The molecular and metabolic essentials for long-distance flight in insects

Summary The mechanism of long-distance flight in insects was investigated by comparing lipid mobilization and transport in gregarious- and solitary-phase locusts and in the American cockroach. Unlike the gregarious-phase locust, both the American cockroach and the solitary locust were unable to form low-density lipophorin (loaded with increased amount of diacylglycerol) even when injected with adipokinetic hormone (AKH). The cockroach fat body responded to AKH. However, not only does the American cockroach lack apolipophorin-III (apoLp-III) in the haemolymph, but the fat body contains only an extremely small amount of diacylglycerol and a relatively large triacylglycerol pool. By contrast, the solitary-phase locust had apoLp-III in the haemolymph, but the fat body was only one-seventh or less in weight of the fat body of the gregarious locust. Furthermore, the fat body of the solitary locust contains a very small amount of triacylglycerol (1/20 or less of that of the gregarious locust) with only a trace of diacylglycerol. It was concluded that in the American cockroach and the solitary locust, the stores of fuel in the fat body are insufficient to maintain prolonged flight.Abbreviations AKII adipokinetic hormone - apoLp-III apolipophorin III - HDLp high-density lipophorin - LDLp low-density lipophorin - LTP lipid transfer particle - MW molecular weight - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis     

Oxidation of 3,4-dihydroxybenzyl alcohol: a sclerotizing precursor for cockroach ootheca.

The oxidation of 3,4-dihydroxybenzyl alcohol, one of the sclerotizing precursors for the tanning of the ootheca of cockroach Periplaneta americana, is reported for the first time. Mushroom tyrosinase catalyzed oxidation of 3,4-dihydroxybenzyl alcohol generated the corresponding quinone which was found to be unstable and readily transformed to produce 3,4-dihydroxybenzaldehyde as the stable product probably through the intermediary formation of a quinone methide. Phenoloxidase isolated from the left collateral gland of P. americana also catalyzed this new reaction. When the enzymatic oxidation of 3,4-dihydroxybenzyl alcohol was performed in the presence of a test protein such as lysozyme, the reactive species formed, caused the oligomerization of test protein. Similar studies with collateral gland proteins, failed to generate oligomers, but produced insoluble polymeric proteins. The probable fate of 3,4-dihydroxybenzyl alcohol for the tanning of cockroach ootheca is discussed.     

Virulence, horizontal transmission, and sublethal reproductive effects of Metarhizium anisopliae (Anamorphic fungi) on the German cockroach (Blattodea: Blattellidae)

Virulence of Metarhizium anisopliae (Metschnikoff) Sorokin strain EAMa 01/121-Su against the German Cockroach, Blatella germanica (L.), was determined using four concentrations ranging from 4.2 x 10(6) to 4.2 x 10(9) spores per milliliter. The LD50 value was 1.4 x 10(7) spores per milliliter (56,000 spores per cockroach) and LT50 values were 14.8 days and 5.3 days for 4.2 x 10(8) and 4.2 x 10(9) spores per milliliter, respectively. An experiment was conducted to evaluate whether a fungal transmission could exist among infected and healthy cockroaches. Percentage mortality at a ratio of 1:10 of infected to unexposed cockroaches was 87.5% and LT50 was 12.2 days, which indicated the potential of this strain to be horizontally transmitted and to rapidly spread the infection in the insect population. The effect of a sublethal dose (ca. LD60) of M. anisopliae EAMa 01/121-Su strain, applied topically on German cockroaches, was studied by reciprocal crossing. Othecal production, oothecal hatchability, and nymphal production declined upon exposure to M. anisopliae EAMa 01/121-Su strain. The mean number of oothecae laid by female was progressively and significantly reduced by fungal treatment from second oviposition period onwards. Oothecal hatch of fungally challenged females was reduced by 46-49%, oothecal viability by 48-85%, and nymphal production by 22-35%. Only treated females showed an effect on oothecal production, oothecal hatch, and nymphal production, although oothecal hatch was also governed by treated males at a higher significance level. Our results on virulence and horizontal transmission of fungal conidia of M. anisopliae EAMa 01/121-Su strain and its sublethal reproductive effects on German cockroach females are discussed in terms of its potential to decrease the pest status of B. germanica in the short and long terms.     

Sedimentary and poroperm anatomy of shoal-water carbonates (Muschelkalk,South-German Basin): an outcrop-analogue study of inter-well spacing scale

Outcrop-analogue studies are rarely carried out on a very detailed scale of just several hundred metres, which represents a common inter-well spacing. Superb outcrop conditions in south Germany for Upper Muschelkalk shoal-water carbonates located on a carbonate ramp allowed us to perform a detailed analysis of their sedimentary and poroperm organisation. The cyclic structure of the carbonates is evident in three types of genetic sequences 1–3 m thick, which in turn build larger-scale sequences. Lateral variations of microfacies in the study area are restricted to a few percent of individual components, leading to an excellent degree of correlation of sequences. Microfacies do not correlate well with porosity and permeability. Therefore, in order to characterise reservoir properties of the carbonate-sand shoal it is necessary to integrate rock fabric and pore type. The cyclic framework outlined in this outcrop analogue provides a predictive tool for subsurface reservoir characterisation. The stratigraphic sequences correspond to fluid-flow units showing the thickest (up to 2 m) and best reservoir qualities ( up to 20%, k up to 53 md) towards the overall regressive maximum.     

First record of habitat of Daulocoris formosanus (Hemiptera: Aradidae): Colonies discovered in nests of Salganea taiwanensis ryukyuanus (Dictyoptera: Blaberidae)

We collected colonies of Daulocoris formosanus from nests of the subsocial wood‐feeding cockroach Salganea taiwanensis ryukyuanus for the first time. To understand the ecology of D. formosanus, we observed and characterized their behavior in a laboratory setting. We provide the first detailed record of the habitat, colony structure and feeding behavior of D. formosanus.     

Improved conditions for culture of biosynthetically active cockroach corpora allata

Summary Currently, short-term culture of insect corpora allata is most often performed in TC199. We now show that L-15B, a medium widely used in arthropod tissue culture, is superior to TC199 for both short- and long-term culture of cockroach corpora allata. In 3-h and 48-h incubations, juvenile hormone biosynthesis by corpora allata from Diploptera punctata was significantly higher in L-15B than in TC199. In addition, in both media, corpora allata activity was significantly improved by flotation of glands at the medium surface. Characteristics of L-15B responsible for its superiority were examined by comparison of gland activities in several TC199 formulations that had been modified in different ways to be more similar to L-15B. Adjusting the osmotic pressure of TC199 (288 mOsm/l) to near that of L-15B (362 mOsm/l) and D. punctata hemolymph (360 mOsm/l) significantly improved gland activity during the second 12 h of a 36-h incubation. Increasing the concentrations of amino acids, sugars, and organic acids in TC199 to the same levels as in L-15B significantly improved gland activity during both the second and third 12-h intervals of a 36-h incubation. These results suggest that L-15B is superior to TC199 because L-15B is isoosmotic with D. punctata hemolymph and because L-15B, like cockroach hemolymph, contains a high level of organic constituents. It is therefore more appropriate to use L-15B than TC199 for short-term in vitro assays of juvenile hormone biosynthesis and for extended corpora allata culture.     

Ultrastructural changes in corpora allata during a cycle of juvenile hormone biosynthesis in embryos of the viviparous cockroach, Diploptera punctata

We have observed changes with time in the fine structure of corpora allata (CA) during a known cycle of increasing and decreasing juvenile hormone (JH) synthesis in late embryos of Diploptera punctata. A previous report showed that rates of JH release were relatively low in 28-day-old embryos, but CA activity subsequently rose linearly to a peak on about day 42, and thereafter steadily declined to a low level on day 64 just before birth (Holbrook et al., 1997). We now show that, regardless of rate of JH synthesis, CA cells are large and replete with organelles which nevertheless exhibit variable morphology in embryos of different age. Highly active CA cells on day 40 contain abundant ring-form mitochondria, whereas CA cells of low activity on days 28 and 64 contain mitochondria that are rod-shaped or globular. Mitochondrial cristae were scarce and indistinct on day 28 but numerous and well developed on day 64. Endoplasmic reticula (ER) are rare on day 28 and appear in increasing numbers when CA activity rises. On day 40, ER are abundant and often exhibit a whorl-like appearance which is not observed on day 28. After day 44, when biosynthetic activity is declining, whorls of ER gradually decrease in number and are ultimately replaced by vesicular smooth ER on day 64. Neurosecretions are found only after day 38, by which time rates of JH synthesis have increased substantially from those of day 28. Except for membranous autophagic vacuoles, which are frequently found when ER whorls disintegrate as rates of JH synthesis decline toward birth, most autophagic vesicles such as multivesicular vesicles and dense bodies occur only sporadically among CA cells at all examined ages. We conclude that synchronous autophagy of exhausted organelles, which results in atrophy of CA cells and long-term arrest of JH synthesis in adult females of D. punctata, does not occur in embryos. The slow cyclic change in rate of JH synthesis in embryonic CA is most likely due to asynchronous autophagic activity and to alterations in certain unique features of intracellular organelles.     

The interaction of surface and dust particle size on the pick-up and grooming behaviour of the German cockroachBlattella germanica

The relationship between the particle size of an inert silica dust, its up-take from different surfaces and the grooming behaviour of males, gravid females, and fifth and sixth instar nymphs of the German cockroachBlattella germanica (Dictyoptera: Blattellidae) (L.) was investigated. The normal grooming behaviour of gravid females, nymphs and males differed according to sex and age. The gravid females and nymphs exhibited greater grooming activity than the males, especially of the antennae and the legs. Gravid females, nymphs, and adult males exhibited increased grooming activity after exposure to dust in the size range 0.5–63 μm, but there was no significant difference in grooming behaviour from the control when cockroaches were exposed to dust sizes greater than 70 μm. Antennal grooming by males was greater than leg grooming when exposed to all dust sizes, except size particles ranging 4.5–7.5 μm. A dust pick-up experiment indicated that the average amount of dust transferred toB. germanica is affected by particle size, the porosity of the treated surface, and the sex and age of the cockroaches. Gravid females picked up greater amounts of dust than fifth and sixth instar nymphs, which in turn picked up more dust than males. Silica dust particles (0.5–7.5 μm) were picked up more effectively than larger particle sizes, by all three categories, males, females and fifth and sixth instar nymphs of cockroach on all three test surfaces plastic, ceramic and unpainted plywood. Plywood was the least effective surface for transfer of dust, of all sizes, to males, females and nymphs.     

Adaptation of the cockroach Blattella germanica to human habitats: circadian and noncircadian factors

To survive, an animal must respond to the environmental stimuli (Zeitgebers) precisely coinciding with a 24‐h light/dark cycle. In human habitats, both natural and artificial Zeitgebers intermingle, entraining the circadian clocks of animals. Whether a circadian clock can respond to Zeitgebers effectively is closely related to the level of adaptive competitiveness. In the present review, the German cockroach (Blattella germanica L.) is compared with the double‐striped cockroach (Blattella bisignata Brunner von Wattenwyl) and the reasons why B. germanica is a more competitive dweller than its sibling species in human habitats are discussed. For example, sensitive adjustment of circadian clocks allows a male B. germanica to coordinate itself to the changes of daily light/dark cycles more efficiently; by contrast, it takes male B. bisignata more than 3 days to adjust. In a given dark phase, male B. germanica appear more to be resistant than B. bisignata to interference from light pulses. Ovary‐dependent masking factors enable female B. germanica to take advantage of the light phase to feed or mate, during which time a female B. bisignata typically remains inert. Furthermore, the gregariousness levels, fertilization and hatching rates, as well as mating behaviours of both cockroach species are compared. All of these comparisons suggest that B. germanica surpasses B. bisignata with respect to adapting to the artificial constraints within human habitats as a result of the adoption of an integrated strategy consisting of circadian and noncircadian approaches.     

Endocrine regulation of female contact sex pheromone production in the German cockroach, Blattella germanica

ABSTRACT The amount of the major component of the cuticular sex pheromone, 3, 11-dimethyl-2-nonacosanone, on individual female German cockroaches, Blattella germanica (L.), as a function of age was determined by gas-liquid-chromatographic analysis. Accumulation of phermone increased with age in both virgin and mated females. During the first gono-trophic cycle, the pheromone accumulated most rapidly when oocyte growth rates were maximal (days 5–10), and least rapidly while the female carried an ootheca (days 11–32). Pheromone accumulation was similar in virgin and mated females when the same physiological stages (determined by oocyte maturation) were considered. Inhibition of Juvenile Hormone release, through allatectomy, chemicals (precocene or fluoromevalonate), or through mechanical egg case implants, suppressed or delayed pheromone production and oocyte growth. The Juvenile Hormone analogue ZR512 induced allatectomized or head-ligated females and females with chemically or mechanically inhibited corpora allata to produce pheromone and enlarge their basal oocytes. Finally, ZR512 applied to intact females stimulated pheromone production in a dose-dependent manner.