Ants dominate many terrestrial ecosystems, yet we know little about their nutritional physiology and ecology. While traditionally viewed as predators and scavengers, recent isotopic studies revealed that many dominant ant species are functional herbivores. As with other insects with nitrogen-poor diets, it is hypothesized that these ants rely on symbiotic bacteria for nutritional supplementation. In this study, we used cloning and 16S sequencing to further characterize the bacterial flora of several herbivorous ants, while also examining the beta diversity of bacterial communities within and between ant species from different trophic levels. Through estimating phylogenetic overlap between these communities, we tested the hypothesis that ecologically or phylogenetically similar groups of ants harbor similar microbial flora. Our findings reveal: (i) clear differences in bacterial communities harbored by predatory and herbivorous ants; (ii) notable similarities among communities from distantly related herbivorous ants and (iii) similar communities shared by different predatory army ant species. Focusing on one herbivorous ant tribe, the Cephalotini, we detected five major bacterial taxa that likely represent the core microbiota. Metabolic functions of bacterial relatives suggest that these microbes may play roles in fixing, recycling, or upgrading nitrogen. Overall, our findings reveal that similar microbial communities are harbored by ants from similar trophic niches and, to a greater extent, by related ants from the same colonies, species, genera, and tribes. These trends hint at coevolved histories between ants and microbes, suggesting new possibilities for roles of bacteria in the evolution of both herbivores and carnivores from the ant family Formicidae.

Female honeybees have two castes, queens and workers. Developmental fate is determined by larval diet. Coding sequences made available through the Honey Bee Genome Sequencing Consortium allow for a pathway-based approach to understanding caste determination. We examined the expression of several genes of the insulin signalling pathway, which is central to regulation of growth based on nutrition. We found one insulin-like peptide expressed at very high levels in queen but not worker larvae. Also, the gene for an insulin receptor was expressed at higher levels in queen larvae during the 2nd larval instar. These results demonstrate that the insulin pathway is a compelling candidate for pursing the relationship between diet and downstream signals involved in caste determination and differentiation.

No abstract

No abstract

Fourth-instar larvae of the autogenous mosquito, Aedes atropalpus, synthesize three hexamerins or hexameric storage proteins which are distinguished by different methionine and aromatic amino-acid contents. One protein, Hexamerin-1.2 (AatHex-1.2) is only found in female larvae and pupae. In order to investigate the molecular basis for this sex-specific accumulation, we have cloned and sequenced the cDNA encoding AatHex-1.2 and isolated and sequenced over 1 kb of the 5 0 flanking region of the AatHex-1.2 gene. The AatHex-1.2 transcript encodes a 81.6-kDa hexamerin subunit which contains 19.8% phenylalanine, tyrosine and tryptophan and 8.6% methionine residues. The single-copy AatHex-1.2 gene consists of three exons and two small introns located at its 5 0 end. A 2.3-kb AatHex-1.2 mRNA accumulates only in female larvae and pupae and is expressed at very low levels in adult female mosquitoes. The temporal expression profile of this transcript is typical of other mosquito hexamerin genes, with rapid disappearance of the mRNA shortly after pupation. Hence this is the first observation of exclusively female-specific gene activity during preadult development of an insect. In the 5 0 flanking region of the AatHex-1.2 gene, we identified putative binding sites for transcription factors, such as GATA, C/EBP and Doublesex, typically involved in fat body-and femalespecific gene activity in Diptera. These findings suggest that mechanisms for sex-specific transcription in the fat body may be well conserved between flies and mosquitoes.Keywords: mosquito; Aedes atropalpus; autogeny; hexamerin; sex-specific gene expression.In holometabolous insects, which have a nonfeeding, pupal stage, the accumulation of nutrient reserves, such as lipids, glycogen and protein, during the larval period can play an important role in the reproductive capacity of the adult (reviewed in [1 -3]). These reserves may be important in hematophagous insects which are autogenous, having the ability to produce at least a few eggs in the absence of a blood meal. The most abundant protein reserves carried over from the larval stage into the pupal period are the hexamerins or hexameric storage proteins. Hexamerins are typically synthesized in the larval fat body, secreted into the hemolymph and then taken up and stored by the fat body [4][5][6]. Storage of hexamerin is believed to provide a reserve of amino acids for use in protein synthesis and energy metabolism during nonfeeding stages such as metamorphosis and diapause (reviewed in [5,6]). Constitutive and/or inducible synthesis of hexamerins in adult insects from a number of orders [7 -13] also suggests that hexamerin use may be related to reproductive capacity.Hexamerins belong to a large arthropod protein family which includes hemocyanins, prophenoloxidases and dipteran hexamerin receptors [14]; reviewed in [15]. Like hemocyanins, hexamerins are proteins of < 500 kDa (native molecular mass) with subunits of 70 -80 kDa. According to their biochemical properties, hexamerin subunits can be categorized in...