Phylogenetic Studies on Miniature Electrical Oscillation in Insect Muscles
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PHYLOGENETIC STUDIES ON MINIATURE ELECTRICAL OSCILLATION IN INSECT MUSCLES TSUTOMU WAKABAYASHI ANDKAZUO IKEDA* Depertmentof Physiology,School of Medicine,University of Tokyo,Tokyo Previously, Wakabayashi and Hagiwara (1) reported that a spontaneous irregular electrical oscillation of small size was often observed in the sound muscle of Cicadidae at rest and they supposed that it might be due to the injury caused by inserted electrodes. Hagiwara (2) reported again this irregular oscil- lation (miniature electrical oscillation) as injury discharges . In the first part of the present study an experiment was carried out to decide its nature. Fur- thermore, the oscillation was investigated in the thoracic and tymbal muscle of various insects, and the results were considered from phylogenetic point of view. MATERIALSAND METHOD Since it had been found by a preliminary experiment that miniature electrical oscillation was not observable in a muscle which does not contract so rapid as tymbal muscle, for example leg muscle, so in this study thoracic muscles (in- direct wing-muscles) of various species of insects and tymbal muscles of Cicadidae were adopted. The materials used were the several species of various orders of insect which could be caught in the suburb of Tokyo. The following species were used for the electrical activity of thoracic muscle: Odonata: Platicnemis foliacea sasakii, Calopterix virgo japonica, Mnais stri- gata, Epiophrebia sperstes, Gomphus melampus, Antogaster sie- boldii, Aeschna juncea, Anax palthenope julius, Orthetrum albitylum sPeciosum, Orthetrum triangulare melania, Orthetrum japonicum japonicum, Sympetrum darwinianum, Sympetrum frequens, Rhyo- themis foliginosa. Neuroptera: Chrysopa intima, Hagenomyia micans. Orthoptera: Tettix jaPonicus, Euprepocnemis shiraki, Locusta migratoria danica, Paratenodera sinensis. Hemiptera: Terpnosia vacua, Platypleura kaepheri, Graptopsaltria nigrofuscata, Cryptotympana japonensis, Tanna japonensis, Oncotympana macu- laticollis, Meimna opalifera. Lepidoptera: Pyrgus maculatus, Pieris rapae crucivora, Pieris melete, Eurema hecabe mandarina, Colias hyale poliographus, Neope goshkevitschii, Polygonia c-aureum, Parnassius glatiaris, Menelaides alcinosis, Received for publication June20, 1957. *若 林 勳 池田和夫 222 ELECTRICAL ACTIVITY IN INSECT MUSCLES 223 Papilio machaon, Papilio prothenor, Paj,ilio xuthus. Coleoptera: Mallambyx raddei, Melolontha japonica, Xylotrupes dichotomus, Anomala cuPrea. Hymenoptera: Ophion pungenus, Apis indica jaPonica, Vespa mandarinia, Polistes fadwigae, Parapolybia varia. Diptera: Bibiocephara infuscata, Eristalomyia tenax, Volucella jeddona, Musca domestica, Sarcophaga melanura. The following species were used for the activity of the tymbal muscle: Terpnosia vacua, Platypleura kaempheri, Graptopsaltria nigrofuscata, CryP- totym _pana jaPonensis, Tanna jaPonensis, Oncotympana maculaticollis, Meimna opalifera. The experiment was performed with an antero-posterior muscle, a dorso- ventral muscle of thorax and a tymbal muscle. In order to attach or insert the recording electordes into a muscle, a pore was made on mesothoracic, meta- thoracic notum, pleuron or abdominal segment in accordance with the structure of each species. The apparatus for extracellular recording consisted of a pair of fine silver-wire electrodes, resistance-condenser-coupled amplifier, an electro- magnetic oscillograph and a cathode-ray oscilloscope. Often for the purpose of intracellular recording, a capillary microelectrode filled with3M KCL, a direct- coupled amplifier with a cathode-follower imput and a cathode-ray oscilloscope were employed. After the extracellular recording of miniature electrical oscil- lation with a muscle innervated by thoracic ganglion, the recording by the same means was performed with the muscle which was set free from thoracic ganglion by crashing it. Moreover, with the material in which the existence of miniature electrical oscillation had already been recognized by extracellular recording, intracellular recording was made. After each recording, it was ascertained that miniature electrical oscillation was extinguished by applying alcohol to the muscle, to make sure that the miniature electrical oscillation was free from artefact. RESULTS 1. Extracellular recording of potentials of an innervated muscle Among the species which were investigated here, no miniature electrical oscillation was observed in thoracic muscles of Odonata (except Antogaster), Neurofitera, Orthofitera, Hemiptera, Lepidoptera and Coleoptera. But small elec- trical oscillation was observed, as shown in fig.1, in the dorso-ventral muscle of Antogaster. Usually it began after the cessation of an ordinary wing-beat and increased its amplitude in several seconds. It appeared, moreover, only after the wing-beat and dissappeared soon, so it looked like an afterpotential, but its form was very similar to the miniature electrical oscillation which will be described later. In some species of Diptera and Hymenoptera, the miniature electrical oscil- lation of the thoracic muscle was observed. In Diptera, miniature electrical oscillation was observed in Eristalomyia, Volucella and Musca but not in the other species. The amplitude of the minia- 224 T. WAKM3AYASHI AND K. IKEDA FIG.1.•@ Antogaster sieboldii (dragon-fly)-Thoracic muscle. Long lasting after-discharges following after action potential. Extracellular record- ing. After cessation of the natural wing-beat (left of A), train of discharges was initiated gradually (A) and grew in amplitude till regular discharge continued for a while (B and C). Temp.: 27•Ž. August24, 1954. FIG.2 FIG.3 FIG.2.•@ Eristalomyia tenax (gad-fly )-Thoracic muscle. Extrcellular recording of miniature electrical oscillation: examples of various activity. Time-scale: 50c/s. Temp.: 20•Ž. November5, 1954. FIG.3.•@ Volucella jeddona (gad-fly )-Thoracic muscle. Extracellular recording of miniature electrical oscillation: examples of various activity. Time-scale: 50c/s. Temp.: 14•Ž. November27, 1954. ELECTRICAL ACTIVITY IN INSECT MUSCLES 225 ture electrical oscillation which was recorded ranged from200to300pV. The discharge pattern characteristic of each species was rather irregular. In Hymenoptera, miniature electrical oscillation was observed in Vespa, Apis and Parapolybia but not in the other species. In general, the amplitude of the miniature electrical oscillation which was recorded in Hymenoptera attained up to800pV and was higher than that in Diptera. The discharge pattern of the species in this order was alike and, was similar to that of the tymbal muscle of Cicadidae. In the tymbal muscle of Cicadidae, miniature electrical oscillation was ob- tained in all species examined. It was somewhat superior to that of the thoracic muscle of Hymenoptera in amplitude and frequency. 2. Extracellular recording of potentials of a denervated muscle In the thoracic muscle of Eristalomyia, Volucella, Musca, Apis, Vespa and FIG.4 FIG.5 FIG.4.•@ Parapolybia varia (wasp)-Thoracic muscle. Extracellular recording of miniature electrical oscillation: Examples of various activity. Time-scale: 50c/s. Temp.: 19•Ž. November2, 1954. FIG.5.•@ Apis indica japonica (honey bee)-Thoracic muscle. Extracellular recording of miniature electrical oscillation: Examples of various activity. Time-scale: 50c/s. Temp.: 18•Ž. November1, 1954. 226 T. WAKABAYASHI AND K. IKEDA FIG.6 FIG.7 FIG.6.•@ Vespa mandarinia ( wasp )-Thoracic muscle. Extracellular recording of miniature electrical oscillation: spontaneous fructuation of regularity. Time-scale: 50c/s. Temp.: 15•Ž. November12 , 1954. FIG.7.•@ Vespa mandarinia (wasp)-Thoracic muscle. Extracellular recording of miniature electrical oscillation: regular discharges and fructuation of intervals. Time-scale: 50c/s. Temp.: 15•Ž. November12 , 1954. Parapolybia and tymbal muscle of Terpnosia, Platypleura, Graptopsaltria, Cryp- totympana, Tanna, Oncotympana and Meimna, the miniature electrical osillation was observed not only with the innervated preparation but also with the pre- paration the ganglion of which was crashed. No difference of the discharge pattern was obtained between the two cases. The miniature electrical oscillations of Diptera are shown in figs.2and3; they consisted of lower amplitude than that of Hymenoptera and Cicadidae. The miniature electrical oscillations of Hymenoptera are shown in figs.4, 5, 6and7. As shown in these figures the discharge pattern of Parapolybia borders on that of Diptera. Sometimes the irregular oscillation was transformed gradually into the passable regular one concerning amplitude and frequency. Figs.6 and 7show the transformation of irregular oscillation into regular one. In most cases, this regular wave lasted for20-60seconds until it turned gradually into irregular oscillation again. Snch regular oscillations were scarcely observed in the thoracic muscle of Diptera, while they were generally observed in the ELECTRICAL ACTIVITY IN INSECT MUSCLES 227 thoracic muscle of Apis and Vespa and in the tymbal muscle of Cicadidae. During the continuation of trains of discharges it was noted that the frequency of discharges increased or decreased, and in extreme cases discharge stopped for a while (fig.7). But the cause of it could not be made clear. The miniature electrical oscillation of the tymbal muscle of Cicadidae showed FIG.8.•@ Graptopsaltria nigrofuscata (cicada)-Tymbal muscle. Extracellular recording of miniature electrical oscillation: spontaneous transforma- tion of the pattern. Time-scale: 50c/s. Temp.: 28•Ž. August27,