Grasshoppers

The B24 chromosome variant emerged several decades ago in a Spanish population of the grasshopper Eyprepocnemis plorans and is currently reaching adjacent populations. Here we report, for the first time, how a parasitic B chromosome (a strictly vertically transmitted parasite) expands its geographical range aided by high gene flow in the host species. For six years we analyzed B frequency in several populations to the east and west of the original population and found extensive spatial variation, but only a slight temporal trend. The highest B24 frequency was found in its original population (Torrox) and it decreased closer to both the eastern and the western populations. The analysis of Inter Simple Sequence Repeat (ISSR) markers showed the existence of a low but significant degree of population subdivision, as well as significant isolation by distance (IBD). Pairwise Nem estimates suggested the existence of high gene flow between the four populations located in the Torrox area, wi...

The polyneopteran insect fauna of Dinara Mountain area has been poorly studied in the past, with only scarce data published on the topic. During a study conducted in 2012 and 2013, a total of 19 better-investigated localities were visited and 68 species of Blattodea, Mantodea and Orthoptera were recorded for the first time in the investigated area, one species being recorded for the first time in Croatia. Our results, together with all available museum and literature data, are presented in this paper to complete the picture of polyneopteran insect fauna inhabiting this area.

Previous work has shown that a peptide related to arginine vasopressin is present in the suboesophageal ganglion of the locust, Locusta migratoria. This peptide was determined to be an anti-parallel dimer of the nonapeptide Cys-Leu-Ile-Thr-Asn-Cys-Pro-Arg-Gly-NH2 and was reported to stimulate cyclic AMP production and fluid secretion in a combined Malpighian tubules and midgut preparation from locusts. For these reasons the peptide has been called the arginine-vasopressin-like insect diuretic hormone (AVP-like IDH). Recently, a second diuretic peptide (Locusta-DP), which is related to corticotropin releasing factor, has been identified: this is a potent stimulant of fluid secretion and cyclic AMP production by isolated locust tubules. Because water balance in insects is likely to be controlled by a cocktail of hormones acting on both Malpighian tubules and hindgut, this study directly compares the activity of these two peptides in fluid secretion and cyclic AMP production bioassays ...

We report the results of a study on the neo-sex chromosome systems of six Neotropical Melanoplinae species for contributing to a better understanding of their origin and behaviour of these systems. Our analyses included detailed descriptions of the structure and behaviour of the sex chromosome configurations in male and female meiosis of species belonging to the genera Ronderosia, Dichromatos and Atrachelacris. Three species, R. forcipatus, R. malloi and A. unicolor, showed typical Robertsonian fusion-derived neo sex-chromosomes. However, the male metaphase I orientation of R. bergi sex pair indicated that more than one rearrangement was involved in its origin. The two species of Dichromatos presented a multiple neo-X1X2Y/X1X1X2X2 sex system, with two Robertsonian fusions involved in their genesis. Observations of female meiosis, confirmed the nature of the sex-chromosomes analyzed. Our results also showed different degrees of homology divergence between the neo-sex chromosomes and emphasize the plasticity of the chromosome complement of the Neotropical Melanoplinae to establish Robertsonian fusions and generate novel sex-chromosome systems. We also discuss karyotypic diversity within this group in terms of the centromeric drive theory of chromosomal evolution.

In this article, we identify and characterise the miRNA machinery components Drosha, Dicer-1 and Argonaute-1 of the desert locust. By means of phylogenetic analyses, we reveal important insights in the evolutionary context of these components. Our data illustrate that insect Argonaute-1 proteins form a monophyletic group with ALG-1 and ALG-2 of Caenorhabditis elegans and with the four (non-Piwi) Argonaute proteins present in humans. On the other hand, humans apparently lack clear homologues of the insect Argonaute-2 proteins. In addition, we demonstrate that drosha, dicer-1 and argonaute-1 display wide transcript tissue-distribution in adult desert locusts, and that during locust phase transition and feeding of starved locusts the expression levels of the miRNA pathway are regulated at the transcript level.

The ectoparasitic mite Podapolipoides anacridii n. sp. (Heterostigmatina: Podapolipidae), collected from the basal hindwings of Anacridium sp. (Orthoptera: Acrididae) in central Iran, is described. Podapolipoides Regenfuss, 1968 is defined, and the distribution, host-specificity and host range of its constituent species are discussed.

Background

The California Coastal Prairie has the highest biodiversity of North America's grasslands, but also has the highest percentage of urbanization.  The most urbanized part of the California Coastal Prairie is its southernmost area, in Los Angeles County.  This southernmost region, known as the Los Angeles Coastal Prairie, was historically dotted with vernal pools, and has a unique biodiverse composition.  More than 99.5% of its estimated original 95 km (23,475 acres), as well as almost all its vernal pool complexes, have been lost to urbanization.

The Madrona Marsh Preserve, in Torrance, California, safeguards approximately 18 hectares (44 acres) of Los Angeles Coastal Prairie and includes a complex of vernal pools.  Its aquatic biodiversity had been studied, predominantly to genus level, but its terrestrial macro-invertebrates were virtually unknown, aside from butterfly, dragonfly, and damselfly observations.

Results

In order to better understand the biodiversity at the Madrona Marsh Preserve, a minimally-invasive macro-invertebrate inventory was conducted. The results of this inventory, with 689 invertebrate organisms recorded, covering eight phyla, 13 classes, 39 orders, and 222 families, are presented in this document.

Locusts perform a visual behavior known as peering before jumping to targets. Peering consists of a side to side translational movement of the head. Wallace (1959) first proposed that this behavior is performed in order to obtain depth information through motion parallax. The present study analyzes more quantitatively the role of peering in the locust's (Schistocerca americana) estimation of distance in an attempt to understand the neural mechanisms involved. Jump velocity was found to be related monotonically to target distance and was used as a measure of the locust's judgement of target distance. By presenting locusts with a target which moved laterally while they peered (artificial parallax), it was possible to simulate the motion parallax of a target at any distance. Jump velocities elicited by means of artificial parallax were the same as jump velocities elicited by the corresponding real distances, demonstrating that locusts use motion parallax as a cue to distance. By moving the target in the same direction but further than the locust's head it was possible to simulate targets whose motion parallax specified a position behind the animal. Locusts jump forward to such paradoxical stimuli with the jump velocity appropriate for targets located at the absolute value of the simulated distance. This suggests that locusts are insensitive to the relation between the direction of head and image motion. Measurement of jump velocity in locusts with one eye occluded revealed an interaction between the parallax signals from the two eyes — locusts appear to sum (or average) the motion perceived in each eye. Jump velocity is predicted more accurately by target distance than by either image displacement or image velocity during peering. This implies that the locust's computation of target distance involves signals concerning its own head motion.

Whether chromosomal rearrangements promote speciation by providing barriers to gene exchange between populations is one of the long-standing debates in evolutionary biology. This question can be addressed by studying patterns of gene flow and selection in hybrid zones between chromosomally diverse taxa. Here we present results of the first study of the genetic structure of a hybrid zone between chromosomal races of morabine grasshoppers Vandiemenella viatica, P24(XY) and viatica17, on Kangaroo Island, Australia. Chromosomal and 11 nuclear markers revealed a narrow hybrid zone with strong linkage disequilibrium and heterozygote deficits, most likely maintained by a balance between dispersal and selection. Widths and positions of clines for these markers are concordant and coincident, suggesting that selection is unlikely to be concentrated on a few chromosomes. In contrast, a mitochondrial marker showed a significantly wider cline with centre offset toward the P24(XY) side. We argue that the discordance between the mitochondrial and nuclear/chromosomal clines and overall asymmetry of the clines suggest a secondary origin of the contact zone and potential movement of the zone after contact. Genome-wide scans using many genetic markers and chromosomal mapping of these markers are needed to investigate whether chromosomal differences directly reduce gene flow after secondary contact.

The ecology of phase polyphenism plays a major role in locust swarm formation. We describe how recent advances in the understanding of phase polyphenism can be combined with existing management approaches as part of a preventative Desert locust management strategy. We start with a brief overview of phase polyphenism with particular emphasis on the role that resource distribution patterns play in the process of locust phase change. We then review current perspective on preventative locust management, and conclude by proposing a framework for quantitatively assessing the risk that phase change will occur in local locust populations. Importantly, the data required to implement this framework can be readily collected with little additional effort or cost just by slightly modifying locust habitat survey protocols that are already in operation. Incorporating gregarization risk assessment into existing preventative management strategies stands to make a considerable contribution toward rea...

We investigate regularities and restrictions in chromosome location of ribosomal RNA genes, analysed by fluorescent in situ hybridization (FISH), and their phenotypic expression assessed by nucleolus formation at first meiotic prophase cells, analysed by silver impregnation, in 49 grasshopper species. High variation was found for rDNA location between species within most genera analysed. The mean haploid number of rDNA loci detected by FISH was 2.47, but some species had up to 10 loci. Chromosome distribution of rDNA loci differed between the Gomphocerinae and Oedipodinae subfamilies, most loci being proximal to the centromere in the former and distal to it in the latter. Chromosomes 2, 3 and X frequently carried rDNA in Gomphocerinae species with 2n♂=17 chromosomes, whereas chromosomes 6 and 9 were the most frequent rDNA locations in the Oedipodinae. About 13% of the 126 rDNA loci detected by FISH were silent, although this figure might be even higher. The comparison of FISH and silver-impregnation results also suggested the existence of cryptic NORs, i.e. those forming small nucleoli with no apparent presence of rDNA revealed by FISH. This was especially clear after the same cells in two species were sequentially treated with both silver impregnation and FISH. The abundance of silent and cryptic loci might thus suggest that rDNA spreads through grasshopper genomes by the Dubcovsky and Dvorak mechanism—that is, the transposition of a few rRNA genes to new chromosome locations, their amplification giving rise to new NORs, and the elimination of the old NORs. The cryptic NORs might correspond to nascent NORs, i.e. a few rRNA gene copies moved to new locations, whereas the inactive rDNA loci might correspond to those being in the process of elimination.

Two isolates of Metarhizium spp. were studied for propagule production, because of their pathogenic activity towards locusts and grasshoppers (Mf189 = M. flavoviride (or M. anisopliae var. acridum) strain IMI 330189, and Mf324 = M. flavoviride strain ARSEF324). Both isolates were grown in seven different liquid media, which have been developed for mass production of various Hyphomycetes, considered as candidates for microbial control of noxious insects. Shake-flask experiments were carried out at 28 degress C in the dark. Production was quantified for 72 h and the effects of the tested media were evaluated on propagule concentration, morphology and pathogenicity. Based on preliminary experiments, all tested media were supplemented with 0.4% Tween 80 to avoid the formation of pellets and to produce unicellular propagules. Submerged propagule yields were higher with Mf189 than with Mf324 in all seven media. While high concentrations of propagules (1.4 to 2.4 x 10(8) propagules ml(-1) ...

Uno sciame di domande segue gìi sciami delle locuste, che di tempo in tempo - fra la metà del Trecento e la metà dell'Ottocento - si sono abbattuti su tante regioni del Mediterraneo. A farsi infestare e a infestare con gli interrogativi sono i due storici Elina Gugliuzzo e Giuseppe Restilo, e non tanto per procedere sulla strada della sola rappresentazione culturale di questi animaletti, così piccoIi, così nocivi.

Delta-atracotoxins (delta-ACTXs) from Australian funnel-web spiders differ structurally from scorpion alpha-toxins (Sc(alpha)Tx) but similarly slow sodium current inactivation and compete for their binding to sodium channels at receptor site-3. Characterization of the binding of 125I-labelled delta-ACTX-Hv1a to various sodium channels reveals a decrease in affinity for depolarized (0 mV; Kd=6.5 +/- 1.4 nm) vs.polarized (-55 mV; Kd=0.6 +/- 0.2 nm) rat brain synaptosomes. The increased Kd under depolarized conditions correlates with a 4.3-fold reduction in the association rate and a 1.8-increase in the dissociation rate. In comparison, Sc(alpha)Tx binding affinity decreased 33-fold under depolarized conditions due to a 48-fold reduction in the association rate. The binding of 125I-labelled delta-ACTX-Hv1a to rat brain synaptosomes is inhibited competitively by classical Sc(alpha)Txs and allosterically by brevetoxin-1, similar to Sc(alpha)Tx binding. However, in contrast with classical...