Browsing by Author "Vasconcelos, Raquel Ornelas"
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- Development of vocalization, auditory sensitivity and acoustic communication in the Lusitanian toadfish Halobatrachus didactylusPublication . Vasconcelos, Raquel Ornelas; Ladich, FriedrichThe ontogenetic development of acoustic communication has so far only been investigated in one fish species. In order to determine whether detectability of conspecific sounds changes during growth in a species with limited hearing abilities (generalist), we investigated the development of auditory sensitivity and agonistic vocalizations in the Lusitanian toadfish Halobatrachus didactylus. Agonistic grunts were recorded, their sound pressure levels determined, and auditory sensitivities measured in five different size groups ranging from 3 to 32·cm standard length. Hearing thresholds were obtained using the auditory evoked potentials (AEP) recording technique. Dominant frequency, sound duration and number of pulses decreased, whereas pulse period and sound level increased with increasing fish size. The best hearing was below 300·Hz in all groups. Lower hearing sensitivity was found in the smallest juveniles at 100·Hz as well as at higher frequencies (800 and 1000·Hz). Comparisons between audiograms and sound spectra within the same-sized fish revealed that smaller juveniles would be barely able to detect agonistic grunts, while these vocalizations were clearly perceived by larger fish. In the latter, the main energy of sounds was found at the most sensitive frequencies. This study demonstrates that acoustic communication in the Lusitanian toadfish might be absent in early developmental stages and seems to start when juveniles are able to generate grunts of higher sound level and lower dominant frequency.
- Effects of ship noise on the detectability of communication signals in the Lusitanian toadfishPublication . Vasconcelos, Raquel Ornelas; Amorim, Maria Clara Pessoa; Ladich, FriedrichUnderwater noise pollution is an increasing environmental problem which might affect communication, behaviour, fitness and consequently species' survival. The most common anthropogenic noises in aquatic habitats derive from shipping. In the present study we investigated the implications of noise pollution from a ship on the sound detectability, namely of conspecific vocalizations in the Lusitanian toadfish, Halobatrachus didactylus. Ambient and ferry-boat noises were recorded in the Tagus River estuary (Portugal), as well as toadfish sounds, and their sound pressure levels determined. Hearing sensitivities were measured under quiet lab conditions and in the presence of these masking noises at levels encountered in the field, using the auditory evoked potentials (AEP) recording technique. The Lusitanian toadfish is a hearing generalist, with best hearing sensitivity at low frequencies between 50 and 200 Hz (below 100 dB re. 1 microPa). Under ambient noise conditions, hearing was only slightly masked at lower frequencies. In the presence of ship noise, auditory thresholds increased considerably, by up to 36 dB, at most frequencies tested. This is mainly because the main energies of ferry-boat noise were within the most sensitive hearing range of this species. Comparisons between masked audiograms and sound spectra of the toadfish's mating and agonistic vocalizations revealed that ship noise decreased the ability to detect conspecific acoustic signals. This study provides the first evidence that fishes' auditory sensitivity can be impaired by ship noise and that acoustic communication, which is essential during agonistic encounters and mate attraction, might be restricted in coastal environments altered by human activity.
- Effects of ship noise on the detectability of communication signals in the Lusitanian toadfishPublication . Vasconcelos, Raquel Ornelas; Amorim, Maria Clara Pessoa; Ladich, FriedrichUnderwater noise pollution is an increasing environmental problem which might affect communication, behaviour, fitness and consequently species’ survival. The most common anthropogenic noises in aquatic habitats derive from shipping. In the present study we investigated the implications of noise pollution from a ship on the sound detectability, namely of conspecific vocalizations in the Lusitanian toadfish, Halobatrachus didactylus. Ambient and ferry-boat noises were recorded in the Tagus River estuary (Portugal), as well as toadfish sounds, and their sound pressure levels determined. Hearing sensitivities were measured under quiet lab conditions and in the presence of these masking noises at levels encountered in the field, using the auditory evoked potentials (AEP) recording technique. The Lusitanian toadfish is a hearing generalist, with best hearing sensitivity at low frequencies between 50 and 200·Hz (below 100·dB re. 1· Pa). Under ambient noise conditions, hearing was only slightly masked at lower frequencies. In the presence of ship noise, auditory thresholds increased considerably, by up to 36·dB, at most frequencies tested. This is mainly because the main energies of ferry-boat noise were within the most sensitive hearing range of this species. Comparisons between masked audiograms and sound spectra of the toadfish’s mating and agonistic vocalizations revealed that ship noise decreased the ability to detect conspecific acoustic signals. This study provides the first evidence that fishes’ auditory sensitivity can be impaired by ship noise and that acoustic communication, which is essential during agonistic encounters and mate attraction, might be restricted in coastal environments altered by human activity.
- Ontogenetic development of the inner ear saccule and utricle in the Lusitanian toadfish: Potential implications for auditory sensitivityPublication . Chaves, Patrícia Alexandra Pereira; Valdoria, Ciara M.C.; Amorim, Maria Clara Pessoa; Vasconcelos, Raquel OrnelasStudies addressing structure-function relationships of the fish auditory system during development are sparse compared to other taxa. The Batrachoididae has become an important group to investigate mechanisms of auditory plasticity and evolution of auditory-vocal systems. A recent study reported ontogenetic improvements in the inner ear saccule sensitivity of the Lusitanian toadfish, Halobatrachus didactylus, but whether this results from changes in the sensory morphology remains unknown. We investigated how the macula and organization of auditory receptors in the saccule and utricle change during growth in this species. Inner ear sensory epithelia were removed from the end organs of previously PFA-fixed specimens, from non-vocal posthatch fry (<1.4 cm, standard length) to adults (>23 cm). Epithelia were phalloidin-stained and analysed for area, shape, number and orientation patterns of hair cells (HC), and number and size of saccular supporting cells (SC). Saccular macula area expanded 41x in total, and significantly more (relative to body length) among vocal juveniles (2.3-2.9 cm). Saccular HC number increased 25x but HC density decreased, suggesting that HC addition is slower relative to epithelial growth. While SC density decreased, SC apical area increased, contributing to the epithelial expansion. The utricule revealed increased HC density (striolar region) and less epithelial expansion (5x) with growth, contrasting with the saccule that may have a different developmental pattern due to its larger size and main auditory functions. Both macula shape and HC orientation patterns were already established in the posthatch fry and retained throughout growth in both end organs. We suggest that previously reported ontogenetic improvements in saccular sensitivity might be associated with changes in HC number (not density), size and/or molecular mechanisms controlling HC sensitivity. This is one of the first studies investigating the ontogenetic development of the saccule and utricle in a vocal fish and how it potentially relates to auditory enhancement for acoustic communication.
- Representation of complex vocalizations in the Lusitanian toadfish auditory system: Evidence of fine temporal, frequency and amplitude discriminationPublication . Vasconcelos, Raquel Ornelas; Fonseca, Paulo Jorge; Amorim, Maria Clara Pessoa; Ladich, FriedrichMany fishes rely on their auditory skills to interpret crucial information about predators and prey, and to communicate intraspecifically. Few studies, however, have examined how complex natural sounds are perceived in fishes. We investigated the representation of conspecific mating and agonistic calls in the auditory system of the Lusitanian toadfish Halobatrachus didactylus, and analysed auditory responses to heterospecific signals from ecologically relevant species: a sympatric vocal fish (meagre Argyrosomus regius) and a potential predator (dolphin Tursiops truncatus). Using auditory evoked potential (AEP) recordings, we showed that both sexes can resolve fine features of conspecific calls. The toadfish auditory system was most sensitive to frequencies well represented in the conspecific vocalizations (namely the mating boatwhistle), and revealed a fine representation of duration and pulsed structure of agonistic and mating calls. Stimuli and corresponding AEP amplitudes were highly correlated, indicating an accurate encoding of amplitude modulation. Moreover, Lusitanian toadfish were able to detect T. truncatus foraging sounds and A. regius calls, although at higher amplitudes. We provide strong evidence that the auditory system of a vocal fish, lacking accessory hearing structures, is capable of resolving fine features of complex vocalizations that are probably important for intraspecific communication and other relevant stimuli from the auditory scene.
- Seasonal variation of sound production in the Lusitanian toadfish Halobatrachus didactylusPublication . Amorim, Maria Clara Pessoa; Vasconcelos, Raquel Ornelas; Marques, José Frederico; Almada, Frederico José Oliveira deSeasonal variation of sound production, which includes boatwhistles, grunts, croaks and double croaks, was studied in the Lusitanian toadfish Halobatrachus didactylus. Boatwhistles were emitted during the mating season in contrast with the other sound types, which were emitted all year round.
- Variability in the mating calls of the Lusitanian toadfish Halobatrachus didactylus: Cues for potential individual recognitionPublication . Amorim, Maria Clara Pessoa; Vasconcelos, Raquel OrnelasThe mating sounds (boatwhistles) of nesting batrachoidid Halobatrachus didactylus males were recorded in the Tagus Estuary from piers. Thirteen males with 16 boatwhistles per fish were analysed for 20 acoustic features. All variables showed larger between-male than within-male variation and differed significantly among individuals. Discriminant function analyses (DFA) considering seven of these variables assigned 90–100% of boatwhistles to the correct individual, depending on the number of males and number of sounds per male included in the model. The acoustic features that consistently best discriminated individuals were the dominant frequency of the middle tonal segment of the boatwhistle (P2) and dominant frequency modulation, followed by P2 pulse period, amplitude modulation and sound duration. These results suggest the possibility of individual recognition based on acoustic cues.
- Variability in the sonic muscles of the lusitanian toadfish (Halobatrachus didactylus): Acoustic signals may reflect individual qualityPublication . Amorim, Maria Clara Pessoa; Vasconcelos, Raquel Ornelas; Parreira, BárbaraAnimal vocalizations are good examples of signals that have been shaped by sexual selection and often contribute to resolve contests or the choice of mates. We relate the mass of the sound-producing muscles of a highly vocal fish species, the Lusitanian toadfish (Halobatrachus didactylus (Bloch and Schneider, 1801)), with the sender’s physical features, such as body size, and reproductive and body condition. In this species, both sexes are known to emit sounds during agonistic interactions and males rely on their mate attraction vocalizations to reproduce. Sonic muscles were highly variable among males (CV = 40%) and females (CV = 33%) and showed sexual dimorphism. Regression analysis showed that variability in the sonic muscles was best explained by total length and fish condition in males and females. Liver mass in both genders, and the mass of the testes accessory glands, also explained sonic muscle variability. These variables explained 96% and 91% of the sonic muscle mass variability in males and females, respectively. As in teleost fishes sonic muscle mass correlates to particular sound acoustic features, we propose that in the Lusitanian toadfish sounds can inform the receiver about the sender’s quality, such as body size and condition, which are critical information in contests and mate choice.
- Vocal behavior during territorial intrusions in the lusitanian toadfish: Boatwhistles also function as territorial ‘keep-out’ signalsPublication . Vasconcelos, Raquel Ornelas; Simões, José Miguel; Almada, Vítor Carvalho; Fonseca, Paulo Jorge; Amorim, Maria Clara PessoaMale signals are frequently studied in a single behavioral context, but in some cases they may assist multiple functions, namely for both male– male competition and female mate choice. Boatwhistles are known as the mate attraction calls of toadfishes typically produced during the breeding season. However, recent observations with the Lusitanian toadfish Halobatrachus didactylus (Batrachoididae) indicate that the emission of boatwhistles is not restricted to this period, which suggests a function in other behavioral contexts such as agonistic territorial interactions. We experimentally manipulated the social context of toadfish males to investigate whether boatwhistles are produced during territorial defense, by introducing ‘intruders’ in an experimental tank containing nesting ‘resident’ males. Furthermore, we examined whether parental care (eggs in the nest) affected the behavioral responses of resident males during territorial defense. Resident males defended their shelters producing sounds, mostly boatwhistles, towards intruders. Parental males revealed higher aggression levels, exhibiting additional threatening and attack behaviors. Boatwhistles registered during agonistic events were compared with the mate advertising boatwhistles recorded from small aggregations of nesting males in a natural breeding intertidal area. Agonistic boatwhistles were produced in lower and variable calling rates comparing with the advertising ones that were typically emitted in long series of calls. Agonistic boatwhistles were similar in duration and frequency harmonic structure (with a middle tonal phase) to the advertising calls, but presented less amplitude modulation, and lower dominant and fundamental frequencies. These acoustic differences were probably related to differences in calling rates and broadcast demands associated to the distance to the intended receiver. We provide first evidence that, apart from attracting mates, the toadfish boatwhistles also function as active ‘keep-out’ signals during territorial defense.
- Vocal behavior predicts reproductive success in a teleost fishPublication . Vasconcelos, Raquel Ornelas; Carriço, Rita; Ramos, Andreia; Modesto, Teresa; Fonseca, Paulo Jorge; Amorim, Maria Clara PessoaThe 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.