Enzyme variation in the grasshopper Chorthippus brunneus (Thunberg)

Forty-two populations of the grasshopper Chorthippus brunneus from four different areas were scored for polymorphism at 15 enzyme loci. The areas sampled were Nottinghamshire, inland Essex, the Essex coast and Dovedale in Derbyshire. Five loci were found to be polymorphic (isocitrate dehydrogenase (2), malate dehydrogenase, glyceroI-3-phosphate dehydrogenase and phosphoglucomutase) but levels of heterozygosity were generally low. Differences in enzyme variation between different areas were demonstrated using multivariate analysis.     

Adipokinetic response of a flightless grasshopper (Barytettix psolus): Functional components,defective response

The mature flightless grasshopper Barytettix psolus shows a very small adipokinetic response when injected with extracts of its own corpora cardiaca, although the fat body contains enough lipid for a strong response. When these extracts were injected into Melanoplus differentialis, a grasshopper capable of flight, or the moth Manduca sexta, much stronger adipokinetic responses were observed. Upon analysis of B. psolus extracts by HPLC, two components with adipokinetic activity were obtained. The major component appears to be identical to locust adipokinetic hormone (AKH) I. Extracts of B. psolus corpora cardiaca also activated fat body glycogen phosphorylase in B. psolus. This activation, however, did not result in an increase in hemolymph sugar, probably because of low levels of glycogen in the fat body. B. psolus hemolymph contains a high-density lipophorin (HDLp) consisting of the apolipophorins (apoLp) I and II and lipid. Both apoproteins are glycosylated. The hemolymph also contains apoLp-III, although this apoprotein apparently does not associate with HDLp to form a low-density lipophorin (LDLp) following AKH or corpora cardiaca extract injections. When B. psolus lipophorin and AKH were injected into Schistocerca americana, lipophorin took up lipids and combined with apoLp-III, forming LDLp. ApoLp-III from B. psolus injected into S. americana can also form LDLp, demonstrating that the components are functional. A lipid transfer particle isolated from M. sexta and injected into B. psolus does not improve the adipokinetic response. Thus, it appears that the adipokinetic response of B. psolus is not deficient because of the lack of AKH or functional lipophorins, but may be caused by the lack of a full response to AKH by fat body or the deficiency in hemolymph of some as yet unknown factor.     

Oviposition date and pattern of embryogenesis in the grasshopper Chorthippus brunneus (Orthoptera, Acrididae)

The morphological development of eggs of the grasshopper Chorthippus brunneus , laid during successive periods through a single season, was closely monitored in the field at a site in NW England. Eggs within the same clutch developed synchronously. However, there were significant differences between clutches laid at the same time, reflecting spatial variation in microclimate (and possibly maternal effects and/or genetic differences). Eggs laid early in the season entered diapause and hatched relatively synchronously in the following spring. Eggs laid later failed to reach the diapause-stage before winter, but hatched, albeit late and with greater variance. Diapause was averted in these eggs. Plasticity in the nature of diapause has been documented from laboratory studies of many insect species (including C. brunneus ,) but this study directly relates the incidence of such developmental plasticity to oviposition date and seasonal temperature cycles in the field. The adaptive significance of diapause aversion and the evolutionary consequences for female reproductive behaviour are considered.     

Recognition of a two-element song in the grasshopper Chorthippus dorsatus (Orthoptera: Gomphocerinae)

Summary Males of the grasshopper Chorthippus dorsatus produce songphrases which contain two differently structured elements — pulsed syllables in the first part (A) and ongoing noise in the second part (B). Females of Ch. dorsatus answer to artificial song models only if both elements A and B are present. Females strongly prefer song models in which the order of elements is A preceding B. Females discriminate between the two elements mainly by the existence of gaps within A-syllables. Pulses of 5–8 ms separated by gaps of 8–15 ms make most effective A-syllables, while syllable duration and syllable intervals are less critical parameters. Females respond to models which contain more than 3 A-syllables with high probability. Female model preferences lie well in the range of parameter values produced by singing males, except for B-parts which must be longer than those of any natural song to be most effective. In ancestors of Ch. dorsatus the two elements of the songs might have been directed towards females (part A) and males (part B).     

The B-chromosome system of the grasshopper Eyprepocnemis plorans subsp. plorans (Charpentier)

Supernumerary chromosomes of two types have been observed in the grasshopper Eyprepocnemis plorans subsp. plorans. One of these (the B-type) is similar in size to an S autosome; the other is smaller (B-type). Both are telocentric and mitotically stable. The frequencies of individuals with the B-type supernumeraries in five natural populations were 56, 56, 70, 71 and 30 per cent respectively. The equivalent levels of the B-type supernumerary were 0, 0, 13, 3 and 0 per cent respectively. Because of the relative infrequency of the B-type only the B-type has been studied in detail. In males with 1B, anaphase I segregation of X and B was random in four populations but non-random in that from Otivar. Here the B was distinctive in having a secondary constriction near the centromere. A study of chiasma frequency among A-chromosomes revealed that the B-type supernumerary increases significantly both the mean chiasma frequency and the between-cell variance. A comparison of body morphometrics failed to reveal any effect of these B-chromosomes on the exophenotype.     

Colour-pattern variation in relation to habitat in the grasshopper Chorthippus brunneus (Thunberg)

Abstract. 1. Chorthippus brunneus were collected from twenty-two different sites in Nottinghamshire, Derbyshire and Essex.
2. Discrete characters of the head, pronotum and forewings and hind femora were scored. The results were compared with the types of habitat from which the grasshoppers were collected.
3. Associations between striped and mottle-winged varieties were found.
4. The relationships between colour and habitat were examined.     

Population density, phenotype and mortality in the grasshopper Chorthippus brunneus

ABSTRACT.

• 1 The patterns of mortality in laboratory populations of the grasshopper Chorthippus brunneus Thunberg are examined at a range of densities and at different stages of nymphal development with particular reference to the phenotypes of nymphs that die or survive.
• 2 Total mortality during nymphal development rises from density-independence at the lowest densities to approximately compensating density-dependence at the highest densities.
• 3 The greatest proportion of total mortality occurs in the first two instars. The stage broadly covering the second instar is the ‘key-stage’ determining adult density. The mortality during these stages is largely density-independent. There is relatively little mortality during stages broadly covering the final instar, but it is density-dependent and also plays a significant part in determining final adult density.
• 4 As the mortality becomes more density-dependent, either with density itself or with cohort age, the smallest individuals become increasingly disproportionately prone to mortality.
• 5 Males, which are smaller, are more susceptible to mortality than females, but their susceptibility relative to their size is less than that of females.

     

The b chromosome polymorphism in Armenian and Turkey populations of the grasshopper Eyprepocnemis plorans plorans (Charpentier) (Orthoptera, Acrididae, Eyprepocnemidinae)

Karyotype analysis of the grasshopper Eyprepocnemis plorans samples derived from Armenian and Turkey populations was performed using C-banding technique. Chromosome polymorphism was associated only with B chromosomes that were revealed in all studied populations. Six new B chromosome morphotypes were described. Four morphotypes were found only in Armenian populations. One morphotype was revealed only in Turkey populations. One B chromosome morphotype was present in Armenian and Turkey populations. B chromosomes derived from Asian populations consisted mostly from C-positive regions. In some of the B chromosomes small C-negative regions were also registered. Morphotypes of the B chromosomes derived from Armenian and Turkey populations drastically differed from the B chromosomes described in the Iberian Peninsula and North African populations. In contrast to the B chromosomes from Armenian and Turkey populations the B chromosomes from Spain populations contained C-positive and C-negative regions alternated in their arms.     

Environmental stress and fluctuating asymmetry in the grasshopper Chorthippus parallelus (Acrididae: Gomphocerinae)

We examined the effect of agrochemical pollution/fertilisation of the soil and climatic conditions at high altitudes on fluctuating asymmetry (FA) level in hindfemur and forewing lengths of the grasshopper Chorthippus parallelus (Zetterstedt). All traits and samples exhibited ideal FA. Forewings, which are less functionally significant in this species, generally exhibited greater FA than the more functionally significant femora. Forewing FA was also more affected by stress induced by climatic conditions at high altitudes than femur FA. The high altitude sample was the most asymmetric sample for both traits, followed by the two control samples. The two samples from agrochemically contaminated habitats showed the lowest asymmetry in femora and forewings of C. parallelus. These results suggest that high altitude imposes more stress on this grasshopper species than does agrochemical contamination although the stress response was more dramatic in the less functional trait.     

Recognition of sex in the acoustic communication of the grasshopper Chorthippus biguttulus (Orthoptera, Acrididae)

Many gomphocerine grasshoppers communicate acoustically: a male's calling song is answered by a female which is approached phonotactically by the male. Signals and recognition mechanisms were investigated in Chorthippus biguttulus with regard to the cues which allow sex discrimination. (1) The stridulatory files on the hindfemur of both sexes are homologous in that they are derived from the same row of bristles, but convergent with respect to the “pegs”. In males the pegs are derived from the bristles, and in females from the wall of the bristle's cup. (2) Male and female songs are generated by similar, probably homologous motor programs, but differ in the duration, intensity, “gappyness” of syllables, risetime of pulses, and the frequency spectra. The hindleg co-ordination during stridulation and the resulting temporal song patterns are less variable in males than in females. (3) For both sexes, recognition of a mate's signal depends on species-specific syllable structure. For males it is essential that the female syllables consist of distinct short pulses, whereas females reject “gappy” syllables. Males strongly prefer “ramped” pulses, females respond to syllables irrespective of steeply or slowly rising ramps. Males react only to the low-frequency component, whereas females prefer spectra containing both, low and high frequency components. Accepted: 20 November 1996     

Population density, phenotype and reproductive output in the grasshopper Chorthippus brunneus

ABSTRACT. 1. The effects of population density on the reproductive output of individual female grasshoppers ( Chorthippus brunneus Thunberg) and the relationships between reproductive output and component elements of each female's phenotype, were investigated.
2. Reproductive output was primarily determined by the rate of egg-pod production. Increased density led to significant reductions in the rate of egg-pod production and reproductive output.
3. Exoskeleton size (reflecting nymphal experience) was positively correlated with clutch size at both high and low densities, but condition (reflecting adult experience) showed no such correlation. At high density, exoskeleton size was more strongly correlated with the rate of egg-pod production and reproductive output than condition. It is concluded that the nymphal aspects of size are more important than the adult aspects.
4. At low density, females with small exoskeletons compensated for their smaller clutches by producing egg-pods at a faster rate. Thus, there was no overall relationship between reproductive output and any of the phenotypic characteristics.
5. The effects of competition were weakly asymmetric in high density populations. The weakness of the asymmetry suggests scramble-like interactions for resources. It is concluded that not only are the effects of competition influenced by individual differences, but also that competition may reveal differences that would not otherwise be apparent.     

Divergence in cuticular hydrocarbons between parapatric subspecies of the meadow grasshopper, Chorthippus parallelus (Orthoptera, Acrididae)

Two subspecies of the grasshopper Chorthippus parallelus (Orthoptera; Acrididae) meet and form a hybrid zone in the Pyrenees. Here we investigate whether the subspecies differ in the blend of cuticular hydrocarbons. Such differences may function as chemical signals, being detected via contact chemoreception and used during mate choice as in other insects. Gas chromatography shows that the subspecies have diverged in the composition of their cuticular hydrocarbons. This difference between subspecies exists over and above variation in cuticular hydrocarbons among individual populations. The majority of the difference can be attributed to the relative amounts of a small group of compounds present in the cuticle. The possible consequences of this chemical divergence for mating encounters between the subspecies are discussed.     

The elytra-to-body binding mechanism of the flightless rainforest species Tabarus montanus Kaszab (Coleoptera: Tenebrionidea)

The elytra-to-body binding mechanism of the flightless rainforest species Tabarus montanus Kaszab (Coleoptera: Tenebrionidea) is described. Previously, studies on this complex character system in tenebrionids have focused mostly on either fully-winged or flightless, desert-dwelling species with a hermetically sealed subelytral cavity. Data presented here show that the rainforest species Ta. montanus has permanently joined interlocking macrostructures between the two elytra along the midline and between the elytral epipleuron and the sides of the body. These are very similar adaptations to ones found in flightless desert tenebrionids. Frictional patches of microtrichia, previously reported in all wing-folding beetle suborders including flightless taxa, are completely absent in Ta. montanus. This constitutes the first report of the complete loss of frictional microtrichia patches in a beetle with fully-developed elytra. Sensory organs (hair sensilla), usually involved in the correct positioning of the elytra over the beetles’ body at rest are also absent in Ta. montanus. The significance of these results relating to the evolution of the tenebrionid subelytral cavity is discussed.     

Effects of forest-dune ecotone management on the endangered heath grasshopper, Chorthippus vagans (Orthoptera: Acrididae)

Dry, oligotrophic ecosystems are highly threatened in Europe due to massive changes in land use and eutrophication. The conservation of these xeric habitats has received much attention, whereas the ecotones between xeric habitats and other habitat types are often disregarded. One species which mainly inhabits the transition zone between pine forests and adjacent xeric habitats is the heath grasshopper, Chorthippus vagans. This species is endangered in large parts of Europe. One of the largest populations in northern Germany is found on a degraded inland dune near Hanover. This population is threatened by dense growth of deciduous trees and litter accumulation. We analyzed changes in the distribution of this population after the implementation of conservation measures (thinning out the forest and removal of leaf litter). Moreover, we examined dispersal distances of the species in order to assess its colonization potential. We also studied the microhabitat preferences of C. vagans to assess key factors influencing its local distribution. Our data show a substantial growth in population size, which might be a consequence of the conservation measures. New patches on the dune were colonized, promoting dispersal between the subpopulations. We propose that restoration of forest-dune ecotones should be considered more often in landscape planning and conservation management.     

Postglacial expansion and genome subdivision in the European grasshopper Chorthippus parallelus

A noncoding nuclear DNA marker sequence (Cpnl-1) was used to investigate subdivision in the grasshopper Chorthippus parallelus and deduce postglacial expansion patterns across its species range in Europe. Investigation of the spatial distribution of 71 Cpnl-1 haplotypes and estimation of levels of genetic differentiation (K_ST values) between populations and geographic regions provided evidence for subdivision of C. parallelus into at least five major geographic regions and indicated that the French form of C. parallelus originated after range expansion from a Balkan refugium, Further evidence for subdivision of C. parallelus between Italy and northern Europe suggests that the Alps may have formed a significant barrier to gene flow in this grasshopper.     

Response patterns of two auditory interneurons in a freely moving grasshopper (Chorthippus biguttulus L.)

Summary Summated nerve potentials were recorded from the neck connectives in intact, freely moving grasshoppers of the speciesChorthippus biguttulus by means of chronically implanted hook electrodes. The action potentials of two auditory interneurons, known as the G₁- and the B₁-neuron, respectively (Kalmring 1975a, b), were distinguishable (Fig. 1) in the recordings and the neurons were identified by their morphology (Fig. 2).The G-neuron exhibits a very rapid and another, much slower, response decrement; the times required for recovery from both these effects show the opposite time courses (Fig. 3). The response versus intensity curve of the G-neuron has the shape of a saturating characteristic for noise stimuli and high frequencies whereas at low frequencies inhibitory effects can be observed for high intensities. The B-neuron has a bell-shaped intensity characteristic at all frequencies with position and width of the bell being frequency-dependent (Fig. 5). The directional characteristic of the G-neuron is nearly circular (for noise stimuli); the B-neuron responds preferentially to sound from the ipsilateral side (Fig. 6). With increasing temperature the threshold, latency, and spike interval of the G-neuron strongly decrease, while the number of spikes per stimulus increases (Fig. 7).In general, the response properties of both auditory interneurons as determined in almost intactChorthippus biguttulus, largely resemble those previously reported forLocusta migratoria in extensively dissected preparations. However, a few, probably interspecific, differences were observed.     

Reproductive potential of gamma-irradiated males of the meadow grasshopper Chorthippus parallelus (Zetterstedt) (Orth., Acrididae)

Males of the meadow grasshopper Chorthippus parallelus were treated with five doses ranging from 0 (control) to 140 Gy of gamma irradiation. There was a negative correlation between irradiation dose and post-treatment longevity. Individuals irradiated with the lowest dose lived, on average, longer than the controls. This was presumably not attributable to an energy allocation from tissue since at the time of death there were no dry weight differences. There was a negative correlation between irradiation dose and number of faecal pellets excreted in a period 6–9 days after treatment but not before. There were no negative correlations between irradiation dose and the time required to copulate, copulation duration and ejaculate size. The proportion of tail-less sperm did not differ between the treatments.     

Pathfinding of peripheral neurons in the central nervous system of an embryonic grasshopper (Chorthippus biguttulus)

The peripheral leg nerves of grasshoppers are initially formed by a set of pioneer neurons and guidepost cells. These cells are used as guiding structures for later-arising axons of sensory neurons. The development of the central projections of the pioneer cells, the guidepost cells and some sensory cells is shown with Lucifer Yellow injection or with DiI application. The axons of the pioneer cells Ti1 enter the central nervous system at 38% of embryonic development. They turn anteriorly close to the midline and ascend with no major branching to the brain. The axons of the guidepost cells Fe1 and Tr1 follow the same path but do not ascend to the brain. Sensory axons of the subgenual organ and the femoral organ probably do not follow the central path pioneered by the former neurons. They end ipsilaterally in the respective thoracic neuromere, as is found in the adult.     

Timing of life cycles in a seasonal environment: the temperature-dependence of embryogenesis and diapause in a grasshopper (Chorthippus brunneus Thunberg)

Summary The durations of the stages in the embryonic development of Chorthippus brunneus (Thunberg) have been estimated at constant temperatures of 20° C and 30° C. There was stage-dependent variation in the temperaturedependence of morphogenesis-a pattern apparently not previously described. The earliest and latest stages of morphogenesis proceeded relatively rapidly at higher temperatures. But intermediate stages, which would tend to occur around the diapause stage in a temperate winter, proceeded relatively rapidly at lower temperatures, as did diapause development. At a given temperature, there was individual variation between eggs such that some developed consistently faster than others. However, these intrinsic differences could be altered by exposure to diapause-breaking conditions at different morphological stages. The results are discussed in terms of their adaptive significance, their effect on population dynamics in a seasonal environment, and their implications for the nature of diapause in insects generally.