M. Lugli

Sound production during courtship and spawning among freshwater gobiids (pisces, gobiidae)

In this paper the breeding sound production among gobiids is reviewed. Results of recent comparative studies on both pre‐spawning (courtship) and spawning sound production in the three italian freshwater gobiids are reported. A significant production of sounds associated to mating was discovered in two of these species. Furthermore, the quantification of acoustic behaviour across the spawning period (i.e., from the beginning of oviposition until the departure of the female from the males nest) revealed a pattern of spawning sound production similar in the two species.

Spawning vocalizations in male freshwater gobiids (Pisces, Gobiidae)

SynopsisMales of two freshwater Italian gobies, the common goby, Padogobius martensii and the panzarolo goby, Knipowitschia punctatissima, emit trains of low-frequency pulses, i.e. ‘drumming’ sounds, in the presence of a ripe female in the nest. In P, martensii the drumming sound is usually followed by a tonal sound (complex sound). Examination of the pulse structure suggests that these sounds are produced by muscles acting on the swimbladder. Both species exhibited high emission rates of spawning sounds, especially before the beginning of oviposition. Moreover, spawning sound production ceased only after the female abandoned the nest, which always occurred at the end of oviposition. This is the first study reporting the production among fishes of distinct sounds during protracted spawning. Unlike sounds produced just before mating by fishes with planktonic or demersal zygotes, the spawning sound production of these gobies does not function to coordinate mating events in the nest. The presence of a two-part vocalization by male P. martensii even suggests a functional dichotomy of spawning sounds in this species.

A quantitative analysis of the courtship acoustic behaviour and sound patterning in male sand goby, Pomatoschistus minutus

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 males 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 20–30 Hz to 500 Hz and reached a peak around 100 Hz. The absolute sound pressure level ranged from 118 to 138 dB re 1 µPa at 1–3 cm. 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.

ANALYSIS OF SOUNDS PRODUCED BY MALE PADOGOBIUS MARTENSI (PISCES, GOBIIDAE) AND FACTORS AFFECTING THEIR STRUCTURAL PROPERTIES

ABSTRACT In this paper a detailed analysis of the physical structure of sounds produced by male Padogobius martensi is reported. Sound production occurs during courtship and inter-male agonistic encounters. Both aggressive and courtship calls are made up of rapidly repeated pulses, with a pulse repetition rate decreasing through the course of the emission. By means of computerized analysis, the pulse repetition rate, its modulation and sound duration were determined. The water temperature was found to exert a marked and significant effect on the above parameters. In particular, the temperature directly affects the pulse rate and its decrease through the course of the emission (i.e. frequency modulation) and inversely affects sound duration. By contrast, size of the calling animal does not significantly influence the sound parameters considered. Aggressive sounds last longer and have a lower pulse repetition rate than the courtship sounds. Moreover, aggressive sounds appear more variable than the courtship...

Breeding ecology and male spawning success in two hill-stream populations of the freshwater goby, Padogobius martensi

SynopsisThis investigation was carried out at two study sites to examine the influence of shelter availability, nest site quality and male body size on spawning success of malePadogobius martensi. At Stirone Stream (first study site) individuals were not randomly distributed with respect to usable stones; larger males and females were consistently found to occupy larger stones. Laboratory experiments showed that the bottom surface area of the shelter was the relevant cue for the choice. The number of nesting males settled in a given area increased with increasing availability of local stone cover; inter-nest distance was directly correlated with male size. At Rivarolo Stream (second study site), which was characterized by lower nest density and a greater shortage of large stones, the pattern of shelter occupation was similar. These results suggest the presence of competition among individuals for the possession of larger-sized shelter sites. At both sites, the number of eggs in the nest increased as stone size increased; however, at the first study site, male body size played a major role in male spawning success as it concerns both the numbers of females mated and the number of eggs, while at the second study site, male body size was not shown to influence male spawning success. Factors responsible for between-site differences in male spawning success are discussed.

The importance of breeding vocalizations for mate attraction in a freshwater goby with a composite sound repertoire

Male gobies, Padogobius martensii, emit ‘tonal’ sounds during courtship, and ‘drumming’ and ‘complex’ sounds during spawning. The complex sound is a two-part vocalization consisting of a drumming sound followed without pause by a tonal sound. In the laboratory, the playback of both the tonal sound and the drumming sound to ripe females P. martensii determined oriented approaching and increased the time spent by the subject within the loudspeaker area. Response levels to the sound playback (drumming sounds) tended to be correlated with degree of ripeness of the female. Functional aspects of the female response to both types of acoustic stimuli are discussed.

Male Courtship Sounds in a Teleost with Alternative Reproductive Tactics, the Grass Goby, Zosterisessor ophiocephalus

Male grass gobies show two alternative breeding tactics, territorial and sneaker, distinguished by body size and difference in ray elongation on the second dorsal fin. The larger males, with elongated fins, are territorial and emit sounds during courtship. Smaller males, without elongated fins, act as sneakers. Both large and small males produce sounds in the presence of a ripe female. Males produce a grunt, lasting about 300 ms, made up of pulses repeated at a low rate (22–68 pps). Pulse duration, number, and repetition rate, did not differ between the two male types, but dominant frequency and sound amplitude did. Dominant frequency had a strong, inverse relationship with body size, whereas sound amplitude showed a weak positive relation to body size. Male size, and not the particular reproductive male tactic employed, is the most important correlate of sound properties in this species.

A quantitative analysis of the occurrence of visual and acoustic displays during the courtship in the freshwater goby, Padogobius martensi (Günther, 1961) (Pisces, Gobiidae)

Abstract Seventeen pairs of Padogobius martensi were observed to compare the relative occurrence of the acoustic and visual displays performed by the male during courtship. The results show that the visual display, which gradually decreases when the male approaches the nest, is the main signal to orient and attract the female towards the males nest; sound production, on the other hand, becomes more frequent when the male approaches and enters his nest. So, the acoustic signal has an important role when the visual one becomes ineffectual, when the male is hidden in the shelter. Visual and acoustic signals seem to have a complementary role and the male P.martensi uses the most effective signal in each particular situation.

Response of male goby, Padogobius martensii, to aggressive sound playback following pre-experimental visual stimulation

Three playback experiments with a freshwater goby, Padogobius martensii, examined the effects of recent aggressive experience on the response of the territorial fish to the aggressive sound alone. Experiments 1 and 2 were conducted on a first group of fifteen resident males (i.e. males individually housed within laboratory tanks for at least 5 days). Experiment 1 simply consisted of playing back the sound to the resident male not exposed to social stimulation for at least 48 h. In experiment 2 the same male was exposed to its mirror image before the start of playback. Results showed that in experiment 1 males ignored or even tended to avoid the site of sound stimulation, whereas in experiment 2 they attended the sound site more frequently during the sound playback. In both experiments the mirror and the loudspeaker were placed on the same side of the tank. The third playback experiment was therefore developed to include mirror and loudspeaker on opposite sides of the tank. A different group of sixteen males was used for these experiments. Results showed that the sound playback may be more important than the mirror site in directing the approach response of the male. Furthermore, the magnitude of sound interference was positively correlated with the level of mirror aggressiveness shown by the male before playback. Functional implications of the responses to the aggressive sound alone for the territorial fish are discussed.

The response of the male freshwater goby to natural and synthetic male courtship sound playback following exposure to different female sexual stimuli

Among teleosts, field and laboratory experiments have shown the playback of male courtship sounds often elicits competitive courtship and sound emission in the territorial male. However, the importance of female stimulation for the male response to the sound is poorly understood. In this study, playback experiments with the freshwater goby, Padogobius martensii, examined the response of resident males (i.e. males individually housed within laboratory tanks for at least 5 days) to natural and synthetic male courtship sounds after exposure to chemical or visual stimuli from a ripe female. All playback tests consisted of one experimental (sound playback) and two control treatments, all of equal duration. Three experiments were conducted on a first group of 12 males using natural courtship sounds. Experiment 1 consisted of playing back the sound to a male that had not exposed to female stimulation for at least 24 hr. The same male was exposed to the “female pheromone” by dropping a few cm3 of female holding water into the males tank, just prior to playback (Experiment 2), or to the view of a live ripe female in a close-by tank, during playback (Experiment 3). The sound playback failed to elicit positive responses by males not exposed to female stimuli (Experiment 1), and did not increase courtship activity of the male in visual contact with the female (Experiment 3). However, it increased swimming activity and facilitated courtship and sound production in the male after an increase in sexual arousal by prior chemical stimulation (Experiment 2). In Experiment 4, the synthetic version of the courtship sound and one deprived of pulse-rate modulation and harmonic content (pure tone) were played back to 10 resident males following prior chemical stimulation. The synthetic courtship sound, but not the pure tone, was effective in eliciting positive responses by the sexually aroused male. Functional implications of the responses to the courtship sound for the territorial male are discussed. The results are relevant to the understanding of the role of sound communication and interception among gobies and to develop playback experiments in the field.