Innervation is necessary for the development of fast contraction kinetics of singing muscles in a katydid

The twitch duration of mesothoracic wing muscles of the male katydid Neoconocephalus robustus (Insecta; Orthoptera; Tettigoniidae) decreases rapidly within the first 5 days of adulthood, to about half of its value in newly molted adults. To determine if this change is dependent upon neural input, male mesothoracic first tergocoxal muscles were unilaterally denervated on the second day of adulthood. The contraction kinetics of the denervated and contralateral innervated muscles were tested four days later. The development of rapid contraction kinetics was slowed or stopped in the denervated muscles, while the contralateral innervated muscles did become faster. Mesothoracic wing muscles of females do not develop faster contraction kinetics. When the female mesothoracic first tergocoxal muscle is denervated, there is no difference in twitch duration after 4 days between the innervated and contralateral denervated muscles. Therefore, denervation in newly molted adult male katydids interrupts a developmental program for the acquisition of adult contraction kinetics.     

Neural activity pattern is not necessary for the development of adult ultrastructure in katydid (Neoconocephalus robustus) singing muscles

Summary The singing muscles of the katydid Neoconocephalus robustus develop adult ultrastructure late in the last nymphal instar and during the first few days of adult life. The ultrastructural changes during early adulthood were not affected by unilateral axotomy shortly after the adult molt. Both denervated and innervated muscles developed adult proportions of mitochondria, myofibril, and sarcoplasmic reticulum and transverse tubules.     

Differentiation of slow and fast muscles in chickens

1. The development of the characteristic histochemical appearance of the slow anterior latissimus dorsi (ALD) and fast posterior latissimus dorsi (PLD) was studied in chickens during embryonic development as well as during regeneration of minced muscle. 2. During embryonic development the activity of the oxidative enzyme succinic dehydrogenase (SDH) is higher in the slow ALD muscle already at 16 days of incubation. At this time the fast PLD has a higher activity of the glycolytic enzyme, phosphorylase. Although the histochemical appearance of the two types of muscle is already different at 16 days, their contractile speeds are still similar. No difference in myosin ATP-ase was found in the two muscles in young embryos but in 20-day old embryos the two muscles became distinctly different when stained for this enzyme. 3. When PLD muscles in hatched chickens redeveloped during regeneration in place of ALD the histochemical characteristics of the regenerated muscle resembled ALD, and when ALD regenerated in place of PLD it resembled PLD. 4. It is concluded that the histochemical characteristics of slow and fast muscles become determined during early development, even before any difference in contractile properties can be detected and that they are determined by the nerve.     

Silent katydid females are at higher risk of bat predation than acoustically signalling katydid males

Males that produce conspicuous mate attraction signals are often at high risk of predation from eavesdropping predators. Females of such species typically search for signalling males and their higher motility may also place them at risk. The relative predation risk faced by males and females in the context of mate-finding using long-distance signals has rarely been investigated. In this study, we show, using a combination of diet analysis and behavioural experiments, that katydid females, who do not produce acoustic signals, are at higher risk of predation from a major bat predator, Megaderma spasma, than calling males. Female katydids were represented in much higher numbers than males in the culled remains beneath roosts of M. spasma. Playback experiments using katydid calls revealed that male calls were approached in only about one-third of the trials overall, whereas tethered, flying katydids were always approached and attacked. Our results question the idea that necessary costs of mate-finding, including risk of predation, are higher in signalling males than in searching females.     

Antennal muscles and fast antennal movements in ants

The antennal movements of eight ant species (subfamilies Ponerinae, Myrmicinae, and Formicinae) are examined by high-frequency videography. They show a wide range of antennal velocities which is generated by antennal muscles composed of particularly diverse muscle fibers. Fiber diameter, sarcomere length and histochemically assessed myosin ATPase activity suggest that some thin fibers are fairly slow, while the bulk of antennal muscle fibers show intermediate or fast properties. These morphological properties correlate with the antennal movement velocities measured for the respective species. Based on their morphology, the fibers that generate the fast antennal retraction in some trap-jaw ants appear particularly fast and comprise the shortest sarcomeres yet described (1.1 μm). Accepted: 2 January 1997     

The sounds of silence: cessation of singing and song pausing are ultrasound-induced acoustic startle behaviors in the katydid Neoconocephalus ensiger (Orthoptera; Tettigoniidae)

Previous studies of acoustic startle in insects have dealt with behavioral and/or neural mechanisms employed in evading aerially hawking, echolocating bats; however, insects also face terrestrial predators. Here we describe an acoustic startle response of the nocturnal katydid, Neoconocephalus ensiger. Stridulating males disturbed in the field perform obvious anti-predatory behaviors – cessation of singing, freezing, jumping, and evasive flight. Under controlled laboratory conditions we found that cessation of singing and song pausing are ultrasound-specific behaviors: when stimulated with pulsed ultrasound (20–100 kHz), but not audio-sound (<20 kHz), males cease mate calling or insert pauses in their song. A second factor influencing acoustic startle is the phase of stimulation: an acoustic startle response occurs only when the pulse of ultrasound arrives during the window of silence between stridulatory syllables. The average startle threshold and response latency was 70 ± 5 dB SPL and 34.2 ± 6.0 ms, respectively. N. ensiger is particularly useful for examining acoustic startle responses of non-flying insects because (1) its calling song is broadband and contains ultrasound, thus the possibility exists of confusion over the biological meaning of ultrasound, and (2) this species shows the classic bat-avoidance response while flying, so a direct comparison between two types of acoustic startle is possible within the same species. Accepted: 6 November 1999     

Development of coordinated singing in a newly formed siamang pair (Hylobates syndactylus)

The study traced the development of coordinated singing in a newly formed male-female siamang pair. Forty-five song bouts were observed during 18 wk following the pairs' initial introduction to one another. Of particular interest was the development of vocal coordination between pair members in the great-call sequence of the duet. The percentage of successfully completed great-call sequences rose from 24% for the first three sessions to 79% for the last three sessions. Types of “errors” that led to incomplete great calls were identified. The two most common errors were: uninvited female high-bark series, which accounted for the premature termination of 30% of the great-call attempts during the first three sessions and of 11% of the attempts during the last three sessions, and a premature male ululating scream and/or locomotion call, which accounted for the premature termination of 34% of the great-call attempts during the first three sessions and of 5% of the attempts during the final three sessions. The fully coordinated great-call sequences that finally developed closely resembled the siamang great-call sequence described by Haimoff (Behaviour 76:128–151, 1981; Semiotica 68:89–120, 1988). The role of experience in the development of vocal coordination is discussed.     

The fine structure of fast and slow crustacean muscles

Known phasic and tonic muscle fibers of the crab Cancer magister were studied by electron microscopy. Phasic fibers have sarcomeres about 4.5 µ long, small polygonal myofibrils, and a well-developed sarcoplasmic reticulum. The thick myofilaments, disposed in hexagonal array, are each surrounded by six thin filaments. The tonic fibers have a sarcomere length of about 12 µ, larger myofibrils, a poorly developed sarcoplasmic reticulum, and a disorderly array of myofilaments. Each thick myofilament is surrounded by 10–12 thin filaments. The same morphological type of slow muscle has been found in the crustaceans, Macrocyclops albidus, Cypridopsis vidua, and Balanus cariosus, in each case in an anatomical location consistent with tonic action. A search of the literature indicates that this type of muscle is found in all classes of arthropods and is confined to visceral and postural muscles or specializations of these.     

Growth-dependent toxicity of Photorhabdus temperata in katydid Paratlanticus ussuriensis

The oral toxicity of the symbiotic bacteria Photorhabdus temperata was investigated in various developmental stages of Paratlanticus ussuriensis. Supernatants of Photorhabdus culture medium were mixed into an artificial diet, which was fed to various stages of immature nymphs and adults of P. ussuriensis. Mortality was highest in the first instar nymph but decreased in older stages of immature nymphs. Adult females were not killed upon oral ingestion of P. ussuriensis, but their fecundity was significantly inhibited to 29.3% of that of control. In addition, the effects of oral ingestion of the symbiont culture media on the expression rates of three heat shock protein 70 genes (hsp70a, hsp70b, and hsp70c) in third instar nymphs of P. ussuriensis were determined by quantitative real-time RT-PCR analysis. There were no significant changes in expression levels in comparison with control, which suggests that hsp genes may not be associated with the mechanism of Photorhabdus toxicity. Our results imply that Photorhabdus culture media is highly effective in killing younger immature nymphs and also suppressing adult reproduction of P. ussuriensis.     

Enzymatic activities in slow and fast denervated old rat muscles

The activities of five enzymes have been studied quantitatively in denervated extensor digitorum longus, gastrocnemius and soleus muscles of 24-month-old rats. The results have been compared with those obtained from normal muscles of a similar age group of rats. Three weeks after denervation, the activity of hexokinase was increased in gastrocnemius and extensor digitorum longus. Phosphofructokinase, lactate dehydrogenase, malate dehydrogenase and 3-hydroxyacyl-CoA-dehydrogenase showed decreased activities. These results suggest that enzyme which represents glucose uptake increased its activity in fast muscles and that enzymes for anaerobic glycolysis, lactate fermentation, citric acid cycle and beta-oxidation had a decreased activity in slow and fast muscles.     

Regulation of glucose uptake in rat slow and fast skeletal muscles

1. Regulation of glucose uptake was compared between extensor digitorum longus (EDL) and soleus (Sol) muscles in rats. 2. Insulin stimulated glucose uptake more in EDL than in Sol. 3. Under high concentrations of insulin, the glucose uptake was higher in EDL than Sol. 4. Inhibition of oxidative phosphorylation by anoxia or an uncoupler stimulated glucose uptake more in EDL than in Sol. 5. Anoxia abolished the effect of insulin on glucose uptake in both EDL and Sol. 6. The blocker to glucose transport system reduced glucose uptake more in Sol than in EDL.     

Structural organization of two fast,rhythmically active crustacean muscles

Summary The organization of the flagellum abductor muscle and of a scaphognathite levator muscle of the green crab, Carcinus maenas, has been compared quantitatively using light and electron microscopy. These muscles are rhythmically active at relatively high frequencies and for long durations. Fibers of both muscles are interconnected to form fascicles of 50 or more fibers within which there is cytoplasmic continuity. A single muscle is made up of 8–12 fascicles. Individual fibers consist of a peripheral rind of densely packed mitochondria, a thick region of glycogen granules, and myofibrils arranged into scattered central islands. Less than half the volume-density of these muscles is contractile material, the balance being largely mitochondria and glycogen. The fibers within a muscle are structurally similar. They have short sarcomeres (about 2 m), thin to thick filament ratios of about 3:1, and junctions between the sarcoplasmic reticulum and the transverse tubules at the M line. Sarcoplasmic reticulum occupies about 10% of the myofibrillar volume-density. A well developed sarcoplasmic reticulum appears to underlie the capacities of these two muscles for high frequency contraction; extensive mitochondria and glycogen stores should confer fatigue resistance under both aerobic and anaerobic conditions.     

Motor and sensory reinnervation of fast and slow mammalian muscles

Summary 1. The formation of endplates outside the original endplate region of a muscle fibre was studied in slow and fast rat muscles. It was found that such new endplates are readily formed on the soleus muscle, whereas hardly at all in the fast extensor digitorum longus. Most new endplates appear to be morphologically normal within 2 months after nerve implantation.2. The time course of recovery of slow and fast cat muscles was followed after crushing the sciatic nerve. It was found that the slow soleus muscle recovers more rapidly than the fast flexor hallucis longus muscle.3. The endplates of reinnervated cat muscles are more complicated than those of the control muscles, but have nevertheless fewer nerve terminals per endplate. Reinnervated muscles are more sensitive to curare and it is suggested that this is due to a decrease in transmitter release, for it was found that less acetylcholine is released from reinnervated rat hemidiaphragms than from control ones.4. Motor and sensory reinnervation of spindles and tendon organs was studied. At the time when motor reinnervation is almost completed the sensory endings from spindles and tendon organs are highly abnormal. Thus sensory reinnervation proceeds much more slowly than motor.     

31P NMR study of phosphorus metabolites in fast and slow muscles

1. 31P NMR was used to characterize phosphate pools in perchloric acid extracts of muscles with various composition of muscle fibre types. 2. The white m. pectoralis major (MPM) of chickens 15 min post mortem is characterized by 1.6-times higher relative content of phosphocreatine (PCr) in comparison with mixed leg muscle (LM) of this species. The glycerophosphorylcholine (GPC) does not occur in MPM at NMR detectable level in contrast to the leg muscles. Relative amounts of other phosphates are similar in both muscles. 3. The intermediate MPM of pigeons as well as mixed LM of this species contain 15 min post mortem a very small amount of PCr and ATP but a large amount of inorganic phosphate. Relative content of GPC is higher in leg muscles than in intermediate MPM. 4. Muscles with higher occurrence of white fibres contain relatively more PCr than muscles with lower occurrence of white fibres. 5. The occurrence of GPC seems to be connected with metabolism of red muscle fibres.     

Myosin transitions in developing fast and slow muscles of the rat hindlimb

Abstract. Myosin isozymes from the slow soleus and fast EDL muscles of the rat hindlimb were analyzed by pyrophosphate gel electrophoresis, by peptide mapping of heavy chains, and by antibody staining. At the earliest stage examined, 20 days gestation, distinctions between the developing fast and slow muscles were seen by all these criteria; all fibers in the distal hindlimb reacted strongly with antibody to adult fast myosin. Some fibers also reacted with antibody to adult slow myosin; these fibers had a precise, axial distribution in the hindlimb. This pattern of staining which includes the entire soleus, foreshadows the adult distribution of slow fibers and may indicate that the specific pattern of innervation of the limb is already determined. In the early developing soleus there are four fetal and neonatal isozymes plus two isozymes present in equal proportions in the 'slow' area of the pyrophosphate gel. The mobility of these two slow isozymes decreases with maturity and the slowest moving isozyme gradually becomes the dominant species. Thus early diversity between the soleus and EDL is expressed by myosins which are distinct from the mature isozymes. The relative proportion of slow isozymes significantly increases with development and as this occurs the fetal and neonatal isozymes are progressively eliminated. Transiently at least one mature fast isozyme appears in the soleus. This is present at 15 days postpartum and probably correlates with the population of fast, type II fibers, which comprise 50% of this muscle cell population at 15 days. The EDL contained three fetal and neonatal isozymes and only one slow isozyme which does not change in mobility with age. Slow isozymes in the soleus and EDL are thus not identical. Each muscle underwent a unique series of changes until the adult pattern of isozymes and heavy chains was reached about one month postpartum.