ALBERT

Description: ▪ Abstract  The diversity of the Insecta is reflected in the large and varied microbial communities inhabiting the gut. Studies, particularly with termites and cockroaches, have focused on the nutritional contributions of gut bacteria in insects living on suboptimal diets. The indigenous gut bacteria, however, also play a role in withstanding the colonization of the gut by non-indigenous species including pathogens. Gut bacterial consortia adapt by the transfer of plasmids and transconjugation between bacterial strains, and some insect species provide ideal conditions for bacterial conjugation, which suggests that the gut is a “hot spot” for gene transfer. Genomic analysis provides new avenues for the study of the gut microbial community and will reveal the molecular foundations of the relationships between the insect and its microbiome. In this review the intestinal bacteria is discussed in the context of developing our understanding of symbiotic relationships, of multitrophic interactions between insects and plant or animal host, and in developing new strategies for controlling insect pests.

Description: ▪ Abstract  The concept that an insect species' genome could be altered in a manner that would result in the control of that species (i.e., autocidal control) or in the replacement of a pestiferous strain of the species with a more benign genotype was first proposed in the mid-twentieth century. A major research effort in population genetics and ecology followed and led to the development of a set of classical genetic control approaches that included use of sterile males, conditional lethal genes, translocations, compound chromosomes, and microbe-mediated infertility. Although there have been a number of major successes in application of classical genetic control, research in this area has declined in the past 20 years for technical and societal reasons. Recent advances in molecular biology and transgenesis research have renewed interest in genetically based control methods because these advances may remove some major technical problems that have constrained effective genetic manipulation of pest species. Population genetic analyses suggest that transgenic manipulations may enable development of strains that would be 10 to over 100 times more efficient than strains developed by classical methods. Some of the proposed molecular approaches to genetic control involve modifications of classical approaches such as conditional lethality, whereas others are novel. Experience from the classical era of genetic control research indicates that the population structure and population dynamics of the target population will determine which, if any, genetic control approaches would be appropriate for addressing a specific problem. As such, there continues to be a need for ongoing communication between scientists who are developing strains and those who study the native pest populations.

Description: ▪ Abstract  Polydnavirus genome sequencing is providing new insights into viral genome organization and viral gene function. Sequence analyses demonstrate that the genomes of these viral mutualists are largely noncoding but maintain genes and gene families that are unrelated to other viral genes. Interestingly, these organizational patterns in polydnavirus genomes are evident in both the bracovirus and ichnovirus genera, even though these two genera are evolutionarily unrelated. The identity and function of some polydnavirus gene families are considered with some functions experimentally supported and others implied by homology relationships with known insect genes. The evidence relative to polydnavirus origins and evolution is considered but remains an area of speculation. However, sequencing of these viral genomes has been informative and provides opportunities for productive investigation of these unusual mutualistic insect viruses.

Description: With the advent of significant collaborations between researchers who study insect walking and robotics engineers interested in constructing adaptive legged robots, insect walking is once again poised to make a more significant scientific contribution than the numbers of participants in the field might suggest. This review outlines current knowledge of the physiological basis of insect walking with an emphasis on recent new developments in biomechanics and genetic dissection of behavior, and the impact this knowledge is having on robotics. Engineers have begun to team with neurobiologists to build walking robots whose physical design and functional control are based on insect biology. Such an approach may have benefits for engineering, by leading to the construction of better-performing robots, and for biology, by allowing real-time and real-world tests of critical hypotheses about how locomotor control is effected. It is argued that in order for the new field of biorobotics to have significant influence it must adopt criteria for performance and an experimental approach to the development of walking robots.

Description: ▪ Abstract  The melon fly, Bactrocera cucurbitae, is a destructive insect of cucurbit and other fruits. It invaded the Southwestern Islands of Japan from 1919 to 1974. The sterile insect technique (SIT) was successfully applied from 1972 to 1993 to eradicate the melon fly. Technical research into SIT functions, such as suppression of density, mass-rearing, sterilization, shipment, release, evaluation of efficacy, and quality control of mass-reared insects, was conducted for this eradication project. Fundamental research into the dispersion, mating and oviposition behavior, population dynamics and estimation of density, eradication models, spatial distribution, genetics, and evolution of the melon fly was also undertaken and supported the success of the eradication project.

Description: ▪ Abstract  Neuropeptides regulate all important physiological, developmental, and behavioral processes in insects. Here, I review two major physiological events that are hormonally controlled, namely intermediary metabolism and ion and water transport. Peptides belonging to the family of adipokinetic hormones (AKHs) increase hemolymph carbohydrates, lipids, and proline by activating the enzyme glycogen phosphorylase or lipase in the fat body. Moreover, these pleiotropic and multifunctional peptides inhibit protein-, lipid-, and RNA synthesis, and stimulate the frequency of contraction of certain muscles. Diuretic hormones that are related to the vertebrate corticotropin-releasing factor (CRF-related DHs) or belong to the family of kinins (which also have a myotropic action) or the cardioacceleratory peptides (CAPs), which increase the frequency of the heartbeat, all stimulate the secretion of fluid in Malpighian tubules (MTs) in vitro. Only a few true antidiuretic hormones are known: those from mealworms that inhibit the fluid transport in MTs in vitro, probably neuroparsins that stimulate water absorption by everted rectal sacs in vitro, and the desert locust's ion-transport peptide (ITP). Biosynthesis, release, receptors, mode of action, inactivation, structure-activity studies, and biological functions are discussed for the various peptides.

Description: ▪ Abstract  Current research on human louse biology has focused on the long-standing debate about speciation of head and body lice but using new tools of DNA and enzyme analysis. These studies have indicated that head and body lice from the same geographical zone may be more closely allied than insects inhabiting the same ecological niche in other regions. However, the majority of research over the past decade has involved clinical aspects including transmission, treatment, and the appearance and identification of resistant strains within populations of lice. Despite advances, there is a need for a better understanding of louse biology, as existing therapies fail and lice remain potential vectors of disease for millons of people.

Description: ▪ Abstract  Wasp parasitoids use a variety of methods to commandeer their insect hosts in order to create an environment that will support and promote their own development, usually to the detriment of the host insect. Parasitized insects typically undergo developmental arrest and die sometime after the parasitoid has become independent of its host. Parasitoids can deactivate their host's immune system and effect changes in host hormone titers and behavior. Often, host tissues or organs become refractory to stimulation by tropic hormones. Here we present an overview of the manipulative capabilities of wasp-injected calyx fluid containing polydnaviruses and venom, as well as the parasitoid larva and the teratocytes that originate from the serosal membrane that surrounds the developing embryo of the parasitoid. Possibilities for using regulatory molecules produced by the parasitoid or its products that would be potentially useful in developing new, environmentally safe insect control agents are discussed.

Description: ▪ Abstract  Venezuelan equine encephalitis virus (VEEV) remains a naturally emerging disease threat as well as a highly developed biological weapon. Recently, progress has been made in understanding the complex ecological and viral genetic mechanisms that coincide in time and space to generate outbreaks. Enzootic, equine avirulent, serotype ID VEEV strains appear to alter their serotype to IAB or IC, and their vertebrate and mosquito host range, to mediate repeated VEE emergence via mutations in the E2 envelope glycoprotein that represent convergent evolution. Adaptation to equines results in highly efficient amplification, which results in human disease. Although epizootic VEEV strains are opportunistic in their use of mosquito vectors, the most widespread outbreaks appear to involve specific adaptation to Ochlerotatus taeniorhynchus, the most common vector in many coastal areas. In contrast, enzootic VEEV strains are highly specialized and appear to utilize vectors exclusively in the Spissipes section of the Culex (Melanoconion) subgenus.

Description: ▪ Abstract  One key advantage of eusociality is shared defense of the nest, brood, and stored food; nest defense plays an important role in the biology of eusocial bees. Recent studies on honey bees, Apis mellifera, have focused on the placement of defensive activity in the overall scheme of division of labor, showing that guard bees play a unique and important role in colony defense. Alarm pheromones function in integrating defensive responses; honey bee alarm pheromone is an excellent example of a multicomponent pheromonal blend. The genetic regulation of defensive behavior is now better understood from the mapping of quantitative trait loci (QTLs) associated with variation in defensiveness. Colony defense in other eusocial bees is less well understood, but enough information is available to provide interesting comparisons between A. mellifera and other species of Apis, as well as with allodapine, halictine, bombine, and meliponine bees. These comparative studies illustrate the wide variety of evolutionary solutions to problems in colony defense in the Apoidea.