Publications by authors named "Sonny Ramaswamy"

We consider using non-host plants that express both a toxin and oviposition deterrence for to increase stability for insect resistance management. The two traits reinforce each other ecologically. We used a two-gene model to evaluate this combination of traits.

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Neonate larvae of codling moth, Cydia pomonella (L.), modify their behavior in the presence of saccharin, monosodium glutamate (MSG), or L(+)-2-amino-4-phosphonobutyric acid (L-AP4) by commencing their feeding earlier. Previously published pharmacological analysis demonstrated that phagostimulatory effects of MSG and L-AP4 (which elicit umami taste sensation in humans) are reversed by adenylate cyclase activator and phosphodiesterase inhibitor.

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Entomopathogenic nematodes of the family Steinernematidae and their mutualistic bacteria (Xenorhabdus spp.) are lethal endoparasites of insects. We hypothesized that growth of the nematode's mutualistic bacteria in the insect host may contribute to the production of cues used by the infective juveniles (IJs) in responding to potential hosts for infection.

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Scanning and transmission electron microscopy were used to study the morphology and formation of the eggshell in the tarnished plant bug, Lygus lineolaris. Eggs are bean-shaped, with an operculum at the anterior end surrounded by a row of 36-40 respiratory horns. Three micropylar openings are on the operculum, and are sealed in oviposited eggs.

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Insect oocytes sequester nutritive proteins from the hemolymph under the regulation by juvenile hormone (JH), in a process called patency. Here, a pharmacological approach was used to decipher the role for calcium in ovarial patency in the moth, Heliothis virescens. Follicular epithelial cells were exposed in calcium-free or calcium-containing media to JH I, JH II or JH III alone, or in combination with various inhibitors of signal transduction.

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Near-infrared spectroscopy (NIRS) was used to develop a simple and quick technique to differentiate two economically important species, the tobacco budworm, Heliothis cirescens (F.), and corn earworm, Helicoverpa zea (Boddie), which are major pests of cotton, Gossypium hirsutum L., in the southern United States.

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Ecdysteroids and juvenile hormones (JHs) regulate many physiological events throughout the insect life cycle, including molting, metamorphosis, ecdysis, diapause, reproduction, and behavior. Fluctuation of whitefly ecdysteroid levels and the identity of the whitefly molting hormone (20-hydroxyecdysone) have only been reported within the last few years. An ecdysteroid commitment peak that is associated with the reprogramming of tissues for a metamorphic molt in many holometabolous and some hemimetabolous insect species was not observed in last nymphal instars of either the sweet potato whitefly, Bemisia tabaci (Biotype B), or the greenhouse whitefly, Trialeurodes vaporariorum.

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The quality of an insect as a host to an entomopathogenic nematode infective juvenile depends in part on whether or not the insect is already infected and on the stage of that infection. Previous research has shown that nematode response to hosts can change after infection and that, for uninfected hosts, CO(2) can be an important cue used by infective stage juveniles during attraction. We hypothesized that CO(2) production from an insect changes after it is infected, and that these changes could influence nematode infection decisions.

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The storage of large quantities of juvenile hormone (JH) in male abdomens is a phenomenon known from some species of moths. Juvenile hormone, stored in male accessory sex glands (ASG), may be transferred to the female during copulation, but the physiological significance of the JH transfer remains unclear. Here, using the moth Heliothis virescens as a model, we show that JH transferred from male to the promiscuous female promotes JH synthesis and egg development in the female.

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The mating-induced increase in juvenile hormone (JH) biosynthesis in Heliothis virescens females may be stimulated by production and/or release of stimulatory neuropeptides such as allatotropins (AT). Although there is evidence that H. virescens allatotropin may be structurally related to Manduca sexta allatotropin (Manse-AT), little is known of its occurrence and distribution in H.

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Feeding in codling moth caterpillars was induced by the general glutamate receptor activator monosodium glutamate (MSG) and by three different mGluR agonists known to specifically stimulate different classes of vertebrate metabotropic glutamate receptors, including: (1S,3R)-ACPD, which stimulates group I mGluRs (2R,4R)-APDC, which stimulates group II mGluRs and L-AP4, which stimulates some group III mGluRs. Experiments exposing larvae to combinations of specific mGluR agonists and specific signal transduction modulators suggest that each tested mGluR uses a different signaling pathway. First, feeding stimulatory effects of (1S,3R)-ACPD were abolished by phospholipase C inhibitor, U 73122, but remained unaffected by adenylate cyclase activator, NKH 477, or phosphodiesterase inhibitor, Rolipram.

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The insect oocyte sequesters nutritive proteins during patency, which is facilitated as a result of intercellular spaces occurring between follicular epithelial cells under the influence of juvenile hormone (JH). Patency was analyzed in the moth, Heliothis virescens, using a pharmacological approach, in which we used different JH homologues and chemicals that specifically target elements of two second-messenger pathways in vertebrates, the cAMP-dependent and inositol triphosphate/diacylglycerol signaling pathways. JH I and JH III evoked dose-dependent patency in H.

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Mark-release-recapture experiments to study insect dispersal require the release of marked insects that can be easily identified among feral conspecifics. Oil-soluble dyes have been used successfully to mark various insect species. Two oil-soluble dyes, Sudan Red 7B (C.

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In Heliothis virescens, reproduction is strictly dependent on juvenile hormone (JH). In females, mating induces a sharp increase in JH titers, which stimulates increased vitellogenin biosynthesis and higher rates of egg production. JH biosynthesis is presumably stimulated by production and/or release of stimulatory neuropeptides such as allatotropins.

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In vitro catabolism of juvenile hormone (JH) in haemolymph of adult female Cydia pomonella was ascribed mainly to juvenile hormone esterase (JHE) activity. No significant differences were noted between virgin and mated females 0-96 h post-emergence. Changes in JHE activity did not appear dependent upon fluctuations in JH titre; conversely, changes in JHE activity could not explain the changes in JH titres.

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