Mating calls of three prochilodontid fish species from Brazil

Passive acoustic monitoring (PAM) of fish sounds has been used as a means of detecting the presence and abundance of fishes. Prior to PAM, bioacoustical analyses of sounds are needed to characterize species-specific characteristics of calls. With hydrophones placed in outdoor ponds, we recorded the mating calls of three species of prochilodontid fishes (Prochilodus argenteus, P. costatus, P. lineatus). Fish were induced to spawn and call by injection of carp (Cyprinus carpio) pituitary gland extract. We recorded a total of 394 pulse train calls and additional single pulse calls that were not associated with trains. The trains of all three species were similar in nature - series of low frequency pulses that lasted from 1 to 11 s, often with an initial rapid rise followed by a slow tapering of pulse amplitude. Dominant frequency of single pulses and trains was greatest in P. lineatus, with P. costatus and P. argenteus exhibiting lower single pulse dominant frequencies, and P. costatus having lower train dominant frequency. With data from the three species combined, the dominant frequency of pulses significantly increased with fish standard length. There was also a significant linear relationship between the dominant frequency of pulses and trains. Discriminant function analysis showed that differences in train dominant frequency, pulse duration, and pulse period between the three species were significant enough to discriminate between them. This study was the first to fully characterize the sounds of these three Prochilodus species, and should assist fisheries biologists monitoring spawning behavior in these species.     

Sound production in two species of damselfishes (Pomacentridae): Plectroglyphidodon lacrymatus and Dascyllus aruanus

Agonistic sounds of two pomacentrid species, Plectroglyphidodon lacrymatus and Dascyllus aruanus , were recorded in captivity. Plectroglyphidodon lacrymatus produced trains of 2–5 pops, each composed of 18–25 cycles, with an average duration of 56 ms; most energy ranged from c. 100 to 1000 Hz. Dascyllus aruanus produced pops and chirps. Pops were generally composed of a single pulse, with 2–14 peaks and an average duration of 6·7 ms. Pops contained energy >4 kHz, and peak frequency ranged from 680 to 1300 Hz. Chirps consisted of trains of 12–42 short pulses of three to six cycles, with durations varying from 0·6 to 1·27 ms; peak frequency varied from 3400 to 4100 Hz. Sound production in P. lacrymatus suggested that pomacentrids are derived from an ancestral taxon capable of sound production and that this capacity is a synapomorphy for the family. Although in the Pomacentridae, pops are typically composed of a single pulse, which is longer and higher pitched than chirps composed of a series of shorter pulses, D. aruanus chirps were higher pitched than its pops. Thus, acoustic variation in the genus Dascyllus is probably not more restricted than in the Pomacentridae.     

THE CLICK-SOUNDS OF NARWHALS (MONODON MONOCEROS) IN INGLEFIELD BAY, NORTHWEST GREENLAND

We studied the sounds of narwhals ( Monodon monoceros ) foraging in the open waters in Northwest Greenland. We used a linear, vertical array of three hydrophones (depth 10 m, 30 m, 100 m) with a fourth hydrophone (depth 30 m) about 20 m from the vertical array. A smaller fifth hydrophone (depth 2 m) allowed for registering frequencies up to 125 kHz (± 2 dB) when signals were recorded at 762 mm/set on an instrumentation tape recorder. Clicks were the prevalent signals, but we heard whistles occasionally. We separated the clicks into two classes: click trains that had rates of 3-10 clicks/sec and click bursts having rates of 110-150 clicks/sec. The spectra of train clicks had maximum amplitudes at 48 ± 10 kHz and a duration of 29 ± 6 psec. The spectra of burst clicks had maximum amplitudes at 19 ± 1 kHz and a duration of 40 ± 3 psec. By analogy with other dolphin species, narwhals presumably use the clicks for echolocation during orientation and for locating prey. The narwhal click patterns resemble those of insectivorous bats. Click trains might correspond to bat searching signals and click bursts to the bat's terminal "buzz", emitted just before prey capture.     

Dynamic properties of Renshaw cells: Frequency response characteristics

The dynamic properties of Renshaw cells located in the lumbar spinal cord of intercollicular decerebrate cats were measured. The responses of these interneurones were recorded extracellularly, while the ventral root was stimulated with sinusoidally frequency-modulated trains of electrical pulses. The frequency of the Renshaw cell discharges resulting from such stimulation varied sinusoidally. The amplitude of modulation about the average (or carrier) rate of discharge exhibited a linear dependence on the modulation amplitude of the stimulus pulse train. Renshaw cells were able to follow modulated stimulus trains in the entire range of modulation frequencies (0.2 to 80 Hz) encompassed by the present study. Above modulation frequencies between 20 and 50 Hz, the amplitude of modulation of the responses declined. Frequency responses measured at low average frequencies of the stimulus pulse train (centre frequencies 30 and 40 Hz) showed comparatively little dependence on modulation frequency. The higher the centre frequency, however, the greater was the enhancement of the modulation amplitudes at high modulation frequencies compared with those observed at low modulation frequencies. Some aspects of the functional implications of these results are considered and an approximate formula for the transfer function of Renshaw cells is presented.     

VOCALIZATIONS OF A CAPTIVE JUVENILE AND FREE-RANGING ADULT-CALF PAIRS OF BRYDE'S WHALES, BALAENOPTERA EDENI

Abstract: Vocalizations were recorded from a captive juvenile Bryde's whale, Balaenoptera edeni , that stranded off the gulf coast of Florida (Pinellas Co.) and was held at Sea World of Florida. The most common vocalization was a pulsed moan with durations of 0.5–51 set and acoustic energy from 200–900 Ht. Although these sounds are unlike any reported previously from this species, there are similarities to moans recorded opportunistically during a feeding study of free-ranging B. edeni in the Gulf of California (GOC). The pulsed moans recorded from Bryde's whale adults in the GOC were shorter in duration (0.7–1.4 set) than those recorded from the captive juvenile, but the frequencies were similar (165–875 Hz). In addition, a series of discrete, regularly spaced pulses (interpulse interval = 0.5–1.0 set, 700–950 Hz) were recorded only in the presence of Bryde's whale calves in the GOC.
Pulse rates produced by the captive juvenile (20–70 pulses/set) were intermediate between those recorded in the presence of GOC adults (60–130/sec) and calves (10–20/set). With these limited data it is not possible to determine to what extent the intermediate qualities of the juvenile call reflect maturational differences in the sound production apparatus, a phase of learning to vocalize like an adult, or the characteristics of a context-dependent call not recorded in the GOC.     

Courtship and spawning sounds in bird wrasse Gomphosus varius and saddle wrasse Thalassoma duperrey

Acoustic signals from the bird wrasse Gomphosus varius and saddle wrasse Thalassoma duperrey were recorded on coral reefs in Hawaii. Terminal phase males in both species emit two types of pulse trains (type I and type II). Type I pulses were produced during spawning and courtship, while type II pulses were associated only with courtship behaviours. Gomphosus varius type I pulses were of lower frequency than T. duperrey type I pulses (271 v. 840 Hz) and were of narrower band. Discriminant function analyses revealed interspecific differences between type I pulse trains and individual pulses of both types. This study is the first documentation of courtship and spawning sounds in sympatric labrids and shows divergence in acoustic signals.     

Photoresponses of Halobacterium salinarum to repetitive pulse stimuli.

Halobacterium salinarum cells from 3-day-old cultures have been stimulated with different patterns of repetitive pulse stimuli. A short train of 0.6-s orange light pulses with a 4-s period resulted in reversal peaks of increasing intensity. The reverse occurred when blue light pulses were delivered as a finite train: with a 3-s period, the response declined in sequence from the first to the last pulse. To evaluate the response of the system under steady-state conditions of stimulation, continuous trains of pulses were also applied; whereas blue light always produced a sharply peaked response immediately after each pulse, orange pulses resulted in a declining peak of reversals that lasted until the subsequent pulse. An attempt to account for these results in terms of current excitation/adaptation models shows that additional mechanisms appear to be at work in this transduction chain.     

5-HT offsets homeostasis of synaptic transmission during short-term facilitation.

In this study, we approach the topic of vesicle recruitment and recycling by perturbing neurotransmission at the crayfish neuromuscular junction with altered electrical activity and the presence of the neuromodulator serotonin (5-HT). After induction of short-term facilitation (STF) with stimulus pulse trains (40 Hz, 20 pulses), the amount of synaptic transmission can be maintained at a relatively constant level, producing a plateau in the amplitude of the excitatory postsynaptic potentials (EPSPs) throughout the remaining stimuli within a train of a few hundred milliseconds. With an increase in the frequency of the stimuli within a train (60 Hz, 20 pulses), an altered plateau of larger EPSP amplitudes occurs. This suggests that differential rates of vesicle recruitment can be rapidly reached and maintained. Exposure of nerve terminals to 5-HT further enhances the EPSP amplitudes to yet a higher plateau level. The effect of 5-HT is more pronounced for 40-Hz pulse trains than for 60-Hz trains. This suggests that 5-HT can recruit vesicles into the readily releasable pool (RRP) and that the recruitment is limited at higher stimulation frequencies. The attainment of a larger amplitude in the plateaus of the EPSPs at 60 Hz compared with 40 Hz also suggests that the rapid induction of STF enhances the entry of vesicles into the RRP. By direct quantal counts, mean quantal content increases linearly during STF, and 5-HT offsets the linear release. We propose that 5-HT and electrically induced recruitment of vesicles from a reserve pool to the RRP may share similar recruitment mechanisms.     

Influence of the temporal distribution of electric pulses on transcallosal single unit responses

We examined how differently timed stimuli to one auditory cortex affect the spike trains they drive in the controlateral homotopic field of anesthetized rats. Bipolar electrical stimulations consisted of trains of pulses (100 micro s, <500 micro A) at rates of 25, 50 or 125 pulses/s and with different stimulus patterns (i.e., dispersions, sequences), called "pacemaker", "accelerando" or "decelerando". Trains lasted for 342 ms and were separated by 4 s. When trains were evaluated over times comparable to the stimulus duration changes characteristically involved an initial slowing followed by recovery and several discharges both stimulus- and neuron-dependent. When evaluated by cross-correlations between cortical cell pairs, the changes extended far beyond the stimulus end. Results suggest that interhemispheric projections, by way of their averages and patterns, play key, long duration roles in the spike-dependent properties of cortical synapses (e.g., potentiation, depression) and thus of cortical circuit operations.     

Sounds recorded in salt marshes and attributed to the European eel

The sounds were recorded in coastal ponds off the French Atlantic coast. They are characterized by continuous series of regularly spaced sounds, each sound being composed of one to four pulses of 7.8-ms duration. The main frequencies of these sounds are under 350 Hz. Due to the special characteristics of these sounds, their temporal patterning, their coastal pond provenance and their close similarity to sounds made by the American eel (Anguilla rostrata), we attribute them to the European eel (Anguilla anguilla).     

Sound production by the Shi drum Umbrina cirrosa and comparison with the brown meagre Sciaena umbra: a passive acoustic monitoring perspective

Sounds produced by the Shi drum Umbrina cirrosa were short trains of pulses with an average pulse period of 180 ms, pulse duration of c. 40 ms and an average peak frequency of 400 Hz; average values of acoustical properties differed from those recorded from the brown meagre Sciaena umbra in previous studies. The present study provides a preliminary tool for discriminating between these two species while conducting passive acoustic monitoring. The potential effects of ontogeny on sound production in both species are discussed and recommendations are made for further research.     

Cloning and expression of a calcium-activated chloride channel reveal a novel protein candidate

Purkinje neurons fire spontaneous action potentials at ~50 spikes/sec and generate more than 100 spikes/sec during cerebellum-mediated behaviors. Many voltage-gated channels, including Ca channels, can inactivate and/or facilitate with repeated stimulation, raising the question of how these channels respond to regular, rapid trains of depolarizations. To test whether Ca currents are modulated during firing, we recorded voltage-clamped Ca currents, predominantly carried by P-type Ca channels, from acutely dissociated mouse Purkinje neurons at 30-33{degree sign}C (1 mM Ca). With 0.5 mM intracellular EGTA, 1-second trains of either spontaneous action potential waveforms or brief depolarizing steps at 50 Hz evoked Ca tail currents that were stable, remaining within 5% of the first tail current throughout the train. Higher frequency trains (100 and 200 Hz) elicited a maximal inactivation of     

Mouse Postganglionic Sympathetic Neurons

Basic properties of noradrenaline release were studied in primary cultures of thoracolumbar postganglionic sympathetic neurons taken from 1-3-day-old NMRI mice. After 7 days in vitro, the cultures were preincubated with [3H]noradrenaline and then superfused and stimulated electrically. Conventional trains of pulses (for example, 36 pulses at 3 Hz) as well as single pulses and brief high-frequency trains (for example, four pulses at 100 Hz) elicited a well-measurable overflow of tritium, which was abolished by 0.3 microM tetrodotoxin or omission of Ca2+, but not changed by 1 microM rauwolscine. In trains of one, two, four, six, eight, or 10 pulses at 3 Hz, the evoked overflow of tritium remained constant from pulse to pulse at 1.3 mM Ca2+, but declined slightly at 2.5 mM Ca2+. Tetraethylammonium at 10 mM selectively increased the overflow elicited by small pulse numbers and especially by a single pulse. In trains of 10 pulses delivered at 0.3, 1, 3, 10, 30, or 100 Hz, the evoked overflow of tritium increased from 0.3 to 30 Hz and then declined at 100 Hz. This relationship was particularly pronounced at low Ca2+ concentrations (for example, 0.3 mM). Tetraethylammonium at 10 mM selectively increased the overflow elicited by low frequencies of stimulation. It is concluded that primary cultures of mouse postganglionic sympathetic neurons can be used to investigate release of [3H]noradrenaline. The release is well measurable, even upon a single electrical pulse. It agrees with release in intact sympathetically innervated tissues in a number of fundamental properties, including the pulse number and frequency dependence. The preparation may be of special interest in conjunction with genetic manipulations in the donor animals.     

A Quantitative Analysis of the Courtship Acoustic Behaviour and Sound Patterning in Male Sand Goby, <Emphasis Type="Italic">Pomatoschistus minutus</Emphasis>

Many animal groups use sounds in reproduction in order to court mates or repel rivals. We describe the sounds and behavioural context of courtship sound production in male sand gobies, Pomatoschistus minutus, and examine the variability of acoustic parameters and the fine temporal patterning of sound units. Male sand gobies excavate a nest under a suitable solid substrate and attract females to mate, attaching the eggs to the ceiling of the nest. Before mating a female may repeatedly enter and leave a male's nest. Sounds were not detected during the courtship phase outside the nest, but were recorded when females were in the nest before spawning. Sounds were produced in 44–100% of such nest visits, varying with individual males. The sand goby sound consists of a train of pulses repeated at a rate of 23–29 pulses per second. The frequency spectrum of single pulses was continuous from 20–30Hz to 500Hz and reached a peak around 100Hz. The absolute sound pressure level ranged from 118 to 138dB re 1µPa at 1–3cm. The sand goby emits sound in distinct sound groups (bursts). Sound temporal features (duration, pulse repetition rate) vary systematically over the course of the burst. Within- and between-male variation of acoustic parameters was examined from sounds emitted by the male. Sound amplitude (peak-to-peak, mV) and pulse rate varied significantly among males, despite low individual stereotypy. Furthermore, sound pressure level correlated with body size. The potential informative content of acoustic parameters is discussed in the light of a possible role of the sand goby sound in mate choice.     

The structure and function of songs emitted by southern green stink bugs from Brazil, Florida, Italy and Slovenia

Nezara viridula (L.) (Pentatomidae: Heteroptera) from Brazil, Florida, Italy and Slovenia, communicate by vibratory songs associated with long‐range calling and close‐range courting, rivalry and repelling. Each song is composed of spectrally and temporally different units. Spectrally different pulses of duration less than 300 ms are present in the male calling song. The female calling song is characterized by pulse trains composed of pulses shorter than 150 ms and pulse trains composed of a longer (> 700 ms) and shorter (< 250 ms) pulse. Shorter and longer pulses have different spectral characteristics. The male and female courtship songs are characterized by fusion of shorter (< 150 ms) pulses into a pulse train usually followed by a shorter (< 200 ms) postpulse in the case of the male courtship song. The female repelling song is a several seconds long vibration of irregular temporal structure. The short (< 400 ms) male rival song pulses are frequency modulated. The dominant frequency peaks of the songs investigated lie between 70 and 130 Hz. The dominant frequency and the microstructure of song spectra show no population specificity. The average duration varies more in calling than in courtship songs. The repetition time varies extensively in songs of different populations. Normal communication followed by copulation was observed between mates from Slovenia and Brazil and between mates from Florida and Italy. The potential role of different temporal and spectral parameters for species recognition and mate location is discussed in view of the expected distortion of the characteristic signal structure during transmission through plants.     

Ephaptic feedback in identified synapses of terrestrial snails

A hypothesis for the existence of the intrasynaptic ephaptic feedback (EFB) in the invertebrate central nervous sytem was tested. Excitatory postsynaptic potentials (EPSPs) and currents (EPSCs) evoked by the activation of the recently described monosynaptic connection between the identified snail neurons were recorded intracellularly. In case of the EFB presence, the postsynaptic tetanization with hyperpolarization pulses could activate presynaptic Ca2+ channels and enhance the EPSP amplitude, whereas a steady postsynaptic hyperpolarization should induce a "supralinear" increase in EPSC amplitudes as it has been found in the rat hippocampus. In the first series of the experiments, 10 trains of hyperpolarizing pulses (40-50 mV, 1 Hz, pulse duration 0.5 s, train duration 45 s) were delivered postsynaptically. No significant changes in EPSP amplitudes were found. In the second series of the experiments, the EPSC amplitudes were measured during varying postsynaptic hyperpolarization. At the membrane potential 100 mV, the EPSP amplitude was significantly higher than theoretically predicted from the classical linear dependence. Such a "supralinear" effect of postsynaptic depolarization can be explained by the presence of the EFB. This finding is the first evidence for the EFB existence in the invertebrate central nervous system.     

KILLER WHALE (ORCINUS ORCA) AUDITORY EVOKED POTENTIALS TO RHYTHMIC CLICKS

Temporal auditory mechanisms were measured in killer whales ( Orcinus orca ) by recording auditory evoked potentials (AEPs) to clicks. Clicks were presented at rates from 10/sec to 1,600/sec. At low rates, clicks evoked an AEP similar to the auditory brainstem response (ABR) of other odontocetes; however, peak latencies of the main waves were 3–3.7 msec longer than in bottlenose dolphins. Fourier analysis of the ABR showed a prominent peak at 300–400 Hz and a smaller one at 800–1,200 Hz. High-rate click presentation (more than 100/sec) evoked a rate-following response (RFR). The RFR amplitude depended little on rate up to 400/sec, decreased at higher rates and became undetectable at 1,120/sec. Fourier analysis showed that RFR fundamental amplitude dependence on frequency closely resembled the ABR spectrum. The fundamental could follow clicks to around 1,000/sec, although higher harmonics of lower rates could arise at frequencies as high as 1,200 Hz. Both RFR fundamental phase dependence on frequency and the response lag after a click train indicated an RFR group delay of around 7.5 msec. This corresponds to the latency of ABR waves PIII-NIV, which indicates the RFR originates as a rhythmic, overlapping ABR sequence. The data suggest the killer whale auditory system can follow high click rates, an ability that may have been selected for as a function of high-frequency hearing and the use of rapid clicks in echolocation.     

Sound production in the whitemouth croaker and relationship between fish size and disturbance call characteristics

The whitemouth croaker produces two different sounds using extrinsic sonic muscles: (1) male advertisement calls during the spawning season and (2) disturbance calls, produced by both sexes. The advertisement call, related to courtship, was recorded in the field and from two marked spawning males of 28 and 30.5 cm L_T in the laboratory. It consists of individual pulses with average durations of 19.7 ms and 17.8 ms for the two males respectively, interpulse intervals of 496 ms and 718 ms, and dominant frequencies of 280 Hz and 316 Hz. Pulses are emitted in bouts of one to three min duration. Disturbance calls consist of a burst of pulses produced at short intervals, and the pulse duration, interpulse interval and dominant frequency of the pulses average 19.8 ms, 17.1 ms, and 363 Hz, respectively. Dominant frequency and interpulse interval decrease and pulse duration increases with fish size. Sound characteristics change markedly in young of the year individuals (lower than 25 cm L_T) after which they appear to stabilize. Higher dominant frequency in the advertisement than in the disturbance call and the relationship of dominant frequency to pulse duration suggest that dominant frequency is determined as a forced response to muscle contraction parameters rather than by the natural frequency of the swimbladder.     

Effects of activation pattern on nonisometric human skeletal muscle performance.

During volitional muscle activation, motor units often fire with varying discharge patterns that include brief, high-frequency bursts of activity. These variations in the activation rate allow the central nervous system to precisely control the forces produced by the muscle. The present study explores how varying the instantaneous frequency of stimulation pulses within a train affects nonisometric muscle performance. The peak excursion produced in response to each stimulation train was considered as the primary measure of muscle performance. The results showed that at each frequency tested between 10 and 50 Hz, variable-frequency trains that took advantage of the catchlike property of skeletal muscle produced greater excursions than constant-frequency trains. In addition, variable-frequency trains that could achieve targeted trajectories with fewer pulses than constant-frequency trains were identified. These findings suggest that similar to voluntary muscle activation patterns, varying the instantaneous frequency within a train of pulses can be used to improve muscle performance during functional electrical stimulation.     

Spawning sounds in meagre Argyrosomus regius recorded in the Gironde estuary, France

During their spawning period (June to mid-July) in the Gironde estuary, meagre Argyrosomus regius produce two distinct sounds: regular long grunts, the most common calls, and sometimes also short grunts. It is suggested that long grunts serve the formation of spawning aggregations and short grunts announce the beginning of courtship behaviour. The meagre's long grunts include long series of 30–112 closely spaced pulses placed into call units. Each pulse produces multiple and rapidly decaying swimbladder vibrations with a dominant frequency varying between 336 and 444 Hz.