four normal male subjects were studied on the treadmill at several levels of exercise while they were breathing air and again while breathing a mixture of approximately 11% oxygen in nitrogen. An alteration in the linear relationship between oxygen uptake and work, established with the subjects breathing air, was observed when the subjects were restudied breathing 11% oxygen. In each case, this alteration indicated that the subject took up less oxygen while breathing a low-oxygen mixture despite the accomplishment of similar work loads. That this phenomenon is explicable on the basis of slower attainment of the steady state was excluded by prolonging each exercise period in two subjects. Another possible explanation, i.e. that the subjects effect greater utilization of anaerobic metabolic sources while hypoxic, was excluded by direct measurement of the oxygen debt after each period of exercise. It is concluded that exercising normal subjects exhibit an adaptive mechanism under conditions of induced hypoxia permitting reduced oxygen uptake for a given work load.