A black-and-red stick insect from the Philippines – observations on the external anatomy and natural history of a new species of Orthomeria

A new stick insect of the genus Orthomeria Kirby, 1904 (Phasmatodea, Aschiphasmatidae) is described from the Philippines. Orthomeria (Orthomeria) kangi sp. n. is readily distinguished from all other congeners by the distinctive blood red colouration of the costal region of the hind wings. Major features of the external morphology of adults, eggs, and first-instar nymphs are illustrated. Locomotory attachment pads are of the smooth type with irregular microgrooves on the contact surface. An unusual condition of male terminalia is the absence of tergal thorn pads on segment 10. The male clasping organs are represented by an elongated vomer terminating in a prominent spine, and by incurved cerci featuring a bilobed apex equipped with a sharp blade-like ridge. Intraspecific variation in body colouration and hind wing length occurs in females. The new species lives at 400-650 m elevation in the surroundings of the Sablang and Tuba regions, in the Benguet Province of Luzon island. Host plants include Ficus spp. (Moraceae), and Pipturus spp. and Leucosyke spp. (Urticaceae). Observations on the mating and defensive behaviour are presented. Orthomeria (Orthomeria) catadromus (Westwood, 1859) is recognised as a junior synonym of Orthomeria (Orthomeria) pandora (Westwood, 1859), syn. n. A lectotype is designated for both species. Finally, an updated identification key to the species of the subgenus Orthomeria is provided.     

Cutting the forest to see a single tree?

The development of single-molecule tools has significantly impacted the way we think about biochemical processes. Watching a single protein in action allows us to observe kinetic details and rare subpopulations that are hidden in ensemble-averaging techniques. I will discuss here the pros and cons of the single-molecule approach in studying ligand binding in macromolecular systems and how these techniques can be applied to characterize the behavior of large multicomponent biochemical systems.     

Development of pigment-dispersing hormone-immunoreactive neurons in the American lobster: homology to the insect circadian pacemaker system?

We have examined the development of pigment-dispersing hormone (PDH)-immunoreactive neurons in embryos of the American lobster Homarus americanus Milne Edwards, 1837 (Decapoda, Reptantia, Homarida) by using an antiserum against β-PDH. This peptide is detectable in the terminal medulla of the eyestalks and the protocerebrum where PDH immunoreactivity is present as early as 20% of embryonic development. During ontogenesis, an elaborate system of PDH-immunoreactive neurons and fibres develops in the eyestalks and the protocerebrum, whereas less labelling is present in the deuto- and tritocerebrum and the ventral nerve cord. The sinus gland is innervated by PDH neurites at hatching. This pattern of PDH immunoreactivity has been compared with that found in various insect species. Neurons immunoreactive to pigment-dispersing factor in the medulla have been shown to be a central component of the system that generates the circadian rhythm in insects. Our results indicate that, in view of the position of the neuronal somata and projection patterns of their neurites, the immunolabelled medulla neurons in insects have homologous counterparts in the crustacean eyestalk. Since locomotory and other activities in crustaceans follow distinct circadian rhythms comparable with those observed in insects, we suggest that PDH-immunoreactive medulla neurons in crustaceans are involved in the generation of these rhythms. This study was supported by Deutsche Forschungsgemeinschaft (DFG) grant Ha 2540 and National Science Foundation grant IBN 0344448. S.H. was a Heisenberg Fellow of the DFG during the experimental part of this study. Bill Hansson and the Max Planck Society provided support during the final period of work reported in this paper.     

Self-incompatibility in a distylous species of Rubiaceae: is there a single incompatibility response of the morphs?

Heterostyly is a genetically controlled floral polymorphism usually associated with an incompatibility system. This set of features is known to occur in several angiosperm families, but some aspects of its biology has not been well studied. The present study investigates cellular aspects of the pollen–pistil interaction after compatible and incompatible pollinations of Psychotria nuda, to increase our knowledge of heteromorphic self-incompatibility (HetSI). The use of bright field, fluorescence and transmission electron microscopy methods allowed us to demonstrate that pollen tubes behave differently after incompatible and compatible pollinations. Pollen tubes were particularly distinct after incompatible pollinations of L- and S-morph flowers. Relative to compatible pollen tubes, incompatible L-morph tubes had a drastic reduction in cellular contents, but no cell rupture. Incompatible S-morph tubes exhibited dense cytoplasm in apical regions, as well as in other regions, accompanied by a rupture of the apex. These results support the hypothesis that L- and S-morph flowers have different incompatibility mechanisms during HetSI.     

Brief communication: Is variation in the cranial capacity of the Dmanisi sample too high to be from a single species?

This study uses data resampling to test the null hypothesis that the degree of variation in the cranial capacity of the Dmanisi hominid sample is within the range variation of a single species. The statistical significance of the variation in the Dmanisi sample is examined using simulated distributions based on comparative samples of modern humans, chimpanzees, and gorillas. Results show that it is unlikely to find the maximum difference observed in the Dmanisi sample in distributions of female-female pairs from comparative single-species samples. Given that two sexes are represented, the difference in the Dmanisi sample is not enough to reject the null hypothesis of a single species. Results of this study suggest no compelling reason to invoke multiple taxa to explain variation in the cranial capacity of the Dmanisi hominids.     

Determination of the 13C chemical-shift tensors in a single crystal of methyl α-d-glucopyranoside.

The chemical shielding tensors and their direction cosines of the ¹³C nuclei in a single crystal of methyl α-d-glucopyranoside were determined by the high-resolution solid state n.m.r. technique. The results were used to assign the ¹³C cross-polarization, magic angle spinning (c.p.-m.a.s.) spectrum of a polycrystalline sample of that compound. The differences between the ¹³C chemical shifts observed in the c.p.-m.a.s. spectrum of the solid and of solutions of methyl α-d-glucopyranoside are discussed in terms of the different types of hydrogen bonds formed in the crystalline state and in solution.     

Erosion of insect diversity in response to 7000 years of relative sea-level rise on a small Mediterranean island

We have investigated the potential effects of global sea-level rise on Mediterranean coastal wetlands by studying the Coleoptera and pollen fossil remains in a 7000-year sedimentary record, which we obtained from a coastal marshy area on a small Mediterranean island (Cavallo, southern Corsica). Using beetle structural diversity and plant composition as recorded prior to marine and human influences as a ‘past analogue’, we reconstructed the impact of the Holocene relative sea-level rise on the coastal ecosystem. Our results show that beetle species richness and diversity were highest when freshwater was predominant, which was the case until about 6200 years ago. We also found that a major increase in salinity had occurred over the last 5300 years, experiencing a peak rate of increase at about 3700 years ago. These changes are clearly reflected in the fossil records of the following key taxa: halophilous beetles (Ochthebius sp., Pterostichus cursor), halophilous plants (Chenopodiaceae, Tamarix) and non-pollen palynomorphs (microforaminiferal linings). In particular, we note that the majority (60%) of wetland beetle fauna became locally extinct in response to the salinity changes, and these changes were exacerbated by the recent aggravation of human pressures on the island. The major part of this diversity loss occurred 3700 years ago, when the relative Mediterranean sea-level rose above ?1.5 ± 0.3 meters. These findings demonstrate the value of fossil beetle assemblage analysis as a diagnostic for the response of coastal wetland biodiversity to past salinity increases, and serve as a means of forecasting the effects of sea-level rise in the future. The conservation of inland freshwater bodies could ultimately prove essential to preserving freshwater insect diversity in threatened coastal environments.     

Reversal of the ΔdegP phenotypes by a novel rpoE allele of Escherichia coli

RseA sequesters RpoE (σ(E)) to the inner membrane of Escherichia coli when envelope stress is low. Elevated envelope stress triggers RseA cleavage by the sequential action of two membrane proteases, DegS and RseP, releasing σ(E) to activate an envelope stress reducing pathway. Revertants of a ΔdegP ΔbamB strain, which fails to grow at 37°C due to high envelope stress, harbored mutations in the rseA and rpoE genes. Null and missense rseA mutations constitutively hyper-activated the σ(E) regulon and significantly reduced the major outer membrane protein (OMP) levels. In contrast, a novel rpoE allele, rpoE3, resulting from the partial duplication of the rpoE gene, increased σ(E) levels greater than that seen in the rseA mutant background but did not reduce OMP levels. A σ(E)-dependent RybB::LacZ construct showed only a weak activation of the σ(E) pathway by rpoE3. Despite this, rpoE3 fully reversed the growth and envelope vesiculation phenotypes of ΔdegP. Interestingly, rpoE3 also brought down the modestly activated Cpx envelope stress pathway in the ΔdegP strain to the wild type level, showing the complementary nature of the σ(E) and Cpx pathways. Through employing a labile mutant periplasmic protein, AcrA(L222Q), it was determined that the rpoE3 mutation overcomes the ΔdegP phenotypes, in part, by activating a σ(E)-dependent proteolytic pathway. Our data suggest that a reduction in the OMP levels is not intrinsic to the σ(E)-mediated mechanism of lowering envelope stress. They also suggest that under extreme envelope stress, a tight homeostasis loop between RseA and σ(E) may partly be responsible for cell death, and this loop can be broken by mutations that either lower RseA activity or increase σ(E) levels.     

Investigating the effect of a single glycine to alanine substitution on interactions of antimicrobial peptide latarcin 2a with a lipid membrane

Latarcins are linear, α-helical antimicrobial peptides purified from the venom of the Central Asian spider Lachesana tarabaevi, with lytic activity against Gram-positive and Gram-negative bacteria, erythrocytes, and yeast at micromolar concentrations. In this work, we investigated the role of the hinge in latarcin 2a (ltc2a, GLFGKLIKKFGRKAISYAVKKARGKH-COOH), which adopts a helix–hinge–helix conformation in membrane-mimicking environments, on peptide–membrane interactions and its potential effect on the selective toxicity of the peptide. A modified latarcin 2a, ltc2aG11A, obtained by replacing the glycine at position 11 with alanine (ltc2aG11A, GLFGKLIKKFARKAISYAVKKARGKH-COOH), adopts a more rigid structure due to the reduced conformational flexibility. Langmuir monolayer measurements combined with atomic force microscopy and X-ray photoemission electron microscopy (X-PEEM) indicate that both peptides bind and insert preferentially into anionic compared with zwitterionic phospholipid monolayers. Modified ltc2aG11A was found to be more disruptive of supported phospholipid bilayer modeling mammalian cell membrane. However, no considerable difference in lytic activity of the two peptides toward bacterial membrane was found. Overall the data indicate that decrease in the flexibility of ltc2a induced by the modification in the hinge region is likely to increase the peptide’s nonspecific interactions with zwitterionic cell membranes and potentially increase its toxicity against eukaryotic cells.     

Morphology and ultrastructure of the germarium in panoistic ovarioles of a basal “apterygotous” insect,Thermobia domestica

It has been shown that in Drosophila the germline stem cells (GSCs), similar to the germline and non-germline stem cells of other species, develop and function in specialized microenvironments formed by somatic cells, referred to as the niches. In the fruit fly ovaries, the female GSCs divide asymmetrically to produce new GSCs and the progenitor cells, the cystoblasts (Cbs). Each Cb then divides to generate the cyst composed of 16 interconnected sibling cells, the cystocytes. After cyst formation, specific molecules are transferred to one of the cystocytes which differentiates into the oocyte, whereas the other 15 cystocytes become the nurse cells. We have studied morphology and ultrastructure of the germaria in the ovarioles (ovaries) of a basal “apterygotous” insect, the firebrat (Thermobia domestica). Our analyses have revealed that in this insect, putative GSCs are present along the anterior apex of the germarium. These cells are separated from each other and from the basement lamina covering the ovariole by characteristic somatic cells, termed the apical somatic cells (ASCs), or their elongated processes. We believe that all the ASCs of a given ovariole constitute a “dispersed” niche in which putative GSCs are anchored. Our analyses have additionally shown that in Thermobia, both the Cbs and young (meiotic) oocytes are always individual and never form syncytial cysts. These findings indicate that in certain basal insects the syncytial phase of oogenesis has been eliminated during evolution. Finally, we show that in the early meiotic oocytes of Thermobia, during the so-called bouquet stage, prominent Balbiani bodies (Bbs) are formed. Analysis of serial micrographs indicates that the Bbs invariably arise next to the segment of the nuclear envelope to which the telomeres of the bouquet chromosomes are attached. We suggest, in the light of these data, that the localization of the Bb together with the polar attachment of the bouquet chromosomes play a crucial role in the early asymmetrization of Thermobia oocytes.     

Computer simulation of the motoneuron pool–muscle complex. I. Input system and motoneuron pool

 The aim of the present study was to simulate the input system and the motoneuron (MN) pool of the MN pool–muscle complex (MNPMC). Input fibers, which can originate from command centers in the central nervous system or from sensory organs, activate the MN pool. They generate sequences of action potentials, the frequency of which is proportional to a time-dependent activation factor (which is an input to the model). Different connection patterns between the input fibers and motor units (MUs) are allowed. For simplicity and since no precise experimental data are available, 70 input fibers and 4 boutons per fiber and MN are simulated (this corresponds approximately to the monosynaptic group-Ia input of the cat medial gastrocnemius muscle). Each bouton generates the same conductance change in the postsynaptic membrane. The MNs are modeled with a single compartment and a homogenous membrane. According to experimental data, the membrane leakage conductance and capacitance are MU dependent. Since the precise relation is unknown: (a) the computed relation between MU contraction force and the MN leakage conductance was taken from a steady-state MNPMC model, and (b) the capacitance was assumed to be proportional to the leakage conductance. The MN membrane includes time- and voltage-dependent ionic channels (fast and slow K⁺ and low- and high-threshold Ca²⁺ channels). The density and time constant of the slow K⁺ channels and the density of the Ca²⁺ channels were fitted to approximate afterhyperpolarization characteristics and frequency-injected current relations of type-identified cat MNs. If the membrane reaches a voltage threshold the MNs generate action potentials, which were simulated by voltage pulses. The activation of the MN pool of the human first dorsal interosseus muscle was simulated with injected and synaptic currents in order to illustrate the size principle, synaptic noise, and other features of muscle activation. It is concluded that the present model reproduces the main properties of the input–output relations of different MN types within a muscle. Together with the simulation of the muscle force and the surface EMG, which will be published in subsequent papers, it will be a powerful tool for reproducing experiments on the motor system and investigating functional mechanisms of motor control. Received: 17 April 2001 / Accepted in revised form: 6 November 2001     

Fire modulates the effects of introduced ungulates on plant–insect interactions in a Patagonian temperate forest

Disturbances like biological invasions and fire may affect in unexpected ways plant-animal interactions. In northwestern Patagonia, introduced ungulates (cattle, horses and deers) are widespread and very common occupying more than 50% of forests and shrublands, widely affecting these habitats. In addition, fire play a major role in creating landscape patterns in this region. We evaluated whether fire modify the impacts of introduced ungulates on plant-animal interactions. In a mature forest (unburnt) and in an early post-fire area (burnt) we used structural equation modeling (SEM) to analyzed the impacts of introduced ungulates on insect herbivory, pollination and pre-dispersal seed predation on Berberis darwinii, one of the most common understory shrub of temperate forests. We found that the effects of cattle on pollination and fruit set depended on the habitat condition (i.e. unburnt or burnt). Introduced ungulates in unburnt forest decreased fruit set through a reduction on pollinator visits. Conversely, introduced ungulates in burnt forest increased pollinator visits and flower production without affecting fruit set. On the other hand, damage patterns (herbivory and fruit/seed predation) were unaffected by cattle in both forests types. Either, low browsing pressure or induction of plant defences may explain our results. This study illustrates how modifications on biotic and abiotic conditions produced by fire may affect in complex ways the effect of introduced ungulates on plant-animal interactions.     

From single cells to tissue architecture—a bottom-up approach to modelling the spatio-temporal organisation of complex multi-cellular systems

Collective phenomena in multi-cellular assemblies can be approached on different levels of complexity. Here, we discuss a number of mathematical models which consider the dynamics of each individual cell, so-called agent-based or individual-based models (IBMs). As a special feature, these models allow to account for intracellular decision processes which are triggered by biomechanical cell-cell or cell-matrix interactions. We discuss their impact on the growth and homeostasis of multi-cellular systems as simulated by lattice-free models. Our results demonstrate that cell polarisation subsequent to cell-cell contact formation can be a source of stability in epithelial monolayers. Stroma contact-dependent regulation of tumour cell proliferation and migration is shown to result in invasion dynamics in accordance with the migrating cancer stem cell hypothesis. However, we demonstrate that different regulation mechanisms can equally well comply with present experimental results. Thus, we suggest a panel of experimental studies for the in-depth validation of the model assumptions.     

Is histamine a neurotransmitter in insect photoreceptors?

Summary Intracellular recordings were made from the large monopolar cells (LMC's) in the first visual neuropil (lamina) of the flyMusca, whilst applying pharmacological agents from a three-barrelled ionophoretic pipette (Fig. 1). Most of the known neurotransmitter candidates (except the neuropeptides) were tested. The LMC's were most sensitive to histamine, saturating with ionophoretic pulses of less than 2 nC. The responses to histamine were fast hyperpolarizations with maximum amplitudes similar to that of the light-induced response (Fig. 3). Like the light response, the histamine response was associated with a conductance increase (Fig. 5). The histamine responses were not blocked by a synaptic blockade induced by ionophoretic application of cobalt ions (Fig. 6). Several histamine antagonists, and also atropine, were effective at blocking or reducing both the response to histamine and the response to light (Fig. 7). Other transmitter candidates having marked effects on the LMC's were: a) the acidic amino-acids, L-aspartate and L-glutamate, which evoked slower hyperpolarizations that could be blocked by cobalt (Fig. 11); b) GABA, which induced a depolarization associated with an inhibition of the light response (Fig. 9); and c) acetylcholine which also caused a depolarization (Fig. 10). Substances with no obvious effect on the LMC's included serotonin (5-HT),-alanine, dopamine, octopamine, glycine, taurine and noradrenalin. Together with the evidence of Elias and Evans (1983), which shows the presence, synthesis and inactivation of histamine in the retina and optic lobes of the locust, the data suggest that histamine is a neurotransmitter in insect photoreceptors.Abbreviations HA histamine - GABA -amino butyric acid - ACh acetylcholine - 5-HT 5-hydroxy-tryptamine (or serotonin) - R1-6 class of fly photoreceptors - LMC large monopolar cell - L1, L2 andL3 classes thereof     

Genetics of insect hemolymph β-N-acetylglucosaminidase in the silkworm,Bombyx mori

The distribution of insect hemolymph -N-acetylglucosaminidase was investigated in the silkworm, Bombyx mori. Activity in 115 varieties was 6.92±3.22 units/ml, ranging from 1.4 to 17.0 units/ml. No enzyme-deficient individuals were observed. By selecting individuals showing either high or low enzyme activities, homozygotes were separated with activities varying 10-fold between isolates. No differences in activity of -mannosidase and -galactosidase were observed. Thus, it appears that high- or low-enzyme silkworms (High or Low lines) shared the same genetic background except for the gene concerning the activity of -N-acetylglucosaminidase. Studies on the heredity of the enzyme indicated that the synthesis of the enzyme protein was controlled by an autosomal allele. Examination by immunotitration and CM₅₂-cellulose column chromatography revealed that the difference in activity between High and Low lines was due to the amount of the active enzyme, but not to an endogeneous activator or inhibitor. Furthermore, there was no isozymic difference in -N-acetylglucosaminidase. Slab gel electrophoresis on polyacrylamide showed a species of enzyme (A) that stained more intensely in the High line. For the second species of enzyme (B), the converse was true. This evidence suggests that enzyme levels in hemolymph are under the control of a gene affording association of enzyme subunits to the active enzyme molecule.