Lethal(1)fibrillardysgenesis (I(1)fdg), a mutation affecting muscle development in the embryo of Drosophila melanogaster

The I(1)fdg mutation demonstrates two separate phases of lethality, depending on developmental conditions. At 32–33°C, an embryonic lethality is expressed whereas at lower temperatures a larval-pupal lethality is observed. This larval-pupal lethality characteristically produces noncondensed, curved puparia, and since the contraction of the pupa depends on strong muscular contraction, this phase of lethality implicates some involvement of abnormal musculature. The embryonic expression of I(1)fdg at 32–33°C is the subject of this study. In these embryos, which are alive but immobile (incapable of hatching), the fibrillar organization and fiber morphology of the somatic musculature varies from being apparently normal to being grossly abnormal. While the abnormalities appear as unusual distributions of fiber organelles, abnormal convolutions of the muscle fibers, and disorganizations of fibrillar components, it seems most probable that the underlying defect ultimately responsible resides in some system essential for Z body alignment and sarcomere formation. Accompanying the embryonic lethality, certain abnormalities in midgut development are observed which at present do not appear to be related to the defects observed in the somatic muscle.     

Silencing downstream of receptor kinase gene (drk) impairs larval-pupal ecdysis in Leptinotarsa decemlineata (Say)

In insects, an insulin-like peptide (ILP) triggers the formation of the insulin receptor (InR)/the insulin receptor substrate Chico complex. The complex then recruits downstream of receptor kinase (Drk) and phosphatidylinositol-3-kinase (PI3K) to initiate two signaling branches, i.e., Drk-mitogen-activated protein kinase (MAPK) and Pi3K-protein kinase B subdivisions. Previous findings reveal that RNA interference (RNAi) of LdILP2 or Ldchico, rather than Ldpi3k92E, impairs larval-pupal and pupal-adult molting in the Colorado potato beetle Leptinotarsa decemlineata. It is accordingly hypothesized that the Drk-MAPK branch regulates larval metamorphosis. In the present paper, we first found that silencing LdILP2, Ldchico or Ldpi3k92E did not decrease the expression level of Lddrk, indicating other receptor tyrosine kinases’ signaling except insulin pathway is not affected in the RNAi larvae. Moreover, two InRs and Torso were highly expressed in the final larval instars. Furthermore, RNAi of either Lddrk or Ldchico, or both of them equally affected larval-pupal and pupal-adult molts, and similarly repressed the expression of representative MAPK (Ldras and Ldraf), ecdysteroidogenesis (Ldphm and Ldsad), and 20E signaling (LdEcR, LdUSP, LdHR3 and LdE75) genes. 20E feeding by Lddrk RNAi larvae completely restored the reduced mRNA levels of LdEcR, LdHR3 and LdE75, but did not rescued the decreased Lddrk and LdUSP levels and the lowered pupation and emergence rates. Therefore, our findings suggest that the Drk-MAPK branch is involved in metamorphosis regulation in L. decemlineata.     

Effect of a juvenile hormone analogue on phosphatase activity in pupae of the stable fly, Stomoxys calcitrans.

The alkaline phosphatase activity of stable fly pharate pupae treated with 10 ng of an insect juvenile hormone analogue (JHA), Stauffer R-20458, or untreated pupae was rhythmic and peaked 48 and 96 hr after larval-pupal apolysis. Those treated with 10 μg were not rhythmic and peaked at 48 and 120 hr. Acid phosphatase activity showed a general increase throughout pupal-adult transformation and was three- to four-fold higher than alkaline phosphatase activity. At 24 and 48 hr after larval-pupal apolysis, acid phosphatase was lower in the treated animals, but at 72 and 120 hr, it was higher. Neither inhibition nor enhancement of acid and alkaline phosphatase activity or by three other JHAs could be demonstrated in vitro.     

Prothoracic gland involution related to moulting hormone levels during the metamorphosis of Tenebrio molitor L.

Prothoracic gland (PG) of Tenebrio shows ultrastructural changes which can be correlated with ecdysteroid levels (measured by radioimmunoassay) during larval-pupal development. However, the gland cells begin to degenerate before pupal-adult ecdysis: the PG involution is completed before the moulting hormone peak which triggers pupal-adult development. These facts strongly suggest that another endocrine organ produces moulting hormone needed for adult development.     

Fluorescent insect growth regulators (FIGR's): A new tool for insect physiologists

A compound was synthesized that fluoresces in the visible spectrum and has the properties of an insect juvenile hormone. When it was assayed against Aedes aegypti larvae, it produced larval-pupal and pupal-adult intermediates; when injected into allatectomized adult females, it restored normal egg development. The fluorescent insect growth regulator (5-[[[5-(dimethylamino)-1-naphthalenyl]sulfonyl]amino]-1,3-benzodioxole) when injected into females, could be traced into eggs and newly hatched larvae. Microspectrofluorometric and chromatographic studies indicate that it is metabolically stable. Fluorescent insect growth regulators constitute new tools for the investigation of the action of insect growth regulators in general.     

Studies on the diapause of Trogoderma granarium: Effects of juvenile hormone analogues on growth and metamorphosis

Trogoderma granarium larvae reared at 30°C on wheat flour containing appropriate concentrations of farnesyl methyl ether (FME) resembled normal diapause larvae in their growth characteristics and reactions to diapauseterminating conditions. When these larvae were transferred to 37°C either without food or with normal food, normal adults resulted. But when the diapause-like state was broken at 37°C in the presence of the original FME-containing food the insects either died before pupal-adult ecdysis or gave abnormal adults. At 35°C FME did not inhibit the larval-pupal ecdysis, but only a few adults emerged and these were abnormal.Farnesol did not inhibit metamorphosis at 30°C and caused less abnormality than did FME.Based on these results, the hypothesis that the density-dependent diapause of this insect is caused by the presence, in faecal pellets, and thereby in contaminated food, of juvenile hormone (JH) analogues is rejected, but the possibility that diapause results from a high physiological level of JH brought about by causes other than the presence of JH analogues in the environment is examined.     

Changes in the amount of the diapause factor in the subesophageal ganglion during development of the silkworm, Bombyx mori

Changes in the diapause factor content of the subesophageal ganglion of the silkworm were examined from the viewpoint of sex and voltinism differences. The diapause factor content was comparatively low from the 4th larval ecdysis to the larval-pupal ecdysis, irrespective of sex and voltinism. However, remarkable changes occurred after the larval-pupal ecdysis. An interesting finding is that the diapause factor content in the female diapause egg-producer decreased gradually with pupal-adult development, but in the male diapause egg-producer as well as in the non-diapause egg-producer it increased up to the half-way stage in the pupal-adult development. This suggests that the diapause factor is not secreted from the subesophageal ganglion of the male pharate adult of the diapause egg-producer. This finding was confirmed by implantation experiments using brain-subesophageal ganglion complex or only subesophageal ganglion.     

Identification,mRNA Expression,and Functional Analysis of Chitin Synthase 1 Gene and Its Two Alternative Splicing Variants in Oriental Fruit Fly,Bactrocera dorsalis

Two alternative splicing variants of chitin synthase 1 gene (BdCHS1) were cloned and characterized from the oriental fruit fly, Bactrocera dorsalis (Hendel). The cDNA of both variants (BdCHS1a and BdCHS1b) consisted of 5,552 nucleotides (nt), with an open reading frame (ORF) of 4,776 nt, encoding a protein of 1,592 amino acid residues, plus 685- and 88-nt of 5′- and 3′-noncoding regions, respectively. The alternative splicing site was located between positions 3,784-3,960 and formed a pair of mutually exclusive exons (a/b) that were same in size (177 nt), but showed only 65% identity at the nucleotide level. During B. dorsalis growth and development, BdCHS1 and BdCHS1a were both mainly expressed during the larval-pupal and pupal-adult transitions, while BdCHS1b was mainly expressed during pupal-adult metamorphosis and in the middle of the pupal stage. BdCHS1a was predominately expressed in the integument whereas BdCHS1b was mainly expressed in the trachea. The 20-hydroxyecdysone (20E) induced the expression of BdCHS1 and its variants. Injection of dsRNA of BdCHS1, BdCHS1a, and BdCHS1b into third-instar larvae significantly reduced the expression levels of the corresponding variants, generated phenotypic defects, and killed most of the treated larvae. Furthermore, silencing of BdCHS1 and BdCHS1a had a similar result in that the larva was trapped in old cuticle and died without tanning completely, while silencing of BdCHS1b has no effect on insect morphology. These results demonstrated that BdCHS1 plays an important role in the larval-pupal transition and the expression of BdCHS1 in B. dorsalis is regulated by 20E.     

Cyclic AMP levels in Drosophila during postembryonic development and in the adults.

The physiological content of Drosophila melanogaster tissues in cyclic AMP has been determined and its variations studied during postembryonic development and in the adults. Marked variations were observed, especially during metamorphosis where the ratio between the lowest and highest values (0·35 to 17·25 pmoles/mg protein) was $\text{1}\text{44}$. In larvae the variations of cyclic AMP level were not clearly related to the larval ecdyses, but the steps of metamorphosis, i.e. formation of the puparium, larval-pupal apolysis, and pupal-adult apolysis, were accompanied with rapid and drastic rises of cyclic AMP, up to the highest value mentioned. We therefore deduce that cyclic AMP is involved in the metamorphosis of D. melanogaster as a chemical signal. In adults, the cyclic AMP level was remarkably constant and was around 7 pmoles/mg protein.     

Effects of a synthetic juvenile hormone and some analogues on Ephestia spp. (Lepidoptera: Phycitidae)

Depending on their stage of development, treatment of mature larvae of Ephestia kühniella with a synthetic juvenile hormone resulted in the production of super larvae (which invariably prolonged larval life) and larval-pupal intermediates. When migrating last-instar larvae were treated with the juvenile hormone analogues (JHA) ethyl-3,7, n-trimethyldodeca-2,4-dienoate (ZR512) and isopropyl ii-methoxy-3,7, ii-trimethyldodeca-2,4-dienoate (ZR515), larval-pupal intermediates and pupal mortality were induced. However, when applied topically, ZR515 appeared more effective than ZR512. Both analogues prevented adult emergence when topically applied to the migrating larvae at doses between 28–52 ng. One-day-old pupae were most susceptible while older individuals became less sensitive with age. When larvae pupated in corrugated cardboard rolls were treated with ZR512 those of both E. cautella and E. kiihniella failed to emerge. At an estimated dose of 179 ng cm^-2, ZR515 prevented 77^-6%E. cautella and 100%E. kühniella larvae from emerging as adults. The control of Ephestia by JHA treatment of the pupation sites is discussed.     

Larvicidal and chemosterilant activity of the acetone fraction of petroleum ether extract from Argemone mexicana L seed

The acetone fraction of the petroleum ether extract of seeds from Argemone mexicana L. exhibited larvicidal and growth inhibiting activity against the second instar larvae of Aedes aegypti (Linn). This activity occurred at higher concentrations (200, 100, 50 and 25 ppm). Chemosterilant activity, including reduction in blood meal utilization (27.70%), reduction in fecundity (19.00%), formation of larval-pupal intermediates, formation of pupal-adult intermediates, adult mortality and sterility of first generation eggs (100%), occurred at low concentration (10 ppm).     

Developmental changes in midgut trehalase activity and its localization in the silkworm, Bombyx mori

The changes in trehalase activity and its localization in the midgut of the silkworm, Bombyx mori, were studied during larval-pupal-adult development. Trehalase activity in larval midgut epithelium increased with the larval growth, reached a maximum level at the middle of the fifth instar, and then decreased gradually. Trehalase activity in larval midgut was found in the epithelial tissue but not in the digestive juice or the midgut contents.The trehalase activity in the whole midgut started to rise at the onset of spinning and increased abruptly at larval-pupal ecdysis to reach an extremely high level 3 days later. This high activity was maintained throughout the subsequent pharate adult development and dropped suddenly at emergence. The midgut trehalase activity during pupal-adult development was mainly found in the midgut contents but scarcely any in the epithelium.Subcellular distribution of midgut trehalase depended upon larval-pupal-adult development. The activity was concentrated in a precipitate fraction of the epithelium until the middle of the fifth instar. During larval-pupal development, however, the activity increased in the soluble fraction with a concomitant decrease in the precipitate fraction. Almost all the trehalase activity in pupal and pharate adult midgut was recovered in the soluble fraction of the midgut contents. The data are discussed from a viewpoint of the histolysis.     

Pupal and larval-pupal parasitoids (Hymenoptera) obtained fromAnastrepha Spp. andCeratitis capitata (Dipt.: tephritidae) pupae collected in four localities of Tucuman province,Argentina

Pupal and larval-pupal parasitoids were obtained from 5 % of the 1,413 tephritid puparia collected in four localities of the Tucumán province, Argentina, from April, 1991 to April, 1993.Ceratitis capitata (Wiedemann) was attacked byPachycrepoideus vindemmiae (Rondani) (Pteromalidae), a pupal parasitoid, andAganaspis pelleranoi (Brèthes) (Eucoilidae), a larval parasitoid.Anastrepha spp. were attacked byDoryctobracon areolatus (Szépligeti) (Braconidae), a larval parasitoid, and also byA. pelleranoi. Information about parasitism, percentage of emergence of tephritid species and pupal viability in different localities is provided.     

Activities of hormone metabolizing enzymes in house flies treated with some substituted urea growth regulators.

The insect growth regulators (IGR) TH 6038 and TH 6040 affect larvae of various species by interfering with cuticle development. In a biochemical study of their effects, larvae of the house fly, $\text{Musca domestica}$ L. were reared for 2 days on diets containing 1.7 to 166.7 ppm of these compounds, then assayed for activities of the microsomal oxidases and the enzyme(s) which metabolize β-ecdysone. The activities of these enzymes were compared with the percentage of treated larvae completing pupal-adult ecdysis. The two compounds reduced the activity of the β-ecdysone metabolizing enzyme(s) by as much as 57%, reduced pupal-adult ecdysis by 43% to 100%, and stimulated microsomal oxidase activity 4- to 12-fold. Supplementation of the diet of the treated insects with the Cecropia juvenile hormone, JH I, partially restored pupal-adult ecdysis but supplementation with β-ecdysone had no effect. The mode of action indicated by these results is that the IGRs cause an accumulation of β-ecdysone in the treated larvae. This stimulates the enzyme, chitinase, which degrades chitin in preparation for formation of the new cuticle. The hormone may also cause a JH deficiency and the stimulation of DOPA decarboxylase and phenol oxidase which would further disrupt the normal molting process.     

Ecdysone 20-hydroxylation in imaginal wing discs of Pieris brassicae (lepidoptera): Correlations with ecdysone and 20-hydroxyecdysone titers in pupae

Ecdysone 20-hydroxylase activity has been detected in pupal wing discs of Pieris brassicae. This activity is due to an enzyme system located in microsomal fractions. Its apparent Km is 58 nM for ecdysone. The enzyme is inhibited by the reaction product 20-hydroxyecdysone with an apparent Ki of 2.6 μM. Its activity varied during pupal-adult development with a maximum on day 4, when ecdysone levels are the highest in the animal. Although low, the peak activity is sufficient to assure 25% of the conversion of endogenous ecdysone into 20-hydroxyecdysone in pupae. Ecdysone and 20-hydroxyecdysone levels were measured in hemolymph and whole animals; ecdysone appears to be mainly located in hemolymph, whereas 20-hydroxyecdysone seems to be equally distributed between hemolymph and tissues. All these findings are discussed in relation to the roles of ecdysone and 20-hydroxyecdysone during pupal-adult development.     

The effect of L-canavanine and L-canaline on the hemolymph amino acid composition of the tobacco hornworm,Manduca sexta (L.) (Sphingidae)

Tobacco hornworm larvae, Manduca sexta (L.) (Sphingidae), were administered L-canaline either by parenteral injection or by dietary consumption. The overt toxicity and the alteration of hemolymph amino acids caused by these nonprotein amino acids were evaluated. The LD₅₀ value for parenterally administered canavanine and canaline is 1.0 and 2.5 mg/g fresh body weight, respectively. A dietary concentration of 5.2 mM for canavanine and over 20 mM for canaline represent the respective LC₅₀ values. A large percentage of the larvae reared on diets supplemented with additional arginine, ornithine, or 2,4-diaminobutyric acid in addition to canavanine or canaline were unable to complete larval-pupal ecdysis. These toxic effects were associated with a decreased glutamic acid hemolymph titer and dramatically elevated ornithine. On the other hand, larvae administered canavanine or canaline alone, either by dietary consumption or parenteral injection, experienced less drastic developmental aberrations. These symptoms were in some cases correlated with increased ornithine and glutamic acid titers. Evidence is presented that even a canavanine- and canaline-sensitive insect such as M. sexta has a marked ability to eliminate these protective allelochemicals.     

The effects of Farinocystis tribolii on the growth and development of the flour beetle Tribolium castaneum

Farinocystis tribolii multiplied only in the fatbody of Tribolium castaneum larvae. In the advanced stages of infection, the fatbody was destroyed and the albuminoid granules were completely depleted. Larvae in late stages of infection were “C” shaped. Diseased pupae were flat and straight with the head and mouth parts not completely flexed with the pupal body. Infected pupae failed to develop into adults. Heavily infected adults were distended. Larvae of third, fourth, and fifth instars, although succumbing to the infection ultimately, continued to live even after the healthy larvae of the same age had entered pupation, indicating a prolongation of larval period. Molting was either affected or delayed in infected insects. F. tribolii infection induced a juvenile hormonal effect producing larval-pupal and pupal-adult intermediate forms. Ether extract of spores of F. tribolii when applied on pupae of T. castaneum and final instar nymphs of Dysdercus cingulatus produced adultoids.     

Effects of X-irradiation on egg hatchability, larval and pupal survival in the tobacco hornworm, Manduca sexta

The effects of X-irradiation upon Manduca sexta egg hatchability and larval survival were studied using LD₅₀'s. Radiosensitivity declined with age in developing eggs (LD₅₀ of 9.4 kR in 2.5 to 3-days eggs contrasted to 18.2 kR in 4 to 4.5-day eggs) and in larvae. The dose-response patterns obtained agree with those previously reported for other insects.The maximal (ED₀) and minimal (ED₁₀₀) X-ray exposures resulting in eclosion successes of 100% and 0%, respectively, were utilized throughout pupal-adult development as measures of radiation sensitivity. A pronounced decrease in radiosensitivity was noted through the day of eclosion (Day 0: ED₀ = 7.3 kR; ED₁₀₀ = 18.7 kR; Day 22: ED₀ = 45.0 kR, ED₁₀₀ = 105.0 kR). X-irradiation during the pupal-adult transformation was observed to inhibit eclosion without disrupting normal metamorphosis.     

Penetration of phytoecdysones through the pupal cuticle of the silkworm, Bombyx mori

The penetrability of some phytoecdysones, ecdysterone, inokosterone, ponasterone A, and cyasterone, through silkworm pupal cuticle was tested and their effect on pupal-adult development is described. The first three chemicals applied topically to fresh pupae accelerated the pupal-adult development and induced abnormal adults with aberrant legs and antennae, indicating penetration of phytoecdysones through fresh pupal cuticle. Females were more sensitive to the chemicals than males as they showed many more abnormalities. When pupae 1 day after ecdysis were treated topically with phytoecdysones, they transformed into normal adults, suggesting no penetration of ecdysones through old pupal cuticle.