Blood digestion In Ormthodorus moubata murray Sensu stricto walton females (Ixodoidea : Argasidae)

Abstract

SUMMARY.The cellular organisation of midgut cells (see Grandjean, in press) depends on the digestive cycle which follows a bloodmeal. The phases of this cycle are characterised in O. moubata, and various " cell-types" are described, correlated and discussed. Mating triggers digestion : a) by an increased intracellular digestion µncluding the formation of heterophagolysosomes) during the rapid phase of digestion ; b) by reactivating midgut cells in starving females, which then may perform vitellogenesis and lay few normal eggs. La digestion du sang chez les femelles d'Ornithodorus moubata O. GRANDJEAN1 -In trod uction Digestive cycle after ingestion of a bloodmealThe blood taken up by 0. moubata is made available for the tick body mass and energy requirements by intracellular digestion (Grandjean, in press). This type of digestion is phylogenetically prim itive, but well adapted to the a b ility of the ticks to survive over prolonged periods : the food reserves of the midgut lumen may be mobilised at a very low rate in a fasting tick. Due to the intracellular type of digestion, the midgut cells have to perform diversified functions which have to be coordinated between the single cells.Sequential modifications of midgut cells are studied in relation w ith the digestive cycle. The latter is analysed mainly in mated females ; but virgin females were also considered in order to investigate the action of mating on digestion.Midgut cells of males were also investigated to a lesser extent. No fundamental differences were found, as compared to those of females. Action of matingIn adult females, energy and nutrient reserves provided by digestion of bloodmeals allow vitellogenesis and egglaying. Except in rare cases of parthenogenesis, mating is an absolute necessity for normal egglayings (Aeschlimann and Grandjean, 1973a).Yet it is possible to induce vitellogenesis and egglaying in unfed females by delayed mating (without previous bloodmeal) or by injections of male gonad homo genates (Aeschlimann and Grandjean, 1973a ; Germond and Aeschlimann, 1977 ; Ducommun, in prep.). The process of vitellogenesis following mating is dependent on an increased mobilisation of food reserves, which means an activation of digestive functions of the midgut epithelium. The triggering action on midgut cells may be demonstrated both for mating occuring at feeding time and for delayed mating in starving ticks. -Materials and Methods Tick material0. moubata sensu stricto females, originally from Tanzania (Ulanga D istrict) and bred according to Geigy and Herbig (1955), were fed on guinea-pigs, either in presence or in absence of males, and taken at various intervals after bloodmeal for gravimetric, histological or cytological investigations.Other virgin females were fed and fasted during 110 days before males were added to half of them for delayed mating. MethodsHistology (H) : Tissue pieces fixed and embedded as for transmission electron microscopy were cut into sections of 1 µm thickness and stained w ith toluidine blue (1 %, 6 parts + sodi...

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