No abstract

Understanding genetic variation among populations of medically significant pest insects is important in studying insecticide resistance and insect dispersal. The bed bug, Cimex lectularius L. (Hemiptera: Cimicidae), is widespread hematophagus insect pest around the world, including North America, and it has recently been identified as an emerging resurgent pest. To date, no studies have been conducted on genetic variation of this species. For this study, 136 adult bed bugs representing 22 sampled populations from nine U.S. states, Canada, and Australia were subjected to genetic analysis using polymerase chain reaction (PCR) to amplify and sequence a region of the mitochondrial DNA (mtDNA) 16S rRNA gene and a portion of the nuclear rRNA internal transcribed spacer (ITS) 1 region. For the 397-bp 16S marker, a 12 nucleotide sites in total were polymorphic, and 19 unique haplotypes were observed. Heterozygosity was observed within many of the sampled populations for the mtDNA marker. This suggests that bed bug populations did not undergo a genetic bottleneck as one would expect from insecticide control during the 1940s and 1950s, but instead, that populations may have been maintained on other hosts such as birds and bats. In contrast to the high amount of heterozygosity observed with the mitochondrial DNA marker, no genetic variation in the 589-bp nuclear rRNA marker was observed. This suggests increased gene flow of previously isolated bed bug populations in the United States, and given the absence of barriers to gene flow, the spread of insecticide resistance may be rapid.

Microclimatic and vegetative effects on the population size and activity patterns of larval Eutrombicula alfreddugesi Oudemans, 1910 (Acari: Trombiculidae), were investigated in Nebraska between latitude 40 degrees 0'0" N and 40 degrees 1'21" N. Larval population densities along a forest edge were greatest in areas of high relative humidity, moderate temperature, low incident sunlight, and increasing substrate vegetation. Although chigger populations existed throughout the forest edge, larger populations concentrated in short- to tall-grass transition zones. Chiggers were rarely found in the undergrowth beneath the tree canopy. Chigger activity correlated with a microclimatically driven diurnal rhythm. Activity was greatest during the late afternoon-early evening, between 1530 and 1930 hours (CDST). Larval activity dropped to low levels and remained so until sunrise; this period of reduced activity occurred between 1930 and 0530 hours. Small increases in larval activity occurred around sunrise (approximately 0600-0700 hours). Between about 0700 and 1530 hours, larval E. alfreddugesi were inactive and did not respond to normal sampling stimuli. Larval populations appeared in late April through early May, peaked in abundance in late June and early July, diminished through late summer, and disappeared in midautumn as the ground began to freeze.

No abstract

Long-lived animals, including social insects, often display seasonal shifts in foraging behavior. Foraging is ultimately a nutrient consumption exercise, but the effect of seasonality per se on changes in foraging behavior, particularly as it relates to nutrient regulation, is poorly understood. Here, we show that field-collected fire ant colonies, returned to the laboratory and maintained under identical photoperiod, temperature, and humidity regimes, and presented with experimental foods that had different protein (p) to carbohydrate (c) ratios, practice summer- and fall-specific foraging behaviors with respect to protein-carbohydrate regulation. Summer colonies increased the amount of food collected as the p:c ratio of their food became increasingly imbalanced, but fall colonies collected similar amounts of food regardless of the p:c ratio of their food. Choice experiments revealed that feeding was non-random, and that both fall and summer ants preferred carbohydrate-biased food. However, ants rarely ate all the food they collected, and their cached or discarded food always contained little carbohydrate relative to protein. From a nutrient regulation strategy, ants consumed most of the carbohydrate they collected, but regulated protein consumption to a similar level, regardless of season. We suggest that varied seasonal food collection behaviors and nutrient regulation strategies may be an adaptation that allows long-lived animals to meet current and future nutrient demands when nutrient-rich foods are abundant (e.g. spring and summer), and to conserve energy and be metabolically more efficient when nutritionally balanced foods are less abundant.

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

This study describes the expression of the Zymomonas mobilis genes coding for pyruvate decarboxylase (pdc) and alcohol dehydrogenase (adh) in Lactobacillus casei 686. To promote transcription, the promoter and ribosome binding site (RBS) from the Lactococcus lactis subsp. lactis-derived vector, pMGE36e, were inserted upstream of the pdc gene. The former sequences were positioned such that translation of pdc was coupled to translation of an 81-base pair open reading frame terminating within the pdc initiation site. The recombinant plasmid (pRSG02) was electroporated into L. casei, and transformants were obtained. Northern analysis confirmed the production of a 3. 1-kb transcript corresponding to the predicted size of the PET operon. Western blot analyses revealed that the recombinant strain expressed both enzymes. The recombinant produced more than twice the ethanol produced by the parental L. casei strain.

The tawny crazy ant (Nylanderia fulva) is a new invasive pest in the United States. At present, its management mainly relies on the use of synthetic insecticides, which are generally ineffective at producing lasting control of the pest, necessitating alternative environmentally friendly measures. In this study, we evaluated the feasibility of gene silencing to control this ant species. Six housekeeping genes encoding actin (NfActin), coatomer subunit β (NfCOPβ), arginine kinase (NfArgK), and V-type proton ATPase subunits A (NfvATPaseA), B (NfvATPaseB) and E (NfvATPaseE) were cloned. Phylogenetic analysis revealed high sequence similarity to homologs from other ant species, particularly the Florida carpenter ant (Camponotus floridanus). To silence these genes, vector L4440 was used to generate six specific RNAi constructs for bacterial expression. Heat-inactivated, dsRNA-expressing Escherichia coli were incorporated into artificial diet. Worker ants exhibited reduced endogenous gene expression after feeding on such diet for 9 d. However, only ingestion of dsRNAs of NfCOPβ (a gene involved in protein trafficking) and NfArgK (a cellular energy reserve regulatory gene in invertebrates) caused modest but significantly higher ant mortality than the control. These results suggest that bacterially expressed dsRNA can be orally delivered to ant cells as a mean to target its vulnerabilities. Improved efficacy is necessary for the RNAi-based approach to be useful in tawny crazy ant management.