The dynamics of release and the possible identity of bursicon in Locusta migratoria migratorioides

A bioassay for bursicon, the hardening and darkening hormone, is described. Using this bioassay, the site of release of bursicon in Locusta migratoria migratorioides is shown to be the abdominal ganglia, where the bursicon is probably stored for release in an inactive state before ecdysis, rather than passed down the nerve cord for release during ecdysis. The bursicon is shown to be released into the haemolymph with a maximum concentration, only minutes after the start of release, of one-fifth of that reported for the blowfly. The hormone is shown to disappear from the haemolymph in two distinct stages. The distribution of bursicon in three insects, L. m. migratorioides, Schistocerca gregaria, and Periplaneta americana is described, and the bursicon of the corpus cardiacum of these insects characterized in the form of dose-response curves with the Phormia bioassay. The reactions of various parts of the nervous systems of these insects to some simple histological and histochemical tests are also described, and these reactions compared with each other and the distribution of bursicon in these tissues. It is concluded that bursicon is probably a neurosecretion of the class A.     

Neuromuscular correlates of rhythmical cheliped flexion behavior in hermit crabs

Journal of Comparative Physiology A -     

In vitro and in vivo effects of formamidines in locust (Locusta migratoria migratorioides)

In vivo and in vitro experiments were used to study the effects of formamidines in the locust, Locusta migratoria migratorioides. In vivo the lethal and the antifeeding effects, in vitro the inhibition of the binding of a selective 3H-ligand to the receptors of octopamine, tyramine, dopamine, serotonin and gamma-amino butiric acid were studied. We have demonstrated that demethylchlordimeform is specific agonist to octopamine receptor, having high affinity to octopamine receptor, a moderate affinitiy to tyramine receptor and a low affinity to dopamine, serotonin and to gamma-amino butiric acid receptors. The demethylated chlordimeform analogoues, demethylchlordimeform and didemethylchlordimeform have higher affinity to the octopamine receptor than the parent compound. The formamidines had a toxic and an antifeeding effects when injected into the locust. The half lethal doses (LD50) and the feeding inhibition were correlated with the affinity of the compounds (Ki). The ring substitutions of the mulecule have alterated the both affinity and in vivo effect of the compounds. The most effective ring substitution pattern is 2,4-disubstitution with a combination of methyl groups or halogens. Our results suggest that the lethal effect of formamidines is mediated through the octopamine receptor.     

A fine structural analysis of serosal cuticulogenesis in the egg of Locusta migratoria migratorioides

The typical outer coat (the yellow cuticle) disclosed in the Locusta migratoria migratorioldes egg appears to be a usual formation in Acrididae; its physiological significance is discussed. There is a diversification of the epicuticle in the anterior egg pole, very likely related to a diversified water permeability of the egg. Three main regions of the endocuticle show that the cuticulogenesis proceeds in three main phases, each region being characterized by its own texture. The change in texture appears to be related to changes in water loading by the developing egg. Elucidation of the factors controlling the texture of the serosal cuticle was attempted. The assumption, that change in texture may reflect a phase behaviour reminiscent of that of a lyotropic liquid crystal polymer in aqueous solution, is discussed.     

Sperm competition and the evolution of the precopulatory passive phase behaviour in Locusta migratoria migratorioides

An account is given of sperm competition in Locusta migratoria, for cases where the competing ejaculates occur either as one per oviposition cycle or as two per cycle. These situations exert quite different sperm competition effects; evolutionary reasons for this are discussed. The adaptive value of the male precopulatory passive phase behaviour is considered in relation to sexual selection and sperm competition.     

Flight fuel related differences between solitary and gregarious locusts (Locusta migratoria migratorioides)

Abstract. Flight fuel relations of crowded and isolated Locusta migratoria migratorioides were investigated in younger (12–16 days after fledging) and older (27–30 or 27–32 days after fledging) adult males.No phase polymorphism dependent differences were found in resting haemolymph carbohydrate levels of the younger locusts.In the older age group, resting haemolymph carbohydrate levels were slightly though significantly higher in the isolated than in the crowded locusts.Injection of various doses of synthetic adipokinetic hormones (AKHs) did not induce marked changes in haemolymph carbohydrate levels and no differences were found between crowded and isolated locusts.A 30 min flight led to the same decrease in haemolymph carbohydrate levels of isolated and crowded locusts, 43.3% and 44.6% of the resting levels, respectively.We concluded, therefore, that the results do not seem to indicate that isolated locusts rely more heavily on carbohydrates as flight fuel than crowded locusts.Hyperlipaemic responses to flight were less intense in isolated than in crowded locusts, but phase polymorphism dependent differences in flight-induced increase of haemolymph lipid levels were not parallel in 12–16-day-old and 27–32-day-old males.In the younger age group the difference was mainly in the duration of flight needed to induce full response which appeared already after 20 min of flight in the crowded locusts, but only after 45 or 60 min of flight in the isolated ones.In contrast, the older isolated locusts showed markedly lower haemolymph lipid elevations than the crowded locusts even after 30, 45 or 60 min of flight.The hypothesis is forwarded that isolated locusts have a rather coarse adipokinetic strategy focused on a single long-distance migratory flight, whereas gregarious locusts possess a fine adipokinetic balance for reiterative migratory flights and saving fuel reserves for unpredictable long-distance migrations.     

The fine structure of the eggshell of the laid egg of Locusta migratoria migratorioides

Ultrastructural analysis disclosed a regional diversification of the eggshell of the Locusta migratoria m. (L.m.m.) egg. This diversification is discussed taking into account the data about water permeability of the L.m.m. egg. The presence of several kinds of openings in the exochorion implies that in addition to the micropyles, the L.m.m. egg is provided with a respiratory system, especially in its anterior pole. The respiratory system of insect eggs is briefly reviewed. The presence of a wax layer in the L.m.m. egg is also discussed.     

Inhibition of an abdominal proprioceptive reflex in crayfish

Summary Stimulation of the tonic muscle receptor organs inProcambarus clarkii results in reflex activation of the superficial extensors. This pathway is inhibited by activity in the lateral giant fibers and both medial giants. A labile synapse in the same pathway works synergistically with the giant fiber-mediated inhibition to prevent maladaptive activation of the superficial extensors during escape behavior. Evidence did not support the notion of giant fiber-mediated peripheral inhibition (via the accessory nerve) of MRO activity.This work was supported by NIH grant NS 02944 (to D. Kennedy). I would like to thank Drs. Kennedy, Wine, and the members of the Kennedy laboratory for their help and support.     

Thiol-activated serine proteinases from nymphal hemolymph of the African migratory locust,Locusta migratoria migratorioides

Two unique serine proteinase isoenzymes (LmHP-1 and LmHP-2) were isolated from the hemolymph of African migratory locust (Locusta migratoria migratorioides) nymphs. Both have a molecular mass of about 23 kDa and are activated by thiol-reducing agents. PMSF abolishes enzymes activity only after thiol activation, while the cysteine proteinase inhibitors E-64, iodoacetamide, and heavy metals fail to inhibit the thiol-activated enzymes. The N-terminal sequence was determined for the more-abundant LmHP-2 isoenzyme. It exhibits partial homology to that of other insect serine proteinases and similar substrate specificity and inhibition by the synthetic and protein trypsin inhibitors pABA, TLCK, BBI, and STI. The locust trypsins LmHP-1 and LmHP-2 constitute a new category of serine proteases wherein the active site of the enzyme is exposed by thiol activation without cleavage of peptide bonds.     

Oviposition by the African migratory locust, Locusta migratoria migratorioides, in a crop environment in South Africa

Oviposition by the African migratory locust, Locusta migratoria migratorioides (Orthoptera: Acrididae), was studied in maize and wheat crops on the Orange Free State Highveld. Maize was shown to be the most important oviposition habitat with peak laying taking place in autumn and early winter when highest pod densities were recorded. Laying was mainly concentrated along the middle of the crop interrows in maize and within clearings in the wheat crop. Despite the uniform layout of these crops, the distribution of egg pods was found to be aggregated. Non-reproductive behaviour, such as locust aggregation, basking and feeding, as well as environmental factors appeared to influence the distribution of egg pods in these crops. Secondary selection for optinum soil moisture and compaction on the laying site enhanced the aggregation of pods.     

Cytochemical localization of adenylate cyclase in the various tissues of Locusta migratoria (migratorioides R.F.)

Summary The ultrastructural cytochemical procedure to demonstrate adenyl cyclase in mammalian organs was used in insects. After several modifications, an utilizable method was applied for the detection of the enzyme in the various tissues. Adenylate cyclase which can be stimulated with octopamine was localized on the membrane of the glial cells and the axolemma of certain large axons in the insect brain. Adenylate cyclase which could be activated by NaF and isoproterenol was also demonstrated in the lipid droplets of glial cells of the brain. With the simultaneous application of NaF and isoproterenol, rather strong adenylate cyclase activity could be detected on the surface of the corpora allata cells both in the cells situated on the glandular surface and the central part of the gland. In contrast in the corpus cardiacum enzyme activity was only observable on the basal lamina of the glandular surface. An appreciable amount of reaction product, indicating the presence of the enzyme, could be found on the surface of the lipid droplets in the fat body situated near the glandular tissues. In the heart muscle, reaction product referring to enzyme activation could not be demonstrated with the help of the methods applied.     

Circadian rhythm changes in toxicity of the insecticide dieldrin on larvae of the migratory locust Locusta migratoria migratorioides.

Circadian changes in toxicity of the insecticide dieldrin were documented in the larvae (fifth stage) of the migratory locust, Locusta migratoria migratorioides. Insects were housed under light (L): dark (D) = 12:12, with L from 0800 to 2000 h. Topical applications of dieldrin at fixed clock hours, with doses ranging from 0.1 to 8 micrograms/gm body weight, were carried out in a series of experiments on male and female larvae. Twenty-four h after dosing, mortality was recorded to quantify the median lethal dose (LD50) values with reference to time of treatment. Experiments were performed during February, early and late June, and August. Larvae were more susceptible to dieldrin when dosed during the night rather than during the day [analysis of variance (ANOVA); p less than 0.05]. Moreover, female larvae were less susceptible to dieldrin than were male larvae (ANOVA; p less than 0.05). Cosinor analysis revealed circadian rhythms in susceptibility-resistance to the insecticide in all experiments except no. 2. Toxicity was found to be greatest during the nighttime. Cosinor analysis of pooled data of the four experiments documented circadian rhythmicity to toxicity of dieldrin in female but not in male larvae. Regardless of sex, the timing of least susceptibility (greatest resistance and highest LD50 value) to the insecticide, dieldrin, was around 1500.     

Dopaminergic control of foregut contractions in Locusta migratoria

Tyrosine hydroxylase-like immunoreactivity is present in cell bodies and processes in the brain and optic lobes of Locusta migratoria, with processes projecting along the frontal connectives to form a neuropile within the frontal ganglion. Immunoreactive cell bodies and processes are also evident in the hypocerebral and ventricular ganglia with processes extending over the foregut. Tyrosine hydroxylase is the rate-limiting enzyme in dopamine biosynthesis, and high-performance liquid chromatography coupled to electrochemical detection was used to confirm the presence of dopamine in the innervation to the foregut. Spontaneous foregut contractions are under the control of the ventricular ganglia and are absent when these ganglia are removed. Dopamine leads to an inhibition of both the amplitude and frequency of phasic contractions of the foregut that are produced when the ventricular ganglia are left attached. Dopamine has direct effects on the foregut muscle in the absence of the ventricular ganglia, inhibiting a proctolin-induced contraction in a dose-dependent manner.     

Neuromuscular and hormonal control of post-eclosion processes in flies

Flies (exemplified by Sarcophaga bullata) expand after eclosion from the puparium by processes of “pulsing” (slow rhythmical abdominal contractions) and “pumping” of air (fast rhythmical contractions of the cibarial pump). Pulsing and pumping are inhibited if a newly eclosed fly is kept in an enclosed space (sand, a glass tube, an empty puparium). This inhibition no longer applies if such flies are injected with either hemolymph from flies 10–15 min old or cAMP, or are confined at the age of 10 min. This suggests a hormonal control of pulsing and pumping. Pumping alone, without pulsing, occurs in flies treated with certain paralyzing agents like ether, tetrodotoxin, bee venom, or “FlyNap,” or have the connectives in the neck cut or interrupted by cauterization. Application of FlyNap or neck cauterization leads to excessive pumping which results in bloating. Expansion by bloating is confined to the soft membranes, leaving sclerites and wings largely unexpanded. The function of pulsing is probably that of “plasticizing” and stretching the cuticle to make it respond to increased steady pressure by air-pumping. Flies ligated at the proboscis show almost regular pulsing and pumping, but without intake of air, and consequently no expansion. Cuticle (sclerites) and wings, however, become plasticized. Some plasticization occurs even in the absence, or reduction, of pulsing (in a neck-cauterized fly), brought about by a hormonal process. Eclosion from the puparium is also initiated by a hormonal action. Thus, the following processes during fly emergence are controlled by hormones: eclosion proper, pulsing, pumping, plasticization, and tanning. These hormones are separate entities, with the possible exception of the pulsing/pumping hormone(s).     

Neuromuscular control: introduction and overview.

This paper introduces some basic concepts of the interdisciplinary field of neuromuscular control, without the intention to be complete. The complexity and multifaceted nature of neuromuscular control systems is briefly addressed. Principles of stability and planning of motion trajectories are discussed. Closed-loop and open-loop control are considered, together with the inherent stability properties of muscles and the geometrical design of animal bodies. Various modelling approaches, as used by several authors in the Philosophical Transactions of the Royal Society of London, Series B, May 1999 issue, such as inverse and forward dynamics are outlined. An introductory overview is presented of the other contributions in that issue.