Studies on the role of serum proteins in the ovarian function of the tsetse fly, Glossina palpalis palpalis

Nutritional factors in the diet of the obligatory haematophagous tsetse fly Glossina p. palpalis have been investigated, as an initial step towards the development of an artificial diet for this insect. Emphasis was laid on the role of serum proteins in the reproductive physiology, particularly with respect to the development and functioning of the ovaries.In this study flies were fed on fresh defibrinated bovine blood, in which the red cell fraction was left unchanged, but in which the serum fraction had been replaced by artificial solutions resembling serum. It is shown that G. p. palpalis females accept and imbibe the semi-artificial diets as readily as normal blood. Similarly diuresis and water excretion (defaecation) were not seriously impaired, especially when glucose was present in the serum substitutes (article 1). The relevance for the fly's physiology of food- acceptance, - uptake and excretion of excess water is discussed. In article 2 the effect of semi-artificial diets on G. p. palpalis ' performance has been described. Flies were fed up to 50 or 80 days on semi-artificial diets. It was found that absence of serum albumin in the food resulted in high mortality and a seriously impaired productivity: mostly eggs and non-viable larvae were extruded. The addition of increasing levels of serum albumin improved the fecundity until it was similar to that of flies fed on a control diet. The serum albumin concentration in the diet appeared to be positively correlated with the size of newly produced larvae. It was suggested that albumin was an essential nutritional factor in the diet of G. p. palpalis .To investigate the physiological effects of serum albumin on the reproductive performance, flies were fed on semi-artificial diets, which were prepared differently. from those used in the previous experiments because the new diets were reconstituted from a mixture of bovine red cells and serum- substitutes that previously had been lyophilized. The composition of thelyophilized diets, however, was the same as used in the previous experiments. on a serum albumin deficient diet, egg maturation and ovulation were seriously impaired and egg follicles were observed to be retained and lysed in the ovaries (article 3). Flies fed on serum albumin containing diets ovulated, but the fecundity was low and puparia were smaller than those obtained from control flies. It is discussed how dietary substances might affect egg maturation, ovulation and egg hatching.Article 4 describes the results of a study on the rate of ovarian development and lipid incorporation and the fatty acid composition of flies. Fed on semi-artificial diets over a 30-day period. ovulation did not take place in flies fed serum albumin deficient diets, while flies fed serum albumin containing diets ovulated and produced larvae though at a lower rate than control flies. compared with control flies, lipid incorporation was reduced in experimental flies, but more in the albumin deficient group than in the albumin containing group. Dietary composition had no marked influence on the relative fatty acid composition in any one group.In general, it is concluded that serum albumin is a highly essential nutritive element for cow-blood fed G. p. palpalis , without which flies fail to reproduce and have a high mortality.