Metabolic strategies of male and female tsetse (Diptera: Glossinidae) in the field

Abstract

AbstractA scattergram method was developed for explaining the variability in the levels of fat, residual blood-meals and residual dry weights (RDW) of field samples ofGlossina. The pattern of changes in mean RDW and fat levels was shown to be similar for five species ofGlossina (G. morsitans morsitansWestw.,G. swynnertoniAust.,G. fuscipes fuscipesNewst.,G. palpoiis palpalis(R.-D.) andG. tachinoidesWestw.) but different for the two sexes. On the basis of previous laboratory and field work, a simple descriptive model is developed that suggests priority pathways during the life of the adult fly for the products of successive blood-meals. Initially, for tenerals of both sexes, the priority is to increase thoracic musculature (RDW) without excessive production of fat. Subsequently, male flies devote each blood-meal exclusively to the production of fat, an energy store used mainly for flight activity. Females show a gradual increase in both fat and RDW levels, which probably corresponds with the development of the larva in utero. Wing-fray measurements support this interpretation. During each pregnancy cycle, females accumulate a reserve of fat over and above that necessary for the production of each larva. This is apparently required at the end of each cycle when res piratory losses exceed the energy supply from blood-meals taken. Mean thaematin levels of the four larger species studied (G. morsirans, G. swynnertoni, G. fuscipesandG. palpails) also showed a consistent pattern of change during each pregnancy cycle. Females apparently feed once at the beginning of each cycle, once at a stage of pregnancy when the larva in utero is approaching the moult from the second to the third instar and finally during the middle of the third larval instar, when the meal may be quite small and repeated.