The effect of exercise on the growth of mitochondria and myofibrils in the flight muscles of the tsetse fly,Glossina morsitans

Exercise affects the growth of the dorsal longitudinal flight muscles in the tsetse fly. Examination of electron micrographs of flight muscles taken from flies subjected to enforced exercise, “ormal” exercise and no exercise reveals that both mitochondrial and myofibrillar fractions of the muscles are stimulated to grow at a faster rate by enforced exercise but that the mitochondria respond more rapidly.     

Development of the indirect flight muscles of Drosophila.

We have followed the pupal development of the indirect flight muscles (IFMs) of Drosophila melanogaster. At the onset of metamorphosis larval muscles start to histolyze, with the exception of a specific set of thoracic muscles. Myoblasts surround these persisting larval muscles and begin the formation of one group of adult indirect flight muscles, the dorsal longitudinal muscles. We show that the other group of indirect flight muscles, the dorsoventral muscles, develops simultaneously but without the use of larval templates. By morphological criteria and by patterns of specific gene expression, our experiments define events in IFM development.     

A comparative study of motor patterns during pre-flight warm-up in hawkmoths

Summary Temporal patterns of activation of flight muscles were recorded by means of wires placed extracellularly in thoracic muscles. In the five species of hawkmoths studied, wingstrokes of small amplitude were produced during a preflight warm-up by synchronous contractions of certain groups of muscles which are antagonists in flight. The main depressor muscle, the dorsal longitudinal, was excited in synchrony with some or all of the indirect elevator muscles. Three direct muscles, the subalar, basalar and third axillary muscles, were usually excited out of phase with the dorsal longitudinal muscle. However, details of the motor pattern varied from species to species. During fixed flight phase changes comparable in magnitude to those which occur during the transition from warm-up to flight were observed in Manduca sexta and Smerinthus cerisyi. The results (summarized in Table 2) suggest that a variety of warm-up patterns evolved within the Sphingidae as modifications of a common mechanism generating flight motor patterns.I thank Dr. Harry Lange for assistance in the initial collecting of Manduca sexta and for identifying specimens of this species.     

Flight initiations in Drosophila melanogaster are mediated by several distinct motor patterns

We have monitored the patterns of activation of five muscles during flight initiation of Drosophila melanogaster: the tergotrochanteral muscle (a mesothoracic leg extensor), dorsal longitudinal muscles #3, #4 and #6 (wing depressors), and dorsal ventral muscle #Ic (a wing elevator). Stimulation of a pair of large descending interneurons, the giant fibers, activates these muscles in a stereotypic pattern and is thought to evoke escape flight initiation. To investigate the role of the giant fibers in coordinating flight initiation, we have compared the patterns of muscle activation evoked by giant fiber stimulation with those during flight initiations executed voluntarily and evoked by visual and olfactory stimuli. Visually elicited flight initiations exhibit patterns of muscle activation indistinguishable from those evoked by giant fiber stimulation. Olfactory-induced flight initiations exhibit patterns of muscle activation similar to those during voluntary flight initiations. Yet only some benzaldehyde-induced and voluntary flight initiations exhibit patterns of muscle activation similar to those evoked by giant fiber stimulation. These results indicate that visually elicited flight initiations are coordinated by the giant fiber circuit. By contrast, the giant fiber circuit alone cannot account for the patterns of muscle activation observed during the majority of olfactory-induced and voluntary flight initiations.Abbreviations DLM/DLMn dorsal longitudinal muscle/motor neuron - DVM/DVMn dorsal ventral muscle/motor neuron - GF(s) giant fiber interneuron (s) - PSI peripherally synapsing interneuron - TTM/TTMn tergotrochanteral muscle/motor neuron     

Modifications of the metapostnotum and origin of the 'propodeal triangle' in Hymenoptera Aculeata

The metapostnotum of aculeate Hymenoptera shows three trends of modification: simple reduction in Bethyloidea, invagination and reduction in Vespoidea and enlargement (forming the ‘propodeal triangle’) in Sphecoidea (including bees). The second phragma is also variously modified in thete three groups to allow maximal development of the dorsal longitudinal indirect flight muscles of the mesothorax.     

Thoracic morphology of a flightless mexican grasshopper,Barytettix psolus: Comparison with the locust,Schistocerca gregaria

The thoracic morphology of a flightless grasshopper, Barytettix psolus, is described and compared to that of locusts, Schistocerca gregaria, to evaluate modifications to skeleton, muscles, and the nervous system which have accompanied secondary loss of flight. Barytettix lacks hindwings, has immobile vestiges of forewings and is devoid of skeletal specializations for wing movement and flight. Its pterothoracic musculature resembles that of Schistocerca except for the absence of those muscles which, in locusts, have the primary function of moving the wings, the dorsal longitudinal, tergosternal, first basalar, pleuroalar, and dorsal accessory muscles. Pterothoracic ganglia of Barytettix resemble those of Schistocerca in their gross features, number, and primary branching pattern of nerves, with differences in detail relating to reduction of the flight muscles. The combination of features exhibited in Barytettix represents an extreme reduction in the specialization for wing movements and flight displayed by most acridids, at a level which exceeds that of many brachypterous and some apterous species. While skeletal fusion and loss of muscles indicate loss of flight, the accompanying thoracic stiffening and increase in overall body density may promote more efficient jumping as a means of locomotion.     

The tracheal supply and muscle metabolism during muscle growth in the puparium of Calliphora vomitoria

Thirty hours after puparium formation in Calliphora, the larval tracheal system is replaced by an air-filled pupal system. This is characterized initially by many tufts of tracheae and coiled tracheoles lying in the blood. Between the third and fourth day, the sixth dorsal longitudinal flight muscles are practically without attached tracheae and their longitudinal growth can partially occur when oxygen uptake is inhibited with potassium cyanide. Sodium iodoacetate prevents muscle growth. After the fifth day of development the pupal tracheoles spread out over the surface of the developing adult muscles. Between the seventh and ninth day, longitudinal growth and increases in the diameter of the myofibrils are halted by cyanide and iodoacetate. Some longitudinal growth and an increase in the total protein content of the muscles can occur in 1% oxygen. Air filling of the adult tracheae takes place 2–3 hr before the emergence of the adult and is accompanied by an increase in oxygen consumption of the thorax. The metabolism and growth of the muscles is discussed with respect to their changing oxygen supply.     

The role of feedback during singing and flight in Drosophila melanogaster

ABSTRACT. During Drosophila courtship 'pulse song', muscle potentials occur at two points during the cycle of neuromuscular events which result in a sound pulse being produced. The dorsal longitudinal, second and third dorsal ventral and axillary muscles show potentials 18 ms before each sound pulse while the first dorsal ventral, basalar and sternobasalar muscles fire 3 ms after the onset of each pulse. The timing of these events remains unaltered in animals with the antennae removed, indicating that acoustic feedback is not an important factor. Courting vestigial flies, in the absence of detectable wing base movements, produce indirect muscle potentials at the appropriate song inter-pulse intervals. Thus proprioceptive feedback is also unimportant in determining the intervals between pulses. During putative 'sine song', 'pulse song' and flight in vestigial flies, however, the timing of basalar muscle potentials is abnormal. Also, if the wing is driven externally at a frequency different from that of normal flight, basalar and, to a lesser extent, first dorsal ventral muscles, are phase locked to the driving frequency. These two results suggest that the timing of those muscles which fire at the beginning of the sound pulses is set by proprioceptive feedback. A model of song production is proposed which takes into account the data from this and from previously published papers.     

Generation of motor patterns for walking and flight in motoneurons supplying bifunctional muscles in the locust

In the flight system of Locusta migratoria certain muscles move a wing and a leg (bifunctional muscles) and are active during the performance of walking and flight. A preparation that allowed intracellular recordings during these behaviors was developed to analyze the activity of motoneurons supplying these and other muscles. Motoneurons innervating bifunctional muscles were active during walking and flight, whereas motoneurons innervating unifunctional flight muscles were active only during flight. Both motor patterns, walking and flight, were sometimes generated simultaneously in our preparation. In bifunctional motoneurons the two patterns were superimposed, whereas in unifunctional motoneurons only the flight motor pattern was observed. All flight interneurons we examined were either inactive or tonically inhibited during walking. All interneurons that were strongly modulated during walking were either inactive, inhibited, or only weakly modulated during flight. Anatomical investigations showed that unifunctional flight motoneurons have their main processes in the extreme dorsal region of neuropil. With the exception of the second basalar motoneurons, all bifunctional motoneurons have their processes extending more ventrally in the neuropil. Flight interneurons have their processes restricted to the dorsal neuropil. Interneurons that were rhythmically active during walking had their processes distributed more ventrally. We conclude that motoneurons innervating bifunctional muscles are active during both motor patterns, walking and flight, and that these patterns are produced by two distinct interneuronal networks. The pattern-generating network for flight appears to be located in the extreme dorsal regions of the thoracic ganglia, and the network for walking is located more ventrally.     

饥饿和交配对小地老虎飞行肌发育的影响

小地老虎Agrotis ypsilon(Rottemburg)成虫飞行肌的发育常受一些因素影响而发生变化,为探讨饥饿和交配行为对飞行肌发育的影响,通过电子显微镜对雌虫飞行肌(背纵肌)的肌原纤维、线粒体结构进行观察,结果显示:4日龄饥饿雌虫,肌原纤维直径、肌节长度、肌原纤维体积均显著(P<0.05)小于取食的。7日龄饥饿雌虫肌原纤维直径、肌节长度、肌原纤维体积分数较4日龄的差异均不显著(P≥0.05),而7日龄饥饿的肌原纤维直径显著(P<0.05)大于7日龄取食的;羽化10 d后,饥饿雌虫肌节长度显著(P<0.05)大于取食雌虫的,而肌纤维体积分数和线粒体体积分数均却小于后者。7、10、13日龄交配雌虫肌原纤维横切直径分别显著(P<0.05)小于同日龄非交配的;7、10、13日龄交配雌虫肌原纤维体积分数显著(P<0.05)小于非交配的,线粒体体积分数虽然无差异(P≥0.05),但是交配雌虫的早在4日龄便已明显(P<0.05)减小。上述结果表明:正常取食的小地老虎飞行肌4日龄后会发生降解现象;饥饿抑制飞行肌前期发育和中期的降解,而促进成虫末期肌原纤维的分解;交配能促进飞行肌的降解。     

Possible migration of imaginal myoblasts from adjacent nerve sheath into the developing flight muscle of Chironomus

The emplacement of the first imaginal myoblasts along the larval muscles which are precursors of the dorsal longitudinal flight muscles, has been studied in Chironomus (Diptera, Nematocera), by light and electron microscopy. At the beginning of larval life there are no imaginal myoblasts stored along these muscles. These cells are discerned only at the beginning of the last larval instar. They first appear in the median region of the muscles near the neuromuscular junction. Prior to this, however, there are cells possessing the same cytological characteristics as the imaginal myoblasts inside the sheath of the motor nerves that supply the muscles. These observations suggest that myoblasts could arrive by the nerve sheath. The presence of a thick, continuous basal lamina around the larval muscles seems to exclude all other possibility of access to these muscles. The extension of this hypothesis to the Cyclorrhaphan Diptera is discussed.     

Neural- and endocrine control of flight muscle degeneration in the adult cricket,Gryllus bimaculatus

Neural- and endocrine mechanisms controlling degeneration of a dorsal longitudinal flight muscle, M112a, have been studied in adult Gryllus bimaculatus (Orthoptera: Gryllidae). Decapitation completely prevented muscle degeneration. Implantation of a pair of corpora allata or injection of juvenile hormone III into decapitated crickets caused muscle degeneration. Denervation of M112a resulted in reduction of muscle mass compared with that in sham-operated crickets. Denervation of M112a in decapitated crickets, however, did not affect muscle mass. Birefringence and ultrastructure of M112a showed an obvious regional difference in the onset of degeneration. Fibrillar structures of M112a always disappeared from the ventral to dorsal part. Distribution of axon terminals of motor neurons and mechanical responses to the motor nerve stimuli showed that M112a is composed of five motor units with similar twitch properties. When M112a was fully denervated, regional differences in degeneration disappeared. Partial denervation resulted in denervated muscle fibers losing birefringence earlier than innervated fibers. These results suggest that juvenile hormone causes breakdown of flight muscles, and neural factors control degeneration of flight muscles to some extent under the presence of the juvenile hormone.     

The dorsal, unpaired, median neurons of the locust metathoracic ganglion

Neurons having large cell bodies in the anterior dorsal median cluster in the metathoracic ganglion of the locust Schistocerca gregaria and the grasshopper Romalea microptera were studied by direct dye injection and reverse filling combined with elyctrical stimulation and recording. Eight, possibly nine, are of the unpaired type, with a T branch leading into left and right axons that leave the ganglion to terminate in muscles. Another six are probably paired, and may be interneurons. Five of the 8 or 9 unpaired neurons have one axonal branch in both N4 and N5, on both sides: the others have but a single branch. One of the nine, DUMETi, has left and right axons exclusively innervating the jumping muscles, and another, DUMDL, has left and right axons exclusively innervating the dorsal longitudinal flight muscles. Neither the locations, sizes or numbers of somata, nor their locations were as constant as is the case for ordinary ventral motoneurons.     

Flight muscle myofibrillogenesis in the pupal stage of Drosophila as examined by X-ray microdiffraction and conventional diffraction

In the asynchronous flight muscles of higher insects, the lattice planes of contractile filaments are strictly preserved along the length of each myofibril, making the myofibril a millimetre-long giant single multiprotein crystal. To examine how such highly ordered structures are formed, we recorded X-ray diffraction patterns of the developing flight muscles of Drosophila pupae at various developmental stages. To evaluate the extent of long-range myofilament lattice order, end-on myofibrillar microdiffraction patterns were recorded from isolated quick-frozen dorsal longitudinal flight muscle fibres. In addition, conventional whole-thorax diffraction patterns were recorded from live pupae to assess the extent of development of flight musculature. Weak hexagonal fluctuations of scattering intensity were observed in the end-on patterns as early as approximately 15 h after myoblast fusion, and in the following 30 h, clear hexagonally arranged reflection spots became a common feature. The result suggests that the framework of the giant single-crystal structure is established in an early phase of myofibrillogenesis. Combined with published electron microscopy results, a myofibril in fused asynchronous flight muscle fibres is likely to start as a framework with fixed lattice plane orientations and fixed sarcomere numbers, to which constituent proteins are added afterwards without altering this basic configuration.     

Atypical ‘fibrillar’ flight muscle in strepsiptera

The fine structure of the principal and ancillary metathoracic flight muscle fibres in the adult male of a strepsipteran, Elenchus tenuicornis, is described. Power-producing dorsal longitudinal and dorso-ventral flight muscles show features consistent with myoneural asynchrony: myofibrils are large and discrete and are separated by large closely packed mitochondria; the sarcoplasmic reticulum is very reduced but engages with T-system membranes in dyads at the mid-sarcomere H-band level. With respect to other asynchronous insect flight muscles, the fibres of Elenchus are anomalous (i) in the small fibre diameter, (ii) in the variable contour of the myofibrils and (iii) in the absence of tracheolar invagination. The functional significance of these structural features is discussed. Ancillary metathoracic muscles are structurally comparable with other synchronous fibres in possessing an extensive SR compartment. Structural evidence for asynchrony in the flight mechanism of Strepsiptera is considered in the context of the evolution of this mechanism throughout the insect Orders.     

An ultrastructural study of tettigoniid muscle in relation to function

The modian dorsal longitudinal indirect flight muscles from the mesothorax and metathorax of Homorocoryphus nitidulus vicinus have been studied to determine whether structural differences might offer an explanation for reports that the mesothoracic musculature effects a wing-beat rate of 140 beats/sec during stridulation, whereas during flight, it, like that of the metathorax, effects wing-beat frequencies of 14 to 20 beats/sec. No differences were observed and it is concluded that the high wing-beat rate, reported during stridulation, is not reflected in any specific modification of mesothoracic muscle fine structure.     

Development of mitochondrial and contractile components of the flight muscle in adult tsetse flies, Glossina morsitans

Estimates have been made of the phospholipid, the water, and the cytochrome-c content of the dorsal longitudinal flight muscles of the tsetse fly, and of the total non-fatty dry weight of the thorax, at different stages of adult development. The results have served as a basis for the partitioning of the dry weight of flight muscle into its three main components—contractile protein, mitochondrial protein, and phospholipid. Development is shown to involve a twofold increase in the amount of contractile protein, and a threefold increase in the amount of mitochondrial protein. These changes are discussed in relation to associated changes in wingbeat frequency.     

Auditory input to motor neurons of the dorsal longitudinal flight muscles in a noctuid moth (Barathra brassicae L.)

Summary Motor neurons innervating the dorsal longitudinal muscles of a noctuid moth receive synaptic input activated by auditory stimuli. Each ear of a noctuid moth contains two auditory neurons that are sensitive to ultrasound (Fig. 1). The ears function as bat detectors. Five pairs of large motor neurons and three pairs of small motor neurons found in the pterothoracic ganglia innervate the dorsal longitudinal (depressor) muscles of the mesothorax (Figs. 2 to 5). In non-flying preparations the motor neurons receive no oscillatory synaptic input. Synaptic input to a cell resulting from ultrasonic stimulation is consistent and can be either depolarizing or hyperpolarizing (Figs. 6 to 9). Quiescent neurons only rarely fire a spike in response to auditory inputs. Motor neurons in flying preparations receive oscillatory synaptic drive from the flight pattern generator and usually fire a spike for each wingbeat cycle (Figs. 10 to 12). Ultrasonic stimulation can provide augmented synaptic drive causing a neuron to fire two spikes per wingbeat cycle thus increasing flight vigor (Fig. 11). The same stimulus presented on another occasion can also inhibit spiking in the same motor neuron, but the rhythmic drive remains (Fig. 12). Thus, when the flight oscillator is running auditory stimuli can modulate neuronal responses in different ways depending on some unknown state of the nervous system. Sound intensity is the only stimulus parameter essential for activating the auditory pathway to these motor neurons. The intensity must be sufficient to excite two or three auditory neurons. The significance of these responses in relation to avoidance behavior to bats is discussed.     

Ultrastructural changes during growth of the flight muscles in the adult tsetse fly, Glossina austeni

In laboratory-reared male Glossina austeni the ultrastructure of the dorsal longitudinal flight muscles has been studied in flies ranging from 2-day-old tenerals to flies which have had 10 blood meals. Mitochondrial volume increases throughout this period at a relatively uniform rate but myofibril volume increases until around the third and fourth blood meal (8 to 10 days after emergence) when it reaches a level above which it does not rise significantly. Sarcoplasmic volume correspondingly declines steeply at first, therefter more slowly.     

A new peptide in the FMRFamide family isolated from the CNS of the hawkmoth, Manduca sexta

We have purified a FMRFamide-like peptide from extracts of brain-subesophageal ganglion of the moth, Manduca sexta. The purification was monitored with a new, competitive ELISA, and accomplished with ion exchange and reverse-phase HPLC. The peptide structure was determined by a combination of tandem mass spectrometry and automated Edman degradation. The amino acid sequence of the peptide is less than Glu-Asp-Val-Val-His-Ser-Phe-Leu-Arg-Phe-amide (pEDVVHSFLRF-NH2). In a separate purification, an identical peptide was isolated from extracts of brain-associated neurohemal structures. We have named this peptide ManducaFLRFamide, to indicate its homology with other members of the "FMRFamide" family. In bioassays, chemically synthesized peptide increased the force of neurally evoked contractions in the major power-producing flight muscles, the dorsal longitudinal muscles. This observation suggests that hormonally released ManducaFLRFamide may play a role in sustaining or promoting the flight behavior necessary for mate-seeking (in males) or oviposition (in females) in sphingid moths.