Physiological characteristics of the tympanic organ in noctuoid moths

Summary We show the variations in the spike activity of both auditory receptors inSpodoptera frugiperda, Mocis latipes, Ascalapha odorata (Noctuidae),Maenas jussiae andEmpyreuma pugione (Arctiidae) immediately after 45 ms and 5 s acoustic stimuli at different intensities. The frequency of the applied stimuli was 34 kHz forE. pugione and 20 kHz for the other species. The electrical activity of the auditory receptors was recorded at the tympanic nerve with a stainless steel hook electrode. When the 45 ms pulses cease there is an afterdischarge from both auditory receptors in all the species. The number of spikes in the afterdischarge activity of both receptor cells (A₁ and A₂) shows a linear relation with stimulus intensity (Table 1). This number increases monotonically with increments in stimulus intensity, except for the A₁ cell activity inE. pugione, which decreases at intensities higher than 55 dB (Fig. 1). There are significant species-specific differences in the slope values of the number of spikes in the afterdischarge of both auditory receptors. After a 5 s stimulusM. latipes andM. jussiae show a rapid recovery of the standard spontaneous A₁-cell discharge level. Poststimulus A₁-cell spike activity inS. frugiperda shows a silent period, the duration of which increases with stimulus intensity (Fig. 3).E. pugione andA. odorata show such a silent period after low and moderately intense stimuli, but at high intensities the post-stimulus activity exceeds the pre-stimulus spontaneous discharge (Fig. 3). We demonstrate statistically that these variations cannot be explained by the random fluctuations of the standard spontaneous discharge. They are thus considered a silent and a rebound period respectively (Fig. 5). The presence and duration of either type of period seem to depend on the magnitude of the response to the acoustic stimulus. They thus seem related to the adaptation rate and the previously suggested existence of peripheral inhibitory interaction between the auditory receptors.     

Responses of the less sensitive acoustic sense cells in the tympanic organs of some noctuid and geometrid moths

The separate impulses contributed by the A1 and A2 acoustic sense cells in the tympanic organs of the noctuids, Autographa pseudogamma and Noctua c.-nigrum, and by the A1, A2, and A3 sense cells in the tympanic organ of the geometrid, Ennomos magnarius, were identified and counted from oscillograms grams made as the moths were exposed to ultrasonic pulses of different intensities. These data were used to construct curves relating the response/intensity characteristics of the less sensitive acoustic sense cells to that of the most sensitive unit, A1. The A2 sense cells of the noctuids were found to be from 20 to 30 dB less sensitive than A1 at sound frequencies to which these ears are most sensitive. In the geometrid it was found that the A2 sense cell was 15 dB less sensitive than A1 and 12 dB more sensitive than A3. Only traces of the response of the fourth geometrid acoustic sense cell (A4) could be identified at high sound intensities. In both noctuids and geometrids the acoustic sensitivity of A2 relative to A1 remained unchanged when tested at selected ultrasonic frequencies between 28 and 50 kHz. This confirms the conclusion that the ears of these moths are incapable of pitch discrimination over this frequency range. Each of the systems had a dynamic range of 40 to 45 dB, that of the geometrid showing greater range overlap of the four A cells and hence greater capacity for sound intensity discrimination.     

Physiological characteristics of the tympanic organ in noctuoid moths

Summary The tympanic organ ofSpodoptera frugiperda, Mocis latipes, Erebus odorata (Noctuidae) andMaenas jussiae (Arctiidae) was stimulated with acoustic stimuli of 20 kHz, 45 ms and 5 s duration, and intensities ranging from 30 to 100 dB. The electric activity of the auditory receptors was recorded at the tympanic nerve with a stainless steel hook electrode. In all of these moth species there is an intensity range (ca. 20 dB) in which the response of each auditory receptor (A₁ and A₂ cells) to 45 ms pulses varies in a linear relation to the logarithm of stimulus intensity. For intensities higher than this value, depending on the species and the cell analysed, the spike discharge may continue to increase, may saturate or may diminish (Fig. 2). InE. odorata andM. latipes the A₁-cell response shows a decrease for stimulus intensities higher than 30 dB above the threshold. In the former species there is a statistically significant linear relation between the A₂-cell response and the decrease of the A₁-cell response, but this is not the case inM. latipes (Fig. 3). The similarity of the responses ofE. odorata to those described inEmpyreuma pugione (Coro and Pérez 1984) suggest that also in this noctuid species one may assume that the A₂ cell inhibits the A₁ receptor. In all of these moth species there is a maximum firing rate of the auditory cells at the beginning of the response to pure tones of 5 s and an exponential decrease of their discharge frequency with the course of time (Fig. 5). The analysed species differ in the adaptation rates of their auditory receptors. In all of these species the A₂ cell adapts more rapidly than the A₁ cell. In most of these species the stimulus intensity influences the adaptation rate of the auditory receptors (Fig. 7). These results are compared with data obtained by other authors, and it is concluded that there are more interspecific differences in the physiological characteristics of the auditory receptors in noctuoid species than those reported so far.Abbreviation AP action potential     

Relative suitability of the common pistachio psyllid,Agonoscena pistaciae (Hemiptera: Aphalaridae), as prey for the two-spotted ladybird,Adalia bipunctata (Coleoptera: Coccinellidae)

The suitability of Agonoscena pistaciae Burckhardt & Lauterer as a prey for Adalia bipunctata (Linnaeus) was evaluated by studying the predator’s development and reproduction on this species in comparison to reference diets of nymphs of Myzus persicae (Sulzer) and eggs of Ephestia kuehniella Zeller. Both larval and adult A. bipunctata fed voraciously on A. pistaciae. The development time of the ladybird was shorter when fed on M. persicae and A. pistaciae and longer on E. kuehniella. The survival rate was 87% on M. persicae and 85% on A. pistaciae, both significantly greater than on E. kuehniella eggs (63%). The ladybirds were heaviest at eclosion and their fecundity was higher on M. persicae than on A. pistaciae or E. kuehniella. Both the aphid and psyllid diets yielded higher R₀, r_m values and lower T and DT values than E. kuehniella eggs. Based on total development time, immature survival and adult fecundity, the relative suitability for A. bipunctata was M. persicae > A. pistaciae > E. kuehniella. When ladybirds were reared on psyllids, they showed no preference between aphid or psyllid diets, but when raised on M. persicae, they preferred an aphid diet. A field experiment showed that A. bipunctata preferred to oviposit on pistachio trees at a height of 150–200 cm, i.e. towards the top. The results indicate that A. pistaciae constitutes a complete food for A. bipunctata, supporting both completed development and successful reproduction.     

Isolation and characterization of a new Bacillus thuringiensis strain Lip harboring a new cry1Aa gene highly toxic to Ephestia kuehniella (Lepidoptera: Pyralidae) larvae

The aim of this study was to characterize new Bacillus thuringiensis strains that have a potent insecticidal activity against Ephestia kuehniella larvae. Strains harboring cry1A genes were tested for their toxicity, and the Lip strain showed a higher insecticidal activity compared to that of the reference strain HD1 (LC₅₀ of Lip and HD1 were 33.27 and 128.61 μg toxin/g semolina, respectively). B. thuringiensis Lip harbors and expresses cry1Aa, cry1Ab, cry1Ac, cry1Ad and cry2A. DNA sequencing revealed several polymorphisms in Lip Cry1Aa and Cry1Ac compared to the corresponding proteins of HD1. The activation process using Ephestia kuehniella midgut juice showed that Lip Cry1A proteins were more stable in the presence of larval proteases. Moreover, LipCry1A proteins exhibited higher insecticidal activity against these larvae. These results indicate that Lip is an interesting strain that could be used as an alternative to the worldwide used strain HD1.     

Electrical properties of skeletal muscle fibres of the flour moth larva Ephestia kuehniella

The electrical properties of the ventral longitudinal muscle fibres in the flour moth larva Ephestia kuehniella were investigated at rest and during electrical activity. The membrane resting potential was only partially dependent on the K-concentration gradient across the muscle membrane. The electrical constants λ, τ, R_m, R_i, and C_m were determined according to the equations for ‘short cables’ (Table 1). Current-voltage relationships of the muscle membrane were measured: they revealed anomalous as well as delayed rectification of the membrane. Stimulation of the muscle fibres with intracellular current pulses elicited graded action potentials in most fibres; in some fibres ‘all-or-none’ action potentials were generated. In contrast to graded action potentials these ‘all-or-none’ action potentials were propagated without decrement along the muscle fibre. Indirect stimulation of the muscle fibres resulted in large excitatory junction potentials which generally gave rise to action potentials.     

Potential utilization of Artemia franciscana eggs as food for Coleomegilla maculata

A major hindrance to mass rearing predators for augmentative biological control is the limited availability of inexpensive, alternative foods in lieu of natural prey or target prey. We tested the hypothesis that brine shrimp eggs (Artemia franciscana) are a suitable alternative food that support the development of the predatory ladybird beetle, Coleomegilla maculata. Laboratory bioassays determined the effects of A. franciscana on C. maculata growth, development and reproduction. In comparison to Mediterranean flour moth eggs (Ephestia kuehniella), A. franciscana eggs were suitable for growth and development, but not for reproduction. C. maculata females oviposited less often when fed A. franciscana rather than E. kuehniella. One reason for the low oviposition rate could be less soluble protein in A. franciscana than in E. kuehniella, as determined by biochemical analysis. Further research is needed to identify all deficiencies in A. franciscana and explore the possibility of using supplemental nutrients to counteract them.     

Central projections of the thympanic fibres in noctuid moths

The receptor mechanism mediating the avoidance behaviour of flying noctuid moths in response to brief ultrasonic pulses may require only a single pair of acoustic sense cells, one A1 cell in each tympanic organ (Roeder, 1966c). Introduction of the fluorescent dye, procion yellow, into the nerve fibres leaving the tympanic organ has allowed the reconstruction of the central morphology of A1, the more sensitive of the two acoustic cells. The A1 axon follows a superficial course for the first ～100 μ auterior to its dorsal root of entry (3N1) into the thoracic ganglia, then plunges ventrally into the posterior mesothoracic neuropil where it branches. The posterior part reaches through two-thirds of the metathoracic ganglion. The anterior branch bifurcates in the anterior mesothoracic ganglion to give rise to a posteriorly directed branch extending through the ventral mesothoracic neuropil and an anterior branch which passes through the connective into the posterior half of the prothoracic ganglion. Here it ramifies along the midline. The cell remains strictly ipsi-lateral with numerous processes extending right up to the midline in the ventral neuropil of all three ganglia. This morphology correlates well with the map of sites from which A1 acoustic responses can be recorded in the central nervous system.     

Population-specific behavioral electrosensitivity of the European blind cave salamander,Proteus anguinus

In nine salamanders from different Slovenian populations of the urodele Proteus anguinus, including three specimens of its ‘black’ variety, P anguinus parkelj, thresholds of an overt avoidance response to electrical field stimuli were estimated as a function of frequency (continuous sine-waves in water). Thresholds down to 0.3 mV/cm (ca 100 nA/cm²) and up to 2 mV/cm (670 nA/cm²), at ‘best frequencies’ of around 30 Hz were found. Sensitivity covered a total frequency range of below 1 Hz, excluding DC, up to 1–2 kHz with up to 40 dB higher thresholds. Thresholds and tuning curves are compared with those of a Proteus population raised in captivity for more than 35 years. The biological significance and the apparently still ongoing evolution of the electrical sense in urodeles, ie in the genus Proteus, are interpreted in terms of comparative sensory physiology and ethological ecology as a result of more recent evolutionary diversification during and since glaciation in the Pleistocene.     

Neural mechanisms underlying acoustic behaviour of the frog Pseudophryne semimarmorata (Anura: Leptodactylidae)

Pseudophryne semimarmorata lacks a columella and tympanic membrane. However, at least males are relatively sensitive to sound. The mating call in this species can be inhibited by certain acoustic stimuli. The range of stimuli that inhibited calling was compared with that which evoked neural activity in midbrain auditory units. One of three types of unit which can be distinguished on the basis of best frequency, the high frequency unit, is presumed to be derived from the basilar papilla. High frequency units responded to the same range of sounds that inhibited calling. It is suggested that production of the mating call is initiated by a neural pacemaker, and sufficient neural input to this centre from the basilar papilla inhibits the pacemaker.     

The jamming avoidance response ofEigenmannia: properties of a diencephalic link between sensory processing and motor output

Summary Brain regions participating in the control ofEigenmannia's electric organ discharge frequency were localized by electrical microstimulation and anatomically identified by means of horseradish peroxidase deposition. A diencephalic region was found which, when stimulated, caused electric organ discharge (EOD) frequency increases of similar magnitude and time course as the frequency increases seen during the jamming avoidance response. Single unit recordings from this region revealed one cell type which preferentially responded to stimuli that cause the acceleration phase of the jamming avoidance response (electric organ discharge frequency increase). A second cell type responded preferentially to stimuli which cause EOD frequency decrease, and both cell types were tuned to stimuli which evoked maximal jamming avoidance behaviors.The results of the horseradish peroxidase experiments showed that the recording and stimulation sites correspond to the previously described nucleus electrosensorius. Our results confirm the earlier finding that this nucleus receives output from the torus semicircularis and we also found that the N. electrosensorius projects to the mesencephalic prepacemaker nucleus. The prepacemaker projects to the medullary pacemaker nucleus which generates the commands that evoke electric organ discharges.The anatomical and physiological results described here establish this diencephalic region as a link between the major sensory processing region for the jamming avoidance response, the torus semicircularis, and a mesencephalic pre-motor region, the prepacemaker nucleus.Abbreviations AM amplitude modulation - DF Delta F - ELLL electrosensory lateral line lobe - EOD electric organ discharge - JAR jamming avoidance response - NE nucleus electrosensorius - PPN prepacemaker nucleus - PN pacemaker nucleus     

Corollary discharge inhibition and audition in the stridulating cricket

The romantic notion of crickets singing on a warm summer’s evening is quickly dispelled when one comes ear to ear with a stridulating male. Remarkably, stridulating male crickets are able to hear sounds from the environment despite generating a 100 db song (Heiligenberg 1969; Jones and Dambach 1973). This review summarises recent work examining how they achieve this feat of sensory processing. While the responsiveness of the crickets’ peripheral auditory system (tympanic membrane, tympanic nerve, state of the acoustic spiracle) is maintained during sound production, central auditory neurons are inhibited by a feedforward corollary discharge signal precisely timed to coincide with the auditory neurons’ maximum response to self-generated sound. In this way, the corollary discharge inhibition prevents desensitisation of the crickets’ auditory pathway during sound production.     

Differential responses of two types of electroreceptive afferents to signal distortions may permit capacitance measurement in a weakly electric fish,Gnathonemus petersii

Summary Gnathonemus petersii discriminates between ohmic and capacitive objects. To investigate the sensory basis of this discrimination we recorded from primary afférents that innervate either A or B mormyromast sensory cells. Modified and natural electric organ discharges were used as stimuli. In both A and B fibres frequencies below the peak-power frequency (3.8 to 4.5 kHz) of the electric organ discharge caused minimal first-spike latencies and a maximum number of spikes. A fibres did not discriminate phase-shifted stimuli, whereas B fibres responded significantly with a decrease in first-spike latency if the phase shift was only — 1°. In both A and B fibres an amplitude increase caused a decrease in spike latency and an increase in spike number; an amplitude decrease had the reverse effect. If stimulated with quasi-natural electric organ discharges distorted by capacitive objects, the responses of A fibres decreased with increasing signal distortion. In contrast, the responses of B fibres increased until amplitude effects began to dominate. Gnathonemus may use the physiological differences between A and B fibres to detect and discriminate between capacitive and purely ohmic objects.Abbreviations ELL electrosensory lateral line lobe - EOD electric organ discharge - LFS local filtered signal - p-p peak-to-peak     

Preliminary x-ray diffraction studies on the "goose-type" lysozyme from the egg-white of the black swan Cygnus atratus

The “goose-type” lysozyme isolated from the egg-white of the black swan Cygnus atratus has been crystallized. The space group is P2₁ with one molecule of protein in the asymmetric unit. The cell parameters are $\text{a = 46.2}\text{A}\text{?}\text{, b = 65.1}\text{A}\text{?}\text{, c = 38.7}\text{A}\text{?}$, β = 110 °. The crystals diffract to a resolution of 2.25 Å and a set of diffraction data for the native protein has been collected photographically.     

Characteristics of a transverse RF discharge in Xe/Cl<Subscript>2</Subscript> mixtures

Results are presented from the study of the electrical and optical characteristics of a transverse RF discharge in Xe/Cl₂ mixtures at pressures of p≤400 Pa. The working mixture was excited by a modulated RF discharge (f=1.76 MHz) with a transverse electrode configuration (L≤17 cm). The emission spectrum in the spectral range of 210–600 nm and the waveforms of the discharge current, discharge voltage, and plasma emission intensity were investigated. The UV emission power from the discharge was studied as a function of the pressure and composition of a Xe/Cl₂ mixture. It is shown that a discharge in a xenon-chlorine mixture acts as planar excimer-halogen lamp operating in the spectral range of 220–450 nm, which contains a system of overlapping XeCl(D, B-X; B, C-A) and Cl₂(D′-A′) bands. Transverse RF discharges in Xe/Cl₂ mixtures can be used to create a wideband lamp with two 50-cm² planar apertures and the low circulation rate of the working mixture.     

The Electrophysiology of Electric Organs of Marine Electric Fishes : III. The electroplaques of the stargazer, Astroscopus y-graecum

The electroplaques of Astroscopus y-graecum were studied in situ with microelectrode recordings. Despite the distant taxonomic relations and the different origins of the organs, their properties in the teleost and torpedine marine electric fishes are remarkably similar. Only the innervated membrane (the dorsal) is electrogenically reactive in Astroscopus, and it, too, does not respond to electrical stimuli. As in the torpedine fishes, the uninnervated membrane of the electroplaques offers a very low resistance to the discharge of the innervated membrane. Additional direct evidence for electrical inexcitability of the reactive surface was obtained by denervating one of the bilateral organs. The denervated one did not respond to strong electrical stimuli which evoked responses in the opposite, innervated organ. The denervated electroplaques had a normal resting potential and were depolarized by acetylcholine and carbamylcholine similarly to normal cells. Other properties related to electrical inexcitability were also demonstrated. A pharmacological finding of considerable theoretical significance is that desensitization occurred on depolarizing cells with acetylcholine but was absent on depolarizing them with carbamylcholine.     

Glucose transport and metabolism in the perfused hindquarters of lean and obese-hyperglecemic (db/db) mice effects of insulin and electrical stimulation

Changes in glucose transport and metabolism in skeletal muscles of the obese-diabetic mice (db/db) was characterized using the perfused mouse hindquarter preparation. Metabolism of [5-³H]glucose, uptake of 3-O-[methyl-³H]glucose (methylglucose) and [2-¹⁴C]deoxyglucose (deoxyglucose) was studied under resting, electrically stimulated contracting, and insulin-stimulated conditions. Basal rate of methylglucose uptake was 255 ± 18 and 180 ± 9 μl/15 min per ml intracellular fluid space for lean and db/db mice, respectively. The V_? of methylglucose transport was decreased with no change in K_m in the db/db mice. Both electrical stimulation and insulin (1/mU/ml) increased methylglucose uptake rate 2-fold in both lean and obese mice. We observed no significant change in insulin sensitivity in the db/db mice in stimulating methylglucose uptake which was subnormal under all conditions. Similar results were obtained using deoxyglucose. Likewise, uptake of glucose and ³H₂O production from [5-³H]glucose were significantly reduced, both at rest and during electrically stimulated contraction in the db/db mouse. However, lactate production in the electrically stimulated db/db mouse preparations was not significantly different from that in the lean mice. These data suggest a major contribution from an impaired glucose transport activity to the reduction in glucose metabolism in the db/db mouse skeletal muscle.     

Tympanic and extratympanic sound transmission in the leopard frog

Summary The inner ear of the leopard frog,Rana pipiens, receives sound via two separate pathways: the tympanic-columellar pathway and an extratympanic route. The relative efficiency of the two pathways was investigated. Laser interferometry measurements of tympanic vibration induced by free-field acoustic stimulation reveal a broadly tuned response with maximal vibration at 800 and 1500 Hz. Vibrational amplitude falls off rapidly above and below these frequencies so that above 2 kHz and below 300 Hz tympanic vibration is severely reduced. Electrophysiological measurements of the thresholds of single eighth cranial nerve fibers from both the amphibian and basilar papillae in response to pure tones were made in such a way that the relative efficiency of tympanic and extratympanic transmission could be assessed for each fiber. Thresholds for the two routes are very similar up to 1.0 kHz, above which tympanic transmission eventually becomes more efficient by 15–20 dB. By varying the relative phase of the two modes of stimulation, a reduction of the eighth nerve response can be achieved. When considered together, the measurements of tympanic vibration and the measurements of tympanic and extratympanic transmission thresholds suggest that under normal conditions in this species (1) below 300 Hz extratympanic sound transmission is the main source of inner ear stimulation; (2) for most of the basilar papilla frequency range (i.e., above 1.2 kHz) tympanic transmission is more important; and (3) both routes contribute to the stimulation of amphibian papilla fibers tuned between those points. Thus acoustic excitation of the an uran's inner ear depends on a complex interac tion between tympanic and extratympanic sound transmission.Abbreviations dB SPL decibels sound pressure level re: 20 N/ m² - AP amphibian papilla - BP basilar papilla - BEF best excitatory frequency     

Characterization of Tunisian Bacillus thuringiensis Strains with Abundance of kurstaki Subspecies Harbouring Insecticidal Activities Against the Lepidopteran Insect Ephestia kuehniella

The study of 257 crystal-producing Bacillus thuringiensis isolates from bioinsecticide free soil samples collected from different sites in Tunisia, was performed by PCR amplification, using six primer pairs specific for cry1, cry2, cry3, cry4, and vip3A genes, by the investigation of strain plasmid pattern, crystal morphology and delta-endotoxin content and by the assessment of insecticidal activities against the lepidopteran insect Ephestia kuehniella. Based on plasmid pattern study, 11 representative strains of the different classes were subjected to morphological and molecular analyses. The comparison of the PFGE fingerprints confirmed the heterogeneity of these strains. B. thuringiensis kurstaki strains, harbouring at the same time the genes cry1A, cry2, cry1Ia, and vip3A, were the most abundant (65.4%). 33.34% of the new isolates showed particular delta-endotoxin profiles but no PCR products with the used primer sets. B. thuringiensis israelensis was shown to be also very rare among the Tunisian B. thuringiensis isolates diversity. These findings could have considerable impacts for the set up of new pest control biological agents.     

Characterization of two crystal forms of neutrophil cationic protein NP2, a naturally occurring broad-spectrum antimicrobial agent from leukocytes

A hexagonal crystal form (P6₃22, $\text{a = b = 34.0}\text{A}\text{?}\text{, c = 113.5}\text{A}\text{?}$) and a monoclinic form (P2₁, $\text{a = 37.1}\text{A}\text{?}\text{, b = 32.2}\text{A}\text{?}\text{, c = 32.4}\text{A}\text{?}\text{, β = 110 °}$) of neutrophil cationic protein NP2, isolated from rabbit leukocytes, have been characterized. The monoclinic form, containing two promoters (M_r = 3844) per asymmetric unit, diffracts to at least 1.8 Å and is suitable for high-resolution structural studies.