Abstract
Tsetse flies, sole members of the genus Glossina, family Glossinidae (77, 79), are the well-known vectors of trypanosome diseases, including both human African sleep ing sickness and the cattle disease nagana (6). Tsetse flies are biological peculiarities; not only are they obligate blood feeders, but they reproduce by adenotrophic viviparity [giving birth to live offspring, nourished within the mother by secretion from highly modified accessory glands, and born at an advanced stage of develop ment (see 25, 36)]. The female produces a single offspring at regular intervals. It passes three larval instars within the mother and derives all its nourishment from her during this time. After parturition (larviposition) the larva does not feed and usually pupariates within 1-2 hr. Approximately 30 days later, the adult fly emerges. Thus all the nutrients required for developplent to the adult stage are maternally derived, and accordingly at parturition the larva usually weighs at least as much as the mother ( 103). In addition, at regular intervals the mother takes blood meals that weigh up to several times the weight of the unfed fly ( 103). Thus the female fly undergoes large changes in volume and weight during each pregnancy cycle; short term changes are associated with feeding and long-term changes are associated with the growth of the larva ( 103). However, these changes impose limitations in terms of feeding and flying, which become more severe as pregnancy progresses. The female fly leads a precarious existence and both nutrition and reproduction must be precisely regulated to ensure reproductive success. The interaction between repro ductive events and the transfer of nutrients from mother to larva are therefore of importance to our understanding of the physiology of Glossina, and these areas will be of particular concern in the present paper.
Published Version
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