Eric Schoeters

Chemistry of metapleural gland secretions of three attine ants,Atta sexdens rubropilosa, Atta cephalotes, andAcromyrmex octospinosus (Hymenoptera: Formicidae).

The chemical composition of the secretions of the metapleural glands of workers and soldiers of twoAtta species,Atta sexdens rubropilosa andA. cephalotes, and workers ofAcromyrmex octospinosus, has been studied. As indicated by infrared spectrometry and confirmed by the ninhydrin test, the secretions contain chiefly proteins. Of the volatile acidic portion, which is present as ionized salts, phenylacetic acid is the major component in workers and soldiers ofA. s. rubropilosa andA. cephalotes. BothAtta species also contain 3-hydroxydecanoic acid and its homolog as minor components together with indoleacetic acid. While there are qualitative similarities in the acidic composition in the secretions ofA. s. rubropilosa andA. cephalotes, they differ quantitatively. The secretion ofAcromyrmex octospinosus contains 3-hydroxydecanoic and indoleacetic acids, but lacks phenylacetic acid. The bactericidal and fungicidal actions of the three major substances have been confirmed.

Effective Symbiosis between Rhizobium etli and Phaseolus vulgaris Requires the Alarmone ppGpp

The symbiotic interaction between Rhizobium etli and Phaseolus vulgaris, the common bean plant, ultimately results in the formation of nitrogen-fixing nodules. Many aspects of the intermediate and late stages of this interaction are still poorly understood. The R. etli relA gene was identified through a genome-wide screening for R. etli symbiotic mutants. RelA has a pivotal role in cellular physiology, as it catalyzes the synthesis of (p)ppGpp, which mediates the stringent response in bacteria. The synthesis of ppGpp was abolished in an R. etli relA mutant strain under conditions of amino acid starvation. Plants nodulated by an R. etli relA mutant had a strongly reduced nitrogen fixation activity (75% reduction). Also, at the microscopic level, bacteroid morphology was altered, with the size of relA mutant bacteroids being increased compared to that of wild-type bacteroids. The expression of the sigma(N)-dependent nitrogen fixation genes rpoN2 and iscN was considerably reduced in the relA mutant. In addition, the expression of the relA gene was negatively regulated by RpoN2, the symbiosis-specific sigma(N) copy of R. etli. Therefore, an autoregulatory loop controlling the expression of relA and rpoN2 seems operative in bacteroids. The production of long- and short-chain acyl-homoserine-lactones by the cinIR and raiIR systems was decreased in an R. etli relA mutant. Our results suggest that relA may play an important role in the regulation of gene expression in R. etli bacteroids and in the adaptation of bacteroid physiology.

Expression of a novel neuropeptide, NVGTLARDFQLPIPNamide, in the larval and adult brain of Drosophila melanogaster.

Advances in mass spectrometry and the availability of genomic databases made it possible to determine the peptidome or peptide content of a specific tissue. Peptidomics by nanoflow capillary liquid chromatography tandem mass spectrometry of an extract of 50 larval Drosophila brains, yielded 28 neuropeptides. Eight were entirely novel and encoded by five not yet annotated genes; only two genes had a homologue in the Anopheles gambiae genome. Seven of the eight peptides did not show relevant sequence homology to any known peptide. Therefore, no evidence towards the physiological role of these ‘orphan’ peptides was available. We identified one of the eight peptides, IPNamide, in an extract of the Drosophila adult brain as well. Next, specific antisera were raised to reveal the distribution pattern of IPNamide and other peptides from the same precursor, in larval and adult brains by means of whole‐mount immunocytochemistry and confocal microscopy. IPNamide immunoreactivity is abundantly present in both stages and a striking similarity was found between the distribution patterns of IPNamide and TPAEDFMRFamide, a member of the FMRFamide peptide family. Based on this distribution pattern, IPNamide might be involved in phototransduction, in processing sensory stimuli, as well as in controlling the activity of the oesophagus.

Variation with caste of the mandibular gland secretion in the leaf-cutting antAtta sexdens rubropilosa.

InAtta sexdens rubropilosa, a strongly polyethic and polymorphic species of myrmicine ant, the contents of the mandibular gland vary with caste. Small workers of head width 0.5–1.8 mm, those generally engaged in duties inside the nest, contain chiefly 4-methyl-3-heptanone. Larger workers, those chiefly engaged in foraging, and the soldier caste contain a mixture dominated by neral and geranial, with very little of the ketone of the smaller workers. The soldiers have massive glands containing milligram amounts of neral and geranial. Virgin and mated females contain essentially only 4-methyl-3-heptanone, the amount increasing after mating, while virgin males have 4-methyl-3-heptanone and 4-methyl-3-heptanol in approximately equal proportions. Mated males have less secretion and lose the 4-methyl-3-heptanol.

The importance of the spermathecal duct in bumblebees.

The elongated spermathecal duct of bumblebees has been studied in hibernating queens, queens shortly after hibernation, mature egg-laying queens and uninseminated queens captured during summer, and workers. Only rather small size differences are found when comparing spermathecae of queens and workers. Clear differences between bumblebee queens and workers are found when comparing the histochemistry of the spermathecal ducts. Adult queens, regardless of age and reproductive status have spermathecal ducts that contain PAS positive material, whereas workers do not. It is suggested that the polysaccharides in the spermathecal ducts of queens are necessary as a source of energy for the rapid activation of spermatozoa passing through the duct prior to oocyte fertilization. An ultrastructural investigation revealed the presence of high glycogen content in the cells lining the duct of queens. Assuming that sperm cells are kept in a rather inactive state in the reservoir, the carbohydrate (glycogen) probably serves as an energy source for the sperm. The comparatively increased spermathecal duct length of bumblebees may increase the retention time of sperm inside the lumen.

The intramandibular gland, a novel exocrine structure in ants (Insecta, Hymenoptera)

SummaryA novel glandular structure is described within the mandibles of a series of representatives of the Formicidae. It consists of a variable number of secretory cells with their accompanying duct cells, located in the vicinity of the mandibular cuticle. Because of its localization inside the mandibles, we propose to designate this structure as the intramandibular gland of ants. Ultrastructural observations reveal the development of smooth endoplasmic reticulum in the glandular cells. Several electron-lucid and electron-dense inclusions occur in the cytoplasm. Until now, the function of this widespread gland among the Formicidae remains unknown.

Morphology and ultrastructure of a secretory region enclosed by the venom reservoir in social wasps (Insecta, Hymenoptera)

The morphology and ultrastructure of the convoluted gland inside the venom reservoir of four species of social Vespidae are described. The cells of the venom gland (including the convoluted gland) can be divided into six groups: (1) epithelial cells, (2) glandular cells with the end apparatus secreting into the tubule inside the convoluted gland (internal or embedded tubule), (3) a continuous arrangement of glandular cells with the end apparatus secreting directly into the venom reservoir, (4) glandular cells that are loosely dispersed along the tubule lumen between the free tubules and the embedded tubule of the convoluted gland, (5) secretory cells of the free tubules and (6) duct cells. One kind of secretory cell, hitherto unknown and described in this paper (group 3), is characterized by the presence of a well-developed end apparatus, usually with enlarged extracellular spaces, but lacking the normally associated duct cells. The secretory cells contain several stacks of granular endoplasmic reticulum, but these are mainly concentrated in the middle of the cell. The basal half of the cells contains many lipid droplets. Although the function of the convoluted gland is not yet understood, an hypothesis is related to what is known of the function of reservoir secretory cells in solitary wasps. All wasp species studied showed the same organization of the convoluted gland, which clearly distinguishes their venom gland from that of Sphecidae.

Volatile secretions of old world army ant Aenictus rotundatus and chemotaxonomic implications of army ant dufour gland chemistry

The Dufour glands ofAenictus rotundatus contain a complex mixture of terpenoids with geranylgeraniol comprising over 50% of the secretion. Some novel compounds have been tentatively identified as higher homologs of 1,3,3-trimethyl-2,7-dioxabicyclo[2,2,1]heptane based on GC-MS data. The Dufour gland secretion ofA. rotundatus is more similar in composition to the secretions of members of the subfamily Ecitoninae than to its closer relatives from the tribe Dorylini, a result that further complicates studies on the phylogeny of army ants. The mandibular glands ofA. rotundatus contain a mixture of 4-methyl-3-heptanone and limonene in trace amounts, and the well-developed postpygidial glands contain methyl anthranilate only.

Nuclear omentation measurements on 183Re and 184Re

Abstract 183 Re and 184g, 184m Re nuclei embedded in an iron matrix were oriented at low temperatures. From the temperature dependence of the 0°–90° anisotropies of several γ-rays the magnetic hyperfine interaction in the 183, 184 Re ground states and the 184m Re isomeric state as well as mixing ratios of transitions in the 183, 184 W daughter nuclei were determined. The results for the magnetic moments [μ( 183 Re ) = 3.03±0.11 n.m. , μ( 184 Re ) = 2.53±0.09 n.m. ,μ( 184m Re ) = 2.86±0.13 n.m. ] and the mixing ratios are discussed within the framework of the rotational model.

DISTRIBUTION AND COMPARATIVE MORPHOLOGY OF THE CLOACAL GLAND IN ANTS (HYMENOPTERA: FORMICIDAE)

Abstract The cloacal gland is a paired exocrine structure, which has so far been described only in the formicine species, Camponotus ephippium and Cataglyphis savignyi (Hymenoptera : Formicidae). The gland is formed by 2 clusters of bicellular units with slender duct cells, releasing the glandular secretion through the cloacal membrane. In the present work, a number of ant species, largely of the Formicinae subfamily, have been surveyed for the presence of a cloacal gland. The gland is present in nearly all formicines screened, albeit with a variable development. Cataglyphis , one of the genera with a very prominent cloacal gland, was chosen for a more detailed comparative study. At the ultrastructural level, secretory cells were observed having a well-developed smooth endoplasmic reticulum and Golgi apparatus, typical for pheromone-producing glandular cells. The gland is also present in all dolichoderines screened, but in none of the species of the Aneuretinae, Myrmeciinae, Myrmicinae, Nothomyrmeciinae, or Pseudomyrmecinae investigated. This provides tentative evidence that the cloacal gland is a synapomorphy of the Formicinae and Dolichoderinae, giving support for their hypothesized sister group relationship. Up to now, the function of the cloacal gland remains largely enigmatic.