Eggs of the migratory locust, Locusta migratoria (Orthoptera: Acrididae), hatch synchronously when in a pod, but only sporadically when kept separately. Here, we aimed to detect the vibrational stimuli emitted by eggs that initiate synchronous hatching. First, we recorded the vibrations emitted by an egg pod and single eggs. One bout of vibrations consisted of 2 to 46 vibrations. The total number and amplitude of vibrations in single eggs increased as the time to hatch decreased. Eggs kept separately were continuously subjected during the last 2 days before hatching to recordings of vibrations from a single egg. Recordings made during the last 2.5 h before hatching caused these eggs to hatch significantly earlier than those not subjected to this treatment, the control. In contrast, eggs subjected to recordings made 8 to 10 h before hatching significantly delayed their hatching relative to the controls, which indicates that synchronous hatching of eggs is induced by age-dependent changes in vibrations from neighbouring eggs. Exposure to one large bout of vibrations (consisting of 40 vibrations in 101 s) was sufficient to induce synchronous hatching in eggs kept separately when applied 5 h before hatching, but not 36 or 11.5 h before hatching. Visual inspection of the spectra indicated that the vibrations had two peaks at about 100 Hz and 1.5 kHz. Only exposure to the latter altered the hatching time of eggs. The embryo moved the posterior part of its abdomen when emitting the vibrations. These results indicate that the synchronous hatching of locust eggs is induced when the embryos emit particular vibrations.
Insect peptidyl-dipeptidase A [angiotensin I - converting enzyme (ACE)] is a soluble single-domain peptidyl-dipeptidase that has many properties in common with the C-domain of mammalian somatic ACE and with the single-domain mammalian ACE. In agreement with a variety of insects, immunocytochemical studies reveal the presence of an ACE-like protein in Locusta migratoria. ACE-like immunoreactivity is present in neurosecretory cells of the pars intercerebralis. These cells have axons projecting into the nervus corporis cardiaci I and into the storage part of the corpus cardiacum, a neuroendocrine organ directly releasing into the aorta. The localisation of ACE in neurosecretory cells is consistent with its proposed role as a processing enzyme that is involved in the generation of active peptide hormones., Dirk Veelaert, Liliane Scoofs, Nathalie Macours, Anick Vandingenen, Arnold De Loof, Elwyn Isaac, Michel Salzet, Roger Huybrechts, and Lit
By means of a tracer assay using a labeled synthetic angiotensin converting enzyme (ACE) substrate hippurylglycylglycine, we have detected high ACE activity in the testes of the African migratory locust, Locusta migratoria. Lower, but significant, ACE activity was observed in midgut and hemolymph. In a two-step purification procedure involving anion exchange and gel permeation chromatography, we have purified LomACE from the locust testes. The enzyme of approximately 80 kDa shows substantial amino-acid sequence homology with ACE from both vertebrate and invertebrate origin. The ACE identity of the purified enzyme was further confirmed by cDNA cloning of the Locusta ACE fragment, which, after in silico translation, revealed a mature protein of 623 amino acids with a large structural similarity to other known ACE proteins.
In view of the extremely high metabolic rates involved, insect flight offers a fascinating model system for studying metabolism during exercise, including its regulation by metabolic neurohormones. In our laboratory the African migratory locust, Locusta migratoria, well-known for its long-distance flights, is used as an internationally recognized model insect. The insect is mass-reared under controlled conditions; its size permits convenient handling in vivo and in vitro, while flight activity can be easily evoked. In addition, research on this pest insect may be of economical importance.
A survey of the energy metabolism during locust flight is presented in Fig. 1. Flight activity stimulates the neurosecretory adipokinetic cells in the glandular lobes of the corpus cardiacum, a neuroendocrine gland connected with the insect brain, to release peptide neurohormones, the adipokinetic hormones (AKHs). The target for these hormones is the fat body. Via signal transduction processes, the action of the hormones ultimately results in the mobilization of both carbohydrate and lipid reserves as fuels for flight. Carbohydrate (trehalose) is mobilized from glycogen reserves, implying hormonal activation of the key enzyme, fat body glycogen phosphorylase, by phosphorylation. Similarly, on the lipid side, sn-1,2-diacylglycerol (DAG) is mobilized from stored triacylglycerol (TAG), by hormonal activation of the fat body TAG lipase. The carbohydrate and lipid substrates are transported in the hemolymph to the contracting flight muscles. Carbohydrate provides most of the energy for the initial period of flight, whereas at a later stage, lipid substrate in the blood is increased and gradually takes over. The transport of DAG requires specific lipoprotein carriers (lipophorins) which differ in several respects from the lipoproteins in mammals, and act as a lipid shuttle.
This review is focused on three interrelated topics, covering recent data on the biosynthesis and release of the AKHs, their signal transduction mechanisms in the fat body cells, and the changes in the lipophorin system induced by the AKHs during flight., Dick J. Van Der Horst, Wil J.A. Van Marrewijk, Henk G.B. Vullings, Jacques H.B. Diederen, and Lit
Changes in the content of protein, glycogen, neutral lipids and sterols were investigated in locust eggs from oviposition until larval hatching. The content of all of these nutritional reserves was higher in the eggs of S. gregaria because of their larger size, although relative changes in utilization or synthesis of these materials during embryogenesis showed a more or less parallel course. The amount of protein increased progressively during embryogenesis, while glycogen and neutral lipids were successively metabolized or utilized for development of the embryo. There appeared significant relative differences in the way of utilizing energetic reserves during embryogenesis between the two species. This was especially manifested by a larger relative decrease in the content of neutral lipids (mainly triglyceride) in the eggs of S. gregaria. Conversely, the eggs of L. migratoria showed a larger relative utilization of glycogen reserves. The content of steroids was higher in the eggs of S. gregaria during the initial 6 days of embryonic development. Later on, during advanced stages of pharate larval development, the steroids were rapidly utilized and decreased in both species. The described changes in utilization of the main energetic resources were correlated with periods of tissue growth and differentiation and with the cuticulogenesis of the growing embryo.
The aim of this study was to show that the kind of AKH-mobilized energy substrates in insects can be predicted on the basis of the results obtained with the application of heterologous, i.e. inter-species, AKHs. Four different AKHs, the Locmi-AKH-I inducing hyperlipaemia and hyperglycaemia in Locusta migratoria, Tenmo-HrTH inducing hyperglycaemia in Tenebrio molitor, and Pyrap-AKH and Peram-CAH-II inducing hyperlipaemia in Pyrrhocoris apterus were used, firstly in conspecific tests, secondly in all possible species-AKH combinations, and finally in individual applications on the test species, the cotton bug Dysdercus cingulatus. Since each of the AKHs induced hyperlipaemia in D. cingulatus adults, we predicted that lipids are the only energy substrates which are mobilized in this species by its native AKH. The accuracy of this prediction was subsequently confirmed by the structural identification of the native D. cingulatus AKH and conspecific application tests. The proposed methodical approach can serve as a suitable monitoring system for determination of the kind of energy substrates mobilized by native insect AKHs until the structure of the hormone is identified.
A short-winged morph, whose occurrence is controlled by a simple recessive Mendelian unit, was recently discovered in Locusta migratoria. The existence of trade-offs between flight capability associated with wing length and other fitness-related traits are often documented for insects. The present study investigated the evolutionary significance of the short-winged and long-winged morphs of this locust using two laboratory strains showing wing dimorphism. The life-history traits examined included nymphal development, adult body weight, percentage adult survival, age at first reproduction, egg production and hatchling body weight. The results indicate that there are no consistent morph-specific differences in any of these traits. Of the several possibilities considered, the most likely is that the short-winged morph of this locust is an aberration or represents an initial stage in the evolution of this species., Yudai Nishide, Seiji Tanaka., and Obsahuje seznam literatury