Acoustic communication and sexual selection in Orthoptera (Insecta)

Comparison of calling and courtship songs and mating strategies in different groups of Orthoptera shows that acoustic signals in bush crickets (Tettigonioidea) are used for searching conspecific mates at a distance, and song evolution is primarily driven by the acoustic surroundings and simultaneously singing other species. The role of sexual selection in the evolution of acoustic signals in bush crickets is much less important than in the evolution of other nonacoustic signals employed during direct contact. Acoustic signals of crickets (Grylloidea) are involved in both distant and short-range communication. Acoustic courtship signals, along with other courtship components, may offer the material for sexual selection, although, essentially, evolution of acoustic signals in crickets is determined by the acoustic surroundings. Acoustic communication in the grasshoppers of the subfamily Gomphocerinae is mainly a short-distance communication. Acoustic signals of Gomphocerinae are highly variable and elaborate in temporal parameters, and therefore can serve for evaluation of the mate "quality". Song evolution in this group is to a greater extent driven by sexual selection than by the acoustic surroundings and, therefore, could proceed faster than in other groups of Orthoptera and play a major role in speciation.     

The plurennial life cycles of the European Tettigoniidae (Insecta: Orthoptera)

Summary The effect of drought on embryonic development and on hatching was studied in 13 European Tettigoniidae species. Drought can affect development in three different ways: (1) Embryonic development proceeds slower than if the eggs are in contact with water; (2) it stops (for final diapause) in an earlier embryonic stage; (3) it affects maintenance and termination of the initial embryonic diapause.In many Tettigoniidae species, the initial diapause is prolonged, and may last several years. Without draught stress, between 1 and 7 cold treatments in the laboratory, and with eggs of the Tettigonia-species between 1 and 6 winters in the field were necessary to enable all eggs to complete initial diapause. In Central European species, the number of eggs maintaining initial diapause significantly increased when the eggs had no contact with water at the time when they should recover from diapause. In contrast, termination of initial diapause in Tettigonia caudata from Greece, when the environment became favorable for growth again, was highest in that group of eggs that had lost most water in a preceding period of drought. The importance of the prolonged initial diapause for the survival of unpredictable adverse conditions is discussed.     

Embryonic development of the central projection of auditory afferents (Schistocerca gregaria, Orthoptera, Insecta)

The auditory system of Schistocerca gregaria is a well investigated sensory network in the adult grasshopper. Here we present a first study on the embryonic development of this neuronal network. Focussing on the auditory receptor cells we show that they differentiate axonal processes at around 45% of embryonic development. These axons fasciculate with the intersegmental nerve and enter the central nervous system by 45-50% of development. First collaterals sprout into the major arborization area, the frontal auditory projection area of the metathoracic ganglion by 60%. This projection increases in density until an adult-like morphology is established by 90% of development. Furthermore, by the end of embryogenesis all three types of receptor fiber projections can be distinguished. This development is independent of a hearing ability, which develops much later during postembryonic life. The auditory projection co-develops with the fusion of neuromeres to the metathoracic ganglion, the formation of the target neuropile areas and the expression of the synapse associated molecule synapsin. Fasciclin I and Lachesin, both potential axon-guidance molecules, are expressed strongly on both, peripheral and central auditory pathways and, although much weaker, within the synaptic target area.     

Hematopoiesis in Hematopoietic Organ in Euprepocnemis shirakii (Orthoptera, Insecta)

ABSTRACT The present study was undertaken to investigate the hematopoiesis of the hematopoietic organ found in orthopteran Euprepocnemis shirakii under both light and transmission electron microscopy. It was shown that the hemocyte differentiation of E. shirakii was distinct from features compared to patterns previously reported in other insect species: Their prohemocytes, plasmatocytes, granulocytes I, granulocytes II and spherulocytes were all derived from the hematopoietic stem cells surrounded by reticular cells. This pattern of hematopoiesis was also first observed in the Orthoptera. Thus, findings of this study strongly suggested that the patterns of hematopoiesis in insects differed, among groups, showing the need of an extensive investigation in order to correctly comprehend the patterns of hemocyte differentiation in insects in accordance with first order, and then systematically important taxa.     

Karyotype,heterochromatin content and meiotic features ofPoecilocera picta (Orthoptera,Acrididae)

Cytological study of three distinctly separated populations ofPoecilocera picta revealed a chromosome number of 2N = 18 + XO/ XX. Except for the hemizygosity of a procentric heterochromatic block in the M₆ pair of the Bangalore population, the basic karyotype of the three populations is markedly similar. The autosomal karyotype formula is 2Lt + 4Mt + 1 Mst + 2S st and the telocentric X chromosome is the longest of the complement. All bivalents at pachytene carried procentric heterochromatic blocks. The M₄ is the nucleolus organiser with the NOR region situated interstitially but proximal to the centromere. About 11 μm (4%) of the total (290 μm) autosomal pachytene complement is heterochromatic; a major portion of it is contributed by the S₉ pair which is mostly heterochromatic. Chiasmata are localized proximally and distally and in the S₉ pair their formation is confined to the short procentric euchromatic segment of the long arm. Female meiosis did not reveal any chromomere pattern at pachytene and, unlike in the male, the sex bivalent in the female is indistinguishable from the autosomal bivalents. G- and C-banding patterns in males showed procentric bands in all the chromosomes. In addition there are eight telomeric and two interstitial bands which are C negative. The S₉ pair showed only two bands. The G-banding pattern of the sex chromosome in meiosis showed only a centric band while the heterochromatic body of the facultatively heterochromatic X remained G negative.     

Complete mitochondrial genome of the groundhopper Alulatettix yunnanensis (Insecta: Orthoptera: Tetrigoidea)

In this work, we sequenced the first complete mitochondrial genome of Tetrigoidea species, Alulatettix yunnanensis. The circle genome (15,104 bp) consists of 13 protein-coding, 22 transfer RNA, and 2 ribosomal RNA genes, and an A+T-rich region. It has the typical invertebrate mitochondrial gene arrangement.     

Early embryonic development of the head region of Gryllus assimilis Fabricius, 1775 (Orthoptera,Insecta)

We report our investigations on the embryonic development of Gryllus assimilis, with particular attention to the head. Significant findings revealed with scanning electron microscopy (SEM) images include: (1) the pre-antennal lobes represent the anterior-most segment that does not bear any appendages; (2) each of the lobes consists of central and marginal regions; (3) the central region thereof develops into the protocerebrum and the optic lobes, whereas the marginal region thereof becomes the anterior portion of the head capsule; (4) the initial position of the antennal segment is posterior to the mouth region; (5) appendage anlagen are transitorily present in the intercalary segment, and they later vanish together with the segment itself; (6) a bulged sternum appears to develop from the ventral surface of the mandibular, maxillary and labial segments. Embryonic features are then compared across the Insecta and further extended to the embryos of a spider (Araneae, Chelicerata). Striking similarities shared by the anterior-most region of the insect and spider embryos lead the authors to conclude that such comparison should be further undertaken to cover the entire Euarthropoda. This will help us to understand the embryology and evolution of the arthropod head.     

Effects of an imidazole derivative (KK-42) on development and ecdysteroid production in Locusta migratoria (Insecta, Orthoptera)

The imidazole derivative KK-42 was applied in various experimental conditions to larvae and adult females of Locusta migratoria. The effect of this compound was monitored on the development of larvae, on oocyte growth in adult females and on the development of eggs laid by these females. KK-42 had only minor effects on postembryonic development; anticipation of imaginal moult was never observed. In contrast oocyte and egg development were markedly affected by KK-42: this effect is however not related to modifications of the synthesis of ecdysteroids in the ovaries.     

A taxonomic study of genus Teleogryllus from East Asia (Insecta: Orthoptera: Gryllidae)

Crickets belonging to Teleogryllus spp. are widely distributed in East Asia and they are difficult to distinguish. In this study, a phylogenetic tree of Teleogryllus is reconstructed by COI gene, and all species can be distinguished well. The possible evolutionary histories of male genitalia, songs and life history are discussed. The result supports establishing subgenera Macroteleogryllus and Brachyteleogryllus of Teleogryllus spp. from East Asia. T. boninensis is moved to Brachyteleogryllus. The calling song of four species includes both long and short chirps, and the rest just have single chirps. The species inhabit sympatrically trend to have different type of calling song. Egg overwinter type evolved several times independently.     

Histochemical studies on the male accessory gland of Oxya velox (Insecta: Orthoptera)

The male accessory gland of Oxya velox includes fourteen pair of tubules opening into the ejaculatory duct. Histochemically these tubules can be distinguished into six types (AG1--AG6). Their secretion is the mixture of polysaccharides (Glycogen, sialomucin and neutral mucopolysaccharides), proteins (-NH2 and SH groups, tyrosine, tryptophan, histidine and arginine) and lipids (neutral and phospholipids). The possible role of the accessory glands based on their histochemical analysis has been speculated.     

Translational control in oocyte development

Translational control of specific mRNAs is a widespread mechanism of gene regulation, and it is especially important in pattern formation in the oocytes of organisms in which the embryonic axes are established maternally. Drosophila and Xenopus have been especially valuable in elucidating the relevant molecular mechanisms. Here, we comprehensively review what is known about translational control in these two systems, focusing on examples that illustrate key concepts that have emerged. We focus on protein-mediated translational control, rather than regulation mediated by small RNAs, as the former appears to be predominant in controlling these developmental events. Mechanisms that modulate the ability of the specific mRNAs to be recruited to the ribosome, that regulate polyadenylation of specific mRNAs, or that control the association of particular mRNAs into translationally inert ribonucleoprotein complexes will all be discussed.     

The complete mitochondrial genome of grouse locust Tetrix japonica (Insecta: Orthoptera: Tetrigoidea)

We have determined the complete mitochondrial genome of a species of grouse locust, Tetrix japonica. The total length of the T. japonica mitogenome is 15,128 bp with 75.57% A+T content. It consists of 13 protein-coding, 22 transfer RNA (tRNA), and 2 ribosomal RNA (rRNA) genes, and an A+T-rich region. The A+T-rich region was located between the small rRNA and tRNA-Ile genes and is 531 bp in length.     

Histochemical studies on the male accessory gland of Acrida turrita (Insecta: Orthoptera)

The male accessory reproductive glands of Acrida turrita includes fifteen pairs of tubules opening into the ejaculatory duct. Four of them are white and eleven hyaline glands. Histochemically the hyaline glands are further differentiated into seven types (HG1-HG7). The secretion of all the glands taken together includes polysaccharide (neutral mucopolysaccharide, chondroitin sulphate and sialomucin), protein (-NH2 and -SH groups, and tyrosine, histidine, tryptophan and arginine amino acids) and neutral lipid. The possible role of the accessory glands based on their histochemical analysis, has been speculated.     

Discovery of the genus Crinoedischia in the Middle Permian of France (Insecta: Orthoptera)

New orthopteran Crinoedischia lapeyriei sp. nov. is described and illustrated from the Middle Permian (Guadalupian) of Lodève Basin in southern France. The new species is separated from the Lower Permian (Artinskian) Crinoedischia species by differences in wing venation pattern such as long ScP with anterior branches, RA with prominent distal branches, and MA ending with three branches. The significance and parallels of entomofaunas between Salagou and Wellington formations (Lodève, Elmo, Midco) are briefly discussed.     

Effect of hibernation length on termination of diapause in European Tettigoniidae (Insecta: Orthoptera)

Summary The effect of the length of cold treatment on development time of embryos of eight Central European tettigoniid species was investigated in laboratory experiments, using chilling periods of 3, 4, 5, 6, 9, and 12 months. Two different types of response were observed: (1) The hatching date was not influenced by hibernation length (Conocephalus) or only after the 3-month cold treatment (Phaneroptera, Platycleis), or (2) The time required for post-diapause development was significantly reduced by each 1-month increase in the length of cold treatment up to 6 months (Meconema, Metrioptera, Tettigonia).Thus, the correct timing of hatching is achieved by one of two different strategies. In lat-hatching species, the influence of hibernation length is small. Premature appearance is prevented by a high thermal threshold. In early-hatching species, the embryos are obviously able to measure the length of the chilling period. Thus, they gradually change their physiological state so that the potential speed of postdiapause development increases as the winter is prolonged. This strategy can be understood as an adaptation to the necessity of hatching at low or moderate temperatures. Field experiments with two Tettigonia species confirm the laboratory data.     

Rampant Nuclear Insertion of mtDNA across Diverse Lineages within Orthoptera (Insecta)

Nuclear mitochondrial pseudogenes (numts) are non-functional fragments of mtDNA inserted into the nuclear genome. Numts are prevalent across eukaryotes and a positive correlation is known to exist between the number of numts and the genome size. Most numt surveys have relied on model organisms with fully sequenced nuclear genomes, but such analyses have limited utilities for making a generalization about the patterns of numt accumulation for any given clade. Among insects, the order Orthoptera is known to have the largest nuclear genome and it is also reported to include several species with a large number of numts. In this study, we use Orthoptera as a case study to document the diversity and abundance of numts by generating numts of three mitochondrial loci across 28 orthopteran families, representing the phylogenetic diversity of the order. We discover that numts are rampant in all lineages, but there is no discernable and consistent pattern of numt accumulation among different lineages. Likewise, we do not find any evidence that a certain mitochondrial gene is more prone to nuclear insertion than others. We also find that numt insertion must have occurred continuously and frequently throughout the diversification of Orthoptera. Although most numts are the result of recent nuclear insertion, we find evidence of very ancient numt insertion shared by highly divergent families dating back to the Jurassic period. Finally, we discuss several factors contributing to the extreme prevalence of numts in Orthoptera and highlight the importance of exploring the utility of numts in evolutionary studies.     

Prepulse inhibition of the startle reaction in the locust Locusta migratoria (Insecta: Orthoptera: Acridoidea)

A fast startle reaction of unrestrained sitting locusts (Locusta migratoria) can be elicited by sound pulses of steep rise time above 80 dB. The reaction consists of a fast jerky movement of legs and body with a mean latency of 35 ms and graded amplitude. The fast startle reaction did not result in any positional change; this was in contrast to acoustically induced escape reactions of flying Orthoptera. The startle reaction could be inhibited by pure tone stimuli of much lower intensity (60 dB) presented 160 ms before the startle-eliciting noise. This type of reflex modification is a striking convergence to the well-known prepulse inhibition of the mammalian startle response where it has been used to assess sensory thresholds. In the locust, prepulses between 3 and 20 kHz suppressed the startle reaction completely, with thresholds in the locust's hearing range as known from tympanal nerve recordings. No inhibition could be observed at prepulse frequencies of 40 kHz, although this frequency lies within the locust's hearing range. The presence of prepulse inhibition in an invertebrate preparation shows that it is not restricted to vertebrates.     

Photoperiodic control of larval development and wing form inModicogryllus sp. (Orthoptera: Gryllidae)

The bivoltine cricket locally known as ‘Tambo-Koorogi’ (Modicogryllus sp.) hibernates as a half-grown larva, and shows a developmental response to changing as well as stationary photoperiod. At 25°C, larvae matured in about 7–10 weeks in continuous or 16 h daily light, but took 10–20 weeks or more in 14 h and shorter days. A day of 15 h exerted an intermediate effect, giving a development time of 7–17 weeks. However, an increase in daylength from 12 to 15 h in the early larval life prevented diapause, while a decrease from 15 to 12 h retarded development more than a constant 12 h day. Short-winged adults occurred only when the photophase was 15 h or shorter, and their frequency increased with decreased daylength. Although the short-winged form took longer to mature than the long-winged form under the same conditions of photoperiod, delayed growth was not always associated with brachypterism.