Sonic Muscles Research Articles

Sound production in Onuxodon fowleri (Carapidae) and its amplification by the host shell.

Onuxodon species are well known for living inside pearl oysters. As in other carapids, their anatomy highlights their ability to make sounds but sound production has never been documented in Onuxodon. This paper describes sound production in Onuxodon fowleri as well as the anatomy of the sound production apparatus. Single-pulsed sounds and multiple-pulsed sounds that sometimes last more than 3 s were recorded in the field and in captivity (Makemo Island, French Polynesia). These pulses are characterized by a broadband frequency spectrum from 100 to 1000 Hz. Onuxodon fowleri is mainly characterized by its ability to modulate the pulse period, meaning that this species can produce pulsed sounds and tonal-like sounds using the same mechanism. In addition, the sound can be remarkably amplified by the shell cavity (peak gain can exceed 10 dB for some frequencies). The sonic apparatus of O. fowleri is characterized by a rocker bone in front of the swimbladder, modified vertebrae and epineurals, and two pairs of sonic muscles, one of which (primary sonic muscle) inserts on the rocker bone. The latter structure, which is absent in other carapid genera, appears to be sexually dimorphic suggesting differences in sound production in males and females. Sound production in O. fowleri could be an example of adaptation where an animal exploits features of its environment to enhance communication.

Sound production to electric discharge: sonic muscle evolution in progress in Synodontis spp. catfishes (Mochokidae).

Elucidating the origins of complex biological structures has been one of the major challenges of evolutionary studies. Within vertebrates, the capacity to produce regular coordinated electric organ discharges (EODs) has evolved independently in different fish lineages. Intermediate stages, however, are not known. We show that, within a single catfish genus, some species are able to produce sounds, electric discharges or both signals (though not simultaneously). We highlight that both acoustic and electric communication result from actions of the same muscle. In parallel to their abilities, the studied species show different degrees of myofibril development in the sonic and electric muscle. The lowest myofibril density was observed in Synodontis nigriventris, which produced EODs but no swim bladder sounds, whereas the greatest myofibril density was observed in Synodontis grandiops, the species that produced the longest sound trains but did not emit EODs. Additionally, S. grandiops exhibited the lowest auditory thresholds. Swim bladder sounds were similar among species, while EODs were distinctive at the species level. We hypothesize that communication with conspecifics favoured the development of species-specific EOD signals and suggest an evolutionary explanation for the transition from a fast sonic muscle to electrocytes.

Spatiotemporal variability and sound characterization in silver croaker Plagioscion squamosissimus (Sciaenidae) in the Central Amazon.

BackgroundThe fish family Sciaenidae has numerous species that produce sounds with superfast muscles that vibrate the swimbladder. These muscles form post embryonically and undergo seasonal hypertrophy-atrophy cycles. The family has been the focus of numerous passive acoustic studies to localize spatial and temporal occurrence of spawning aggregations. Fishes produce disturbance calls when hand-held, and males form aggregations in late afternoon and produce advertisement calls to attract females for mating. Previous studies on five continents have been confined to temperate species. Here we examine the calls of the silver croaker Plagioscion squamosissimus, a freshwater equatorial species, which experiences constant photoperiod, minimal temperature variation but seasonal changes in water depth and color, pH and conductivity.Methods and Principal FindingsDissections indicate that sonic muscles are present exclusively in males and that muscles are thicker and redder during the mating season. Disturbance calls were recorded in hand-held fish during the low-water mating season and high-water period outside of the mating season. Advertisement calls were recorded from wild fish that formed aggregations in both periods but only during the mating season from fish in large cages. Disturbance calls consist of a series of short individual pulses in mature males. Advertisement calls start with single and paired pulses followed by greater amplitude multi-pulse bursts with higher peak frequencies than in disturbance calls. Advertisement-like calls also occur in aggregations during the off season, but bursts are shorter with fewer pulses.Conclusions and SignificanceSilver croaker produce complex advertisement calls that vary in amplitude, number of cycles per burst and burst duration of their calls. Unlike temperate sciaenids, which only call during the spawning season, silver croaker produce advertisement calls in both seasons. Sonic muscles are thinner, and bursts are shorter than at the spawning peak, but males still produce complex calls outside of the mating season.

Modifications in call characteristics and sonic apparatus morphology during puberty in Ophidion rochei (actinopterygii: Ophidiidae)

Juveniles, females, and males of Ophidion rochei share similar external morphology, probably because they are mainly active in the dark, which reduces the role of visual cues. Their internal sonic apparatuses, however, are complex: three pairs of sonic muscles, and highly modified vertebrae and ribs are involved in sound production. The sonic apparatus of males differs from juveniles and females in having larger swimbladder plates (modified ribs associate with the swimbladder wall) and sonic muscles, a modified swimbladder shape and a mineralized structure called the "rocker bone" in front of the swimbladder. All of these male traits appear at the onset of sexual maturation. This article investigates the relationship between morphology and sounds in male O. rochei of different sizes. Despite their small size range total length (133-170 mm TL), the five specimens showed pronounced differences in sound-production apparatus morphology, especially in terms of swimbladder shape and rocker bone development. This observation was reinforced by the positive allometry measured for the rocker bone and the internal tube of the swimbladder. The differences in morphology were related to marked differences in sound characteristics (especially frequency and pulse duration). These results suggest that male calls carry information about the degree of maturity. Deprived of most visual cues, ophidiids probably have invested in other mechanisms to recognize and distinguish among individual conspecifics and between ophidiid species. As a result, their phenotypes are externally similar but internally very different. In these taxa, the great variability of the sound production apparatus means this complex system is a main target of environmental constraints.

Development of the ultrastructure of sonic muscles: a kind of neoteny?

BackgroundDrumming muscles of some sound-producing fish are ‘champions’ of contraction speed, their rate setting the fundamental frequency. In the piranha, contraction of these muscles at 150 Hz drives a sound at the same frequency. Drumming muscles of different not closely related species show evolutionary convergences. Interestingly, some characters of sonic muscles can also be found in the trunk muscles of newly hatched larvae that are able to maintain tail beat frequencies up to 100 Hz. The aim of this work was to study the development of sound production and sonic and epaxial muscles simultaneously in the red bellied piranhas (Pygocentrus nattereri) to seek for possible common characteristics.ResultsCall, pulse and period durations increased significantly with the fish size, but the call dominant frequencies decreased, and the number of pulses and the call amplitude formed a bell curve. In epaxial muscles, the fibre diameters of younger fish are first positioned in the graphical slope corresponding to sonic muscles, before diverging. The fibre diameter of older fish trunk muscles was bigger, and the area of the myofibrils was larger than in sonic muscles. Moreover, in two of the biggest fish, the sonic muscles were invaded by fat cells and the sonic muscle ultrastructure was similar to the epaxial one. These two fish were also unable to produce any sound, meaning they lost their ability to contract quickly.ConclusionsThe volume occupied by myofibrils determines the force of contraction, the volume of sarcoplasmic reticulum sets the contraction frequency, and the volume of mitochondria sets the level of sustained performance. The functional outcomes in muscles are all attributable to shifts in the proportions of those structures. A single delay in the development restricts the quantity of myofibrils, maintains a high proportion of space in the sarcoplasm and develops sarcoplasmic reticulum. High-speed sonic muscles could thus be skeletal muscles with delayed development. This hypothesis has the advantage that it could easily explain why high-speed sonic muscles have evolved so many times in different lineages.

A superfast muscle in the complex sonic apparatus of Ophidion rochei (Ophidiiformes): histological and physiological approaches.

In teleosts, superfast muscles are generally associated with the swimbladder wall, whose vibrations result in sound production. In Ophidion rochei, three pairs of muscles were named 'sonic' because their contractions affect swimbladder position: the dorsal sonic muscle (DSM), the intermediate sonic muscle (ISM), and the ventral sonic muscle (VSM). These muscles were investigated thanks to electron microscopy and electromyography in order to determine their function in sound production. Fibers of the VSM and DSM were much thinner than the fibers of the ISM and epaxial musculature. However, only VSM fibers had the typical ultrastructure of superfast muscles: low proportion of myofibrils, and high proportions of sarcoplasmic reticulum and mitochondria. In females, each sound onset was preceded by the onset of electrical activity in the VSM and the DSM (ISM was not tested). The electromyograms of the VSM were very similar to the waveforms of the sounds: means for the pulse period were 3.6±0.5 and 3.6±0.7 ms, respectively. This shows that the fast VSM (ca. 280 Hz) is responsible for the pulse period and fundamental frequency of female sounds. DSM electromyograms were generally characterized by one or two main peaks followed by periods of lower electrical activity, which suggests a sustained contraction over the course of the sound. The fiber morphology of the ISM and its antagonistic position relative to the DSM are not indicative of a muscle capable of superfast contractions. Overall, this study experimentally shows the complexity of the sound production mechanism in the nocturnal fish O. rochei.

Large-scale passive acoustic monitoring of fish sound production on the West Florida Shelf

Sounds from toadfish Opsanus sp., and 4 other suspected fish sounds were identified in passive acoustic recordings from fixed recorders and autonomous underwater vehicles in the eastern Gulf of Mexico between 2008 and 2011. Data were collected in depths ranging from 4 to 984 m covering approximately 39000 km 2 . The goals of this research were to map the spatial and temporal occurrence of these sounds. Sound production was correlated to environmental para - meters (water depth, lunar cycle, and dawn and dusk) to understand the variability in seasonal calling. Toadfish 'boatwhistles' were recorded throughout the diel period, with peaks observed between 15:00 and 04:00 h. Annual peaks coincided with the spawning period in the late spring to early summer. The 4 unknown sounds were termed: '100 Hz Pulsing', '6 kHz Sound', '300 Hz FM Harmonic', and '365 Hz Harmonic'. The 100 Hz Pulsing had the temporal characteristics of a cusk-eel call with frequencies below 500 Hz. Sound production was observed mainly at night with annual peaks in the spring and fall. The 6 kHz Sound was observed exclusively at night between 15 and 50 m bottom depths; occurrence decreased significantly in the winter. The 6 kHz Sound peak frequencies correlated positively to satellite-derived sea surface temperature (SST) and nega tively to chlorophyll concentration. The 300 Hz FM Harmonic was observed largely (89%) at night and appeared offshore (40�200 m depth). The 365 Hz Harmonic was observed 98% of the time at night, inshore (<40 m depth). The fundamental frequency of the 365 Hz Harmonic was positively correlated with SST, reflecting a temperature-driven increase in sonic muscle contrac- tion rate; conversely, call duration was negatively correlated. The ubiquity of these 4 unknown sounds illustrates how little is known about biological communication in the marine environment.

Fast drum strokes: Novel and convergent features of sonic muscle ultrastructure, innervation, and motor neuron organization in the pyramid butterflyfish (hemitaurichthys polylepis)

Sound production that is mediated by intrinsic or extrinsic swim bladder musculature has evolved multiple times in teleost fishes. Sonic muscles must contract rapidly and synchronously to compress the gas-filled bladder with sufficient velocity to produce sound. Muscle modifications that may promote rapid contraction include small fiber diameter, elaborate sarcoplasmic reticulum (SR), triads at the A-I boundary, and cores of sarcoplasm. The diversity of innervation patterns indicate that sonic muscles have independently evolved from different trunk muscle precursors. The analysis of sonic motor pathways in distantly related fishes is required to determine the relationships between sonic muscle evolution and function in acoustic signaling. We examined the ultrastructure of sonic and adjacent hypaxial muscle fibers and the distribution of sonic motor neurons in the coral reef Pyramid Butterflyfish (Chaetodontidae: Hemitaurichthys polylepis) that produces sound by contraction of extrinsic sonic muscles near the anterior swim bladder. Relative to adjacent hypaxial fibers, sonic muscle fibers were sparsely arranged among the endomysium, smaller in cross-section, had longer sarcomeres, a more elaborate SR, wider t-tubules, and more radially arranged myofibrils. Both sonic and non-sonic muscle fibers possessed triads at the Z-line, lacked sarcoplasmic cores, and had mitochondria among the myofibrils and concentrated within the peripheral sarcoplasm. Sonic muscles of this derived eutelost possess features convergent with other distant vocal taxa (other euteleosts and non-euteleosts): small fiber diameter, a well-developed SR, and radial myofibrils. In contrast with some sonic fishes, however, Pyramid Butterflyfish sonic muscles lack sarcoplasmic cores and A-I triads. Retrograde nerve label experiments show that sonic muscle is innervated by central and ventrolateral motor neurons associated with spinal nerves 1-3. This restricted distribution of sonic motor neurons in the spinal cord differs from many euteleosts and likely reflects the embryological origin of sonic muscles from hypaxial trunk precursors rather than occipital somites.

Parvalbumin characteristics in the sonic muscle of a freshwater ornamental grunting toadfish (Allenbatrachus grunniens)

The grunting toadfish, Allenbatrachus grunniens, is an ornamental fish in freshwater aquariums, and it has the ability to produce sounds. The sonic muscle of the toadfish is the fastest vertebrate muscle ever measured, and the rates of Ca(2+) transport and cross-bridge dissociation are also the fastest. Parvalbumins (PAs) are Ca(2+)-binding proteins that help in muscle relaxation in vertebrates. Several PA isoforms have been identified in variable ratios in different muscle types. Both male and female grunting toadfish have intrinsic sonic muscles attached to their swim bladders, but no significant difference in morphology between male and female sonic muscles has been observed. In this study, we used SDS-PAGE and western blotting to characterize the total PA expression and to identify the PAs from the sonic muscle and the white body muscle of A. grunniens. Although the total PA concentrations were similar in sonic and white muscles, there were differences in the isoform percentages. Two and four PA isoforms were identified from sonic muscle and white muscle, respectively. The estimated sizes of PA1, PA2, and PA3 in the sonic muscle of the grunting toadfish were 10, 10.5, and 10.5 kDa, respectively, and the isoelectric points of PA1, PA2, and PA3 in the grunting toadfish were 4.77, 4.58, and 4.42, respectively. In the sonic muscle, the primary PA isoform was PA1, which comprised more than 94 % of total PA, whereas PA2 comprised only 5 % of the total PA content. In contrast, in white muscle, the primary isoform was PA2, which comprised 58 % of the total PA. Both PA1 (with PA1a) and PA3 represented approximately 20 % of the total PA in white muscle. These results indicate that there is no positive correlation between a high PA content and the speed of muscle relaxation; however, PA1 might have the greatest effect on the relaxation of the grunting toadfish's sonic muscle.

Innovations in motoneuron synchrony drive rapid temporal modulations in vertebrate acoustic signaling.

Rapid temporal modulation of acoustic signals among several vertebrate lineages has recently been shown to depend on the actions of superfast muscles. We hypothesized that such fast events, known to require synchronous activation of muscle fibers, would rely on motoneuronal properties adapted to generating a highly synchronous output to sonic muscles. Using intracellular in vivo recordings, we identified a suite of premotor network inputs and intrinsic motoneuronal properties synchronizing the oscillatory-like, simultaneous activation of superfast muscles at high gamma frequencies in fish. Motoneurons lacked spontaneous activity, firing synchronously only at the frequency of premotor excitatory input. Population-level motoneuronal output generated a spike-like, vocal nerve volley that directly determines muscle contraction rate and, in turn, natural call frequency. In the absence of vocal output, motoneurons showed low excitability and a weak afterhyperpolarization, leading to rapid accommodation in firing rate. By contrast, vocal activity was accompanied by a prominent afterhyperpolarization, indicating a dependency on network activity. Local injection of a GABA(A) receptor antagonist demonstrated the necessity of electrophysiologically and immunohistochemically confirmed inhibitory GABAergic input for motoneuronal synchrony and vocalization. Numerous transneuronally labeled motoneurons following single-cell neurobiotin injection together with electrophysiological collision experiments confirmed gap junctional coupling, known to contribute to synchronous activity in other neural networks. Motoneuronal synchrony at the premotor input frequency was maintained during differential recruitment of variably sized motoneurons. Differential motoneuron recruitment led, however, to amplitude modulation (AM) of vocal output and, hence, natural call AM. In summary, motoneuronal intrinsic properties, in particular low excitability, predisposed vocal motoneurons to the synchronizing influences of premotor inputs to translate a temporal input code into a coincident and extremely synchronous, but variable-amplitude, output code. We propose an analogous suite of neuronal properties as a key innovation underlying similarly rapid acoustic events observed among amphibians, reptiles, birds, and mammals.

Sexual dimorphism of sonic apparatus and extreme intersexual variation of sounds in Ophidion rochei (Ophidiidae): first evidence of a tight relationship between morphology and sound characteristics in Ophidiidae

BackgroundMany Ophidiidae are active in dark environments and display complex sonic apparatus morphologies. However, sound recordings are scarce and little is known about acoustic communication in this family. This paper focuses on Ophidion rochei which is known to display an important sexual dimorphism in swimbladder and anterior skeleton. The aims of this study were to compare the sound producing morphology, and the resulting sounds in juveniles, females and males of O. rochei.ResultsMales, females, and juveniles possessed different morphotypes. Females and juveniles contrasted with males because they possessed dramatic differences in morphology of their sonic muscles, swimbladder, supraoccipital crest, and first vertebrae and associated ribs. Further, they lacked the ‘rocker bone’ typically found in males. Sounds from each morphotype were highly divergent. Males generally produced non harmonic, multiple-pulsed sounds that lasted for several seconds (3.5 ± 1.3 s) with a pulse period of ca. 100 ms. Juvenile and female sounds were recorded for the first time in ophidiids. Female sounds were harmonic, had shorter pulse period (±3.7 ms), and never exceeded a few dozen milliseconds (18 ± 11 ms). Moreover, unlike male sounds, female sounds did not have alternating long and short pulse periods. Juvenile sounds were weaker but appear to be similar to female sounds.ConclusionsAlthough it is not possible to distinguish externally male from female in O. rochei, they show a sonic apparatus and sounds that are dramatically different. This difference is likely due to their nocturnal habits that may have favored the evolution of internal secondary sexual characters that help to distinguish males from females and that could facilitate mate choice by females. Moreover, the comparison of different morphotypes in this study shows that these morphological differences result from a peramorphosis that takes place during the development of the gonads.

Vocal behavior predicts reproductive success in a teleost fish

The relation between acoustic signaling and reproductive success is important to understand the evolution of vocal communication systems and has been well studied in several taxa but never clearly shown in fish. This study aims to investigate whether vocal behavior affects the reproductive success in the Lusitanian toadfish (Halobatrachus didactylus) that relies on acoustic communication to attract mates. We recorded 56 nest-holding (type I) males during the breeding season and analyzed the calling performance and acoustic features of the mate advertising sounds (boatwhistles) exhibited over circa 2 weeks. Hormonal levels of the subjects and the number of eggs (reproductive success) present in the respective nests were quantified. Nesting males attracted both females and other males, namely smaller type I males with significantly lower total length (TL), body condition, sonic muscle mass, gonad mass, and accessory glands mass. Calling rate (CR), calling effort (CE) (% time spent calling), and sound dominant frequency were significantly higher in nesting males with clutches than in those without clutches. Sex steroids (11-ketotestosterone and testosterone) were not correlated with vocal parameters or number of eggs. Maximum CR and CE were the best predictors of the number of eggs. In addition, these vocal variables were best explained by male's TL, condition, and sonic muscle mass. We provide first evidence that vocal behavior significantly determines reproductive success in a vocal fish and show that acoustic signaling at higher and constant rates can operate as an indicator of the male's size and body condition and probably of elevated motivation for reproduction.

Acoustic Communication: Sound Advice from Piranhas

An elegant new study has correlated the generation of sound patterns in the red-bellied piranha (Pygocentrus nattereri) with three distinct behaviours.

An Intermediate in the evolution of superfast sonic muscles.

BackgroundIntermediate forms in the evolution of new adaptations such as transitions from water to land and the evolution of flight are often poorly understood. Similarly, the evolution of superfast sonic muscles in fishes, often considered the fastest muscles in vertebrates, has been a mystery because slow bladder movement does not generate sound. Slow muscles that stretch the swimbladder and then produce sound during recoil have recently been discovered in ophidiiform fishes. Here we describe the disturbance call (produced when fish are held) and sonic mechanism in an unrelated perciform pearl perch (Glaucosomatidae) that represents an intermediate condition in the evolution of super-fast sonic muscles.ResultsThe pearl perch disturbance call is a two-part sound produced by a fast sonic muscle that rapidly stretches the bladder and an antagonistic tendon-smooth muscle combination (part 1) causing the tendon and bladder to snap back (part 2) generating a higher-frequency and greater-amplitude pulse. The smooth muscle is confirmed by electron microscopy and protein analysis. To our knowledge smooth muscle attachment to a tendon is unknown in animals.ConclusionThe pearl perch, an advanced perciform teleost unrelated to ophidiiform fishes, uses a slow type mechanism to produce the major portion of the sound pulse during recoil, but the swimbladder is stretched by a fast muscle. Similarities between the two unrelated lineages, suggest independent and convergent evolution of sonic muscles and indicate intermediate forms in the evolution of superfast muscles.

Sound production and pectoral spine locking in a Neotropical catfish (Iheringichthys labrosus, Pimelodidae)

Catfishes may have two sonic organs: pectoral spines for stridulation and swimbladder drumming muscles. The aim of this study was to characterize the sound production of the catfish Iheringichthys labrosus. The I. labrosus male and female emits two different types of sounds: stridulatory sounds (655.8 + 230 Hz) consisting of a train of pulses, and drumming sounds (220 + 46 Hz), which are composed of single-pulse harmonic signals. Stridulatory sounds are emitted during abduction of the pectoral spine. At the base of the spine there is a dorsal process that bears a series of ridges on its latero-ventral surface, and by pressing the ridges against the groove (with an unspecialized rough surface) during a fin sweep, the animal produce a series of short pulses. Drumming sound is produced by an extrinsic sonic muscle, originated on a flat tendon of the transverse process of the fourth vertebra and inserted on the rostral and ventral surface of the swimbladder. The sounds emitted by both mechanisms are emitted in distress situation. Distress was induced by manipulating fish in a laboratory tank while sounds were recorded. Our results indicate that the catfish initially emits a stridulatory sound, which is followed by a drumming sound. Simultaneous production of stridulatory and drumming sounds was also observed. The catfish drumming sounds were lower in dominant frequency than stridulatory sounds, and also exhibited a small degree of dominant frequency modulation. Another behaviour observed in this catfish was the pectoral spine locking. This reaction was always observed before the distress sound production. Like other authors outline, our results suggest that in the catfish I. labrosus stridulatory and drumming sounds may function primarily as a distress call.

Sound production in red-bellied piranhas (Pygocentrus nattereri, Kner): an acoustical, behavioural and morphofunctional study

Piranhas are known to be sound-producing animals. Nevertheless, the biological significance of piranha calls remains unclear because sounds have been recorded only when specimens were held by hand or trapped in a gill net. These sounds are generated by rapid contractions of sonic muscles that insert on a broad tendon surrounding ventrally the cranial sac of the swimbladder. The piranha swimbladder is thought to play an important role in sound production as an impedance-matching device and as a resonator. However, the vibratory capacities of the cranial and caudal sacs and the exact role of both sacs in sound production remain poorly understood. In this study, three sounds were each associated to a specific behaviour. The first sound (type 1) was produced during frontal display; it had numerous pulses and lasted 140!±17 ms, with a fundamental frequency of 120±4 Hz. It corresponded to the sound made by hand-held fishes. The second sound (type 2) was produced during circling and fighting behaviour; it was a single pulse lasting 36±8 ms, with a fundamental frequency of 43±10 Hz. The third sound (type 3) corresponded to chasing behaviour and comprised three to four pulses, each lasting 3±1 ms, with a fundamental frequency of 1739±18 Hz. Using a laser vibrometer to study the swimbladder displacement when stimulated at different frequencies, it was demonstrated that the first two sounds corresponded to the swimbladder mechanism. By contrast, the third sound was associated with the jaw mechanism. The vibrometer indicated that the swimbladder is a highly damping structure, simply copying the sonic muscle contraction rate. This study provides two interesting insights. First, it shows the relationships between three kinds of piranha sound and three specific behaviours. Second, using muscle stimulation at different rates, it shows which simultaneous conditions are required for production of sound in this species. Swimbladder calls were produced by a muscle contraction rate of approximately 100 Hz because this periodicity allowed the swimbladder to vibrate. At this frequency range, the contraction-relaxation cycles of the swimbladder muscles engendered wall displacements that had short amplitudes and with only a small variability between them.

Seasonal changes in atrophy-associated proteins of the sonic muscle in the big-snout croaker, Johnius macrorhynus (Pisces, Sciaenidae), identified by using a proteomic approach

In most sciaenids, males possess sonic muscles and produce sound through the contraction of these muscles and amplification of the swim bladder. The sonic muscles in some fishes exhibit seasonal changes in size. For example, they are hypertrophic in the spawning season, and atrophic in the non-spawning months. The protein profiles of the sonic muscle, red muscle, and white muscle in the Johnius macrorhynus were shown by two-dimensional electrophoresis (2-DE) and were compared to reveal differential protein expressions. About 80 up-regulated protein spots in the sonic muscle, and 30 spots related to six contractile proteins (fast muscle myosin heavy chain, skeletal alpha actin, alpha actin cardiac, tropomyosin, myosin light chain 2, and myosin light chain 3), four energy metabolic enzymes (enolase, acyl-CoA synthetase, creatine kinase, and cytochrome P450 monooxygenase), and two miscellaneous proteins (DEAD box protein and cyclin H) were identified. Seasonal hypertrophy and atrophy of the sonic muscles related to the reproductive cycle were verified in male big-snout croaker. The contents of some proteins were significantly different in the muscles under these conditions. The levels of cytochrome P450 monooxygenase, fast muscle myosin heavy chain, DEAD box proteins, isocitrate dehydrogenase, and creatine kinase were up-regulated in the hypertrophic muscle, but the levels of alpha actin cardiac, myosin light 2, and myosin light 3 were lower than in the atrophic muscle. Potential reasons for these differences in protein expression related to physiological adaptation are discussed.

Convergent evolution and intermediate status of the sonic mechanism in a perciform fish Glaucosoma buergeri (Glaucosomatidae).

Little is known about evolution of swimbladder sound production in fishes. Typical fish sound production utilizes fast muscles that drive the swimbladder to produce sound as a forced but rapidly‐damping response; a muscle contraction rate of 200 times/s will generate a sound with a fundamental frequency of 200 Hz. Recently, slow muscles have been demonstrated in a carapid fish. These muscles slowly extend the anterior swimbladder by stretching a swimbladder fenestra until the bladder snaps back exciting sound production. Here we describe sounds produced by a similar but phylogenetically‐unrelated mechanism in a perciform fish. A pair of extrinsic sonic muscles originates on the pterotic bones and inserts on the anterodorsal swimbladder just forward of a stretchable swimbladder fenestra. A fan‐shaped tendon that ends in a smooth muscle attaches to the bladder just forward of the fenestra. The tendon‐smooth muscle pair will be stretched by contraction of the rostral sonic muscles. Strain energy stored in th...

Calls of the black drum (Pogonias cromis: Sciaenidae): Geographical differences in sound production between Northern and Southern Hemisphere Populations.

Because of apparent reproductive isolation between Northern and Southern hemisphere populations of the black drum Pogonius cromis, we tested the hypothesis that advertisement calls from a southern population would differ from known calls of North American populations. Additionally, we quantified disturbance and advertisement calls, their changes with fish size and sex, not previously examined in this species. Unlike most sciaenids, both sexes of P. cromis possess robust sonic muscles, and both produce disturbance calls when handled. However, only males produce an advertisement call used in courtship. The disturbance call consists of a variable train of short‐duration pulses (average 23 ms). The duration, interpulse interval, and dominant frequency of pulses are similar in males and females and change developmentally: pulse duration and interpulse interval increase and dominant frequency decreases with fish size. Advertisement calls, recorded in the field and in captivity, are long‐duration (average 184 ms) and tonal. Based on variation in fundamental frequency, which decreases with fish size, field choruses are composed of different‐sized individuals. The duration of advertisement calls, about a third of those from Florida populations, suggests genetic differentiation between northern and southern populations.

Comparative study on sound production in different Holocentridae species

BackgroundHolocentrids (squirrelfish and soldierfish) are vocal reef fishes whose calls and sound-producing mechanisms have been studied in some species only. The present study aims to compare sound-producing mechanisms in different Holocentridae genera (Holocentrus, Myripristis, Neoniphon, Sargocentron) from separate regions and, in some cases, at different developmental stages. An accurate comparison was made by recording six species while being hand-held, by observing TEM) the sonic muscles and by dissections of the sound-producing mechanism.ResultsIn all these species, calls presented harmonics, their dominant frequency was between 80 and 130 Hz and they were composed of trains of 4 to 11 pulses with gradual increasing periods towards the end of the call. In each case, the calls did not provide reliable information on fish size. The sounds were produced by homologous fast-contracting sonic muscles that insert on articulated ribs whose proximal heads are integrated into the swimbladder: each pulse is the result of the back and forth movements of the ribs. Small differences in the shape of the oscillograms of the different species could be related to the number of ribs that are involved in the sound-producing mechanism. These fish species are able to make sounds as soon as they settle on the reef, when they are 40 days old. Comparison between Neoniphon from Madagascar and from Rangiroa in French Polynesia showed a new, unexpected kind of dialect involving differences at the level of pulse distribution. Neoniphon calls were characterised by a single pulse that was isolated at the beginning of the remaining train in Madagascar whereas they did not show any isolated single pulses at the beginning of the call in Rangiroa.ConclusionThis family cannot use the acoustic fundamental frequencies (or pulse periods) of grunts to infer the size of partners. Pulse duration and number of pulses are statistically related to fish size. However, these characteristics are poorly informative because the correlation slope values are weak. It remains other features (sound amplitude, resistance to muscle fatigue, calling frequency) could be used to assess the body size. Characteristics of the sound producing mechanisms are conservative. All species possess fast-contracting muscles and have the same kind of sound producing mechanism. They do show some change between clades but these differences are not important enough to deeply modify the waveforms of the calls. In this case, our description of the grunt could be considered as the signature for the holocentrid family and can be used in passive acoustic monitoring.