Condition and fate of larvae from insecticide‐treated female tsetse flies Glossina palpalis

Abstract

Many larvae from wild‐caught female Glossina palpalis palpalis R.‐D. treated topically with dieldrin or sumicidin or sumithrin or permethrin failed to pupariate and many larvae from mothers treated with sumicidin or sumithrin or neopynamin formed small or malformed puparia which failed to eclode. Puparia produced soon after maternal handling often did not emerge and many produced by flies starved more than 3 days also did not emerge. Very many puparia from dieldrin‐treated mothers failed to emerge and nonemergence was common for puparia from flies treated with endosulfan or sumithrin or deltamethrin. Nonemerging puparia were produced soon after pyrethroid‐treatment, probably due to effects on larval integumentand muscles, but were produced later after organochlorine‐treatment, due to ingestion of insecticide by larvae while in utero. RÉSUMÉ Etat et destin des larves issues de Mouches Tsé‐Tsé (Glossina palpalis) traitées aux insecticides Les expériences ont porté sur des femelles sauvages de Glossina palpalis palpalis R.D. capturées dans la nature. Les comparaisons ont porté sur l'état et les performances de lots de pupes provenant de mouches non‐traitées et de larves mûres traitées localement avec de l'acétone (témoin) ou avec 14 insecticides différents. Toutes les larves témoin se sont nymphosées, mais le taux d'échec augmentait avec la diéldrine, la sumicidine, la sumithrine et la permethrine. Les pupes anormales (petites ou déformées) étaient plus nombreuses dans le lot témoin que dans le lot non‐traité, et les fréquences étaient plus élevées que chez le témoin avec la sumidicine, la sumithrine et la néopynamine. Seulement 3 mouches sont issues de 107 pupes anormales; il n'y a eu aucune éclosion pour 28% des pupes du lot témoin contre 15% pour le lot non‐traité. Pour le témoin le taux d'émergence était faible dans les pupes formées le premier jour (jour du traitement), par suite de la manipulation maternelle; il n'a pas augmenté jours 2 et 3, mais a diminué par la suite à cause du jeûne in utero. Les doses élevées de tous les insecticides réduisent plus les émergences que les doses faibles. Les organophosphates et le propoxur ne limitent pas les émergences, mais elles sont réduites par l'endosulfane, la sumithrine et la deltaméthrine, et très fortement par la diéldrine. Les pupes stériles ont été surtout formées dès le traitement aux pyréthroïdes (jour 1); et surtout plus tard (jours 2 et 3) lors des traitements aux organochlorés. L'ingestion par la larve in utero de grandes quantités d'insecticides pendant les 3 jours précédant la parturition était la principale cause de mortalité, et aussi de la forte tolérance aux organochlorés des femelles prégnantes. Les effets de pyréthroïdes sur l'activité musculaire réduisent aussi les émergences. Aucune mouche ne s'est alimentée après les traitements.

Insecticide tolerance of pregnant females of Glossina palpalis palpalis (Robineau-Desvoidy) (Diptera: Glossinidae)

“…Kwan et al (1982) suggested that the development of tolerance of endosulfan by pregnant G. m. morsitans females was due to partitioning of absorbed insecticide into lipid components of the fat-body or of uterine milk, diverting it from site(s) of lethal action in the maternal fly. The same mechanism is suggested elsewhere by Riordan (1987), who showed that the viability of puparia produced by insecticide-treated females was lowest among those in which larviposition took place three days after maternal treatment, due to preferential partitioning of insecticide into the food of the in-utero larva during its period of maximal feeding (Denlinger & Ma, 1974;Langley & Pimley, 1975). The failure in the present work and other reports (Burnett, 1962a;Hadaway, 1972) to show any markedly increased tolerance of pregnant flies to organophosphates suggests that these insecticides do not undergo any preferential diversion into in-utero larvae, possibly due to the fact that many organophosphates, especially thiophosphates, undergo a metabolic transformation into a lethal form subsequent to absorption, perhaps involving an ionized stage of low lipid solubility.…”

“…Langley & Pimley (1975) concluded, for well-fed G. m. morsitans females, that larvae have received enough nutrients by day 5 to complete in-utero development. It is reported elsewhere (Riordan, 1987) that many full-sized larvae were deposited more than three days after the start of the enforced maternal starvation and could pupariate and ultimately emerge as adults successfully. These findings indicate that the last 3-4 days of in-utero life constitute late pregnancy and that, in the present work, the proportions of larvipositing females among control (acetone-treated) flies and among flies that were treated with the lowest doses of insecticides indicated the true proportion (about 25%) of the test flies that were in late pregnancy.…”

“…For the pyrethroid Sumithrin, all batches tested contained flies larvipositing in the expected proportion (about 25%), and calculated LD50s showed that pregnant flies were less tolerant than non-pregnant ones. This insecticide differs from other pyrethroids in that most full-sized larvae were deposited very soon (within 24 h) after treatment and that a majority of these failed to form viable puparia (Riordan, 1987). This suggests that larviposition was accelerated by maternal poisoning and can explain that the great susceptibility of their mothers was due to the short period during which absorbed Sumithrin could be diverted into the in-utero larvae.…”

“…Similar diversion of DDT into the in-utero larva was termed inert storage by Irving (1968), and Kwan et al (1982) suggested that partitioning of endosulfan into lipids, in the maternal fat-body during early pregnancy and in uterine milk during later pregnancy, explained increasing maternal tolerance throughout each pregnancy cycle. It is reported elsewhere (Riordan, 1987) that preferential partitioning at the time of maximal larval feeding (Denlinger & Ma, 1974) was responsible for decreased viability of the offspring of mothers treated with dieldrin or endosulfan or deltamethrin.…”

“…Treated flies were kept individually in 7-5 x 2-5-cm glass tubes closed by clean net, and deaths were recorded daily. Abortions (eggs or immature larvae) were recorded daily (Riordan, 1986) and full-sized larvae were recorded to identify pregnant flies and then kept singly in fresh tubes to examine the condition and viability of resultant puparia (Riordan, 1987).…”