Modeled global invasive potential of Asian gypsy moths, Lymantria dispar

Asian populations of gypsy moths, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), remain poorly characterized – indeed, they are not presently accorded any formal taxonomic status within the broader species. Their ecology is similarly largely uncharacterized in the literature, except by assumption that it will resemble that of European populations. We developed ecological niche models specific to Asian populations of the species, which can in turn be used to identify a potential geographic distributional area for the species. We demonstrated statistically significant predictivity of distributional patterns within the East Asian range of these populations; projecting the Asian ecological niche model to Europe, correspondence with European distributions was generally good, although some differences may exist; projecting the ecological niche model globally, we characterized a likely potential invasive distribution of this set of populations across the temperate zone of both Northern and Southern Hemisphere.     

Pheromone-mediated upwind flight of male gypsy moths, Lymantria dispar, in a forest

Abstract Lymantria dispar L. males flying upwind in a pheromone plume in a forest were video-recorded at 2.5, 10 and 20 m from the source of pheromone. Males flew slower and steered more across the wind as they approached the source. In concert, their ground speed decreased and track angles increased. In contrast to these changes, their drift angles were fairly constant and the transverse component of image flow, above and/or below the moths eyes, showed almost no change. The inter-turn duration (time between sequential turns), a temporal aspect of the male flight manoeuvres, showed a consistent but relatively small increase as the distance from the source increased. The flight tracks narrowed as the males approached close (2.5 m) to the source. Because of unpredicted correlations between physical variables (i.e. temperature, wind velocity) and the distance from the source, we used principal components analysis to generate a set of completely independent variables. Greater than 90% of the variability in the data could be explained by four principal factors which corresponded well with known relationships in the flight manoeuvres. All four of these factors showed a significant regression against distance to the source. Although uncontrolled factors such as temperature and wind velocity may have contributed to changes in flight behaviour, recent data indicate that, in addition to concentration, certain temporal and spatial characteristics (i.e. burst period, burst return period) of plumes in wind vary systematically with distance from the source. We propose that L.dispar males might adjust their flight manoeuvres in response to these changes.     

The interaction of edge-fixation and negative phototaxis in the orientation of walking gypsy moths,Lymantria dispar

Summary The visual orientation towards single black stripes and more complex patterns, comprising smooth gradients of brightness was studied in walking gypsy moths. Depending on the width of a black stripe, up to three walking directions are preferred within one stimulus situation: towards the centre of the stripe and towards a region within the stripe closer to each edge. The observed responses are explained by a compromise between edge-fixation and negative phototaxis. This hypothesis turned out to be also applicable to more complex patterns.     

Host tree influences on the dispersal of first instar gypsy moths, Lymantria dispar (L.)

Abstract. 1. In laboratory tests, first instar gypsy moths attempted dispersal more frequency when exposed to less acceptable foliage.
2. First instars from small eggs attempted dispersal less frequently than larvae from large eggs when exposed to foliage from highly acceptable or marginally acceptable hosts. Dispersal rates of larvae from medium sized eggs were intermediate.
3. These results (1–2) confirm and expand upon the findings of Capinera & Barbosa (1976).
4. In the field, data on the relative densities of larvae on different host species support the conclusion that the frequency of dispersal attempts is inversely related to host acceptability.
5. The implications of these findings for the population dynamics of the gypsy moth are discussed.     

Development of male-incubated ovaries in the gypsy moth,Lymantria dispar

Ovaries from Lymantria dispar females were transplanted into an environment lacking vitellogenin, the male milieu, in order to determine how the presence of vitellogenin in the hemolymph affects the process of protein uptake by gypsy moth oocytes. When undeveloped ovaries from newly ecdysed last instar females were transplanted into males of the same stage, follicles detached from the germarium and increased in size, but the growth of oocytes proceeded more slowly than those from female controls. Although chorion fromation was delayed in male-grown ovaries, scanning electron microscopy of chorionated eggs recovered from adult males showed that a chorion with normal surface architecture was formed by the adult stage. SDS-PAGE analysis of the male-grown ovaries and hemolymph from males receiving ovaries showed that vitellogenin production was not stimulated by the organ transplant and only male hemolymph proteins were internalized by the male-incubated ovaries. Thus, in the absence of vitellogenin, endocytosis of male hemolymph proteins occurred, but the rate of oocyte growth was slowed.     

Soluble cuticular phenoloxidase in the gypsy moth Lymantria dispar

The soluble enzyme phenoloxidase (tyrosinase) from the larval cuticle of Lymantria dispar has been partially purified using Ultrogel ACA 34, and the activity has been determined using phenolic substrates. The enzyme exhibited more activity toward O-diphenolic substrates and monophenolic substrates. The enzyme is inhibited by diethyl dithiocarbamate, phenylthiourea, and thiourea. The enzyme has been localized in the 7% slab and disc PAGE as an intense band. The enzyme is suggested to be involved in wound healing. © 1992 Wiley-Liss, Inc.     

Ultrastructural studies of male-incubated ovaries of the gypsy moth,Lymantria dispar

Ovaries from Lymantria dispar females were transplanted into an environment lacking the vitellogenin ligand; i.e., the male milieu. Transmission electron micrographs comparing the terminal oocytes of male-grown ovaries and normal ovaries showed that yolk sphere diameters were reduced in the male-grown oocytes. However, there were larger numbers of these small yolk spheres per unit area of cytoplasm, indicating that the coalescence of endosomes into yolk spheres is reduced in the absence of vitellogenin. Although there are larger numbers of yolk spheres in male-grown oocytes, the smaller diameter of yolk spheres resulted in less area being taken up by yolk spheres per unit area of cytoplasm in male-grown oocytes, yielding lowered yolk production. This lowered yolk production is a result at least in part of the lowered number of coated vesicles per unit area of submembrane space and in part of the reduced interfollicular spaces seen in male-grown ovaries.     

Structure-activity studies with pheromone-binding proteins of the gypsy moth,Lymantria dispar

Pheromone olfaction in the gypsy moth, Lymantria dispar, involves accurate distinction of compounds with similar structure and polarity. The identified sex pheromone is (7R,8S)-2-methyl-7,8-epoxyoctadecane, 1a, and a known antagonist is (7Z)-2-methyloctadec-7-ene, 4a. The first step in pheromone olfaction is binding of odorants by small, soluble pheromone-binding proteins (PBPs), found in the pheromone-sensing hairs. We have studied the molecular determinants recognized by the two PBPs found in the gypsy moth, using three pheromone/PBP binding assays. Results indicate that (i) PBPs bind analogs of the pheromone with some discrimination; (ii) PBPs experience enhancement of binding when presented with 1a or its enantiomer and 4a simultaneously; and (iii) the binding enhancement is also seen at high ligand:PBP ratios. We found no evidence of allostery, so the synergistic binding effects and the concentration effect may only be explained by multimerization of PBPs with each other, which leads to more than one population of binding sites. We suggest that the enhanced ligand binding at high ligand:PBP ratios may serve to sequester excess ligand and thereby attenuate very strong signals.     

Underestimated mitochondrial diversity in gypsy moth Lymantria dispar from Asia

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Biomodal patterns of mortality from nuclear polyhedrosis virus in gypsy moth (Lymantria dispar) populations

A bimodal temporal pattern of mortality caused by the nuclear polyhedrosis virus (NPV) was observed in nine gypsy moth (Lymantria dispar) populations of varying densities. In all cases, peak mortality from NPV occurred during the second wave (late larval instars) and the highest mortality occurred in high density populations. Patterns of NPV mortality were established several weeks before being expressed. There was no discernible correlation between weekly mortality rates and temperature, rainfall, or total solar radiation. The bimodality was also apparent in NPV contamination on foliage which was measured by bioassay. A similar pattern was observed in the laboratory among larvae reared in groups from field-collected egg masses and from eggs artificially contaminated with NPV from a laboratory population. As in field populations, the period of low mortality from NPV between the two waves occurred when most larvae were late third and fourth instars. Larvae reared individually did not exhibit the second wave of mortality.     

Vertical transmission and overwintering of microsporidia in the gypsy moth, Lymantria dispar

Vertical transmission and the overwintering success of three different microsporidia infecting Lymantria dispar (Lepidoptera: Lymantriidae) larvae were investigated. Endoreticulatus schubergi, a midgut pathogen, was transmitted to offspring via female and male via the egg chorion (transovum transmission). Between 8% and 29% of the emerging larvae became infected. No spores of E. schubergi were found in surface-washed eggs. Nosema lymantriae, a microsporidium that causes systemic infections, was transovarially transmitted. Between 35% and 72% of the progeny were infected. Vairimorpha disparis, a fat body pathogen, was not vertically transmitted. The infectivity of spores that overwintered in cadavers of infected L. dispar varied by species, placement in the environment, and weather conditions. Spores of E. schubergi were still infective after an eight month exposure period of cadavers on the ground. Spores of N. lymantriae and V. disparis remained highly infective only when cadavers overwintered under a more or less continuous snow cover for four months.     

Iridoid glycosides and insect feeding preferences: gypsy moths (Lymantria dispar, Lymantriidae) and buckeyes (Junonia coenia, Nymphalidae)

Abstract. 1. The effect of increasing concentrations of an iridoid glycoside, catalposide, was tested on a generalist and an adapted specialist lepidopteran, using artificial diets.
2. Two strains of the gypsy moth, Lymantria dispar (L.) (Lymantriidae), were tested. Larvae of a wild strain showed a negative dose-dependent response to increasing concentrations of catalposide (up to 7.2% dry weight), while a laboratory strain showed no such pattern. Choice tests using the laboratory strain showed that these larvae often preferred diets relatively low in catalposide over those with higher concentrations.
3. In contrast, larvae of the iridoid glycoside specialist, the buckeye, Junonia coenia Hübner (Nymphalidae), showed a positive dose-dependent response and grew better on diets with higher doses of catalposide.
4. We tested whether the improved growth of J. coenia at higher concentrations of catalposide may have been due to extra glucose yielded by hydrolysis of catalposide. Larvae were fed increasing doses of glucose equivalent to the amount potentially obtained by hydrolysing the quantities of catalposide used in the previous experiment. However, added glucose did not effect growth, suggesting that increased growth at higher catalposide concentrations was due to increased feeding rates.     

亚洲型舞毒蛾在北美的适生性

采用DYMEX V2.0软件和ArcGIS分析工具相结合的方法,提出亚洲型舞毒蛾Lymantria dispar(L.)的DYMEX参数指标体系和适生性评判标准,分析亚洲型舞毒蛾在北美的适生范围与适生程度。研究表明,加拿大的南部、美国的大部分地区以及墨西哥中南部极少部分区域为该虫的适生区。研究结果将为国家植物保护部门提供有关亚洲型舞毒蛾的植物检疫决策支持。     

Pheromone-modulated optomotor response in male gypsy moths,Lymantria dispar L.: Directionally selective visual interneurons in the ventral nerve cord

In response female pheromone the male gypsy moth flies a zigzagging path upwind to locate the source of odor. He determines wind direction visually. To learn more about the mechanism underlying this behavior, we studied descending interneurons with dye-filled micro-electrodes. We studied the interneuronal responses to combinations of pheromone and visual stimuli.

Photoperiod cues and the modulatory action of octopamine and 5-hydroxytryptamine on locomotor and pheromone response in male gypsy moths,Lymantria dispar

Experiments were conducted to determine whether the biogenic amines octopamine (OA) and 5-hydroxytryptamine (5-HT) exert modulatory effects on pheromone responsiveness and random locomotor activity in male gypsy moths. When injected into males, OA significantly enhanced sensitivity to pheromone, while 5-HT enhanced general locomotor activity, results that were very similar to those previously shown for the cabbage looper. Maximal effect of the amines, however, was observed when injection occurred just prior to the onset of scotophase, rather than photophase, as we had originally hypothesized for this diurnally active insect. Male gypsy moths also displayed a prominent scotophase response, with sensitivity to pheromone greater in the scotphase compared with photophase, but with the level of random locomotor activity lower in scotophase than in photophase. The upwind flight behavior of males to a pheromone source in a wind tunnel, as well as the time spent at the source, were also significantly different in the two light regimes. Furthermore, when exposed to a 1 h scotophase (instead of the normal 8), or to continuous dark conditions, while males exhibited response to pheromone and locomotor activity during the same scotophase and photophase periods as observed in a 16:8 light : dark cycle, the levels of response, as well as qualitative aspects of the upwind flight behaviors in both periods were a function of the light intensity. Our combined results suggest that male gypsy moths display a bimodal rhythm of locomotor and pheromone response over the diel cycle, with light intensity and scotophase onset providing critical cues for the expression of behaviors, as well as the modulatory action of the amines. © 1992 Wiley-Liss, Inc.     

Male death resulting from hybridization between subspecies of the gypsy moth,Lymantria dispar

We explored the origin of all-female broods resulting from male death in a Hokkaido population of Lymantria dispar through genetic crosses based on the earlier experiments done by Goldschmidt and by testing for the presence of endosymbionts that are known to cause male killing in some insect species. The mitochondrial DNA haplotypes of the all-female broods in Hokkaido were different from those of normal Hokkaido females and were the same as those widely distributed in Asia, including Tokyo (TK). Goldschmidt obtained all-female broods through backcrossing, that is, F1 females obtained by a cross between TK females (L. dispar japonica) and Hokkaido males (L. dispar praeterea) mated with Hokkaido males. He also obtained all-male broods by mating Hokkaido females with TK males. Goldschmidt inferred that female- and male-determining factors were weakest in the Hokkaido subspecies and stronger in the Honshu (TK) subspecies. According to his theory, the females of all-female broods mated with Honshu males should produce normal sex-ratio broods, whereas weaker Hokkaido sexes would be expected to disappear in F1 or F2 generations after crossing with the Honshu subspecies. We confirmed both of Goldschmidt''s results: in the case of all-female broods mated with Honshu males, normal sex-ratio broods were produced, but we obtained only all-female broods in the Goldschmidt backcross and obtained an all-male brood in the F1 generation of a Hokkaido female crossed with a TK male. We found no endosymbionts in all-female broods by 4,′6-diamidino-2-phenylindole (DAPI) staining. Therefore, the all-female broods observed in L. dispar are caused by some incompatibilities between Honshu and Hokkaido subspecies.     

DNA hybridization assay for detection of gypsy moth nuclear polyhedrosis virus in infected gypsy moth (Lymantria dispar L.) larvae

Radiolabeled Lymantria dispar nuclear polyhedrosis virus DNA probes were used in a DNA hybridization assay to detect the presence of viral DNA in extracts from infected larvae. Total DNA was extracted from larvae, bound to nitrocellulose filters, and assayed for the presence of viral DNA by two methods: slot-blot vacuum filtration and whole-larval squashes. To test the assays, neonate larvae were fed droplets containing a known concentration of L. dispar nuclear polyhedrosis virus and observed for up to 10 days to determine the percentage of infected larvae. The average percent mortalities were 88.0, 60.7, 26.0, and 5.3% for larvae fed droplets containing 4.0 x 10(4), 1.0 x 10(4), 2.5 x 10(3), and 6.25 x 10(2) polyhedral inclusion bodies (PIBs) per ml, respectively. Other larvae treated with the same virus concentrations were frozen at 2, 4, and 6 days postinoculation and examined by the hybridization techniques. The average percentage of slot blots containing viral DNA equaled 81.0, 58.0, 18.0, and 6.0% for larvae blotted 4 days after treatment with 4.0 x 10(4), 1.0 x 10(4), 2.5 x 10(3), and 6.25 x 10(2) PIBs per ml, respectively, and 89.9, 52.1, 26.6, and 6.0%, respectively at 6 days postinoculation. Thus, the hybridization results were closely correlated with mortality observed in reared larvae. Hybridization of squashes of larvae frozen 4 days after receiving the above virus treatments also produced accurate measures of the incidence of virus infection.