Pectoral sound generation in the blue catfish Ictalurus furcatus

Catfishes produce pectoral stridulatory sounds by “jerk” movements that rub ridges on the dorsal process against the cleithrum. We recorded sound synchronized with high-speed video to investigate the hypothesis that blue catfish Ictalurus furcatus produce sounds by a slip–stick mechanism, previously described only in invertebrates. Blue catfish produce a variably paced series of sound pulses during abduction sweeps (pulsers) although some individuals (sliders) form longer duration sound units (slides) interspersed with pulses. Typical pulser sounds are evoked by short 1–2 ms movements with a rotation of 2°–3°. Jerks excite sounds that increase in amplitude after motion stops, suggesting constructive interference, which decays before the next jerk. Longer contact of the ridges produces a more steady-state sound in slides. Pulse pattern during stridulation is determined by pauses without movement: the spine moves during about 14 % of the abduction sweep in pulsers (~45 % in sliders) although movement appears continuous to the human eye. Spine rotation parameters do not predict pulse amplitude, but amplitude correlates with pause duration suggesting that force between the dorsal process and cleithrum increases with longer pauses. Sound production, stimulated by a series of rapid movements that set the pectoral girdle into resonance, is caused by a slip–stick mechanism

Temporal Aspects Of Calling Behavior In Oyster Toadfish, Opsanus-Tau

The oyster toadfish, Opsanus tau (Linnaeus), produces two calls: an agonistic grunt and a boatwhistle associated with courtship (Fish 1954; Tavolga 1958,1960; Gray and Winn 1961). The boatwhistle is produced only by males on nests (Gray and Winn 1961) and is endogenously driven as well as influenced by calling of surrounding males (Winn 1964, 1967, 1972; Fish 1972). A toadfish, not hearing other males, may still boatwhistle for long periods and attract a female. Although toadfish may be influenced to call by the calling of adjacent males, one would assume the circadian patterning of the boatwhistle to be influenced by photoperiod and the fish\u27s behavioral strategy relative to it. Additionally, the rate of calling may be a key to a male\u27s internal state. Calling rate has been manipulated experimentally (Winn 1967, 1972; Fish 1972; Fish and Offutt 1972), but no one has studied the calling rate of undisturbed individual fish. This note is a preliminary attempt to look at these twin problems (when and how fast toadfish call) by recording the boatwhistles of individual males on their nests

Reduction of the Pectoral Spine and Girdle in Domesticated Channel Catfish is Likely Caused by Changes in Selection Pressure

Locked pectoral spines of the Channel Catfish Ictalurus punctatus more than double the fish\u27s width and complicate ingestion by gape-limited predators. The spine mates with the pectoral girdle, a robust structure that anchors the spine. This study demonstrates that both spine and girdle exhibit negative allometric growth and that pectoral spines and girdles are lighter in domesticated than in wild Channel Catfish. This finding could be explained by changes in selection pressure for spine growth during domestication or by an epigenetic effect in which exposure to predators in wild fish stimulates pectoral growth. We tested the epigenetic hypothesis by exposing domesticated Channel Catfish fingerlings to Largemouth Bass Micropterus salmoides predators for 13 weeks. Spines and girdles grow isometrically in the fingerlings, and regression analysis indicates no difference in proportional pectoral growth between control and predator-exposed fish. Therefore a change in selection pressure likely accounts for smaller pectoral growth in domesticated Channel Catfish. Decreasing spine growth in older fish suggests anti-predator functions are most important in smaller fish. Additionally, growth of the appendicular and axial skeleton is controlled differentially, and mechanical properties of the spine and not just its length are an important component of this defensive adaptation

Stream ambient noise, spectrum and propagation of sounds in the goby Padogobius martensii: Sound pressure and particle velocity

The most sensitive hearing and peak frequencies of courtship calls of the stream goby, Padogobius martensii, fall within a quiet window at around 100Hz in the ambient noise spectrum. Acoustic pressure was previously measured although Padogobius likely responds to particle motion. In this study a combination pressure (p) and particle velocity (u) detector was utilized to describe ambient noise of the habitat, the characteristics of the goby’s sounds and their attenuation with distance. The ambient noise (AN) spectrum is generally similar for p and u (including the quiet window at noisy locations), although the energy distribution of uspectrum is shifted up by 50–100Hz. The energy distribution of the goby’s sounds is similar for p and uspectra of the Tonal sound, whereas the pulse-train sound exhibits larger p–u differences. Transmission loss was high for sound p and u: energy decays 6–10dB∕10cm, and sound p∕u ratio does not change with distance from the source in the nearfield. The measurement of particle velocity of stream AN and P. martensiisounds indicates that this species is well adapted to communicate acoustically in a complex noisy shallow-water environment

Acoustic communication in two freshwater gobies: Ambient noise and short-range propagation in shallow streams

Noise is an important theoretical constraint on the evolution of signal form and sensory performance. In order to determine environmental constraints on the communication of two freshwater gobies Padogobius martensii and Gobius nigricans, numerous noise spectra weremeasured from quiet areas and ones adjacent to waterfalls and rapids in two shallow stony streams. Propagation of goby sounds and waterfall noise was also measured. A quiet window around 100 Hz is present in many noise spectra from noisy locations. The window lies between two noise sources, a low-frequency one attributed to turbulence, and a high-frequency one (200–500 Hz) attributed to bubble noise from water breaking the surface. Ambient noise from a waterfall (frequencies below 1 kHz) attenuates as much as 30 dB between 1 and 2 m, after which values are variable without further attenuation (i.e., buried in the noise floor). Similarly, courtship sounds of P. martensii attenuate as much as 30 dB between 5 and 50 cm. Since gobies are known to court in noisy as well as quiet locations in these streams, their acoustic communication system (sounds and auditory system) must be able to cope with short-range propagation dictated by shallow depths and ambient noise in noisy locations

Acoustic competition in the gulf toadfish Opsanus beta: Acoustic tagging

Nesting male gulf toadfish Opsanus beta produce a boatwhistle advertisement call used in male–male competition and to attract females and an agonistic grunt call. The grunt is a short-duration pulsatile call, and the boatwhistle is a complex call typically consisting of zero to three introductory grunts, a long tonal boop note, and zero to three shorter boops. The beginning of the boop note is also gruntlike. Anomalous boatwhistles contain a short-duration grunt embedded in the tonal portion of the boop or between an introductory grunt and the boop. Embedded grunts have sound-pressure levels and frequency spectra that correspond with those of recognized neighbors, suggesting that one fish is grunting during another’s call, a phenomenon here termed acoustic tagging. Snaps of nearby pistol shrimp may also be tagged, and chains of tags involving more than two fish occur. The stimulus to tag is a relatively intense sound with a rapid rise time, and tags are generally produced within 100 ms of a trigger stimulus. Time between the trigger and the tag decreases with increased trigger amplitude. Tagging is distinct from increased calling in response to natural calls or stimulatory playbacks since calls rarely overlap other calls or playbacks. Tagging is not generally reciprocal between fish, suggesting parallels to dominance displays

Grunt variation in the oyster toadfish Opsanus tau: effect of size and sex

As in insects, frogs and birds, vocal activity in fishes tends to be more developed in males than in females, and sonic swimbladder muscles may be sexually dimorphic, i.e., either larger in males or present only in males. Male oyster toadfish Opsanus tau L produce a long duration, tonal boatwhistle advertisement call, and both sexes grunt, a short duration more pulsatile agonistic call. Sonic muscles are present in both sexes but larger in males. We tested the hypothesis that males would call more than females by inducing grunts in toadfish of various sizes held in a net and determined incidence of calling and developmental changes in grunt parameters. A small number of fish were recorded twice to examine call repeatability. Both sexes were equally likely to grunt, and grunt parameters (sound pressure level (SPL), individual range in SPL, number of grunts, and fundamental frequency) were similar in both sexes. SPL increased with fish size before leveling off in fish \u3e200 g, and fundamental frequency and other parameters did not change with fish size. Number of grunts in a train, grunt duration and inter-grunt interval were highly variable in fish recorded twice suggesting that grunt parameters reflect internal motivation rather than different messages. Grunt production may explain the presence of well-developed sonic muscles in females and suggests that females have an active but unexplored vocal life

Ultrastructural Distribution of the 7 Nicotinic Acetylcholine Receptor Subunit in Rat Hippocampus

Acetylcholine (ACh) is an important neurotransmitter in the mammalian brain; it is implicated in arousal, learning, and other cognitive functions. Recent studies indicate that nicotinic receptors contribute to these cholinergic effects, in addition to the established role of muscarinic receptors. In the hippocampus, where cholinergic involvement in learning and memory is particularly well documented, 7 nicotinic acetylcholine receptor subunits (7 nAChRs) are highly expressed, but their precise ultrastructural localization has not been determined. Here, we describe the results of immunogold labeling of serial ultrathin sections through stratum radiatum of area CA1 in the rat. Using both anti-7 nAChR immunolabeling and -bungarotoxin binding, we find that 7 nAChRs are present at nearly all synapses in CA1 stratum radiatum, with immunolabeling present at both presynaptic and postsynaptic elements. Morphological considerations and double immunolabeling indicate that GABAergic as well as glutamatergic synapses bear 7 nAChRs, at densities approaching those observed for glutamate receptors in CA1 stratum radiatum. Postsynaptically, 7 nAChRs often are distributed at dendritic spines in a perisynaptic annulus. In the postsynaptic cytoplasm, immunolabeling is associated with spine apparatus and other membranous structures, suggesting that 7 nAChRs may undergo dynamic regulation, with insertion into the synapse and subsequent internalization. The widespread and substantial expression of 7 nAChRs at synapses in the hippocampus is consistent with an important role in mediating and/or modulating synaptic transmission, plasticity, and neurodegeneration

Spatiotemporal Variability and Sound Characterization in Silver Croaker Plagioscion squamosissimus (Sciaenidae) in the Central Amazon

Background The 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 croakerPlagioscion 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 Findings Dissections 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 Significance Silver 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