ORCADIAN RHYTHMS OF SENSITIVITY TO INSECTICIDES IN MUSCA DOMESTICA (DIPTERA, MUSCIDAE)

Abstract

Circadian rhythms of LD50 values to DDT, dieldrin and malathion, topically applied, were determined for houseflies reared under LD 14:10 with “dawn” at 06.00 hr. There was a marked increase in susceptibility at 05.00 hr in each case. With “dawn” at 18.00 hr., DDT LD50 values were lowest at 17.00 hr indicating independence of the flies' “biological clocks” from clock time of day. Flies reared under LD 18:6 and 10:14 also had circadian rhythms of sensitivity to DDT. Mean daily LD50 values were inversely related to photophase length. The ratios of mean daily LD50 to “pre‐dawn” values were greatest for the longer photophases. Flies reared under LD 14:10 until the pupal stage, then DD until testing showed a normal circadian rhythm. Flies reared in total darkness (DD) showed no diel variations in susceptibility. W.H.O. standard strain flies were used for all the experiments. A fully susceptible (Cooper) and a DDT resistant (DEH‐DOV) strain also showed significant circadian rhythms of sensitivity to DDT. ZUSAMMENFASSUNG CIRCADIANRHYTHMEN BEI DER EMPFINDLICHKEIT VON MUSCA DOMESTICA (DIPTERA, MUSCIDAE) GEGENUBER INSEKTIZIDEN Circadianrhythmen der LD 50‐Werte gegenüber DDT, Dieldrin und Malathion ‐ topical angewandt wurden bei Stubenfliegen ermittelt, die bei 14:10 h‐Tag mit “Tagesanbruch” um 6.00 Uhr gezüchtet wurden. In allen Fällen war die Empfindlichkeit um 5.00 Uhr wesentlich erhöht. Bei “Tagesanbruch” um 18.00 Uhr waren die niedrigsten LD 50‐Werte um 17.00 Uhr. Dies weist auf die Unabhängigkeit der biologischen Uhr der Fliegen von der Tageszeit hin. Fliegen, die bei 18:6 oder bei 10:14 LD gezüchtet wurden, zeigten ebenfalls einen Circadianrhythmus hinsichtlich der Empfindlichkeit gegenüber DDT. Die mittleren LD 50‐Werte waren umgekehrt proportional zur Länge der Photophase. Das Verhältnis der mittleren täglichen LD 50‐Werte zu den Vortagesanbruchwerten war am grössten bei längerer Photophase. Fliegen, die bei 14:10 LD bis zum Puppenstadium und anschliessend bei DD bis zur Testung gehalten wurden, zeigten einen normalen circadianen Rhythmus. Bei Züchtung in völliger Dunkelheit zeigten sie keine Tagesschwankungen in der Empfindlichkeit. Für alle Versuche wurde ein WHO‐Standardstamm benutzt. Zwei andere Stämme, einer voll emDfindlich (Cooper), der andere resistent (DEH‐DOV) zeigten ebenfalls signifikante Circadianrhythmen in der DDT‐ Empfindlichkeir.

Integrating Circadian Activity and Gene Expression Profiles to Predict Chronotoxicity of Drosophila suzukii Response to Insecticides

“…Since there is evidence that insecticide susceptibility corresponds with activity rate of the target insect due to contact toxicity [12], we set out to determine the activity patterns of D. suzukii using the Drosophila Activity Monitoring System (DAMS). Anticipating that activity patterns will vary over the long California berry-growing season with changes in photoperiod and daily temperature cycles, we subjected male and female D. suzukii flies to locomotor activity assays in environmental conditions, i.e.…”

“…We want to point out that the phase of peak expression for some common detoxification genes tested in our studies and the study by Hooven et al [45] were also different, likely for the same reason. Previous chronotoxicity work has suggested that time of greatest insecticide susceptibility may correspond to the onset of a time of increased activity in the insect [12] and expression of detoxification enzymes has also been proposed as an alternate explanation for varying insecticide susceptibility over a circadian cycle [47], [76].…”

“…Targeting pesticide sprays to peaks of fly activity increases the likelihood of direct contact mortality, especially for products with marginal efficacy. Previous chronotoxicity work has suggested that time of greatest insecticide susceptibility corresponds with the onset of a time of increased activity in the insect [12]. Casual field observations indicate that D. suzukii activity is greatest in warm parts of the day, with little activity observed on extremely hot or cold days.…”

Cross‐resistance to Pesticides and Plant Defenses: A Study of the Two‐spotted Spider Mite

“…To assure ourselves that any differences we found between the strains were genetic and not environmentally induced, all tested mites from both strains were raised on bean plants (see Gould 1979) and were of equivalent age at the time of testing. Only one replicate was conducted at a time so test results were independent of any artifacts which could have been caused by environmental conditions on specific dates (Sun 1960, Shipp & Otton 1976. Paired comparison t-tests of angular transformed data were used to analyze results (Sokal & Rohlf 1969).…”

The sexual dimorphic behaviour of adult Drosophila suzukii: elevated female locomotor activity and loss of siesta is a post-mating response

“…The chronobiology of D. suzukii is of particular interest as it is known that insects can display circadian variability in their susceptibility to chemical insecticides (Cole and Adkisson, 1964;Piechowicz et al, 2012;Shipp and Otton, 1976). It has been shown for both D. suzukii and the related Drosophila melanogaster that levels of enzymes involved in insecticide metabolism fluctuate with a daily rhythm, suggesting that variation in rates of metabolism during the day can influence toxicity to fruit flies (Hooven et al, 2009;Hamby et al, 2013).…”