Stress tolerance and burrowing behaviour in the southern African millipede Alloporus uncinates


*Department of Biological Sciences, University of Botswana, PBag 0022, Gaborone, Botswana


Laboratory experiments were carried out to assess the tolerance and behaviour of the southern African spirostreptid millipede Alloporus uncinates (Attems) to moisture and temperature stress. Rates of water loss in dry air were 0–026 mg H20 cm-2 hour-1 for females and 0021 for males and remained relatively constant with an increase in temperature from 20 to 30°C but at higher temperatures there was a rapid increase in water loss, especially for females. In dry laboratory conditions at 30°C all individuals died within 30 days, whilst at 20°C at least 90% of individuals survived this period. Aggregation appeared to have no significant effect on survivorship but small body size conferred a survivorship advantage. Females burrowed earlier and to a greater depth than males, and initial moisture content of soil had a significant effect on mean burrow depth. Alloporus uncinatus, like other spirostreptid millipedes, appears to have considerable tolerance to dry conditions but the wide geographic and habitat range of this species may mean that the intensity of selection for tolerance to moisture stress may vary.