Experimental evidence that competition between stickleback species favours adaptive character divergence

The ecological character displacement hypothesis assumes that the effects of interspecific resource competition cause divergent selection to favour phenotypes that exploit non-shared resources. This model predicts that interspecific competition declines with increased divergence. Direct tests of this decline are rare despite much comparative evidence for character displacement. We tested this prediction using a pair of divergent brook sticklebacks. Brook sticklebacks sympatric with ninespine sticklebacks have diverged from local allopatric brook populations, and so the two types of brook sticklebacks potentially represent pre- and post-displacement forms. We used enclosures placed in a lake to compare short-term fitness (growth) of sympatric (post-displacement) and allopatric (pre-displacement) brook forms in the presence and absence of ninespine sticklebacks. Brook sticklebacks grew less in the presence vs. absence of ninespine sticklebacks, indicating that interspecific competition occurred. As expected, allopatric brook forms had lower growth than sympatric forms when ninespine sticklebacks were present. This result suggests that ecological character displacement has occurred.     

Fathead minnows avoid conspedfic and heterospedfic alarm pheromones in the faeces of northern pike

Groups of fathead minnows Pimephales promelas were tested to determine if they avoided areas of a test tank labelled with the faeces of a predator (northern pike, Esox lucius ) which had recently been fed minnows, brook sticklebacks Culaea inconstans , or swordtails Xiphophorus helleri. Minnows exhibited a fright reaction upon presentation of sponges labelled with faeces, when the pike had consumed minnows or sticklebacks, but not swordtails (which lack alarm pheromones). The fright reaction was characterized by increased shoal cohesiveness and increased dashing and freezing behaviour. Minnows avoided the area of the tank containing the faeces from pike on diets of minnows or sticklebacks, but not from pike fed a diet of swordtails. These data demonstrate that: (1) minnows actively avoid the faeces of pike fed minnows or brook sticklebacks, and (2) minnows exhibit a fright reaction to the faeces of a pike fed brook sticklebacks.     

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.     

Acquired Recognition of Chemical Stimuli from Pike,Esox lucius,by Brook Sticklebacks,Culaea inconstans (Osteichthyes,Gasterosteidae)

In this study we test whether brook sticklebacks (Culaea inconstans) can acquire predator recognition through releaser-induced recognition learning, i.e. simultaneous exposure to aversive ('releasing') stimuli and neutral stimuli causing learned aversion to the neutral stimuli. We exposed wild-caught pike-naive brook sticklebacks (collected from a creek containing fathead minnows, Pimephales promelas, but not pike, Esox lucius) to chemical stimuli from pike that were mixed with brook stickleback skin extract, fathead minnow skin extract, or a control of distilled water. In subsequent tests 2 d later, when only pike stimuli were presented, sticklebacks conditioned with stickleback skin extract and fathead minnow skin extract exhibited antipredator behaviour (i.e. increased schooling and movement toward the substrate), while those conditioned with distilled water did not. Sticklebacks conditioned with stickleback skin extract responded to pike with a more intense response, in terms of movement toward the substrate, than those conditioned with fathead minnow skin extract, suggesting that conspecific skin extract may be a stronger stimulus than heterospecific skin extract for learning recognition of predators. To our knowledge this is the first study to demonstrate that an acanthopterygian fish can acquire predator recognition through the pairing of conspecific alarm pheromone with the cue of a predator. Furthermore, our results are the first to demonstrate that fish can acquire predator recognition through the pairing of a heterospecific alarm pheromone with the cue of a predator. These results suggest that brook sticklebacks will benefit by being in close proximity to fathead minnows. Acquired predator recognition has long-term consequences in mediating predator-prey interactions.     

Innate sound production in the cichlid Oreochromis niloticus

The mouthbrooding cichlid Oreochromis niloticus is one of the world's best-studied fish and is raised extensively for aquaculture. Although it is a common behavioural model, its acoustic communication has been neglected. Because of extensive parental care, the species is a good candidate for vocal learning. In male O. niloticus , we investigated for the first time sound production in agonistic interactions during nest construction. Males produce short-duration (250–400 ms), often double-pulse sounds. Most energy is below 200 Hz and includes three main low-frequency peaks although energy extends beyond 1 kHz. Males (separated as eggs and raised in isolation) produce similar sounds in the same context as parental fish, indicating that the ability to produce sounds and the basic properties of the sounds are innate.     

Singen mit Kopf und Kragen

Singing with the wings – instrumental sound production in birds Bird wing and tail feathers are able to produce sound in flight and during related movements. Noisy sound is produced primarily as an epiphenomenon to the movements. The sound can, however, also include tonal or harmonic structures and can gain signal value when used in social situations. In a similar way, birds can produce sounds by clattering their keratin covered beaks. For the first time, in this article, the acoustic properties of instrumental bird sounds are analyzed using sonograms. Up to now the biological meaning of instrumental sounds in birds is inferred mainly out of the situations observed.     

The African cichlid fish Astatotilapia burtoni uses acoustic communication for reproduction: sound production, hearing, and behavioral significance

Sexual reproduction in all animals depends on effective communication between signalers and receivers. Many fish species, especially the African cichlids, are well known for their bright coloration and the importance of visual signaling during courtship and mate choice, but little is known about what role acoustic communication plays during mating and how it contributes to sexual selection in this phenotypically diverse group of vertebrates. Here we examined acoustic communication during reproduction in the social cichlid fish, Astatotilapia burtoni. We characterized the sounds and associated behaviors produced by dominant males during courtship, tested for differences in hearing ability associated with female reproductive state and male social status, and then tested the hypothesis that female mate preference is influenced by male sound production. We show that dominant males produce intentional courtship sounds in close proximity to females, and that sounds are spectrally similar to their hearing abilities. Females were 2-5-fold more sensitive to low frequency sounds in the spectral range of male courtship sounds when they were sexually-receptive compared to during the mouthbrooding parental phase. Hearing thresholds were also negatively correlated with circulating sex-steroid levels in females but positively correlated in males, suggesting a potential role for steroids in reproductive-state auditory plasticity. Behavioral experiments showed that receptive females preferred to affiliate with males that were associated with playback of courtship sounds compared to noise controls, indicating that acoustic information is likely important for female mate choice. These data show for the first time in a Tanganyikan cichlid that acoustic communication is important during reproduction as part of a multimodal signaling repertoire, and that perception of auditory information changes depending on the animal's internal physiological state. Our results highlight the importance of examining non-visual sensory modalities as potential substrates for sexual selection contributing to the incredible phenotypic diversity of African cichlid fishes.     

Songbird tap dancing produces non-vocal sounds*

Vocalizations have been elucidated in previous songbird studies, whereas less attention has been paid to non-vocal sounds. In the blue-capped cordon-bleu (Uraeginthus cyanocephalus), both sexes perform courtship displays that are accompanied by singing and distinct body movements (i.e. dance). Our previous study revealed that their courtship bobbing includes multiple rapid steps. This behaviour is quite similar to human tap dancing, because it can function as both visual and acoustic signals. To examine the acoustic signal value of such steps, we tested if their high-speed step movements produce non-vocal sounds that have amplitudes similar to vocal sounds. We found that step behaviour affected step sound amplitude. Additionally, the dancing step sounds were substantially louder than feet movement sounds in a non-courtship context, and the amplitude range overlapped with that of song notes. These results support the idea that in addition to song cordon-bleus produce acoustic signals with their feet.     

Further evidence for size-assortative schooling in sticklebacks

Using brook ( Culaea inconstans ) and 10-spined ( Pungitius pungitius ) sticklebacks we examined body-size related schooling behaviour. Small and large sticklebacks were allowed to choose between two test schools, of small and of large individuals, with and without a piscivorous fish ( Oncorhynchus mykiss ) visible. Sticklebacks of both species preferred the company of fish of matching body size: small fish associating with a school of small fish, large fish with a school of large fish. While no interspecific differences were found in responses to school selection, body size and predator presence did affect selection of school-type. In both species, small fish tended to show a stronger preference for matching schools. The preference was enhanced in small fish with presence of a predator, but not in large fish. These observations are further evidence for assortative schooling in sticklebacks.     

Acoustic detection and communication by decapod crustaceans

This paper reviews behavioral, physiological, anatomical, and ecological aspects of sound and vibration detection by decapod crustaceans. Our intent is to demonstrate that despite very limited work in this area in the past 20 years, evidence suggests that at least some decapod crustaceans are able to detect and use sounds in ways that parallel detection and processing mechanisms in aquatic and terrestrial vertebrates. Some aquatic decapod crustaceans produce sounds, and many are able to detect substrate vibration at sensitivities sufficient to tell of the proximity of mates, competitors, or predators. Some semi-terrestrial crabs produce and use sounds for communication. These species detect acoustic stimuli as either air- or substrate-borne energies, socially interact in acoustic "choruses," and probably use "calls" to attract mates.     

Learned or innate production of acoustic signals in fishes: a test using a cyprinid

No information on the inheritance of the ability to produce sounds exists for fishes. In birds, which usually provide extensive post-hatching parental care, acoustic signals are learned in some species but are innate in others. Almost no fishes provide extensive post-hatching parental care and, consequently, the offspring have little opportunity to hear and learn sounds produced by the parents (usually the male in fishes); they may, however, be exposed to acoustic signals of conspecifics in the same habitat. We used a cyprinid, Codoma ornata, to test whether sound production is learned from the parents or whether it is innate. Fertilized eggs of this species were raised in isolation from adults. Upon maturity, these fish were tested for sound production in aggressive and reproductive contexts. Fish which had no contact with adults, and therefore no opportunity to hear the acoustic signals of their species, produced sounds that were similar to those produced by their parents, and they produced these in the same contexts. Significant differences were observed in dominant frequency for one context, with the smaller F₁ fish having signals of higher frequency than parental fish. Since no opportunity for learning existed, this provided evidence that the ability to produce sounds is innate in this minnow species.     

Acoustic communication in an electric fish,Pollimyrus isidori (Mormyridae)

It has been known since von Frisch's work in the 1930's that mormyrid electric fishes are quite sensitive to sound. We now describe a repertoire of natural sounds produced by the mormyrid, Pollimyrus isidori, during breeding and aggression; reception of communication sounds is probably a major function for mormyrid audition. In aquaria, Pollimyrus isidori produce 'grunts', 'moans', 'growls', 'pops' and 'hoots' at various phases during nesting, courtship, and territory defense. All five sounds are produced primarily at night. Territorial males produce grunts, moans and growls during courtship. Vocalizing is stimulated by the presence of a gravid female on the male's territory and decreases with the onset of spawning. Hoots and pops are given during agonistic behavior. Grunts are bursts of acoustic pulses, stereotyped for an individual, with the potential as individual signatures. The electric organ is silent during grunts and moans and is discharged at a reduced rate during growls. The courtship and spawning of Pollimyrus isidori is described.     

Acoustic signals in katydids (Orthoptera,Tettigonidae). Communication 2

Three basic trends in the development of acoustic communication in Tettigonioidea are distinguished. The first one is observed in predatory tettigoniids and conocephalids. It is associated with the improvement of the territorial behavior and results in the appearance of territorial, aggressive and protest sounds (only males stridulate) in the acoustic repertoire. The second trend is caused by the development of defensive mechanisms. It is observed in phytophagous katydids belonging to the family Bradyporidae dwelling in deserts and other exposed habitats. As a rule, their acoustic repertoire includes long-lasting calling songs and disturbance (protest) sounds; rather often, these sounds are produced both by males and females. The unmasking effect of signals is compensated for by specific defense adaptations. The third evolutionary tendency is most completely expressed in phytophagous Phaneropteridae and phytophilous Bradyporidae (Ephippigerinae) as a result of the predator press and the improvement of sexual behavior. It leads to appearance of a “slow” system of communication, when the unmasking effect of songs is minimized by the decrease in the acoustic activity of males. Females produce response signals, while males produce complex calling, courtship, and confirming sounds. The temporal pattern of a signal is one of the most reliable criteria for the discrimination of species and subspecies. It is difficult to use physical parameters of sounds as a criterion for the differentiation of taxa at the superspecies rank, since acoustical signalling is obviously a subject of evolution of the acoustic community rather than of the taxon. Parallelisms and convergences are observed in the evolution of acoustic communication systems, but complex analysis allows revealing the initial type of the acoustic system and defining the reasons for adaptive reorganizations.     

Within-group variation in the willingness to risk exposure to a predator: the influence of species and size

The costs and benefits associated with feeding in the vicinity of a predator should vary within and among species, depending on an individual's vulnerability to a predator. In this paper, we investigate how willingness to risk exposure to a predator in order to gain access to food is expressed within groups of fish. We provided groups of six individually marked brook sticklebacks ( Culea inconstans ) and fathead minnows ( Pimephales promelas ) with the opportunity to feed in safety, or in the presence of a single predator (walleye, Stizostedion vitreum ). Sticklebacks and fathead minnows are commonly found in the same locations at the same time, but sticklebacks also possess armour and spines that provide defence against some predators. Despite this morphological variation, patterns of individual behaviour were consistent between species. While feeding close to the predator, there was a positive relation between the size of the individual and the proportion of food consumed. No relation existed on the side farthest from the predator. These data suggest that fish may risk exposure to predators to exploit size-related differences in vulnerability to gain a competitive advantage for access to food.     

Sounds Modulate Males’ Aggressiveness in a Cichlid Fish

Acoustic signals are produced in many fish species during agonistic or courtship interactions. A way to test the biological role of these sounds is the use of acoustic playback experiments. However, sounds are usually associated with visual displays and playback experiments performed in fish so far, often failed to match acoustic and visual stimuli. To avoid this mismatch issue, we experimentally separated or coupled visual and acoustic channels to test the role of sounds produced during male–male aggressive interactions in a cichlid fish, Metriaclima zebra. Results show that aggressive behaviour is based on visual stimuli and that acoustic signals alone never trigger aggression. Furthermore, the association between visual and acoustic channels lowers the level of aggressiveness found when fish can only interact visually. This suggests that acoustic signals used during a dispute may complement visual displays to modulate males’ behaviour by reducing their aggressiveness and the risk of escalated fights.     

Behaviours Associated with Acoustic Communication in Nile Tilapia (Oreochromis niloticus)

Background

Sound production is widespread among fishes and accompanies many social interactions. The literature reports twenty-nine cichlid species known to produce sounds during aggressive and courtship displays, but the precise range in behavioural contexts is unclear. This study aims to describe the various Oreochromis niloticus behaviours that are associated with sound production in order to delimit the role of sound during different activities, including agonistic behaviours, pit activities, and reproduction and parental care by males and females of the species.

Methodology/Principal Findings

Sounds mostly occur during the day. The sounds recorded during this study accompany previously known behaviours, and no particular behaviour is systematically associated with sound production. Males and females make sounds during territorial defence but not during courtship and mating. Sounds support visual behaviours but are not used alone. During agonistic interactions, a calling Oreochromis niloticus does not bite after producing sounds, and more sounds are produced in defence of territory than for dominating individuals. Females produce sounds to defend eggs but not larvae.

Conclusion/Significance

Sounds are produced to reinforce visual behaviours. Moreover, comparisons with O. mossambicus indicate two sister species can differ in their use of sound, their acoustic characteristics, and the function of sound production. These findings support the role of sounds in differentiating species and promoting speciation. They also make clear that the association of sounds with specific life-cycle roles cannot be generalized to the entire taxa.     

Overview on the Diversity of Sounds Produced by Clownfishes (Pomacentridae): Importance of Acoustic Signals in Their Peculiar Way of Life

Background

Clownfishes (Pomacentridae) are brightly colored coral reef fishes well known for their mutualistic symbiosis with tropical sea anemones. These fishes live in social groups in which there is a size-based dominance hierarchy. In this structure where sex is socially controlled, agonistic interactions are numerous and serve to maintain size differences between individuals adjacent in rank. Clownfishes are also prolific callers whose sounds seem to play an important role in the social hierarchy. Here, we aim to review and to synthesize the diversity of sounds produced by clownfishes in order to emphasize the importance of acoustic signals in their way of life.

Methodology/Principal Findings

Recording the different acoustic behaviors indicated that sounds are divided into two main categories: aggressive sounds produced in conjunction with threat postures (charge and chase), and submissive sounds always emitted when fish exhibited head shaking movements (i.e. a submissive posture). Both types of sounds showed size-related intraspecific variation in dominant frequency and pulse duration: smaller individuals produce higher frequency and shorter duration pulses than larger ones, and inversely. Consequently, these sonic features might be useful cues for individual recognition within the group. This observation is of significant importance due to the size-based hierarchy in clownfish group. On the other hand, no acoustic signal was associated with the different reproductive activities.

Conclusions/Significance

Unlike other pomacentrids, sounds are not produced for mate attraction in clownfishes but to reach and to defend the competition for breeding status, which explains why constraints are not important enough for promoting call diversification in this group.     

Overriding the oddity effect in mixed-species aggregations: group choice by armored and nonarmored prey

Because "odd" individuals often suffer disproportionately highrates of predation, solitary individuals should join groupswhose members are most similar to themselves in appearance.We examined group-choice decisions by individuals in armoredand nonarmored species and predicted that either (1) the oddityeffect would result in preference for conspecific groups forsolitary individuals of both species, or (2) individuals inthe armored species would prefer to associate with groups containingindividuals of the more vulnerable species. Armored brook sticklebacks(Culaea inconstans) and nonarmored fathead minnows (Pimephalespromelas) have the same predators and often occur together instreams. In mixed-species shoals, yellow perch (Perca flavescens)attacked minnows earlier and more often than sticklebacks. Wetested whether solitary minnows and sticklebacks preferred toassociate with conspecific or heterospecific shoals under conditionsof both low and high predation risk. When predation risk washigh, minnows preferred to associate with conspecifics overheterospecifics, as predicted by the oddity effect. In contrast,sticklebacks preferentially associated with groups of minnowsover groups of conspecifics when predation risk was high. Whenpredation risk was low, solitary individuals of both speciespreferentially associated with conspecific over heterospecificshoals. Stickleback shoal choices under low-risk conditionsmay have been influenced by interspecific competition for food.In feeding experiments, minnows were more efficient foragersthan sticklebacks, so it should benefit sticklebacks to avoidminnows unless predation risk is high. Therefore, for armoredprey, the benefits of associating with more vulnerable preyappear to override the costs of both the oddity effect and foodcompetition when predation risk is high.     

饲养状态真鲂(鱼弗)发声的昼夜与季节变化

本文研究了受水温和光周期等自然变化影响的饲养状态真鲂鮄发声的昼夜与季节变化,并研究了实验鱼活动(鱼类游泳次数)的日变化。声音信号的昼夜节律记录发声活动的日常水平(摄食之外的时期),但是每月变化的记录(季节性式型)则在摄食期间进行,因为摄食时声音信号增加,而日常发声活动较不频繁。实验鱼包括雌雄两性,且未达性成熟。真鲂鮄在白天发声多一些,也更活跃。声音为阵发式的,较不频繁(平均值=0.04发声/min每鱼每天)。最少的发声活动出现在晚上,凌晨和黄昏居中(声音的阵发更频繁,但是声音更少),最多的发声活动出现在白天(声音的阵发更频繁,并且含更多数目的声音)。竞争摄食时声音信号的比率不呈现季节性变化(平均值=3.98发声/min每鱼),与温度也不相关,显示出竞争摄食时声音的发出以最大比率进行。敲击声和呼噜声的某些声学特征与温度相关,特别是在较高的温度下呼噜声的节拍间隔急剧下降。敲击声和呼噜声的声音参数中的季节性变化,多数可以解释为发声肌肉和中央声音控制回路的温度效应。