Fly Eclosion Research Articles

Acute and Reproductive Toxicity of Freeze-dried and Steam-dried Extracts of Tradomal® in Drosophila melanogaster

Background and Purpose: Tradomal® is an herbal preparation containing Senna siamea that is marketed for the treatment of malaria in Northern Nigeria. The study evaluated the acute and reproductive toxicity of freeze-dried and steam-dried extracts of Tradomal® in Drosophila melanogaster.
 Methods: The acute toxic effect of the plant was evaluated by determining its LC50. The reproductive toxicity of the extracts was evaluated via its effect on the eclosion of adult melanogaster flies.
 Results: Both steam-dried and freeze-dried extracts of Tradomal® showed LC50 of 2767.83 mg/10 g and 4475.74 mg/10 g of meal respectively. Although the steam-dried extract did not affect fly eclosion, the freeze-dried extract significantly (P<0.05) inhibited the emergence of adult flies from the pupae.
 Conclusion: The extracts are relatively safe, but the method of drying can influence their effects on reproduction in fruit flies.

The potential of soil amendment with insect exuviae and frass to control the cabbage root fly

AbstractReliable options to control the cabbage root fly, Delia radicum L., are lacking in many countries as restrictions on insecticide use have tightened due to environmental concerns. Although microbial control agents are often considered as a sustainable alternative, their application in agriculture is constrained by inconsistent efficacy owing to low field persistence. To stimulate naturally occurring beneficial microbes, soil amendment with the residual streams of insect production has been suggested as an alternative to synthetic fertilization and a new approach to microbial crop protection. In a set of greenhouse experiments, exuviae and frass of black soldier fly larvae, Hermetia illucens L., house crickets, Acheta domesticus L. and exuviae of mealworms, Tenebrio molitor L., were added to soil from an organically managed field. Exuviae and frass treatments were compared to treatments with synthetic fertilizer. Brussels sprouts, Brassica oleracea L., plants were grown in amended soil for 5 weeks before being infested with cabbage root fly larvae. Insect and plant performance were assessed by recording cabbage root fly survival, biomass and eclosion time and seed germination and plant biomass, respectively. Whereas soil amendment with black soldier fly frass or exuviae reduced cabbage root fly survival and biomass, respectively, amendment with house cricket or mealworm residual streams did not negatively affect root fly performance. Furthermore, seed germination was reduced in soil amended with house cricket exuviae, while amendment with either residual stream derived from black soldier fly larvae or house crickets resulted in lower plant shoot biomass compared with the synthetic fertilizer treatment. Amending soil with black soldier fly residual streams could become a novel and low‐cost tool to be integrated in cabbage root fly management programmes, especially where methods currently available are insufficient. Therefore, the mechanisms underlying the effects of insect‐derived soil amendments described here should be the focus of future research.

Microbiome assembly on Drosophila body surfaces benefits the flies to combat fungal infections

SummaryIn contrast to the well-characterized gut microbiomes, the composition and function of the insect body-surface microbiotas are still elusive and highly underexplored. Here we report the dynamic features of the Drosophila melanogaster surface microbiomes. It was found that the microbiomes assembled on fly surfaces could defend insects against fungal parasitic infections. The substantial increase of bacterial loads occurred within 10 days of fly eclosion, especially the expansion of Gilliamella species. The culturable bacteria such as Lactiplantibacillus plantarum could effectively inhibit fungal spore germinations, and the gnotobiotic addition of the isolated bacteria could substantially delay fungal infection of axenic flies. We found that the fly tarsal segments were largely accumulated with bacterial cells, which could accelerate cell dispersal onto different body parts to deter fungal spore germinations. Our findings will facilitate future investigations of the surface microbiotas affecting insect physiologies.

Host plant stimuli effects on survival and duration of dormancy of Rhagoletis zoqui, Rhagoletis completa (Diptera: Tephritidae) and associated parasitoids.

Tephritid fruit flies in the genus Rhagoletis bridge between predictable periods of fruit availability by becoming dormant. To cope with acyclic unpredictable events (e.g., frost, mast seeding, etc), a proportion of the population can undergo prolonged dormancy. In the case of walnut infesting Rhagoletis, host plant-derived cues such as juglone soil concentration vary seasonally in predictable patterns. Here, we examined the effects of host plant parts and derived compounds on emergence rates and dormancy duration of Rhagoletis completa (Cresson), Rhagoletis zoqui (Bush) (Diptera: Tephritidae), and associated parasitoids. Pupae of both species were exposed to walnut leaves, fruit, or fruit and leaves and compared to a control. In a second experiment, R. zoqui were exposed to 10 mg l-1 of juglone applied to pupation medium during four consecutive 4-week time periods under variable combinations of temperature and frequency of exposure. Overall, the presence of fruit resulted in greater overwintering survival of R. completa but had no effect on the duration of dormancy of either fly species. Application of juglone over two consecutive periods produced greater mortality of R. zoqui than the control. Three parasitoid species emerged from R. completa and one from R. zoqui. Duration of dormancy for parasitoids was longer than that of fly hosts. Regardless of treatment, 13.3-18.4% of R. completa pupae and 1.3-2.8% R. zoqui engaged in prolonged (>year) dormancy. Our results indicate that host plant derived cues have little or no effect on survival and duration of dormancy of walnut infesting Rhagoletis, and at the tested concentration juglone is toxic to R. zoqui pupae. Testing the effect of juglone at lower concentrations is necessary to rule out its role as an environmental cue for regulation of dormancy. So far, host plant fruiting phenology appears to play a greater role than host plant derived cues in selecting for fly eclosion times.

Effect of White Champa Leaf Extract (Plumeria acuminata) on White Fly Eclosion (Aleurolobus barodensis Maskell, Hemiptera; Aleyrodidae)

The white fly explosion might be occurred on the flooded fields and lack of nitrogen fertilizer. Some control methods have to be conducted to prevent further losses. The use of biopesticide was known to be easier, cheaper and environmental friendly control methods. Therefore the aim of this experiment was determining the effect of white champa leaf extract (Plumeria acuminata) as a biopesticide on sugarcane white fly eclosion (Aleurolobus barodensis). Experiment was conducted in the laboratory, using a completely randomized design with 6 treatments of P. acuminata leaf extract concentrations, that were 0% (control), 10%, 20%, 30%, 40% and 50%, and was replicated 4 times. The results showed that P. acuminata leaf extract could be used to control sugarcane white fly. The effective leaf extract concentration was 40%. The results also proved that P. acuminata leaf extract killed the white fly pupae instead of delaying their eclosion.

Contrast in Post-Chill Eclosion Time Strategies Between Two Specialist Braconid Wasps (Hymenoptera: Braconidae) Attacking Rhagoletis Flies (Diptera: Tephritidae) in Western North America.

Parasitoids comprise a speciose insect group, displaying a wide array of life history strategies. In the Pacific Northwest of the United States, the tephritid fruit flies Rhagoletis tabellaria (Fitch) and Rhagoletis indifferens Curran infest red osier dogwood, Cornus sericea L. (Cornaceae), and bitter cherry, Prunus emarginata (Douglas ex Hooker) Eaton (Rosaceae), respectively. The flies are parasitized by different braconid wasps at different life stages; Utetes tabellariae (Fischer) oviposits into R. tabellaria eggs, whereas Diachasma muliebre (Muesebeck) oviposits into R. indifferens larvae feeding in cherries. Because Rhagoletis only have one major generation a year and the wasps attack temporally distinct fly life stages, we predicted that eclosion times of U. tabellariae should more closely follow that of its host than the larval-attacking D. muliebre. As predicted, U. tabellariae eclosed on average 6.0-12.5 d later than R. tabellaria, whereas D. muliebre eclosed on average 32.1 d after R. indifferens. Unexpectedly, however, longer chill duration differentially affected the systems; longer overwinters minimally influenced eclosion times of R. tabellaria and U. tabellariae but caused earlier eclosion of both R. indifferens and D. muliebre. Results imply that in temperate regions, diapause timing in braconid wasps evolves in response to both host life stage attacked and fly eclosion characteristics, possibly reflecting differential effects of winter on host plant fruiting phenology. Differences in phenological sensitivity of the lower host plant trophic level to variation in environmental conditions may have cascading effects, sequentially and differentially affecting eclosion times in higher frugivore (fly) and parasitoid (wasp) trophic levels.

Toxicological Study and Genetic Basis of BTEX Susceptibility in Drosophila melanogaster.

Benzene, toluene, ethylbenzene and xylene, also known as BTEX, are released into environmental media by petroleum product exploratory and exploitative activities and are harmful to humans and animals. Testing the effects of these chemicals on a significantly large scale requires an inexpensive, rapidly developing model organism such as Drosophila melanogaster. In this study, the toxicological profile of benzene, toluene, ethylbenzene, p-xylene, m-xylene, and o-xylene in D. melanogaster was evaluated. Adult animals were monitored for acute toxicity effects. Similarly, first instar larvae reared separately on the same compounds were monitored for the ability to develop into adult flies (eclosion). Further, the impact of fixed concentrations of benzene and xylene on apoptosis and mitosis were investigated in adult progenitor tissues found in third instar larvae. Toluene is the most toxic to adult flies with an LC50 of 0.166 mM, while a significant and dose-dependent decrease in fly eclosion was observed with benzene, p-xylene, and o-xylene. An increase in apoptosis and mitosis was also observed in animals exposed to benzene and p-xylene. Through Genome Wide Association Screening (GWAS), 38 regions of the D. melanogaster genome were identified as critical for responses to p-xylene. This study reveals the strength of D. Melanogaster genetics as an accessible approach to study BTEX compounds.

Effects of microbial evolution dominate those of experimental host-mediated indirect selection.

Microbes ubiquitously inhabit animals and plants, often affecting their host’s phenotype. As a result, even in a constant genetic background, the host’s phenotype may evolve through indirect selection on the microbiome. ‘Microbiome engineering’ offers a promising novel approach for attaining desired host traits but has been attempted only a few times. Building on the known role of the microbiome on development in fruit flies, we attempted to evolve earlier-eclosing flies by selecting on microbes in the growth media. We carried out parallel evolution experiments in no- and high-sugar diets by transferring media associated with fast-developing fly lines over the course of four selection cycles. In each cycle, we used sterile eggs from the same inbred population, and assayed mean fly eclosion times. Ultimately, flies eclosed seven to twelve hours earlier, depending on the diet, but microbiome engineering had no effect relative to a random-selection control treatment. 16S rRNA gene sequencing showed that the microbiome did evolve, particularly in the no sugar diet, with an increase in Shannon diversity over time. Thus, while microbiome evolution did affect host eclosion times, these effects were incidental. Instead, any experimentally enforced selection effects were swamped by uncontrolled microbial evolution, likely resulting in its adaptation to the media. These results imply that selection on host phenotypes must be strong enough to overcome other selection pressures simultaneously operating on the microbiome. The independent evolutionary trajectories of the host and the microbiome may limit the extent to which indirect selection on the microbiome can ultimately affect host phenotype. Random-selection lines accounting for independent microbial evolution are essential for experimental microbiome engineering studies.

EFVb-HAART Increases Mortality, Locomotor Deficits and Reduces Reproductive Capacity in Drosophila melanogaster

Aims: This study was designed to evaluate the effects of Efavirenz-based highly active antiretroviral therapy (EFVb-HAART, Efavirenz/Lamivudine/Tenofovir) with emphasis on survival, longevity, climbing ability, and reproductive capacity in D. melanogaster.
 Methods: The experiments were carried out at the Africa Center of Excellence in Phytomedicine Research and Development (ACEPRD), University of Jos, Nigeria between January 2017 and August 2018. D. melanogaster (both sexes) 1-4 days old were exposed to different concentrations of EFVb-HAART (range 10-1200 mg) in the fly food for initial 7 days to determine the LD50, then 5 day fly exposure to 93.11 mg, 46.56 mg, 23.28 mg or 11.64 mg for negative geotaxis assay, and acetylcholinesterase (AChE) activity. Furthermore, 28-day fly survival and longevity were determined. Statistical significance was presumed at P< 0.05.
 Results: The LD50 of EFVb-HAART in D. melanogaster was 93.11 mg. The HAART exposed flies showed significantly (P<0.001) increased mortality, significant (P<0.001) decreased fly eclosion, acetylcholinesterse (AChE) activity and climbing ability compared to unexposed group at all experimental concentrations.
 Conclusion: The decreased 28-day survival, longevity, climbing ability and reproductive capacity at all experimental concentrations may be attributable to the deleterious effects of EFVb-HAART in D. melanogaster. Our findings suggest that long term use of EFVb-HAART by HIV patients may be associated with accelerated aging, decreased life expectancy, quality of life (due to possible neurotoxicity) and reproductive competence, as evidenced by increased mortality, reduced longevity, AChE activity, and 100% emergence failure respectively in D. melanogaster, and may require further study in humans. We recommend further research to expound the biochemical and molecular toxicodynamics of EFVb- HAART in D. melanogaster with the view of ameliorating same.

Huntingtin-Mediated Axonal Transport Requires Arginine Methylation by PRMT6

The Huntingtin (HTT) protein is centrally involved in bidirectional axonal trafficking. To better understand how HTT-mediated transport is regulated, we studied vesicle-associated HTT and found that it is dimethylated at a highly conserved arginine residue (R118) by the protein arginine methyltransferase 6 (PRMT6). Without R118 methylation, HTT’s association with vesicles is markedly reduced along with anterograde trafficking, and neuronal death ensues — very similar to what is observed in Huntington’s disease (HD), which is caused by polyglutamine (polyQ) expansions in mutant HTT (mHTT). Inhibiting PRMT6 in HD cells exacerbated mutant HTT-induced toxicity, whereas overexpressing PRMT6 rescued axonal transport and neuronal death, except in the presence of a methylation-defective version of mHTT. Overexpressing PRMT6 also rescued axonal defects and eclosion of HD flies. Arginine methylation thus regulates HTT’s activity in vesicular axonal transport, and increasing HTT methylation could be of therapeutic interest for HD.

Toxicity And Physiological Activity of Methoprene, A Juvenile Hormone Analog, Against Development and Metamorphosis of The Grey Flesh Fly, Parasarcophaga argyrostoma (Robineau- Desvoidy)(Diptera: Sarcophagidae).

The grey flesh fly Parasarcophaga argyrostoma plays a role in human cutaneous wounds and eye myiasis and it is also known as parasitoid of various animals. The present study aimed to investigate the efficacy of Methoprene on survival, development and metamorphosis of this fly species. Five dose levels (10.0, 5.0, 1.0, 0.1 and 0.01µg/larva) of Methoprene was topically applied onto the early last instar larvae and prepupae. Methoprene exhibited larvicidal, pupicidal and adulticidal activities against P. argyrostoma. LD50 values were found 0.155 and 0.258 µg/insect after topical treatment of early last instar larvae and prepupae, respectively. The maximal body weight of treated larvae was considerably decreased. The duration of treated larvae was prolonged. The coefficient of growth of treated larvae was depressed. The pupal duration was remarkably prolonged. Some larval-pupal intermediates had been produced, only at the higher two doses. Topical treatment of prepupae only with the lower two doses induced a state of 'permanent prepupae'. The treated last instar larvae pupated in regressed rate. The pupation rate was slightly regressed after topical treatment of prepupae only with the lower two doses. The adult emergence of flies was completely blocked after topical treatment of either the early last instar larvae or prepupae with the highest dose of Methoprene. At other dose levels, the adult eclosion of flies was partially blocked. Different percentages of deformed pupaeand adults were recorded.

Impact of Prolonged Absence of Low Temperature on Adult Eclosion Patterns of Western Cherry Fruit Fly (Diptera: Tephritidae).

Western cherry fruit fly, Rhagoletis indifferens (Curran) (Diptera: Tephritidae), is a serious pest of cherries (Prunus spp.) in the Pacific Northwest of the United States. Previous research suggests that R. indifferens is unlikely to establish in commercial cherry production areas in California and in tropical export markets because cold temperatures, below 5 °C, in those regions appear insufficient to complete diapause. However, it is unclear how prolonged absence of cold exposure affects diapause termination in R. indifferens. Here, we examined this question by exposing R. indifferens pupae for 40 wk to simulated temperate and tropical conditions of 23 or 26 °C, 40 or 80% RH, and a photoperiod of 16:8 or 12:12 (L:D) h. Eclosion patterns among fly groups in the four conditions did not differ. For all groups, fly eclosion from pupae not exposed to cold exhibited a bimodal distribution. The first major peak, comprising 3.2% of the total fly emergence, occurred at 1-10 wk. The second major peak, comprising the remaining 96.8%, occurred at a mode of ∼30 wk. Based on responses to no cold and cold (3 ± 1.5 °C) exposures, there were three distinct pupal diapause groups: the first eclosion group was likely nondiapausing pupae; the second eclosion group was likely diapausing pupae; a third group that remained viable but did not produce adults after 40 wk may represent prolonged dormancy pupae. We suggest that eclosion of adults after prolonged absence of cold exposure needs to be incorporated into models for potential fly establishment in warm climates.

Genome-wide association analysis of tolerance to methylmercury toxicity in Drosophila implicates myogenic and neuromuscular developmental pathways.

Methylmercury (MeHg) is a persistent environmental toxin present in seafood that can compromise the developing nervous system in humans. The effects of MeHg toxicity varies among individuals, despite similar levels of exposure, indicating that genetic differences contribute to MeHg susceptibility. To examine how genetic variation impacts MeHg tolerance, we assessed developmental tolerance to MeHg using the sequenced, inbred lines of the Drosophila melanogaster Genetic Reference Panel (DGRP). We found significant genetic variation in the effects of MeHg on development, measured by eclosion rate, giving a broad sense heritability of 0.86. To investigate the influence of dietary factors, we measured MeHg toxicity with caffeine supplementation in the DGRP lines. We found that caffeine counteracts the deleterious effects of MeHg in the majority of lines, and there is significant genetic variance in the magnitude of this effect, with a broad sense heritability of 0.80. We performed genome-wide association (GWA) analysis for both traits, and identified candidate genes that fall into several gene ontology categories, with enrichment for genes involved in muscle and neuromuscular development. Overexpression of glutamate-cysteine ligase, a MeHg protective enzyme, in a muscle-specific manner leads to a robust rescue of eclosion of flies reared on MeHg food. Conversely, mutations in kirre, a pivotal myogenic gene identified in our GWA analyses, modulate tolerance to MeHg during development in accordance with kirre expression levels. Finally, we observe disruptions of indirect flight muscle morphogenesis in MeHg-exposed pupae. Since the pathways for muscle development are evolutionarily conserved, it is likely that the effects of MeHg observed in Drosophila can be generalized across phyla, implicating muscle as an additional hitherto unrecognized target for MeHg toxicity. Furthermore, our observations that caffeine can ameliorate the toxic effects of MeHg show that nutritional factors and dietary manipulations may offer protection against the deleterious effects of MeHg exposure.

Morphological abnormalities in <i>Drosophila</i> with overexpression of human APP gene

Alzheimer’s disease (AD) is the leading and one of the most severe forms of dementia. Molecular mechanisms underlying AD pathogenesis despite much work on this subject still remain unclear. Cleavage of amyloid precursor protein (APP) to amyloid beta peptide (A-beta) and following formation of amyloid plaques are the key events of Alzheimer’s pathology. Thus changes in APP expression and metabolism can lead to pathology development. Here we show that overexpression of human APP in Drosophila neural cells manifests in different morphological abnormalities of Drosophila imago that can be observed immediately after fly eclosion. This observation can help to further understand APP molecular functions and its participation in different molecular pathways.

A model based on oscillatory threshold and build-up of a developmental substance explains gating of adult emergence inDrosophila melanogaster

Adult emergence (eclosion) of fruit flies Drosophila melanogaster under constant laboratory conditions follows a circadian pattern with bouts of eclosion recurring at approximately 24 h intervals. Under periodic light:dark (LD) cycles, adults emerge only during a specific time of the day followed by little or no emergence for the rest of the day. This phenomenon is therefore equated to a gate of emergence that, when open, allows adults to emerge and when closed, no emergence takes place. In this study, we attempt to understand the mechanism underlying adult emergence rhythm in D. melanogaster using a model based on interplay between developmental and circadian clock systems. The model is composed of an oscillatory threshold of a substance that builds up during pre-adult development. Computer simulations based on this model enabled us to make specific predictions about the 'gate width' of the adult emergence rhythm under conditions of fast/slow pre-adult development and short/long circadian periods, which we subsequently tested empirically. The main predictions from the simulations are: (1) flies with faster development have greater gate width and vice versa, and (2) flies with faster circadian clocks have shorter gate width and vice versa. To empirically validate these predictions, we carried out experiments on D. melanogaster populations known to have fast/slow pre-adult development, short/long circadian periods and narrow/wide gate width. Additionally, we manipulated the rate of pre-adult development of the above flies by increasing/decreasing ambient temperature to further examine the influence of developmental rates on gate width of adult emergence rhythm by a complementary approach. The results show that gate width is greatly influenced by the duration of pre-adult development and the length of circadian cycles. This suggests that the adult emergence rhythm of D. melanogaster may be based on mechanisms involving oscillatory threshold and build-up of a developmental substance.

Population persistence of the parasitoid fly Zaira cinerea (Fallén) (Diptera: Tachinidae) utilizing multiple host carabid beetles with different seasonality and quality

Zaira cinerea (Fallen) is a parasitoid fly (Diptera: Tachinidae) that attacks adult carabid beetles. To better understand mechanisms of population persistence in this species, we examined seasonality of host beetle abundance, the frequency of parasitism, and the timing of fly eclosion. In addition, we evaluated host quality using numbers of larvae or puparia per individual beetle as a measure of quality. The fly parasitized only large carabids (≥15 mm body length); the lengths of fly puparia reached 7.4–10.8 mm during development in beetle abdomens, and larger hosts are likely essential. Of the 18 large carabid species collected in this study, we chose two, Carabus maiyasanus Bates and Leptocarabus procerulus (Bates), because they were large and abundant (87% of total catch). The two carabids had different phonologies; C. maiyasanus was abundant from spring to summer, and its abundance dropped sharply in autumn, while L. procerulus was abundant in autumn and rare from spring to summer except July. Parasitism was observed in all the months from May to November except June, and adult flies eclosed more than once a year (in early summer, late summer, and mid-autumn), indicating that the species is multivoltine. Host quality of L. procerulus was higher than that of C. maiyasanus. Carabus maiyasanus was mainly used as a host from spring to summer, and L. procerulus was used in autumn. Thus, adult beetles of one or both species are available over most of spring, summer, and autumn, allowing population persistence of this fly species over time.

Prothoracicotropic Hormone Regulates Developmental Timing and Body Size in Drosophila

In insects, control of body size is intimately linked to nutritional quality as well as environmental and genetic cues that regulate the timing of developmental transitions. Prothoracicotropic hormone (PTTH) has been proposed to play an essential role in regulating the production and/or release of ecdysone, a steroid hormone that stimulates molting and metamorphosis. In this report, we examine the consequences on Drosophila development of ablating the PTTH-producing neurons. Surprisingly, PTTH production is not essential for molting or metamorphosis. Instead, loss of PTTH results in delayed larval development and eclosion of larger flies with more cells. Prolonged feeding, without changing the rate of growth, causes the overgrowth and is a consequence of low ecdysteroid titers. These results indicate that final body size in insects is determined by a balance between growth-rate regulators such as insulin and developmental timing cues such as PTTH that set the duration of the feeding interval.

New sanitation techniques for controlling tephritid fruit flies (Diptera: tephritidae) in Hawaii

New approaches to sanitation in a cropping system susceptible to tephritid fruit flies (Diptera tephritidae) in Hawaii have been investigated. Six trials were conducted in tent-like structures to demonstrate that melon fly larvae ( Bacrocera cucurbitae , Coquillett) are not reliably controlled by malathion sprayed on the surface of whole or smashed fruit. Smashing fruit does not sufficiently reduce the rate of eclosion to be a reliable population control measure. Tilling fruit into the ground only partially reduced eclosion. Burying fruit 0.15 and 0.30 m deep also partially reduced eclosion. Burying fruit 0.46 m deep prevented adult fly eclosion. Screen between the infested fruit and the ground prevented 90.2% of fly eclosion (edges of the screen were buried to prevent the escape of eclosing adult flies). Larvae pupate within 0.7 m from their host fruit (mean distance = 13.88 ± 1.76 cm, 95% Cl = 10.4 to 17.4 cm). Augmentoria entrapped all adult flies eclosing from fruit placed inside the structure. The data suggests that the three (3) methods of interdicting adult fly eclosion should be practiced. They are, in order of effectiveness, placing cull fruit in augmentoria, burying the fruit 0.46 m under ground, or placing fruit on screen under and 0.7 m beyond the fruit pile. Journal of Applied Sciences and Environmental Management Vol 9(2) 2005: 5-14

Tolerance and antibiosis resistance to cabbage root fly in vegetable Brassica species

AbstractFour accessions of the wild species Brassica fruticulosa Cyrillo (Brassicaceae) were studied in order to identify its tolerance and antibiosis resistance to the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae), in comparison to a widely cultivated cauliflower cultivar and a rapid cycling Brassica oleracea L. line. Antibiosis was prominent, as the insects reared on resistant accessions showed reduced individual pupal weight, total pupal weight, adult dry weight, and the longest average fly eclosion time. Host plant resistance, however, did not affect the sex ratio of adult flies. A study of the root architecture of plants with and without root fly inoculation revealed differences in the structure within B. oleracea accessions. A long main root and a high number of lateral roots appeared to be important characteristics for a Brassica type, with a higher tolerance level to cabbage root fly attack.

Multi-Oscillatory Control of Eclosion and Oviposition Rhythms in Drosophila melanogaster: Evidence from Limits of Entrainment Studies

The eclosion and oviposition rhythms of flies from a population of Drosophila melanogaster maintained under constant conditions of the laboratory were assayed under constant light (LL), constant darkness (DD), and light/dark (LD) cycles of 10:10 h (T20), 12:12 h (T24), and 14:14 h (T28). The mean (±95% confidence interval; CI) free-running period (τ) of the oviposition rhythm was 26.34 ± 1.04 h and 24.50 ± 1.77 h in DD and LL, respectively. The eclosion rhythm showed a τ of 23.33 ± 0.63 h (mean ± 95% CI) in DD, and eclosion was not rhythmic in LL. The τ of the oviposition rhythm in DD was significantly greater than that of the eclosion rhythm. The eclosion rhythm of all 10 replicate vials entrained to the three periodic light regimes, T20, T24, and T28, whereas the oviposition rhythm of only about 24 and 41% of the individuals entrained to T20 and T24 regimes, respectively, while about 74% of the individuals assayed in T28 regimes showed entrainment. Our results thus clearly indicate that the τ and the limits of entrainment of eclosion rhythm are different from those of the oviposition rhythm, and hence this reinforces the view that separate oscillators may regulate these two rhythms in D. melanogaster.