Stridulatory Sound-Production and Its Function in Females of the Cicada Subpsaltria yangi

Acoustic behavior plays a crucial role in many aspects of cicada biology, such as reproduction and intrasexual competition. Although female sound production has been reported in some cicada species, acoustic behavior of female cicadas has received little attention. In cicada Subpsaltria yangi, the females possess a pair of unusually well-developed stridulatory organs. Here, sound production and its function in females of this remarkable cicada species were investigated. We revealed that the females could produce sounds by stridulatory mechanism during pair formation, and the sounds were able to elicit both acoustic and phonotactic responses from males. In addition, the forewings would strike the body during performing stridulatory sound-producing movements, which generated impact sounds. Acoustic playback experiments indicated that the impact sounds played no role in the behavioral context of pair formation. This study provides the first experimental evidence that females of a cicada species can generate sounds by stridulatory mechanism. We anticipate that our results will promote acoustic studies on females of other cicada species which also possess stridulatory system.     

A new mechanism of sound production by courting male jumping spiders (Araneae: Salticidae, Saitis michaelseni Simon)

Male Saitis michaelseni Simon (Araneae: Salticidae) produce sounds during courtship which can be heard several metres away. Courting males stridulate on dead leaves and are positioned on the opposite side of the leaf from the female. The courtship display contains both visual and acoustic elements. Courtship consists of three phases. In the first two phases, the male stridulates, and in the third phase, in which he makes tactile contact with the female, he alternates bursts of stridulatory sound with bouts of percussive sound in which the first pair of legs strikes the substratum. Stridulation apparently results from the thickened bases of short hairs on the anterior part of the abdomen moving over two files on the posterior part of the carapace. This stridulatory mechanism has not been previously reported for salticid spiders. The frequency spectra and amplitude modulation patterns of sounds produced by stridulation and percussion are presented.     

EVIDENCE FOR A HYDRODYNAMIC MECHANISM OF SOUND PRODUCTION BY COURTING MALES OF THE NOTCHTONGUE GOBY,BATHYGOBIUS CURACAO (METZELAAR)

ABSTRACT

Male gobies of the genus Bathygobius are soniferous during courtship. The mechanism by which the sounds are produced is, however, unknown. Early studies on sound production by males of B. soporator suggested that these sounds are hydrodynamic in nature, being produced by the forcible ejection of water through the gill opening. The mechanism of sound production by the closely related species B. curacao was investigated and three lines of evidence are presented which support the hydrodynamic hypothesis. First, similarities between the sounds produced by courting males and by ejecting water through a pipette demonstrated that hydrodynamic forces can readily produce such sounds. Second, the behavioural motor patterns occurring during sound production are consistent with the hypothesis that water is being ejected through the gill openings. Finally, morphological examination revealed an apparent lack of specialised features associated with sound production, effectively eliminating stridulatory and swim bladder mechanisms. These results represent the strongest evidence to date in support of any proposed mechanism of sound production in the gobiids.     

A new species of myxosporean (Sphaeromyxidae), a parasite of lined seahorses, Hippocampus erectus, from the Gulf of Mexico

Sphaeromyxa cannolii sp. n. is described from the bile ducts of aquaria-maintained lined seahorses (Hippocampus erectus) from the Gulf of Mexico. Spores of the new species are linear, 17-18 μm long and 5-6 μm wide, with flattened tips; polar capsules measure 4 × 3 μm. Routine necropsies of H. erectus following planned death revealed liver inflammation, bile duct obstruction, bile accumulation, and myxozoan parasites in the bile ducts of 11 of 40 animals sampled (27.5%). The presence of S. cannolii in an aquaculture setting should prompt keepers to carefully quarantine new animals and exclude annelid fauna, a potential intermediate host of myxozoans.     

Parasitic infection of the seahorse (Hippocampus erectus)--a case report

This report details the development of a microsporidan infection in a colony of seahorses (Hippocampus erectus) caused by Glugea heraldi. Of 76 animals imported from Florida Bay (USA), two survived. A myxosporidan (Sphaeromyxa sp.) and an unidentified nematode infection were also diagnosed in the same colony, but these infections were not considered important, causative factors in the mortalities.     

COMPARATIVE ANALYSIS OF SWIMBLADDER (DRUMMING) AND PECTORAL (STRIDULATION) SOUNDS IN THREE FAMILIES OF CATFISHES

ABSTRACT

Among teleosts, only representatives of several tropical catfish families have evolved two sonic organs: pectoral spines for stridulation and swimbladder drumming muscles. Pectoral mechanisms differ in relative size between pimelodids, mochokids and doradids, whereas swimbladder mechanisms exhibit differences in origin and insertion of extrinsic muscles. Differences in vocalization among families were investigated by comparing distress calls in air and underwater. High frequency broad-band pulsed sounds of similar duration were emitted during abduction of pectoral spines in all three families. Adduction sounds were similar to abduction signals in doradids, shorter and of lower sound pressure in mochokids, and totally lacking in pimelodids. Simultaneously or successively with pectoral sounds, low frequency harmonic drumming sounds were produced by representatives of two families. Drumming sounds were of similar intensity as stridulatory sounds in pimelodids, fainter in doradids, and not present in mochokids. Swimbladder sounds were frequency modulated and the fundamental frequency was similar in pimelodids and doradids. The ratio of stridulatory to drumming sound amplitude was higher in air than underwater in both doradids and one of the pimelodids. Also, overall duration of pectoral sounds, compared to swimbladder sounds, was longer in air than underwater in one doradid and pimelodid species. This first comparison of vocalization within one major teleost order demonstrates a wide variation in occurrence, duration, intensity and spectral content of sounds and indicates family- and species-specific as well as context- (receiver-) dependent patterns of vocalization.     

Ultrasound production during stridulation by hydropsychid larvae (Trichoptera)

The stridulatory apparatus of eight species of 5th instar caddis larvae of the family Hydropsychidae were compared using the scanning electron microscope. This revealed the presence of secondary structures associated with each main ridge of the file in some species. Slight differences occur in the number of ridges which form the plectra. The sounds produced by two coexisting species of hydropsychid larvae were recorded and temporal and frequency analysis carried out. These sounds are found to extend far into the ultrasonic range and appear to show only minor interspecific differences. The occurrence of stridulatory behaviour during territorial defence and its significance in relation to the ecology of the larvae is discussed. Some physical parameters affecting sound reception in the near- and far-field are presented and this leads to speculation on the existence of a possible hearing mechanism.     

Zooplankton capture by a coral reef fish: an adaptive response to evasive prey

Synopsis High-speed cinematography and video using modified Schlieren optics and laser illumination helped elicit details of prey capture mechanisms used by Chromis viridis while feeding on calanoid copepods and Artemia. Chromis viridis is capable of a ram-jaw, low-suction feeding, as well as a typical suction feeding behavior described for other species of planktivores. By adjusting the degree of jaw protrusion and amount of suction used during a feeding strike, this fish can modulate its feeding strikes according to the prey type being encountered. The ram-jaw feeding mode enables C. viridis to capture highly evasive calanoid copepods within 6 to 10 msec. The use of specialized feeding behavior for evasive prey and the ability to vary feeding behavior are adaptations for feeding on evasive prey.     

Diet composition of the seahorses, Hippocampus guttulatus Cuvier, 1829 and Hippocampus hippocampus (L., 1758) (Teleostei, Syngnathidae) in the Aegean Sea

The diet composition of the European seahorses, Hippocampus guttulatus and Hippocampus hippocampus was determined based on the analysis of 279 and 19 specimens, respectively, collected in the Aegean Sea. The diet of both species was mainly based on Crustacea, with Amphipoda, Anomura Decapoda and Mysidacea being the dominant prey categories. ANOSIM analyses, however, indicated statistically significant differences in the diet of the two species as well as differences in the diet composition of non-brooding males, brooding males and females within each species. In H. guttulatus , stomach fullness percentages and vacuity coefficient values indicated that female individuals seem to have a higher feeding activity in relation to males.     

Acoustic threat displays and agonistic behaviour in the red-finned loach <Emphasis Type="Italic">Yasuhikotakia modesta</Emphasis>

Agonistic behaviour and the significance of acoustic threat displays were investigated in juvenile red-finned loaches, Yasuhikotakia modesta. This species produced two different vocalizations during agonistic encounters—clicks and butting sounds. Clicks were produced at some distance from the opponent whereas butting sounds were emitted when one fish touched the other with its mouth. This occurred primarily during circling. Both sound types were short broadband signals with the main energies concentrated at about 230 Hz, but clicks were longer in duration and lower in sound level. Agonistic behaviour usually started when one fish approached the other, spread its fins and produced clicks (threat displays), which was followed by parallel displaying, circling and chasing. All fish approached a mirror quickly and displayed aggressively in a parallel position. The number and duration of the threat displays in front of the mirror image were significantly elevated compared with control experiments (rear of the mirror). When playing back click trains in the presence of a mirror image, loaches vocalized significantly less often than during the silent periods, whereas the amount of lateral displaying remained similar. These data indicate that agonistic sounds reduced acoustic displays in red-finned loaches.     

Defensive Sound Production in the Tobacco Hornworm, Manduca sexta (Bombycoidea: Sphingidae)

The tobacco hornworm (Manduca sexta) is a model organism extensively studied for many aspects of its biology, including its anti-predator strategies. We report on a novel component of this caterpillar’s defence repertoire: sound production. Late instar caterpillars produce discrete clicking sounds in response to disturbance. Click trains range in duration from 0.3–20.0 s (mean 3.3 ± 4.8 s) and contain 2–41 clicks (mean 7.1 ± 9.5). Sounds are broadband with a dominant frequency of 29.8 ± 4.9 kHz. We investigated the mechanism of sound production by selectively ablating three identified sets of ridges on the mandibles, and determined that ridges on the inner face strike the outer and incisor ridges on the opposing mandible to produce multi-component clicks. We tested the hypothesis that clicks function in defence using simulated attacks with blunt forceps. In single attack trials 77% of larvae produced sound and this increased to 100% in sequential attacks. Clicks preceded or accompanied regurgitation in 93% of multiple attack trials, indicating that sound production may function in acoustic aposematism. Sound production is also accompanied by other behaviours including directed thrashing, head curling, and biting, suggesting that sounds may also function as a general warning of unprofitability.     

Reverse stridulatory wing motion produces highly resonant calls in a neotropical katydid (Orthoptera: Tettigoniidae: Pseudophyllinae)

This paper describes the biomechanics of an unusual form of wing stridulation in katydids, termed here 'reverse stridulation'. Male crickets and katydids produced sound to attract females by rubbing their forewings together. One of the wings bears a vein ventrally modified with teeth (a file), while the other harbours a scraper on its anal edge. The wings open and close in rhythmic cycles, but sound is usually produced during the closing phase as the scraper moves along the file. Scraper-tooth strikes create vibrations that are subsequently amplified by wing cells specialised in sound radiation. The sound produced is either resonant (pure tone) or non-resonant (broadband); these two forms vary across species, but resonant requires complex wing mechanics. Using a sensitive optical diode and high-speed video to examine wing motion, and Laser Doppler Vibrometry (LDV) to study wing resonances, I describe the mechanics of stridulation used by males of the neotropical katydid Ischnomela gracilis (Pseudophyllinae). Males sing with a pure tone at ca.15 kHz and, in contrast to most Ensifera using wing stridulation, produce sound during the opening phase of the wings. The stridulatory file exhibits evident adaptations for such reverse scraper motion. LDV recordings show that the wing cells resonate sharply at ca. 15 kHz. Recordings of wing motion suggest that during the opening phase, the scraper strikes nearly 15,000 teeth/s. Therefore, the song of this species is produced by resonance. The implications of such adaptations (reverse motion, file morphology, and wing resonance) are discussed.     

Threshold for onset of injury in Chinook salmon from exposure to impulsive pile driving sounds

The risk of effects to fishes and other aquatic life from impulsive sound produced by activities such as pile driving and seismic exploration is increasing throughout the world, particularly with the increased exploitation of oceans for energy production. At the same time, there are few data that provide insight into the effects of these sounds on fishes. The goal of this study was to provide quantitative data to define the levels of impulsive sound that could result in the onset of barotrauma to fish. A High Intensity Controlled Impedance Fluid filled wave Tube was developed that enabled laboratory simulation of high-energy impulsive sound that were characteristic of aquatic far-field, plane-wave acoustic conditions. The sounds used were based upon the impulsive sounds generated by an impact hammer striking a steel shell pile. Neutrally buoyant juvenile Chinook salmon (Oncorhynchus tshawytscha) were exposed to impulsive sounds and subsequently evaluated for barotrauma injuries. Observed injuries ranged from mild hematomas at the lowest sound exposure levels to organ hemorrhage at the highest sound exposure levels. Frequency of observed injuries were used to compute a biological response weighted index (RWI) to evaluate the physiological impact of injuries at the different exposure levels. As single strike and cumulative sound exposure levels (SEL(ss), SEL(cum) respectively) increased, RWI values increased. Based on the results, tissue damage associated with adverse physiological costs occurred when the RWI was greater than 2. In terms of sound exposure levels a RWI of 2 was achieved for 1920 strikes by 177 dB re 1 μPa(2)?s SEL(ss) yielding a SEL(cum) of 210 dB re 1 μPa(2)?s, and for 960 strikes by 180 dB re 1 μPa(2)?s SEL(ss) yielding a SEL(cum) of 210 dB re 1 μPa(2)?s. These metrics define thresholds for onset of injury in juvenile Chinook salmon.     

Anti-bat tiger moth sounds: Form and function

The night sky is the venue of an ancient acoustic battle between echolocating bats and their insect prey. Many tiger moths (Lepidoptera: Arctiidae) answer the attack calls of bats with a barrage of high frequency clicks. Some moth species use these clicks for acoustic aposematism and mimicry, and others for sonar jamming, however, most of the work on these defensive functions has been done on individual moth species. We here analyze the diversity of structure in tiger moth sounds from 26 spe-cies collected at three locations in North and South America. A principal components analysis of the anti-bat tiger moth sounds reveals that they vary markedly along three axes: (1) frequency, (2) duty cycle (sound production per unit time) and frequency modulation, and (3) modulation cycle (clicks produced during flexion and relaxation of the sound producing tymbal) structure. Tiger moth species appear to cluster into two distinct groups: one with low duty cycle and few clicks per modulation cycle that supports an acoustic aposematism function, and a second with high duty cycle and many clicks per modulation cycle that is con-sistent with a sonar jamming function. This is the first evidence from a community-level analysis to support multiple functions for tiger moth sounds. We also provide evidence supporting an evolutionary history for the development of these strategies. Further-more, cross-correlation and spectrogram correlation measurements failed to support a "phantom echo" mechanism underlying sonar jamming, and instead point towards echo interference.     

Intraspecific acoustic communication and mechanical sensitivity of the tympanal ear of the gypsy moth Lymantria dispar

Tympanal ears of female gypsy moths Lymantria dispar dispar (L.) (Lepidoptera: Erebidae: Lymantriinae) are reportedly more sensitive than ears of conspecific males to sounds below 20 kHz. The hypothesis is tested that this differential sensitivity is a result of sex‐specific functional roles of sound during sexual communication, with males sending and females receiving acoustic signals. Analyses of sounds produced by flying males reveal a 33‐Hz wing beat frequency and 14‐kHz associated clicks, which remain unchanged in the presence of female sex pheromone. Females exposed to playback sounds of flying conspecific males respond with wing raising, fluttering and walking, generating distinctive visual signals that may be utilized by mate‐seeking males at close range. By contrast, females exposed to playback sounds of flying heterospecific males (Lymantria fumida Butler) do not exhibit the above behavioural responses. Laser Doppler vibrometry reveals that female tympana are particularly sensitive to frequencies in the range produced by flying conspecific males, including the 33‐Hz wing beat frequency, as well as the 7‐kHz fundamental frequency and 14‐kHz dominant frequency of associated clicks. These results support the hypothesis that the female L. dispar ear is tuned to sounds of flying conspecific males. Based on previous findings and the data of the present study, sexual communication in L. dispar appears to proceed as: (i) females emitting sex pheromone that attracts males; (ii) males flying toward calling females; and (iii) sound signals from flying males at close range inducing movement in females, which, in turn, provides visual signals that could orient males toward females.     

Analysis of the Stridulation in Solifuges (Arachnida: Solifugae)

Stridulation in solifuges has not been investigated yet. We performed a comparative analysis of the stridulatory organs and sounds produced by juveniles of various developmental stages and adults (both sexes) of Galeodes caspius subfuscus Birula. The stridulatory organ is of similar morphology in all developmental stages. The sound that they produced was a broad frequency hissing, composed of one or two chirps with maximum at 2.4 kHz. The intensity of the sound was found to increase with body size. Otherwise, no differences were observed between stridulation in juvenile, male and female individuals. Therefore, we suggest that the stridulation in solifuges has primarily a defensive role. As solifuges are neither venomous nor unpalatable, they might imitate an accoustically aposematic organism that shares the same habitat and has similar circadian activity, e.g. vipers. It may also have an intraspecific function in reduction of cannibalistic tendencies.     

AEPs at the onset and offset of repetitive sound modulation,due to mismatch with the contents of an auditory sensory store

Long latency auditory evoked potentials (AEPs), chiefly consisting of a negative peak at about 150 msec and a positivity at 250 msec, were recorded at the beginning and end of periods during which the interaural time difference of binaural noise was switched between 0.0 and 0.8 msec at a fast rate (ISI = 50 or 25 msec) or the frequency of continuous binaural clicks was switched between 167 and 200 Hz every 80, 50 or 25 msec. In the latter case the offset responses occurred later than onset by a mean of 89, 47 and 27 msec respectively, suggesting they were probably generated at the moment the next switch was expected but failed to occur.The offset responses must be non-specific with respect to the interaural delay or the frequency of clicks, since neurones which respond to particular delays or frequencies and are made refractory by a rapid rate of stimulation should not suddenly become less so at the last in a series of identical stimuli, or be activated by the absence of a further event. It is proposed that the potentials are due to a higher order of neurone which automatically responds to the occurrence of a “mismatch” between the immediate sound and an image of that which was previously present, encoded in a short-term sensory store. In addition to frequency content and interaural delay, the image must contain information about the temporal modulation pattern of the sound over the previous few seconds.     

Foreleg stridulation in male Urania moths (Lepidoptera: Uraniidae)

Males of the uraniid moth genus Urania possess a stridulatory organ on the prothoracic leg. This organ represents an autapomorphy for the genus. The sound-producing mechanism consists of a peg formed of specialized scales on the coxa which produces a train of high pitched clicks when scraped against scales on the proximal end of the femur. The proximal end of the femur is enlarged compared with that of the females and would serve to amplify the sound pulse. Stridulation occurs during a series of rapid forward jerks of the forelegs. The sound produced by Urania consists of a low amplitude pulse audible to humans at short range but with a strong ultrasound component. It has not yet been observed in the wild and its function in these moths is unknown, but it may be used during intrasexual or perhaps intersexual communication. This organ is unlikely to have been evolved originally as a defence against nocturnal predators since the genus is a member of an exclusively diurnal clade and females lack the organ. Stridulation occurs in conjunction with fanning-out of the foreleg femoral hair pencil and this invites speculation as to a route for evolution of the organ.     

Comparisons of aquatic versus terrestrial predatory strikes in the pitviper, Agkistrodon piscivorus

Recent studies comparing terrestrial versus aquatic locomotion in animals have shown that changes in kinematics, muscular activation patterns, and performance across media are often dramatic. Surprisingly, however, despite the importance of feeding to the survival of most animals, few studies have compared differences in feeding behaviour between media. The present study compares prey-capture behaviour, strike success, strike velocity and acceleration, and prey-capture kinematics in a semi-aquatic pitviper (Agkistrodon piscivorus) when capturing both terrestrial (mice) and aquatic (fish) prey in a standardized laboratory setting. Strike velocity and acceleration did not differ significantly between media, but instead were positively correlated with initial prey distance. By contrast, the kinematics of terrestrial and aquatic strikes differed significantly in several aspects: max gape angle during the retraction phase, angular velocity of mouth closing during the strike, and the initial head angle before the strike. Terrestrial strikes were associated with higher gape angles during the retraction phase, higher angular velocities of mouth closure, and a more inclined head angle at the onset of the strike. Finally, strike success differed significantly between strike types, with terrestrial strikes being considerably more successful than aquatic strikes. Strike success likely differed due to the relatively slow mouth-closing velocity of aquatic strikes.     

Genetic monogamy despite social promiscuity in the pot-bellied seahorse (Hippocampus abdominalis)

Sexual selection theory predicts a positive correlation between relative parental investment and mate choice. In syngnathid fishes (seahorses and pipefish), males brood offspring in specialized brooding structures. While female-female mating competition has been demonstrated in some pipefishes, all seahorses (genus Hippocampus) studied to date have been found to have conventional sex roles with greater male-male competition for access to mates despite possessing the most complex brood structures in the family. Although multiple mating is common in pipefish, seahorses are again exceptional, exhibiting strict genetic monogamy. Both demographic and behavioural explanations have been offered to explain the lack of multiple mating in seahorse species, but these hypotheses have not yet been explicitly addressed. We investigated mating systems and brood parentage of the pot-bellied seahorse, Hippocampus abdominalis, a temperate-water species that is socially promiscuous with conventional sex roles in laboratory populations. We observed promiscuous courtship behaviour and sex-role reversal in high density, female-biased field populations of H. abdominalis. We hypothesize that sex roles are plastic in H. abdominalis, depending on local population density and sex ratio. Despite promiscuous courtship behaviour, all assayed male seahorses were genetically monogamous in both laboratory and wild populations. Physiological limitations associated with embryo incubation may explain the absence of multiple mating in seahorses and may have played an important role in the development of the unique reproductive behaviour typical in these species.