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 infection by Nosema whitei on the mating frequency and fecundity of Tribolium castaneum

The effects of infection by Nosema whitei on the mating frequency of Tribolium castaneum were studied. Data indicate that the pathogen, N. whitei, reduces the mating frequency of the beetles. Infection with N. whitei synergistically interacted with aging since infected older beetles mated less frequently than older noninfected beetles. Infected adults also had significantly fewer progeny than noninfected ones.     

Genotype-environment interaction effects on reproductive performance in Tribolium castaneum

Summary The genetical expectations of the means, variances and covariances of populations of doubled haploid lines derived from f₁, F₂, F₃ and intermated F₂ (S₃) generations are presented. These expectations are identical, regardless of genetical architecture, providing there is no linkage disequilibrium. In the presence of linkage disequilibrium differences will occur whose magnitude and direction will depend on the degree of disequilibrium, recombination frequency and the presence or absence of epistasis.Data from an experiment to detect linkage disequilibrium in a cross between two spring barley varieties are presented. This involved a comparison of means, variances and covariances of doubled haploid populations derived from the F₁ and F₂ generations using the H. bulbosum system. Linkage disequilibrium was detected for important agronomic characters and the effect of this disequilibrium on the choice of generation for doubled haploid production is discussed.     

Influence of nutrition on male development and reproduction in Tribolium castaneum

Tribolium beetles have evolved over several thousand years to colonize and exploit various food products that vary widely in their nutritional quality. Here Tribolium castaneum was used as a model organism to explore the effect of nutritional quality on male development and reproduction. The results showed, when tested across different qualities of nutritional diets, Tribolium males developed faster and their body size was larger on a high-quality diet, and there were significant correlations between male developmental traits. However, Tribolium males fed different nutritional diets did not show significant variation in olfactory attractiveness, mating rate, insemination rate, sperm defense (P1), sperm offense (P2), and reproductive success within a population context (RSPC). Moreover, there was no significant correlation of male reproductive performances except RSPC with developmental traits, and except for P2 and RSPC, no significant correlations between male reproductive performances. Therefore, although male developmental performance was significantly influenced by diet quality, reproductive performance was not. We discussed these findings and their sexual selection implications in light of its habitat.     

Metamorphosis and adult development of the mushroom bodies of the red flour beetle, Tribolium castaneum

The insect mushroom bodies play important roles in a number of higher processing functions such as sensory integration, higher level olfactory processing, and spatial and associative learning and memory. These functions have been established through studies in a handful of tractable model systems, of which only the fruit fly Drosophila melanogaster has been readily amenable to genetic manipulations. The red flour beetle Tribolium castaneum has a sequenced genome and has been subject to the development of molecular tools for the ready manipulation of gene expression; however, little is known about the development and organization of the mushroom bodies of this insect. The present account bridges this gap by demonstrating that the organization of the Tribolium mushroom bodies is strikingly like that of the fruit fly, with the significant exception that the timeline of neurogenesis is shifted so that the last population of Kenyon cells is born entirely after adult eclosion. Tribolium Kenyon cells are generated by two large neuroblasts per hemisphere and segregate into an early-born delta lobe subpopulation followed by clear homologs of the Drosophila gamma, alpha'/beta' and alpha/beta lobe subpopulations, with the larval-born cohorts undergoing dendritic reorganization during metamorphosis. BrdU labeling and immunohistochemical staining also reveal that a proportion of individual Tribolium have variable numbers of mushroom body neuroblasts. If heritable, this variation represents a unique opportunity for further studies of the genetic control of brain region size through the control of neuroblast number and cell cycle dynamics.     

The Tribolium castaneum ortholog of Sex combs reduced controls dorsal ridge development

Several constitutional chromosomal rearrangements occur on human chromosome 17. Patients who carry constitutional deletions of 17q21.3-q24 exhibit distinct phenotypic features. Within the deletion interval, there is a genomic segment that is bounded by the myeloperoxidase and homeobox B1 genes. This genomic segment is syntenically conserved on mouse chromosome 11 and is bounded by the mouse homologs of the same genes (Mpo and HoxB1). To attain functional information about this syntenic segment in mice, we have generated a 6.9-Mb deletion [Df(11)18], the reciprocal duplication [Dp(11)18] between Mpo and Chad (the chondroadherin gene), and a 1.8-Mb deletion between Chad and HoxB1. Phenotypic analyses of the mutant mouse lines showed that the Dp(11)18/Dp(11)18 genotype was responsible for embryonic or adolescent lethality, whereas the Df(11)18/+ genotype was responsible for heart defects. The cardiovascular phenotype of the Df(11)18/+ fetuses was similar to those of patients who carried the deletions of 17q21.3-q24. Since heart defects were not detectable in Df(11)18/Dp(11)18 mice, the haplo-insufficiency of one or more genes located between Mpo and Chad may be responsible for the abnormal cardiovascular phenotype. Therefore, we have identified a new dosage-sensitive genomic region that may be critical for normal heart development in both mice and humans.     

Permethrin- and malathion-induced macromolecular abnormalities in adult Tribolium castaneum (herbst)

In Tribolium castaneum adults, sublethal doses of 1 and 2 ppm permethrin and 300 ppm malathion led to significant changes in amylase, trehalase, acid phosphatase, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and isocitrate dehydrogenase activities. Malathion at 150 ppm did not affect phosphatases and lactate dehydrogenase. Both malathion and permethrin significantly increased cholinesterase activity. Mixing of the two insecticides resulted in antagonistic action with reference to various enzymatic activities. Glucose and glycogen contents were at first mobilized for energy supply under insecticidal stress conditions followed by lipid and cholesterol. Soluble protein, total protein, free amino acids, and urea contents remained unaltered under all experimental conditions.     

The karyosphere capsule in Tribolium castaneum oocytes

The structure and composition of the karyosphere (karyosome) capsule of the laboratory insect, Tribolium castaneum, were studied with the use of electron and immunoelectron microscopy. Eight stages that characterized the period of oocyte growth have been established basing on the study of nuclear structure dynamics. At the diplotene stage, T. castaneum oocyte chromosomes are being united early to form a compact karyosphere; however, prominent chromatin condensation does not occur at the same time. The process of karyosphere formation is accompanied by the development of a spacious extrachromosomal capsule surrounding chromatin. The capsule consists of a fibrous material of different morphological types. The most prominent molecular components of T. castaneum karyosphere capsule are represented by the proteins of nuclear matrix, including F-actin and lamin B. Apart from the structural proteins, immunocytochemical approach allowed revealing Sm proteins of small nuclear (sn) RNPs and “mature” snRNAs with 2,2,7-trimetyl guanosine (TMG) cap at the 5’-end of their molecules. These data may serve as a base for further broadening of the conception about the functions of the karyosphere capsule as a specialized oocyte nuclear domain. We believe that T. castaneum karyosphere capsule plays not only a structural role, but may be involved directly in the processes related to gene expression.     

赤拟谷盗微卫星多态性的研究

为了研究赤拟谷盗种群的遗传结构,采用微卫星分子标记技术,对4个不同地理种群共120个个体的遗传多样性水平及种群遗传结构进行了研究.通过提取基因组DNA,用5对微卫星引物进行PCR扩增、电泳分析、凝胶成像系统分析,结果表明CB337218、DN648427、DN647734、EB754173、EB750288这5个位点的等位基因数分别为4、4、3、6和3, 4个不同地理种群赤拟谷盗的遗传杂合度平均值为0.4379,4个不同地理种群赤拟谷盗间的多态信息含量各在0.3771～0.5089之间,都达到中度多态性或高度多态性水平.为进一步研究赤拟谷盗的成灾机理提供了分子遗传学的基础.     

The spatiotemporal dynamics of Tribolium castaneum (Herbst): adult flight and gene flow

Tribolium castaneum (Herbst) has been used as a model organism to develop and test important ecological and evolutionary concepts and is also a major pest of grain and grain products globally. This beetle species is assumed to be a good colonizer of grain storages through anthropogenic movement of grain, and active dispersal by flight is considered unlikely. Studies using T. castaneum have therefore used confined or walking insects. We combine an ecological study of dispersal with an analysis of gene flow using microsatellites to investigate the spatiotemporal dynamics and adult flight of T. castaneum in an ecological landscape in eastern Australia. Flying beetles were caught in traps at grain storages and in fields at least 1 km from the nearest stored grain at regular intervals for an entire year. Significantly more beetles were trapped at storages than in fields, and almost no beetles were caught in native vegetation reserves many kilometres from the nearest stored grain. Genetic differentiation between beetles caught at storages and in fields was low, indicating that although T. castaneum is predominantly aggregated around grain storages, active dispersal takes place to the extent that significant gene flow occurs between them, mitigating founder effects and genetic drift. By combining ecological and molecular techniques, we reveal much higher levels of active dispersal through adult flight in T. castaneum than previously thought. We conclude that the implications of adult flight to previous and future studies on this model organism warrant consideration.     

Crinkled employs wingless pathway for wing development in Tribolium castaneum

Crinkled is associated with embryonic denticle formation and auditory organ development in Drosophila melanogaster. However, the functions of Crinkled have not been fully investigated. Additionally, the genes that participate in the Crinkled pathway are unknown. Phylogenetic analysis indicates that crinkled exhibits a one‐to‐one orthologous relationship in insects. In Tribolium castaneum, the crinkled gene is 6,498 bp in length and consists of six exons. Crinkled expression peaked during two phases in Tribolium: late embryonic and pupal stages. High levels of crinkled mRNA were detected in the fat body, head, epidermis, ovary, and accessory gland of late adults. Knockdown of crinkled using RNA interference (RNAi) severely affected wing morphogenesis in T. castaneum. We further showed that crinkled silencing reduced forked expression through wingless and shaven‐baby, and RNAi of forked phenocopied the effects of crinkled knockdown in T. castaneum. This study investigated the development role of crinkled in postembryonic stages and indicated that forked mediates the functions of crinkled during wing morphogenesis in T. castaneum.     

Chitin synthases are required for survival, fecundity and egg hatch in the red flour beetle, Tribolium castaneum

The synthesis of chitin, the beta-1,4-linked polymer of N-acetylglucosamine, is catalyzed by chitin synthase (CHS). Chitin is essential for the structural integrity of the exoskeletal cuticle and midgut peritrophic membrane (PM) of insects. To study the functions of the two chitin synthase genes, TcCHS-A and TcCHS-B, during embryonic and adult development in the red flour beetle, Tribolium castaneum, RNA interference (RNAi) experiments were carried out. When dsRNA for TcCHS-A was injected into male or female pharate adults, all insects died 5-7 d after the adult molt, and the females failed to oviposit prior to death. When dsTcCHS-A was injected into young adults 1-2 d post-eclosion, a similar lethal phenotype was obtained after 5 d and no oviposition occurred. When dsTcCHS-A injections were delayed until after adult maturation (7-10 d post-eclosion), the treated females did oviposit and the resulting embryos appeared to develop normally. However, the chitin content of the eggs was dramatically reduced, the embryos became twisted and enlarged, and the eggs did not hatch. Adults treated with dsRNA for TcCHS-B exhibited little or no chitin in their PM and died about 2 wk after injection. None of the TcCHS-B-treated females oviposited, which was probably a secondary effect caused by starvation. These results extend our previous findings that CHS genes are required for all types of molt. The present study also demonstrates that these genes have additional roles in embryonic and adult development.