Rapid changes in the reproductive cycle of wild-caught tsetse, Glossina pallidipes Austen, when brought into the laboratory

Abstract

This paper describes differences in reproductive and nutritional conditions that develop within 2 weeks of the transfer of wild-caught female Glossina pallidipes Austen to apparently ideal laboratory conditions. In order to investigate the relative sampling efficiency of baited NG2B traps for female G. pallidipes and the flies' changing feeding behaviour on different days of the pregnancy cycle, samples of female G. pallidipes taken directly from the field and those held in the laboratory for a known number of days after larviposition were subjected to both ovarian dissection (including the measurement of the uterine content and the two largest ovarioles) and fat and haematin analysis. Under the laboratory conditions of slightly lower mean temperature (buffered against diurnal fluctuations), lower activity and higher feeding frequency than in the field, the interlarval period was prolonged, the third larval instar was disproportionately prolonged, the ovarioles and larvae in utero showed differential growth rates, pupal size was increased and the fat reserves of post-partum females was depleted. It is concluded that tsetse are very responsive to the precise environmental conditions in which they find themselves and that absolute quantitative measurements made in the laboratory cannot be applied directly to the field situation. Resume-Cette these decrit les differences en matiere des conditions reproductives et nutritionnelles qui se developpent dans l'espace de deux semaines d'adaptation de la femelle sauvage capturee de tse-tse Glossina pallidipes d'Austen aux conditions apparemment ideales dans un laboratoire. Dans le but d'investiguer l'efficacite relative d'echantillonnage des pieges NG2B ou I'on a mis de appSts pour attraper des femellesG. pallidipes et de faire des recherches sur le changement du comportement alimentaire des mouches au cours du cycle de "grossesse", des echantillons de la femelle G. pallidipes pris directement de leur champ naturel et ceux de celles qui se trouvent dans le laboratoire pendant un nombre jours connus apres le depot de larves ont ete soumises a la dissection de l'ovaires (comprenant le mesurage du contenu ute>in et les tubes ovaires les plus grands) et a l'analyse des matiere grasses et de l'hematine. Sous les conditions Iaboratoires d'une temperature legerement basse (protegee contre les fluctuations diurnes) une basses activite et une frequence alimentaire plus elevee que dans la nature, la periode interlavaire etait prolongee, les tubes ovaires et les larves in utero ont montre des taux grasses des femelles dans la periode post-natale etait epuisees. On est arrivee a la conclusion selon laquelle les tse-tse sont tres sensibles aux conditions environnementales precises dans lesquelles ils se trouvent et que les mesures quantitatives absolues prises dans le laboratoire ne peuvent pas etre appliquees directement dans un environnement naturel. Mots Clefs: Tse'-tse', Glossina pallidipes, cycle reproductif, conditions alimentaires 347

Towards a general rule for estimating the stage of pregnancy in field‐caught tsetse flies

“…Similarly, the length (I) of the larva increased exponentially after eclosion ( Fig. la, b), as implicitly assumed by Randolph et al (1990), and 1, grew exponentially throughout pregnancy, in agreement with the findings of Saunders (1960) and Randolph et al (1990) (Fig. Ic, d).…”

Reproductive under‐performance of tsetse flies in the laboratory, related to feeding frequency

“…to give tsetse the opportunity to feed at least every other day to ensure the regular production of pupae (Randolph el al., 1990;Langley & Stafford, 1990), although when offered a meal every 1 or 2 days not all flies choose to feed at every opportunity, giving a mean feeding interval in the laboratory of between 2 and 2.5 days (Nash et al, 1967;Boyle, 1971;Randolph et al, 1990). This contrasts with conclusions that in the field female tsetse feed three times per interlarval period (i.e.…”

Tsetse population dynamics.

“…Instead they caught wild females and used the pupae that these females produced in the laboratory. Later studies (Randolph et al, 1990(Randolph et al, , 1991Hargrove, 1999b, c) make it clear that the sizes of laboratoryproduced pupae cannot be used to predict the sizes of offspring which the same females would have produced in the field under natural conditions. There is nonetheless evidence from ovarian dissection data (see below) that, at least at Rekomitjie Research Station, Zimbabwe, young female G. pallidipes do suffer severe mortality during the hot dry-season.…”