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PubMed2000

Ultrastructural architecture and mechanical properties of attachment pads in Tettigonia viridissima (Orthoptera Tettigoniidae).

Natural releasable attachment systems of insect legs, where attachment-detachment performances are often very fast, seem to be optimized to get a maximum of real contact to the substratum. Tarsi of Tettigonia viridissima bear flexible attachment pads with unusual ultrastructural architecture of the cuticle. The indentation of the attachment pads was measured under different loads using a force-tester. Since the mechanical properties are influenced by material structure, the freeze-substitution experiments were undertaken to investigate the influence of loads on material structure. Both profile changes of the surface and the orientation of cuticle microfibrils were visualized by means of scanning electron microscopy followed by fracturing of the frozen material. The results show that the flexible pad material deforms replicating the substrate profile down to the micrometer roughness. The pad material showed both elastic and viscous behavior under loads. Elastic deformation of the pad occurred under normal force applied for 4-6 s (elastic modulus 27.2 +/- 11.6 kPa). Two viscous relaxation processes were found, of time constants tau1 = 1.88+/-0.616 s and tau2 =41.2 +/- 9.95 s. Low stiffness of material studied here aids in surface replication and increase of area of real contact between the pad and the underlying substrate.

Animals↗
PubMed1990

The delta 12-desaturase from the house cricket, Acheta domesticus (Orthoptera: Gryllidae): characterization and form of the substrate.

A novel delta 12-desaturase from animals, which converts oleic acid (18:1n-9) to linoleic acid (18:2n-6), was characterized in the house cricket, Acheta domesticus. The delta 12-desaturase product, linoleic acid, was determined by silver nitrate thin-layer chromatography, radio-gas-liquid chromatography and radio-high-performance liquid chromatography with the latter being used for routine analyses. Enzyme activity was located in the microsomal fraction of whole insect homogenates. NADPH or NADH was required for activity, with NADPH being the more efficient electron donor. In short incubation times with oleoyl-CoA as substrate, the highest amount of product, linoleic acid, was found as linoleoyl-CoA. With longer incubation periods, most of the linoleic acid was recovered in the polar lipid fraction containing phospholipid. Preincubation of the microsomal preparation in the absence of NADPH, which allowed 90% of the oleoyl moiety to be transacylated into complex lipid, resulted in no detectable desaturation upon addition of NADPH. These data indicate that the oleic acid moiety used as substrate was in the form of a CoA derivative and not in the form of a phospholipid, as it is for the plant delta 12-desaturase. This is the first characterization of a delta 12-desaturase from an animal system and the first report of a delta 12-desaturase that uses oleoyl-CoA as substrate.

Animals↗
PubMed1983

Rhabdome-bearing cells within the corpus cardiacum of Melanogryllus desertus (orthoptera, gryllidae).

Cells with rhabdomeric structures characteristic of photoreceptor cells occur within the corpus cardiacum of Melanogryllus desertus. These cells are few in number and are larger than intrinsic secretory cells. Each has numerous rhabdomeric microvilli forming a rhabdome within the cell. The arrangement of large mitochondria under the rhabdomeric microvilli around the dilated endoplasmic reticulum membranes and multivesiculated bodies is distinctive. Rhabdome cells have synaptic contacts with the numerous neurosecretory axons that surround them. Other neurosecretory axons come in close contact with the membranes of microvilli.

Animals↗
PubMed1984

Temporal variations of hemolymph esterase activity and juvenile hormone titers during ovocyte maturation in Acheta domesticus (Orthoptera).

Using in vitro methods, juvenile hormone (JH) esterase activity and alpha-naphthylacetate esterase activity were determined in the hemolymph during the first reproductive cycle of the house cricket, Acheta domesticus. Biochemical properties of the hemolymph JH esterase were studied. alpha-Naphthylacetate esterases increased during the first gonotrophic cycle: peaks of their activity could be observed concomitant with peaks of JH esterase activity. The fluctuations in JH esterase activity correlated with those of hemolymph JH titers. The results are discussed.

Animals↗
PubMed1990

Ovaries and regulation of juvenile hormone titer in Acheta domesticus L. (Orthoptera).

A study was performed on females Acheta domesticus to examine the effects of various experimental conditions on the ovarian physiology. Using a radioimmunoassay to determine juvenile hormone (JH) titers as well as in vitro JH biosynthesis, we observed that retention of mature follicles in egg-retaining females, i.e., virgins or mated females not provided an egg-laying substrate, inhibits JH production and consequently oocyte development. Mating in intact as well as ovariectomized females does not affect corpora allata activity. It is only when mating is associated with egg laying that JH biosynthesis and hemolymph titers increased and oocyte development and fecundity are stimulated. Despite lower JH biosynthesis, ovariectomized females present enlarged corpora allata and the levels of JH observed in their hemolymph were intermediate between those of intact egg-laying and virgin females. In intact females, the hemolymph JH titers as well as the JH esterase activities were related to ovarian development. JH esterase activity was very high in ovariectomized animals. Several factors involved in ovarian development of A. domesticus are discussed.

Animals↗
PubMed1992

Insect sex chromosomes, XI. 3H-TdR induces random aberrations in the X chromosome(s) of Gryllotalpa fossor (Orthoptera).

The pattern of titrated thymidine (3H-TdR), a direct precursor of DNA, induced aberrations on the X chromosome of Gryllotalpa fossor was examined. 3H-TdR produced aberrations randomly distributed over the entire length of the X chromosome; breaks were observed in both the eu- and the heterochromatic arms of the X chromosome in both the sexes. Since the eu- and the heterochromatic arms cannot be distinguished cytologically in this insect, the presence of aberrations on both arms of the same X chromosome in the male and damage to both X chromosomes in the female indicate that both euchromatic and heterochromatic regions (facultative or constitutive) are equally liable to aberrations induced by H-TdR. This is in contrast to the non-random induction of aberrations by 3H-UdR, which causes chromosome damage due to the proximity of the labeled RNA to the DNA template during transcription.

Animals↗
PubMed1982

The biosynthetic pathway of ecdysone: studies with vitellogenic ovaries of Locusta migratoria (Orthoptera).

Ovaries of adult females of Locusta migratoria synthesize impressive amounts of the steroid hormone ecdysone (and related ecdysteroids) during the late phases of vitellogenesis. The present study, aimed at elucidating the sequence of the biosynthetic steps that lead from cholesterol to ecdysone, has taken benefit of this remarkable biological model by using a double approach: (1) isolation and physico-chemical identification of endogenous biogenetic intermediates; (2) metabolic study of labelled putative precursor molecules. The data presented in this paper lead us to propose the following sequence of events: conversion of cholesterol to 3 beta-hydroxy-5 beta-cholest-7-en-6-one (via several intermediates not identified in this study) followed by 14 beta-hydroxylation to 3 beta, 14 alpha-dihydroxy-5 beta-cholest-7-en-6-one; hydroxylation on the side-chain at C-25 and C-22 (in this order) to 2-deoxyecdysone; hydroxylation at C-2 to ecdysone.

Animals↗
PubMed1986

Neurons reactive to antibodies against serotonin in the stomatogastric nervous system and in the alimentary canal of locust and crickets (Orthoptera, Insecta).

Immunoreactive neurons in the stomatogastric nervous system and in the alimentary tract of the locust Schistocerca gregaria and the crickets Gryllus bimaculatus and Acheta domesticus have been examined using antibodies against serotonin (5-hydroxytryptamine; 5-HT). For comparative anatomical analysis cobalt chloride infusion was applied. The innervation of the visceral muscles was studied electron microscopically. In all three species the majority of the 5-HT-immunoreactive cell bodies of the stomatogastric nervous system occur in the frontal ganglion in which 30-40% of the total number of cell bodies react with anti-5-HT. In the occipital ganglion only two to four cell bodies (1-2%) are 5-HT-immunoreactive. Single immunoreactive cell bodies were observed in the ventricular ganglia in only a few preparations. The 5-HT-immunoreactive neurons in the frontal ganglion are pseudounipolar or multipolar. The main process of the 5-HT-immunoreactive neurons of the frontal ganglion descend along the entire stomatogastric nervous system. Some arborizations of these processes ascend into the brain and others supply the neuropil of all stomatogastric ganglia. Side branches leave the stomatogastric nervous system and form a plexus along the surface of the entire intestinal tract from where 5-HT-immunoreactive fibers supply: all muscle layers of the muscularis; the external dilator muscles of the foregut and probably some somatic muscles, neurohaemal organs and Malpighian tubules (excretory system). Serotonin-immunoreactive fibers further proceed into salivary gland and the retrocerebral complex (corpora cardiaca and corpora allata). The retrocerebral glandular complex and the hindgut receive additional immunoreactive neurons from the central nervous system. Electron microscopic analysis of nerves innervating the muscle layers of the alimentary tract revealed one type of 5-HT-immunoreactive and one or two types of non-5-HT-immunoreactive fibers. All fiber types contact the sarcolemma of muscle fibers without any obvious synaptic membrane specializations. The 5-HT-immunoreactive fibers are in some regions in close contact with the haemolymph. These regions can be regarded as sites of neurohormonal release. The distribution of serotonin-immunoreactive neurons suggests that 5-HT acts as a neurotransmitter and/or modulator on intestinal muscles and some somatic muscles and glandular cells, and as a neurohormone released from neurohaemal sites into the body fluid.

Animals↗
PubMed2005

Heavy metal accumulation, heat shock protein expression and cytogenetic changes in Tetrix tenuicornis (L.) (Tetrigidae, Orthoptera) from polluted areas.

The orthopteran insect Tetrix tenuicornis, collected from polluted and unpolluted areas, was used to study heavy metal accumulation and its impact on stress protein levels and on changes in the number and morphology of chromosomes in mitotic and meiotic cells. During two consecutive years, insects were collected from polluted areas of zinc-lead mine spoils near Bolesław (Poland) and from unpolluted areas near Busko and Staszów (Poland). T. tenuicornis from the polluted area showed 1.5, 4.03, 4.32 and 41.73 times higher concentrations of copper (Cu), zinc (Zn), lead (Pb) and cadmium (Cd), respectively, than insects of the same species collected from unpolluted areas. Insects exposed to heavy metals showed only small changes, and rather a decrease in the concentration of constitutive and inducible heat shock proteins Hsp70, the level of which increases under stress conditions. A cytogenetic study of T. tenuicornis revealed intra-population anomalies in chromosome number and morphology in mitotic and meiotic cells and the presence of an additional B chromosome in germinal cells. In 50% of females collected from polluted areas, mosaic oogonial mitotic chromosome sets and diploid, hypo- or hypertetraploid, tetraploid, and octoploid chromosome numbers were detected. In turn, 14.6% of males showed a heterozygous deficiency of chromatin in L2 and M3 bivalents in addition to the presence of B chromosomes.

Animals↗
PubMed2005

Molecular phylogeography of Dolichopoda cave crickets (Orthoptera, Rhaphidophoridae): a scenario suggested by mitochondrial DNA.

This study focuses on the phylogenetic relationships among a number of West-Mediterranean cave crickets species belonging to Dolichopoda; primarily a Mediterranean genus, distributed from eastern Pyrenees to Caucasus. In this paper, 11 Dolichopoda species from the French Pyrenees (D. linderi), the island of Corsica (D. bormansi and D. cyrnensis), and northern, central, and southern Italy (D. ligustica, D. schiavazzii, D. aegilion, D. baccettii, D. laetitiae, D. geniculata, D. capreensis, and D. palpata) were studied. Two more species, one from the Caucasus, D. euxina, and one from Greece, D. remyi, were also included in the analyses, together with more distant species within the same family to be used as outgroups. Fifteen hundred base pairs of mitochondrial DNA, corresponding to the small subunit of the ribosomal RNA (16S rRNA) and to the subunit I of the cytochrome oxidase I (COI), were sequenced in order to clarify the phylogenetic relationships and biogeography of this group of Mediterranean cave crickets. The molecular data are congruent with a phylogeographic pattern; with the geographically close species also the most related ones. Based on mtDNA divergence, the present-day distribution of genetic diversity seems to have been impacted by climatic events due to glacial and interglacial cycles that have characterized the Pleistocene era.

Animals↗
PubMed2005

Phylogeny of Ensifera (Hexapoda: Orthoptera) using three ribosomal loci, with implications for the evolution of acoustic communication.

Representatives of the Orthopteran suborder Ensifera (crickets, katydids, and related insects) are well known for acoustic signals produced in the contexts of courtship and mate recognition. We present a phylogenetic estimate of Ensifera for a sample of 51 taxonomically diverse exemplars, using sequences from 18S, 28S, and 16S rRNA. The results support a monophyletic Ensifera, monophyly of most ensiferan families, and the superfamily Gryllacridoidea which would include Stenopelmatidae, Anostostomatidae, Gryllacrididae, and Lezina. Schizodactylidae was recovered as the sister lineage to Grylloidea, and both Rhaphidophoridae and Tettigoniidae were found to be more closely related to Grylloidea than has been suggested by prior studies. The ambidextrously stridulating haglid Cyphoderris was found to be basal (or sister) to a clade that contains both Grylloidea and Tettigoniidae. Tree comparison tests with the concatenated molecular data found our phylogeny to be significantly better at explaining our data than three recent phylogenetic hypotheses based on morphological characters. A high degree of conflict exists between the molecular and morphological data, possibly indicating that much homoplasy is present in Ensifera, particularly in acoustic structures. In contrast to prior evolutionary hypotheses based on most parsimonious ancestral state reconstructions, we propose that tegminal stridulation and tibial tympana are ancestral to Ensifera and were lost multiple times, especially within the Gryllidae.

Animals↗
PubMed2006

Phylogeny of the cricket subfamily Eneopterinae (Orthoptera, Grylloidea, Eneopteridae) based on four molecular loci and morphology.

The phylogenetic relationships of 39 species of Eneopterinae crickets are reconstructed using four molecular markers (16S rRNA, 12S rRNA, cytochrome b, 18S rRNA) and a large morphological data set. Phylogenetic analysis via direct optimisation of DNA sequence data using parsimony as optimality criterion is done for six combinations of weighting parameter sets in a sensitivity analysis. The results are discussed in a twofold purpose: first, in term of significance of the molecular markers for phylogeny reconstruction in Ensifera, as our study represents the first molecular phylogeny performed for this insect suborder at this level of diversity; second, in term of corroboration of a previous phylogeny of Eneopterinae, built on morphological data alone. The four molecular markers all convey phylogenetic signal, although variously distributed on the tree. The monophyly of the subfamily, that of three over five tribes, and of 10 over 13 genera, are recovered. Finally, previous hypotheses on the evolution of acoustic devices and signals in the Eneopterinae clade are briefly tested, and supported, by our new data set.

Animals↗
PubMed2002

Chromosome inversion polymorphisms influence morphological traits in Trimerotropis pallidipennis (Orthoptera).

Trimerotropis pallidipennis is a New World grasshopper whose South-American populations are polymorphic for six pericentric inversions. Previous work has demonstrated that the frequences of these inversions correlate with climatic variables, and hence a possible adaptive pattern was put forward. In the present work we analysed a sample of a natural population of T pallidipennis to ascertain whether the chromosomal inversions have effects on exophenotypes. Two hundred and sixty-eight males coming from a natural population at Uspallata, Mendoza Province, Argentina were analysed, and it was observed that most inversions had significant effects on phenotypes. Furthermore, some body size-related characteristics (such as tegmina length) were correlated with the number of inversions. Individuals from populations at higher altitude or latitude (i.e., at lower minimum temperatures), along with higher frequencies of standard sequences, were significantly smaller, and this coherence between interpopulational with intrapopulational results may indicate that the diminished body size of the standard sequence-carrying individuals may be caused by an effect of the inversions, or genes within the inversions, on body size. We finally put forward the hypothesis that reduced body size in a context of reduced minimum temperature may be a response to shortened development season, and so smaller individuals may be advantageous.

Analysis of Variance↗