The vermiform larva of Schistocerca gregaria (Forskål): Form and activity (Insecta,Orthoptera)

A detailed study of the vermiform larva of Schistocerca gregaria was made using film analysis in combination with morphological studies. The adaptations of the body are illustrated, and the use of these in digging up to the surface of the ground is described. The means of orientation were investigated, and unusual club-tipped hairs are suggested as important mechanoreceptors.Now Centre for Overseas Pest Research.     

Analysis of the mitochondrial genome of Schistocerca gregaria gregaria (Orthoptera: Acrididae)

In the present study, we present the full sequence of the mitochondrial genome of the African desert locust Schistocerca gregaria gregaria. The size of 15625 bp reported matches very well with mitochondrial genomes of other Orthopteriodea. The mitochondrial genome comprises 13 protein‐coding genes, two ribosomal RNAs and 22 t‐RNAs with two t‐RNA (trnD and trnK) rearrangements that are typical for the taxon Caelifera. We compared the sequence with 12 mitochondrial genes of Schistocerca gregaria flaviventris and Schistocerca americana and used some of these data to construct phylogenetic trees, which confirm the close relationship between the two subspecies S. g. flaviventris and S. g. gregaria. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 296–305.     

The anatomy and histology of the maxillary palp of Schistocerca gregaria (Orthoptera, Acrididae)

The general anatomy and histology of the maxillary palp are described with particular attention to the number, distribution and structure of the various sensilla.     

Accessory hemolymph pump in the mesothoracic legs of locusts, (Schistocerca gregaria forskal) (Orthoptera,Acrididae)

An accessory pulsatile organ located in the mesothoracic legs pumps hemolymph towards the tip of the leg ventrally and towards the body near the dorsal side. It consists of a muscle attached to the ventral side of the trochanter and to the central region of a transverse connective tissue diaphragm located at the trochanter-femur border. The diaphragm has a ventral outlet that permits efferent hemolymph flow through a narrow femoral sinus. A second dorsal outlet allows the afferent countercurrent back to the thorax through a separate hemolymph channel. During abdominal ventilation, the pumping rhythm of the legfn2heart is neurally synchronized with abdominal ventilation. Expiratory pressure expands tracheal air sacs in the ventral trochanter and helps driving hemolymph out of this space. In idle periods of resting ventilation, an autonomous myogenic rhythm of the leg–heart can maintain hemolymph circulation in the mesothoracic leg without neural control.     

Embryonic development of the sensory innervation of the antenna of the grasshopper Schistocerca gregaria

The establishment of the sensory nervous system of the antenna of the grasshopper Schistocerca gregaria was examined using immunocytochemical methods and in the light of the appendicular and articulated nature of this structure. The former is demonstrated first by the expression pattern of the segment polarity gene engrailed in the head neuromere innervating the antenna, the deutocerebrum. Engrailed expression is present in identified deutocerebral neuroblasts and, as elsewhere in the body, is continuous with cells of the posterior epithelium of the associated appendage, in this case the antenna. Second, early expression of the glial homeobox gene reversed polarity (repo) in the antenna is by a stereotypic pair of cells at the antenna base, a pattern we show is repeated metamerically for each thoracic appendage of the embryo. Subsequently, three regions of Repo expression (A1, A2, A3) are seen within the antenna, and may represent a preliminary form of articulation. Bromodeoxyuridine incorporation reveals that these regions are sites of intense cell differentiation. Neuron-specific horseradish peroxidase and Lazarillo expression confirm that the pioneers of the ventral and dorsal tracts of the antennal sensory nervous system are amongst these differentiating cells. Sets of pioneers appear simultaneously in several bands and project confluent axons towards the antennal base. We conclude that the sensory nervous system of the antenna is not pioneered from the tip of the antenna alone, but in a stepwise manner by cells from several zones. The early sensory nervous systems of antenna, maxilla and leg therefore follow a similar developmental program consistent with their serially homologous nature.     

PCR primers for polymorphic microsatellite loci in the desert locust,Schistocerca gregaria (Orthoptera: Acrididae)

Nine pairs of polymerase chain reaction (PCR) primers that amplify polymorphic microsatellite loci in the desert locust, Schistocerca gregaria (Forskal), were developed using a magnetic bead‐based enrichment protocol. A sample of 48 locusts collected during the 1993 and 1995 upsurge periods in Eritrea, East Africa, were genotyped. The number of alleles per locus ranged from six to 20; the average was 12.67. Allelic distributions were significantly different between samples from different localities.     

Changes in the auditory neuropil after deafferentation in adult grasshoppers (Schistocerca gregaria)

Nervous systems are capable of structural adjustments. Such plastic changes also occur in the auditory system of the locust Schistocerca gregaria in which a deafferentation leads to compensatory mechanisms, such as collateral sprouting of interneurons. In this study we further investigated lesion related changes in the major auditory neuropil, the median ventral association center (mVAC) of the metathoracic ganglion. The auditory sensory organ of adult locusts was unilaterally extirpated and the mVAC was histologically and immunocytochemically analyzed until 20 days postoperative. Measurements of the neuropil area in transverse sections showed a decrease in size. The putative transmitter of the afferents, acetylcholine, was investigated by acetylcholinesterase histochemistry. Comparisons of staining intensities in the intact and deafferentated mVAC indicated that the amount of acetylcholinesterase in the deafferentated mVAC decreased shortly after the operation. Both, the decreases in size of the mVAC as well as that in acetylcholinesterase histochemistry were only less than 10% compared to the controls. The immunoreactivity against the neurotransmitters γ-amino butyric acid and serotonin was not influenced by the deafferentation.     

Embryonic expression of muscle-specific antigens in the grasshopper Schistocerca gregaria

Monoclonal antibodies (MAbs) are used to investigate molecules that are expressed during embryonic muscle differentiation and that may be involved in muscle pioneer and muscle attachment site formation. MAb F2A5 immunoreactivity appears in all muscle pioneers as soon as they extend processes, and continues in all muscle precursors. MAb 4H1 immunoreactivity is strongly expressed only after mesodermal cells have fused with the muscle pioneers; then it is concentrated at their growth-cone-like ends near developing attachment sites. During later embryonic development, MAb F2A5 and MAb 4H1 immunoreactivity become associated with the myofibrillar network. Biochemical experiments indicate that MAb 4H1 recognises a 47 kDa antigen, and MAb F2A5 recognises an 80 kDa antigen.     

Haemocytic encapsulation in the locust Schistocerca gregaria (Orthoptera) and in the cockroach Periplaneta americana (Dictyoptera)

Summary The numbers and types of haemocytes in adult male Schistocerca gregaria and Periplaneta americana have been studied in an attempt to explain the differences in thickness of haemocytic capsules formed around abiotic particles in the 2 species. Total and differential haemocyte counts and measurements of blood volume using ³H-inulin indicate that there are 3–4 times more plasmatocytes in the cockroach than in the locust. Although the three main haemocyte types are easily recognised by phase-contrast microscopy, there are few distinguishing ultrastructural characteristics and thus defining the cell types that make up the capsule is difficult. In early capsules in the locust, but not in the cockroach, signs of coagulocyte lysis are apparent, and in both species the bulk of the capsule appears to be made up of granular plasmatocyte-like cells. The relatively thinner capsules formed in the locust might be due to the slow, and limited, recruitment of plasmatocytes to the developing capsule. The material coating completed capsules appears ultrastructurally similar to the subepidermal basement membrane, and both these layers stain with Alcian blue. Once the coating material has formed, the capsule appears to be treated as self by the immunorecognition system.     

Physiological responses and central nervous projections of antennal olfactory receptor neurons in the adult desert locust, Schistocerca gregaria (Orthoptera: Acrididae)

Olfactory receptor neurons present in two morphological sensillum types on the male Schistocerca gregaria antenna were for the first time investigated physiologically when stimulated with behaviourally relevant odours. Neurons present in trichoid/basiconic sensilla showed clear excitatory responses to compounds present in the male-produced aggregation pheromone and also to a plant produced compound. Sensilla could be categorised physiologically according to the responses of their receptor neurons to the tested stimuli. Also receptor neurons present in sensilla coeloconica responded to aggregation pheromone components, but always in an inhibitory fashion. These neurons could, however, be excited by a plant produced compound and by some acids present in the nymphal odour. The antennal lobe of the male S. gregaria was observed to contain about 1000 very small glomerular structures. Single receptor neurons were stained from the antenna to the antennal lobe using a cobalt lysine technique. These stainings revealed a multi glomerular axonal branching pattern of antennal receptor neurons.Abbreviations AN antennal nerve - AL antennal lobe - RN receptor neuron     

Fine structure and distribution of antennal sensilla of the desert locust, Schistocerca gregaria (Orthoptera: Acrididae)

The fine structure and distribution of various types of antennal sensilla in three nymphal stages and in adults of both solitary-reared (solitary) and crowd-reared (gregarious) phases of the desert locust, Schistocerca gregaria, were investigated by scanning and transmission electron microscopy. Four types of sensilla were identified: sensilla basiconica, s. trichodea, s. coeloconica and s. chaetica. S. basiconica contain up to 50 sensory neurons, each of which displays massive dendritic branching. The sensillar wall is penetrated by a large number of pores. In contrast, s. trichodea contain one to three sensory neurons that branch to give five or six dendrites in the sensillar lumen; the sensillum wall is penetrated by relatively few pores. The s. coeloconica are situated in spherical cuticular pits on the antennal surface. The s. coeloconica are of two types: one type contains one to three sensory neurons with double sensillar walls penetrated by slit-like pores, whereas the second type contains four sensory neurons with non-porous double sensillar walls. The s. chaetica have a flexible socket and a thick non-porous sensillum wall and contain four sensory neurons that send unbranched dendrites to a terminal pore. A fifth sensory neuron of the s. chaetica terminates in a tubular body at the base of the hair. S. basiconica and coeloconica are normally distributed over the entire antennal flagellum, with a concentration in the middle segments; s. trichodea have three areas of concentration on the 5th, 10th and 14th flagellar segments. Sensilla chaetica are most abundant on the terminal segment. Locusts raised in solitary conditions have more olfactory sensilla (s. basiconica and s. coeloconica) than crowd-reared locusts. The difference in sensillar numbers is more evident in adults than in nymphs. These results suggest that differences in the odour-mediated behaviour of nymphs and adults, and between the phases of S. gregaria, may be attributable to differences at the sensory input level.     

Phase-independent responses to phase-specific aggregation pheromone in adult desert locusts, Schistocerca gregaria (Orthoptera: Acrididae)

Abstract. Volatiles from solitary-reared (solitarious) and crowd-reared (gregarious) adult male desert locusts, Schistocerca gregaria (Forskal) (Orthoptera: Acrididae), were quantitatively and qualitatively different.In particular, solitarious males did not emit phenylacetonitrile, a key component of the aggregation pheromone produced by gregarious adult males.In laboratory bioassays, solitarious and gregarious adults of both sexes responded similarly to the natural aggregation pheromone blend, the major pheromone component phenylacetonitrile, and a synthetic pheromone blend comprising benzaldehyde, guaiacol, phenylacetonitrile and phenol.EAG measurements showed significant differences in the responsiveness of adults of the two phases to the four synthetic components at high doses; however, the general response patterns were similar.These results suggest that the gregarious adult male aggregation pheromone may play a role in the arrestment and subsequent recruitment of solitarious individuals into gregarious or gregarizing groups during the early stages of a locust outbreak.     

Homonomies within the ventral muscle system and the associated motoneurons in the locust,Schistocerca gregaria (Insecta,Caelifera)

To understand the segmental reiteration of an insect, the serially arranged neuromuscular system of the locust, Schistocerca gregaria, is studied. The ventral muscle system is chosen and its motoneuronal supply is described in the thoracic and pregenital segments. In general, repetitively arranged, similar sets of motoneurons (MNs) supply the ventral muscles of these segments. Common criteria of both topology of muscles and neural features (nerve branches and motoneuronal supply) suggest possible homonomies of the ventral longitudinal muscles and ventral diaphragm of the thoracic and abdominal system. Based on a segment-by-segment analysis, muscle topology and motor supply match, in most instances. There are, however, cases where such a parallelism is missing. In a particular cases the supply of apparently homonomous muscles shifts from one set of MNs to another. In another case, putatively equivalent MNs of different ganglia supply morphologically different muscle structures in the adult animal. Therefore, it becomes apparent that muscles and their supplying MNs are, in principle, independent elements which might be subjected autonomously to ontogenetic processes. As a consequence, in the search for the basic segmental Bauplan depending on homonomous structures, muscles and MNs have to be regarded as separate entities.Abbreviations A1–6 abdominal ganglion (or neuromere A1–3) - AS1–6 abdominal segment 1–6 - DUM doisal unpaired median - M muscle (number) - MN motoneuron - N nerve (number) - PMN paramedian nerve - T1–3 pro-, meso-, metathoracic ganglion - TS1–3 pro-, meso-, metathoracic segment - VD ventral diaphragm - VM ventral muscle     

Anatomical studies of the insect central nervous system: A ground-plan of the midbrain and an introduction to the central complex in the locust, Schistocerca gregaria (Orthoptera)

The supra-oesophageal ganglion (brain) of Schistocerca gregaria Forskál has been studied at the light-microscopical level using Wigglesworth's osmic acid-ethyl gallate method. Particular attention was paid to the midbrain. A structural ground-plan is described which incorporates the ocellar nerve roots, the antenno-glomerular bundles, the corpora cardiaca nerves I roots, the antennal lobes, the corpora pedunculata and the central complex. The "undifferentiated" midbrain is described in terms of the distribution of the main features of 15 unique pairs of large neurones all of which have their cell bodies in the brain and which project, either ipsilaterally or contralaterally, to the circumoesophageal connectives. In addition a single unique neurone with bilateral distribution restricted to the brain is described. All these neurones provide a conspicuous and constant framework for further investigation. A ground-plan based on the distribution of 64 individual neurones (central complex system I) is presented for the central complex. This system indicates that the central complex is fundamentally organized on the basis of 16 repetitive groups of neurones.     

Effects of food on the development of the Desert Locust,Schistocerca gregaria (Forskal)

An account is given of the effects of five different food plants on the development of larvae of Schistocerca gregaria reared in the laboratory.     

Qviposition of Schistocerca gregaria (Forskal) (Orthoptera: Acrididae) mated with males unable to transfer spermatophores

An account is given of the oviposition of females paired with males unable to transfer spermatophores. Various influences of the male accessory gland on the gonotrophic cycle are discussed.     

Postembryonic development of astrocyte-like glia of the central complex in the grasshopper Schistocerca gregaria

Central complex modules in the postembryonic brain of the grasshopper Schistocerca gregaria are enveloped by Repo-positive/glutamine-synthetase-positive astrocyte-like glia. Such cells constitute Rind-Neuropil Interface glia. We have investigated the postembryonic development of these glia and their anatomical relationship to axons originating from the w, x, y, z tract system of the pars intercerebralis. Based on glutamine synthetase immunolabeling, we have identified four morphological types of cells: bipolar type 1 glia delimit the central body but only innervate its neuropil superficially; monopolar type 2 glia have a more columnar morphology and direct numerous gliopodia into the neuropil where they arborize extensively; monopolar type 3 glia are found predominantly in the region between the noduli and the central body and have a dendritic morphology and their gliopodia project deeply into the central body neuropil where they arborize extensively; multipolar type 4 glia link the central body neuropil with neighboring neuropils of the protocerebrum. These glia occupy type-specific distributions around the central body. Their gliopodia develop late in embryogenesis, elongate and generally become denser during subsequent postembryonic development. Gliopodia from putatively type 3 glia within the central body have been shown to lie closely apposed to individual axons of identified columnar fiber bundles from the w, x, y, z tract system of the central complex. This anatomical association might offer a substrate for neuron/glia interactions mediating postembryonic maturation of the central complex.     

The integument and sensilla of the pregenital abdomen of the Desert locust (Schistocerca gregaria) (Orthoptera: Acrididae)

The integument and sensilla of the abdominal segments II–VII, together with the tracheal and nerve supply, are described in so far as they can be seen using whole mounts. Such a method often enables the neurons of the sensilla to be seen clearly and to be associated definitely with a certain cuticular structure. The sensilla are compared with those already known from the palps, and it is concluded that probably all those on the abdomen also occur on the palps.